--- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -64,6 +64,7 @@ prototypes: int (*atomic_open)(struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode, int *opened); + int (*dentry_open)(struct dentry *, struct file *, const struct cred *); locking rules: all may block @@ -91,6 +92,7 @@ removexattr: yes fiemap: no update_time: no atomic_open: yes +dentry_open: no Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on victim. --- /dev/null +++ b/Documentation/filesystems/overlayfs.txt @@ -0,0 +1,199 @@ +Written by: Neil Brown <neilb@suse.de> + +Overlay Filesystem +================== + +This document describes a prototype for a new approach to providing +overlay-filesystem functionality in Linux (sometimes referred to as +union-filesystems). An overlay-filesystem tries to present a +filesystem which is the result over overlaying one filesystem on top +of the other. + +The result will inevitably fail to look exactly like a normal +filesystem for various technical reasons. The expectation is that +many use cases will be able to ignore these differences. + +This approach is 'hybrid' because the objects that appear in the +filesystem do not all appear to belong to that filesystem. In many +cases an object accessed in the union will be indistinguishable +from accessing the corresponding object from the original filesystem. +This is most obvious from the 'st_dev' field returned by stat(2). + +While directories will report an st_dev from the overlay-filesystem, +all non-directory objects will report an st_dev from the lower or +upper filesystem that is providing the object. Similarly st_ino will +only be unique when combined with st_dev, and both of these can change +over the lifetime of a non-directory object. Many applications and +tools ignore these values and will not be affected. + +Upper and Lower +--------------- + +An overlay filesystem combines two filesystems - an 'upper' filesystem +and a 'lower' filesystem. When a name exists in both filesystems, the +object in the 'upper' filesystem is visible while the object in the +'lower' filesystem is either hidden or, in the case of directories, +merged with the 'upper' object. + +It would be more correct to refer to an upper and lower 'directory +tree' rather than 'filesystem' as it is quite possible for both +directory trees to be in the same filesystem and there is no +requirement that the root of a filesystem be given for either upper or +lower. + +The lower filesystem can be any filesystem supported by Linux and does +not need to be writable. The lower filesystem can even be another +overlayfs. The upper filesystem will normally be writable and if it +is it must support the creation of trusted.* extended attributes, and +must provide valid d_type in readdir responses, at least for symbolic +links - so NFS is not suitable. + +A read-only overlay of two read-only filesystems may use any +filesystem type. + +Directories +----------- + +Overlaying mainly involves directories. If a given name appears in both +upper and lower filesystems and refers to a non-directory in either, +then the lower object is hidden - the name refers only to the upper +object. + +Where both upper and lower objects are directories, a merged directory +is formed. + +At mount time, the two directories given as mount options are combined +into a merged directory: + + mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper /overlay + +Then whenever a lookup is requested in such a merged directory, the +lookup is performed in each actual directory and the combined result +is cached in the dentry belonging to the overlay filesystem. If both +actual lookups find directories, both are stored and a merged +directory is created, otherwise only one is stored: the upper if it +exists, else the lower. + +Only the lists of names from directories are merged. Other content +such as metadata and extended attributes are reported for the upper +directory only. These attributes of the lower directory are hidden. + +whiteouts and opaque directories +-------------------------------- + +In order to support rm and rmdir without changing the lower +filesystem, an overlay filesystem needs to record in the upper filesystem +that files have been removed. This is done using whiteouts and opaque +directories (non-directories are always opaque). + +The overlay filesystem uses extended attributes with a +"trusted.overlay." prefix to record these details. + +A whiteout is created as a symbolic link with target +"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y". +When a whiteout is found in the upper level of a merged directory, any +matching name in the lower level is ignored, and the whiteout itself +is also hidden. + +A directory is made opaque by setting the xattr "trusted.overlay.opaque" +to "y". Where the upper filesystem contains an opaque directory, any +directory in the lower filesystem with the same name is ignored. + +readdir +------- + +When a 'readdir' request is made on a merged directory, the upper and +lower directories are each read and the name lists merged in the +obvious way (upper is read first, then lower - entries that already +exist are not re-added). This merged name list is cached in the +'struct file' and so remains as long as the file is kept open. If the +directory is opened and read by two processes at the same time, they +will each have separate caches. A seekdir to the start of the +directory (offset 0) followed by a readdir will cause the cache to be +discarded and rebuilt. + +This means that changes to the merged directory do not appear while a +directory is being read. This is unlikely to be noticed by many +programs. + +seek offsets are assigned sequentially when the directories are read. +Thus if + - read part of a directory + - remember an offset, and close the directory + - re-open the directory some time later + - seek to the remembered offset + +there may be little correlation between the old and new locations in +the list of filenames, particularly if anything has changed in the +directory. + +Readdir on directories that are not merged is simply handled by the +underlying directory (upper or lower). + + +Non-directories +--------------- + +Objects that are not directories (files, symlinks, device-special +files etc.) are presented either from the upper or lower filesystem as +appropriate. When a file in the lower filesystem is accessed in a way +the requires write-access, such as opening for write access, changing +some metadata etc., the file is first copied from the lower filesystem +to the upper filesystem (copy_up). Note that creating a hard-link +also requires copy_up, though of course creation of a symlink does +not. + +The copy_up may turn out to be unnecessary, for example if the file is +opened for read-write but the data is not modified. + +The copy_up process first makes sure that the containing directory +exists in the upper filesystem - creating it and any parents as +necessary. It then creates the object with the same metadata (owner, +mode, mtime, symlink-target etc.) and then if the object is a file, the +data is copied from the lower to the upper filesystem. Finally any +extended attributes are copied up. + +Once the copy_up is complete, the overlay filesystem simply +provides direct access to the newly created file in the upper +filesystem - future operations on the file are barely noticed by the +overlay filesystem (though an operation on the name of the file such as +rename or unlink will of course be noticed and handled). + + +Non-standard behavior +--------------------- + +The copy_up operation essentially creates a new, identical file and +moves it over to the old name. The new file may be on a different +filesystem, so both st_dev and st_ino of the file may change. + +Any open files referring to this inode will access the old data and +metadata. Similarly any file locks obtained before copy_up will not +apply to the copied up file. + +On a file opened with O_RDONLY fchmod(2), fchown(2), futimesat(2) and +fsetxattr(2) will fail with EROFS. + +If a file with multiple hard links is copied up, then this will +"break" the link. Changes will not be propagated to other names +referring to the same inode. + +Symlinks in /proc/PID/ and /proc/PID/fd which point to a non-directory +object in overlayfs will not contain valid absolute paths, only +relative paths leading up to the filesystem's root. This will be +fixed in the future. + +Some operations are not atomic, for example a crash during copy_up or +rename will leave the filesystem in an inconsistent state. This will +be addressed in the future. + +Changes to underlying filesystems +--------------------------------- + +Offline changes, when the overlay is not mounted, are allowed to either +the upper or the lower trees. + +Changes to the underlying filesystems while part of a mounted overlay +filesystem are not allowed. If the underlying filesystem is changed, +the behavior of the overlay is undefined, though it will not result in +a crash or deadlock. --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -362,6 +362,7 @@ struct inode_operations { int (*atomic_open)(struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode, int *opened); + int (*dentry_open)(struct dentry *, struct file *, const struct cred *); }; Again, all methods are called without any locks being held, unless @@ -681,6 +682,12 @@ struct address_space_operations { but instead uses bmap to find out where the blocks in the file are and uses those addresses directly. + dentry_open: this is an alternative to f_op->open(), the difference is that + this method may open a file not necessarily originating from the same + filesystem as the one i_op->open() was called on. It may be + useful for stacking filesystems which want to allow native I/O directly + on underlying files. + invalidatepage: If a page has PagePrivate set, then invalidatepage will be called when part or all of the page is to be removed --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -567,6 +567,13 @@ static struct dentry *ecryptfs_mount(str s->s_maxbytes = path.dentry->d_sb->s_maxbytes; s->s_blocksize = path.dentry->d_sb->s_blocksize; s->s_magic = ECRYPTFS_SUPER_MAGIC; + s->s_stack_depth = path.dentry->d_sb->s_stack_depth + 1; + + rc = -EINVAL; + if (s->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { + printk(KERN_ERR "eCryptfs: maximum fs stacking depth exceeded\n"); + goto out_free; + } inode = ecryptfs_get_inode(path.dentry->d_inode, s); rc = PTR_ERR(inode); --- a/fs/internal.h +++ b/fs/internal.h @@ -42,11 +42,6 @@ static inline int __sync_blockdev(struct extern void __init chrdev_init(void); /* - * namei.c - */ -extern int __inode_permission(struct inode *, int); - -/* * namespace.c */ extern int copy_mount_options(const void __user *, unsigned long *); --- a/fs/Kconfig +++ b/fs/Kconfig @@ -67,6 +67,7 @@ source "fs/quota/Kconfig" source "fs/autofs4/Kconfig" source "fs/fuse/Kconfig" +source "fs/overlayfs/Kconfig" config GENERIC_ACL bool --- a/fs/Makefile +++ b/fs/Makefile @@ -107,6 +107,7 @@ obj-$(CONFIG_QNX6FS_FS) += qnx6/ obj-$(CONFIG_AUTOFS4_FS) += autofs4/ obj-$(CONFIG_ADFS_FS) += adfs/ obj-$(CONFIG_FUSE_FS) += fuse/ +obj-$(CONFIG_OVERLAYFS_FS) += overlayfs/ obj-$(CONFIG_UDF_FS) += udf/ obj-$(CONFIG_SUN_OPENPROMFS) += openpromfs/ obj-$(CONFIG_OMFS_FS) += omfs/ --- a/fs/namei.c +++ b/fs/namei.c @@ -402,6 +402,7 @@ int __inode_permission(struct inode *ino return security_inode_permission(inode, mask); } +EXPORT_SYMBOL(__inode_permission); /** * sb_permission - Check superblock-level permissions @@ -2876,9 +2877,12 @@ finish_open_created: error = may_open(&nd->path, acc_mode, open_flag); if (error) goto out; - file->f_path.mnt = nd->path.mnt; - error = finish_open(file, nd->path.dentry, NULL, opened); - if (error) { + + BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ + error = vfs_open(&nd->path, file, current_cred()); + if (!error) { + *opened |= FILE_OPENED; + } else { if (error == -EOPENSTALE) goto stale_open; goto out; --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1421,6 +1421,24 @@ void drop_collected_mounts(struct vfsmou release_mounts(&umount_list); } +struct vfsmount *clone_private_mount(struct path *path) +{ + struct mount *old_mnt = real_mount(path->mnt); + struct mount *new_mnt; + + if (IS_MNT_UNBINDABLE(old_mnt)) + return ERR_PTR(-EINVAL); + + down_read(&namespace_sem); + new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); + up_read(&namespace_sem); + if (!new_mnt) + return ERR_PTR(-ENOMEM); + + return &new_mnt->mnt; +} +EXPORT_SYMBOL_GPL(clone_private_mount); + int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, struct vfsmount *root) { --- a/fs/open.c +++ b/fs/open.c @@ -816,8 +816,7 @@ struct file *dentry_open(const struct pa return ERR_PTR(error); f->f_flags = flags; - f->f_path = *path; - error = do_dentry_open(f, NULL, cred); + error = vfs_open(path, f, cred); if (!error) { error = open_check_o_direct(f); if (error) { @@ -832,6 +831,26 @@ struct file *dentry_open(const struct pa } EXPORT_SYMBOL(dentry_open); +/** + * vfs_open - open the file at the given path + * @path: path to open + * @filp: newly allocated file with f_flag initialized + * @cred: credentials to use + */ +int vfs_open(const struct path *path, struct file *filp, + const struct cred *cred) +{ + struct inode *inode = path->dentry->d_inode; + + if (inode->i_op->dentry_open) + return inode->i_op->dentry_open(path->dentry, filp, cred); + else { + filp->f_path = *path; + return do_dentry_open(filp, NULL, cred); + } +} +EXPORT_SYMBOL(vfs_open); + static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op) { int lookup_flags = 0; --- /dev/null +++ b/fs/overlayfs/copy_up.c @@ -0,0 +1,385 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/file.h> +#include <linux/splice.h> +#include <linux/xattr.h> +#include <linux/security.h> +#include <linux/uaccess.h> +#include <linux/sched.h> +#include "overlayfs.h" + +#define OVL_COPY_UP_CHUNK_SIZE (1 << 20) + +static int ovl_copy_up_xattr(struct dentry *old, struct dentry *new) +{ + ssize_t list_size, size; + char *buf, *name, *value; + int error; + + if (!old->d_inode->i_op->getxattr || + !new->d_inode->i_op->getxattr) + return 0; + + list_size = vfs_listxattr(old, NULL, 0); + if (list_size <= 0) { + if (list_size == -EOPNOTSUPP) + return 0; + return list_size; + } + + buf = kzalloc(list_size, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + error = -ENOMEM; + value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL); + if (!value) + goto out; + + list_size = vfs_listxattr(old, buf, list_size); + if (list_size <= 0) { + error = list_size; + goto out_free_value; + } + + for (name = buf; name < (buf + list_size); name += strlen(name) + 1) { + size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX); + if (size <= 0) { + error = size; + goto out_free_value; + } + error = vfs_setxattr(new, name, value, size, 0); + if (error) + goto out_free_value; + } + +out_free_value: + kfree(value); +out: + kfree(buf); + return error; +} + +static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len) +{ + struct file *old_file; + struct file *new_file; + int error = 0; + + if (len == 0) + return 0; + + old_file = ovl_path_open(old, O_RDONLY); + if (IS_ERR(old_file)) + return PTR_ERR(old_file); + + new_file = ovl_path_open(new, O_WRONLY); + if (IS_ERR(new_file)) { + error = PTR_ERR(new_file); + goto out_fput; + } + + /* FIXME: copy up sparse files efficiently */ + while (len) { + loff_t offset = new_file->f_pos; + size_t this_len = OVL_COPY_UP_CHUNK_SIZE; + long bytes; + + if (len < this_len) + this_len = len; + + if (signal_pending_state(TASK_KILLABLE, current)) { + error = -EINTR; + break; + } + + bytes = do_splice_direct(old_file, &offset, new_file, this_len, + SPLICE_F_MOVE); + if (bytes <= 0) { + error = bytes; + break; + } + + len -= bytes; + } + + fput(new_file); +out_fput: + fput(old_file); + return error; +} + +static char *ovl_read_symlink(struct dentry *realdentry) +{ + int res; + char *buf; + struct inode *inode = realdentry->d_inode; + mm_segment_t old_fs; + + res = -EINVAL; + if (!inode->i_op->readlink) + goto err; + + res = -ENOMEM; + buf = (char *) __get_free_page(GFP_KERNEL); + if (!buf) + goto err; + + old_fs = get_fs(); + set_fs(get_ds()); + /* The cast to a user pointer is valid due to the set_fs() */ + res = inode->i_op->readlink(realdentry, + (char __user *)buf, PAGE_SIZE - 1); + set_fs(old_fs); + if (res < 0) { + free_page((unsigned long) buf); + goto err; + } + buf[res] = '\0'; + + return buf; + +err: + return ERR_PTR(res); +} + +static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat) +{ + struct iattr attr = { + .ia_valid = + ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET, + .ia_atime = stat->atime, + .ia_mtime = stat->mtime, + }; + + return notify_change(upperdentry, &attr); +} + +static int ovl_set_mode(struct dentry *upperdentry, umode_t mode) +{ + struct iattr attr = { + .ia_valid = ATTR_MODE, + .ia_mode = mode, + }; + + return notify_change(upperdentry, &attr); +} + +static int ovl_copy_up_locked(struct dentry *upperdir, struct dentry *dentry, + struct path *lowerpath, struct kstat *stat, + const char *link) +{ + int err; + struct path newpath; + umode_t mode = stat->mode; + + /* Can't properly set mode on creation because of the umask */ + stat->mode &= S_IFMT; + + ovl_path_upper(dentry, &newpath); + WARN_ON(newpath.dentry); + newpath.dentry = ovl_upper_create(upperdir, dentry, stat, link); + if (IS_ERR(newpath.dentry)) + return PTR_ERR(newpath.dentry); + + if (S_ISREG(stat->mode)) { + err = ovl_copy_up_data(lowerpath, &newpath, stat->size); + if (err) + goto err_remove; + } + + err = ovl_copy_up_xattr(lowerpath->dentry, newpath.dentry); + if (err) + goto err_remove; + + mutex_lock(&newpath.dentry->d_inode->i_mutex); + if (!S_ISLNK(stat->mode)) + err = ovl_set_mode(newpath.dentry, mode); + if (!err) + err = ovl_set_timestamps(newpath.dentry, stat); + mutex_unlock(&newpath.dentry->d_inode->i_mutex); + if (err) + goto err_remove; + + ovl_dentry_update(dentry, newpath.dentry); + + /* + * Easiest way to get rid of the lower dentry reference is to + * drop this dentry. This is neither needed nor possible for + * directories. + */ + if (!S_ISDIR(stat->mode)) + d_drop(dentry); + + return 0; + +err_remove: + if (S_ISDIR(stat->mode)) + vfs_rmdir(upperdir->d_inode, newpath.dentry); + else + vfs_unlink(upperdir->d_inode, newpath.dentry); + + dput(newpath.dentry); + + return err; +} + +/* + * Copy up a single dentry + * + * Directory renames only allowed on "pure upper" (already created on + * upper filesystem, never copied up). Directories which are on lower or + * are merged may not be renamed. For these -EXDEV is returned and + * userspace has to deal with it. This means, when copying up a + * directory we can rely on it and ancestors being stable. + * + * Non-directory renames start with copy up of source if necessary. The + * actual rename will only proceed once the copy up was successful. Copy + * up uses upper parent i_mutex for exclusion. Since rename can change + * d_parent it is possible that the copy up will lock the old parent. At + * that point the file will have already been copied up anyway. + */ +static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry, + struct path *lowerpath, struct kstat *stat) +{ + int err; + struct kstat pstat; + struct path parentpath; + struct dentry *upperdir; + const struct cred *old_cred; + struct cred *override_cred; + char *link = NULL; + + ovl_path_upper(parent, &parentpath); + upperdir = parentpath.dentry; + + err = vfs_getattr(parentpath.mnt, parentpath.dentry, &pstat); + if (err) + return err; + + if (S_ISLNK(stat->mode)) { + link = ovl_read_symlink(lowerpath->dentry); + if (IS_ERR(link)) + return PTR_ERR(link); + } + + err = -ENOMEM; + override_cred = prepare_creds(); + if (!override_cred) + goto out_free_link; + + override_cred->fsuid = stat->uid; + override_cred->fsgid = stat->gid; + /* + * CAP_SYS_ADMIN for copying up extended attributes + * CAP_DAC_OVERRIDE for create + * CAP_FOWNER for chmod, timestamp update + * CAP_FSETID for chmod + * CAP_MKNOD for mknod + */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + cap_raise(override_cred->cap_effective, CAP_FOWNER); + cap_raise(override_cred->cap_effective, CAP_FSETID); + cap_raise(override_cred->cap_effective, CAP_MKNOD); + old_cred = override_creds(override_cred); + + mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT); + if (ovl_path_type(dentry) != OVL_PATH_LOWER) { + err = 0; + } else { + err = ovl_copy_up_locked(upperdir, dentry, lowerpath, + stat, link); + if (!err) { + /* Restore timestamps on parent (best effort) */ + ovl_set_timestamps(upperdir, &pstat); + } + } + + mutex_unlock(&upperdir->d_inode->i_mutex); + + revert_creds(old_cred); + put_cred(override_cred); + +out_free_link: + if (link) + free_page((unsigned long) link); + + return err; +} + +int ovl_copy_up(struct dentry *dentry) +{ + int err; + + err = 0; + while (!err) { + struct dentry *next; + struct dentry *parent; + struct path lowerpath; + struct kstat stat; + enum ovl_path_type type = ovl_path_type(dentry); + + if (type != OVL_PATH_LOWER) + break; + + next = dget(dentry); + /* find the topmost dentry not yet copied up */ + for (;;) { + parent = dget_parent(next); + + type = ovl_path_type(parent); + if (type != OVL_PATH_LOWER) + break; + + dput(next); + next = parent; + } + + ovl_path_lower(next, &lowerpath); + err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat); + if (!err) + err = ovl_copy_up_one(parent, next, &lowerpath, &stat); + + dput(parent); + dput(next); + } + + return err; +} + +/* Optimize by not copying up the file first and truncating later */ +int ovl_copy_up_truncate(struct dentry *dentry, loff_t size) +{ + int err; + struct kstat stat; + struct path lowerpath; + struct dentry *parent = dget_parent(dentry); + + err = ovl_copy_up(parent); + if (err) + goto out_dput_parent; + + ovl_path_lower(dentry, &lowerpath); + err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat); + if (err) + goto out_dput_parent; + + if (size < stat.size) + stat.size = size; + + err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat); + +out_dput_parent: + dput(parent); + return err; +} --- /dev/null +++ b/fs/overlayfs/dir.c @@ -0,0 +1,604 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/xattr.h> +#include <linux/security.h> +#include <linux/cred.h> +#include "overlayfs.h" + +static const char *ovl_whiteout_symlink = "(overlay-whiteout)"; + +static int ovl_whiteout(struct dentry *upperdir, struct dentry *dentry) +{ + int err; + struct dentry *newdentry; + const struct cred *old_cred; + struct cred *override_cred; + + /* FIXME: recheck lower dentry to see if whiteout is really needed */ + + err = -ENOMEM; + override_cred = prepare_creds(); + if (!override_cred) + goto out; + + /* + * CAP_SYS_ADMIN for setxattr + * CAP_DAC_OVERRIDE for symlink creation + * CAP_FOWNER for unlink in sticky directory + */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + cap_raise(override_cred->cap_effective, CAP_FOWNER); + override_cred->fsuid = GLOBAL_ROOT_UID; + override_cred->fsgid = GLOBAL_ROOT_GID; + old_cred = override_creds(override_cred); + + newdentry = lookup_one_len(dentry->d_name.name, upperdir, + dentry->d_name.len); + err = PTR_ERR(newdentry); + if (IS_ERR(newdentry)) + goto out_put_cred; + + /* Just been removed within the same locked region */ + WARN_ON(newdentry->d_inode); + + err = vfs_symlink(upperdir->d_inode, newdentry, ovl_whiteout_symlink); + if (err) + goto out_dput; + + ovl_dentry_version_inc(dentry->d_parent); + + err = vfs_setxattr(newdentry, ovl_whiteout_xattr, "y", 1, 0); + if (err) + vfs_unlink(upperdir->d_inode, newdentry); + +out_dput: + dput(newdentry); +out_put_cred: + revert_creds(old_cred); + put_cred(override_cred); +out: + if (err) { + /* + * There's no way to recover from failure to whiteout. + * What should we do? Log a big fat error and... ? + */ + printk(KERN_ERR "overlayfs: ERROR - failed to whiteout '%s'\n", + dentry->d_name.name); + } + + return err; +} + +static struct dentry *ovl_lookup_create(struct dentry *upperdir, + struct dentry *template) +{ + int err; + struct dentry *newdentry; + struct qstr *name = &template->d_name; + + newdentry = lookup_one_len(name->name, upperdir, name->len); + if (IS_ERR(newdentry)) + return newdentry; + + if (newdentry->d_inode) { + const struct cred *old_cred; + struct cred *override_cred; + + /* No need to check whiteout if lower parent is non-existent */ + err = -EEXIST; + if (!ovl_dentry_lower(template->d_parent)) + goto out_dput; + + if (!S_ISLNK(newdentry->d_inode->i_mode)) + goto out_dput; + + err = -ENOMEM; + override_cred = prepare_creds(); + if (!override_cred) + goto out_dput; + + /* + * CAP_SYS_ADMIN for getxattr + * CAP_FOWNER for unlink in sticky directory + */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_FOWNER); + old_cred = override_creds(override_cred); + + err = -EEXIST; + if (ovl_is_whiteout(newdentry)) + err = vfs_unlink(upperdir->d_inode, newdentry); + + revert_creds(old_cred); + put_cred(override_cred); + if (err) + goto out_dput; + + dput(newdentry); + newdentry = lookup_one_len(name->name, upperdir, name->len); + if (IS_ERR(newdentry)) { + ovl_whiteout(upperdir, template); + return newdentry; + } + + /* + * Whiteout just been successfully removed, parent + * i_mutex is still held, there's no way the lookup + * could return positive. + */ + WARN_ON(newdentry->d_inode); + } + + return newdentry; + +out_dput: + dput(newdentry); + return ERR_PTR(err); +} + +struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry, + struct kstat *stat, const char *link) +{ + int err; + struct dentry *newdentry; + struct inode *dir = upperdir->d_inode; + + newdentry = ovl_lookup_create(upperdir, dentry); + if (IS_ERR(newdentry)) + goto out; + + switch (stat->mode & S_IFMT) { + case S_IFREG: + err = vfs_create(dir, newdentry, stat->mode, NULL); + break; + + case S_IFDIR: + err = vfs_mkdir(dir, newdentry, stat->mode); + break; + + case S_IFCHR: + case S_IFBLK: + case S_IFIFO: + case S_IFSOCK: + err = vfs_mknod(dir, newdentry, stat->mode, stat->rdev); + break; + + case S_IFLNK: + err = vfs_symlink(dir, newdentry, link); + break; + + default: + err = -EPERM; + } + if (err) { + if (ovl_dentry_is_opaque(dentry)) + ovl_whiteout(upperdir, dentry); + dput(newdentry); + newdentry = ERR_PTR(err); + } else if (WARN_ON(!newdentry->d_inode)) { + /* + * Not quite sure if non-instantiated dentry is legal or not. + * VFS doesn't seem to care so check and warn here. + */ + dput(newdentry); + newdentry = ERR_PTR(-ENOENT); + } + +out: + return newdentry; + +} + +static int ovl_set_opaque(struct dentry *upperdentry) +{ + int err; + const struct cred *old_cred; + struct cred *override_cred; + + override_cred = prepare_creds(); + if (!override_cred) + return -ENOMEM; + + /* CAP_SYS_ADMIN for setxattr of "trusted" namespace */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + old_cred = override_creds(override_cred); + err = vfs_setxattr(upperdentry, ovl_opaque_xattr, "y", 1, 0); + revert_creds(old_cred); + put_cred(override_cred); + + return err; +} + +static int ovl_remove_opaque(struct dentry *upperdentry) +{ + int err; + const struct cred *old_cred; + struct cred *override_cred; + + override_cred = prepare_creds(); + if (!override_cred) + return -ENOMEM; + + /* CAP_SYS_ADMIN for removexattr of "trusted" namespace */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + old_cred = override_creds(override_cred); + err = vfs_removexattr(upperdentry, ovl_opaque_xattr); + revert_creds(old_cred); + put_cred(override_cred); + + return err; +} + +static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry, + struct kstat *stat) +{ + int err; + enum ovl_path_type type; + struct path realpath; + + type = ovl_path_real(dentry, &realpath); + err = vfs_getattr(realpath.mnt, realpath.dentry, stat); + if (err) + return err; + + stat->dev = dentry->d_sb->s_dev; + stat->ino = dentry->d_inode->i_ino; + + /* + * It's probably not worth it to count subdirs to get the + * correct link count. nlink=1 seems to pacify 'find' and + * other utilities. + */ + if (type == OVL_PATH_MERGE) + stat->nlink = 1; + + return 0; +} + +static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev, + const char *link) +{ + int err; + struct dentry *newdentry; + struct dentry *upperdir; + struct inode *inode; + struct kstat stat = { + .mode = mode, + .rdev = rdev, + }; + + err = -ENOMEM; + inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata); + if (!inode) + goto out; + + err = ovl_copy_up(dentry->d_parent); + if (err) + goto out_iput; + + upperdir = ovl_dentry_upper(dentry->d_parent); + mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT); + + newdentry = ovl_upper_create(upperdir, dentry, &stat, link); + err = PTR_ERR(newdentry); + if (IS_ERR(newdentry)) + goto out_unlock; + + ovl_dentry_version_inc(dentry->d_parent); + if (ovl_dentry_is_opaque(dentry) && S_ISDIR(mode)) { + err = ovl_set_opaque(newdentry); + if (err) { + vfs_rmdir(upperdir->d_inode, newdentry); + ovl_whiteout(upperdir, dentry); + goto out_dput; + } + } + ovl_dentry_update(dentry, newdentry); + ovl_copyattr(newdentry->d_inode, inode); + d_instantiate(dentry, inode); + inode = NULL; + newdentry = NULL; + err = 0; + +out_dput: + dput(newdentry); +out_unlock: + mutex_unlock(&upperdir->d_inode->i_mutex); +out_iput: + iput(inode); +out: + return err; +} + +static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode, + bool excl) +{ + return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL); +} + +static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) +{ + return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL); +} + +static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, + dev_t rdev) +{ + return ovl_create_object(dentry, mode, rdev, NULL); +} + +static int ovl_symlink(struct inode *dir, struct dentry *dentry, + const char *link) +{ + return ovl_create_object(dentry, S_IFLNK, 0, link); +} + +static int ovl_do_remove(struct dentry *dentry, bool is_dir) +{ + int err; + enum ovl_path_type type; + struct path realpath; + struct dentry *upperdir; + + err = ovl_copy_up(dentry->d_parent); + if (err) + return err; + + upperdir = ovl_dentry_upper(dentry->d_parent); + mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT); + type = ovl_path_real(dentry, &realpath); + if (type != OVL_PATH_LOWER) { + err = -ESTALE; + if (realpath.dentry->d_parent != upperdir) + goto out_d_drop; + + /* FIXME: create whiteout up front and rename to target */ + + if (is_dir) + err = vfs_rmdir(upperdir->d_inode, realpath.dentry); + else + err = vfs_unlink(upperdir->d_inode, realpath.dentry); + if (err) + goto out_d_drop; + + ovl_dentry_version_inc(dentry->d_parent); + } + + if (type != OVL_PATH_UPPER || ovl_dentry_is_opaque(dentry)) + err = ovl_whiteout(upperdir, dentry); + + /* + * Keeping this dentry hashed would mean having to release + * upperpath/lowerpath, which could only be done if we are the + * sole user of this dentry. Too tricky... Just unhash for + * now. + */ +out_d_drop: + d_drop(dentry); + mutex_unlock(&upperdir->d_inode->i_mutex); + + return err; +} + +static int ovl_unlink(struct inode *dir, struct dentry *dentry) +{ + return ovl_do_remove(dentry, false); +} + + +static int ovl_rmdir(struct inode *dir, struct dentry *dentry) +{ + int err; + enum ovl_path_type type; + + type = ovl_path_type(dentry); + if (type != OVL_PATH_UPPER) { + err = ovl_check_empty_and_clear(dentry, type); + if (err) + return err; + } + + return ovl_do_remove(dentry, true); +} + +static int ovl_link(struct dentry *old, struct inode *newdir, + struct dentry *new) +{ + int err; + struct dentry *olddentry; + struct dentry *newdentry; + struct dentry *upperdir; + struct inode *newinode; + + err = ovl_copy_up(old); + if (err) + goto out; + + err = ovl_copy_up(new->d_parent); + if (err) + goto out; + + upperdir = ovl_dentry_upper(new->d_parent); + mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT); + newdentry = ovl_lookup_create(upperdir, new); + err = PTR_ERR(newdentry); + if (IS_ERR(newdentry)) + goto out_unlock; + + olddentry = ovl_dentry_upper(old); + err = vfs_link(olddentry, upperdir->d_inode, newdentry); + if (!err) { + if (WARN_ON(!newdentry->d_inode)) { + dput(newdentry); + err = -ENOENT; + goto out_unlock; + } + newinode = ovl_new_inode(old->d_sb, newdentry->d_inode->i_mode, + new->d_fsdata); + if (!newinode) + goto link_fail; + ovl_copyattr(upperdir->d_inode, newinode); + + ovl_dentry_version_inc(new->d_parent); + ovl_dentry_update(new, newdentry); + + d_instantiate(new, newinode); + } else { +link_fail: + if (ovl_dentry_is_opaque(new)) + ovl_whiteout(upperdir, new); + dput(newdentry); + } +out_unlock: + mutex_unlock(&upperdir->d_inode->i_mutex); +out: + return err; + +} + +static int ovl_rename(struct inode *olddir, struct dentry *old, + struct inode *newdir, struct dentry *new) +{ + int err; + enum ovl_path_type old_type; + enum ovl_path_type new_type; + struct dentry *old_upperdir; + struct dentry *new_upperdir; + struct dentry *olddentry; + struct dentry *newdentry; + struct dentry *trap; + bool old_opaque; + bool new_opaque; + bool new_create = false; + bool is_dir = S_ISDIR(old->d_inode->i_mode); + + /* Don't copy up directory trees */ + old_type = ovl_path_type(old); + if (old_type != OVL_PATH_UPPER && is_dir) + return -EXDEV; + + if (new->d_inode) { + new_type = ovl_path_type(new); + + if (new_type == OVL_PATH_LOWER && old_type == OVL_PATH_LOWER) { + if (ovl_dentry_lower(old)->d_inode == + ovl_dentry_lower(new)->d_inode) + return 0; + } + if (new_type != OVL_PATH_LOWER && old_type != OVL_PATH_LOWER) { + if (ovl_dentry_upper(old)->d_inode == + ovl_dentry_upper(new)->d_inode) + return 0; + } + + if (new_type != OVL_PATH_UPPER && + S_ISDIR(new->d_inode->i_mode)) { + err = ovl_check_empty_and_clear(new, new_type); + if (err) + return err; + } + } else { + new_type = OVL_PATH_UPPER; + } + + err = ovl_copy_up(old); + if (err) + return err; + + err = ovl_copy_up(new->d_parent); + if (err) + return err; + + old_upperdir = ovl_dentry_upper(old->d_parent); + new_upperdir = ovl_dentry_upper(new->d_parent); + + trap = lock_rename(new_upperdir, old_upperdir); + + olddentry = ovl_dentry_upper(old); + newdentry = ovl_dentry_upper(new); + if (newdentry) { + dget(newdentry); + } else { + new_create = true; + newdentry = ovl_lookup_create(new_upperdir, new); + err = PTR_ERR(newdentry); + if (IS_ERR(newdentry)) + goto out_unlock; + } + + err = -ESTALE; + if (olddentry->d_parent != old_upperdir) + goto out_dput; + if (newdentry->d_parent != new_upperdir) + goto out_dput; + if (olddentry == trap) + goto out_dput; + if (newdentry == trap) + goto out_dput; + + old_opaque = ovl_dentry_is_opaque(old); + new_opaque = ovl_dentry_is_opaque(new) || new_type != OVL_PATH_UPPER; + + if (is_dir && !old_opaque && new_opaque) { + err = ovl_set_opaque(olddentry); + if (err) + goto out_dput; + } + + err = vfs_rename(old_upperdir->d_inode, olddentry, + new_upperdir->d_inode, newdentry); + + if (err) { + if (new_create && ovl_dentry_is_opaque(new)) + ovl_whiteout(new_upperdir, new); + if (is_dir && !old_opaque && new_opaque) + ovl_remove_opaque(olddentry); + goto out_dput; + } + + if (old_type != OVL_PATH_UPPER || old_opaque) + err = ovl_whiteout(old_upperdir, old); + if (is_dir && old_opaque && !new_opaque) + ovl_remove_opaque(olddentry); + + if (old_opaque != new_opaque) + ovl_dentry_set_opaque(old, new_opaque); + + ovl_dentry_version_inc(old->d_parent); + ovl_dentry_version_inc(new->d_parent); + +out_dput: + dput(newdentry); +out_unlock: + unlock_rename(new_upperdir, old_upperdir); + return err; +} + +const struct inode_operations ovl_dir_inode_operations = { + .lookup = ovl_lookup, + .mkdir = ovl_mkdir, + .symlink = ovl_symlink, + .unlink = ovl_unlink, + .rmdir = ovl_rmdir, + .rename = ovl_rename, + .link = ovl_link, + .setattr = ovl_setattr, + .create = ovl_create, + .mknod = ovl_mknod, + .permission = ovl_permission, + .getattr = ovl_dir_getattr, + .setxattr = ovl_setxattr, + .getxattr = ovl_getxattr, + .listxattr = ovl_listxattr, + .removexattr = ovl_removexattr, +}; --- /dev/null +++ b/fs/overlayfs/inode.c @@ -0,0 +1,372 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/xattr.h> +#include "overlayfs.h" + +int ovl_setattr(struct dentry *dentry, struct iattr *attr) +{ + struct dentry *upperdentry; + int err; + + if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry)) + err = ovl_copy_up_truncate(dentry, attr->ia_size); + else + err = ovl_copy_up(dentry); + if (err) + return err; + + upperdentry = ovl_dentry_upper(dentry); + + if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) + attr->ia_valid &= ~ATTR_MODE; + + mutex_lock(&upperdentry->d_inode->i_mutex); + err = notify_change(upperdentry, attr); + if (!err) + ovl_copyattr(upperdentry->d_inode, dentry->d_inode); + mutex_unlock(&upperdentry->d_inode->i_mutex); + + return err; +} + +static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, + struct kstat *stat) +{ + struct path realpath; + + ovl_path_real(dentry, &realpath); + return vfs_getattr(realpath.mnt, realpath.dentry, stat); +} + +int ovl_permission(struct inode *inode, int mask) +{ + struct ovl_entry *oe; + struct dentry *alias = NULL; + struct inode *realinode; + struct dentry *realdentry; + bool is_upper; + int err; + + if (S_ISDIR(inode->i_mode)) { + oe = inode->i_private; + } else if (mask & MAY_NOT_BLOCK) { + return -ECHILD; + } else { + /* + * For non-directories find an alias and get the info + * from there. + */ + alias = d_find_any_alias(inode); + if (WARN_ON(!alias)) + return -ENOENT; + + oe = alias->d_fsdata; + } + + realdentry = ovl_entry_real(oe, &is_upper); + + /* Careful in RCU walk mode */ + realinode = ACCESS_ONCE(realdentry->d_inode); + if (!realinode) { + WARN_ON(!(mask & MAY_NOT_BLOCK)); + err = -ENOENT; + goto out_dput; + } + + if (mask & MAY_WRITE) { + umode_t mode = realinode->i_mode; + + /* + * Writes will always be redirected to upper layer, so + * ignore lower layer being read-only. + * + * If the overlay itself is read-only then proceed + * with the permission check, don't return EROFS. + * This will only happen if this is the lower layer of + * another overlayfs. + * + * If upper fs becomes read-only after the overlay was + * constructed return EROFS to prevent modification of + * upper layer. + */ + err = -EROFS; + if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && + (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) + goto out_dput; + } + + err = __inode_permission(realinode, mask); +out_dput: + dput(alias); + return err; +} + + +struct ovl_link_data { + struct dentry *realdentry; + void *cookie; +}; + +static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) +{ + void *ret; + struct dentry *realdentry; + struct inode *realinode; + + realdentry = ovl_dentry_real(dentry); + realinode = realdentry->d_inode; + + if (WARN_ON(!realinode->i_op->follow_link)) + return ERR_PTR(-EPERM); + + ret = realinode->i_op->follow_link(realdentry, nd); + if (IS_ERR(ret)) + return ret; + + if (realinode->i_op->put_link) { + struct ovl_link_data *data; + + data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); + if (!data) { + realinode->i_op->put_link(realdentry, nd, ret); + return ERR_PTR(-ENOMEM); + } + data->realdentry = realdentry; + data->cookie = ret; + + return data; + } else { + return NULL; + } +} + +static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c) +{ + struct inode *realinode; + struct ovl_link_data *data = c; + + if (!data) + return; + + realinode = data->realdentry->d_inode; + realinode->i_op->put_link(data->realdentry, nd, data->cookie); + kfree(data); +} + +static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) +{ + struct path realpath; + struct inode *realinode; + + ovl_path_real(dentry, &realpath); + realinode = realpath.dentry->d_inode; + + if (!realinode->i_op->readlink) + return -EINVAL; + + touch_atime(&realpath); + + return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); +} + + +static bool ovl_is_private_xattr(const char *name) +{ + return strncmp(name, "trusted.overlay.", 14) == 0; +} + +int ovl_setxattr(struct dentry *dentry, const char *name, + const void *value, size_t size, int flags) +{ + int err; + struct dentry *upperdentry; + + if (ovl_is_private_xattr(name)) + return -EPERM; + + err = ovl_copy_up(dentry); + if (err) + return err; + + upperdentry = ovl_dentry_upper(dentry); + return vfs_setxattr(upperdentry, name, value, size, flags); +} + +ssize_t ovl_getxattr(struct dentry *dentry, const char *name, + void *value, size_t size) +{ + if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE && + ovl_is_private_xattr(name)) + return -ENODATA; + + return vfs_getxattr(ovl_dentry_real(dentry), name, value, size); +} + +ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) +{ + ssize_t res; + int off; + + res = vfs_listxattr(ovl_dentry_real(dentry), list, size); + if (res <= 0 || size == 0) + return res; + + if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE) + return res; + + /* filter out private xattrs */ + for (off = 0; off < res;) { + char *s = list + off; + size_t slen = strlen(s) + 1; + + BUG_ON(off + slen > res); + + if (ovl_is_private_xattr(s)) { + res -= slen; + memmove(s, s + slen, res - off); + } else { + off += slen; + } + } + + return res; +} + +int ovl_removexattr(struct dentry *dentry, const char *name) +{ + int err; + struct path realpath; + enum ovl_path_type type; + + if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE && + ovl_is_private_xattr(name)) + return -ENODATA; + + type = ovl_path_real(dentry, &realpath); + if (type == OVL_PATH_LOWER) { + err = vfs_getxattr(realpath.dentry, name, NULL, 0); + if (err < 0) + return err; + + err = ovl_copy_up(dentry); + if (err) + return err; + + ovl_path_upper(dentry, &realpath); + } + + return vfs_removexattr(realpath.dentry, name); +} + +static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, + struct dentry *realdentry) +{ + if (type != OVL_PATH_LOWER) + return false; + + if (special_file(realdentry->d_inode->i_mode)) + return false; + + if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) + return false; + + return true; +} + +static int ovl_dentry_open(struct dentry *dentry, struct file *file, + const struct cred *cred) +{ + int err; + struct path realpath; + enum ovl_path_type type; + + type = ovl_path_real(dentry, &realpath); + if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) { + if (file->f_flags & O_TRUNC) + err = ovl_copy_up_truncate(dentry, 0); + else + err = ovl_copy_up(dentry); + if (err) + return err; + + ovl_path_upper(dentry, &realpath); + } + + return vfs_open(&realpath, file, cred); +} + +static const struct inode_operations ovl_file_inode_operations = { + .setattr = ovl_setattr, + .permission = ovl_permission, + .getattr = ovl_getattr, + .setxattr = ovl_setxattr, + .getxattr = ovl_getxattr, + .listxattr = ovl_listxattr, + .removexattr = ovl_removexattr, + .dentry_open = ovl_dentry_open, +}; + +static const struct inode_operations ovl_symlink_inode_operations = { + .setattr = ovl_setattr, + .follow_link = ovl_follow_link, + .put_link = ovl_put_link, + .readlink = ovl_readlink, + .getattr = ovl_getattr, + .setxattr = ovl_setxattr, + .getxattr = ovl_getxattr, + .listxattr = ovl_listxattr, + .removexattr = ovl_removexattr, +}; + +struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, + struct ovl_entry *oe) +{ + struct inode *inode; + + inode = new_inode(sb); + if (!inode) + return NULL; + + mode &= S_IFMT; + + inode->i_ino = get_next_ino(); + inode->i_mode = mode; + inode->i_flags |= S_NOATIME | S_NOCMTIME; + + switch (mode) { + case S_IFDIR: + inode->i_private = oe; + inode->i_op = &ovl_dir_inode_operations; + inode->i_fop = &ovl_dir_operations; + break; + + case S_IFLNK: + inode->i_op = &ovl_symlink_inode_operations; + break; + + case S_IFREG: + case S_IFSOCK: + case S_IFBLK: + case S_IFCHR: + case S_IFIFO: + inode->i_op = &ovl_file_inode_operations; + break; + + default: + WARN(1, "illegal file type: %i\n", mode); + iput(inode); + inode = NULL; + } + + return inode; + +} --- /dev/null +++ b/fs/overlayfs/Kconfig @@ -0,0 +1,4 @@ +config OVERLAYFS_FS + tristate "Overlay filesystem support" + help + Add support for overlay filesystem. --- /dev/null +++ b/fs/overlayfs/Makefile @@ -0,0 +1,7 @@ +# +# Makefile for the overlay filesystem. +# + +obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o + +overlayfs-objs := super.o inode.o dir.o readdir.o copy_up.o --- /dev/null +++ b/fs/overlayfs/overlayfs.h @@ -0,0 +1,70 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +struct ovl_entry; + +enum ovl_path_type { + OVL_PATH_UPPER, + OVL_PATH_MERGE, + OVL_PATH_LOWER, +}; + +extern const char *ovl_opaque_xattr; +extern const char *ovl_whiteout_xattr; +extern const struct dentry_operations ovl_dentry_operations; + +enum ovl_path_type ovl_path_type(struct dentry *dentry); +u64 ovl_dentry_version_get(struct dentry *dentry); +void ovl_dentry_version_inc(struct dentry *dentry); +void ovl_path_upper(struct dentry *dentry, struct path *path); +void ovl_path_lower(struct dentry *dentry, struct path *path); +enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path); +struct dentry *ovl_dentry_upper(struct dentry *dentry); +struct dentry *ovl_dentry_lower(struct dentry *dentry); +struct dentry *ovl_dentry_real(struct dentry *dentry); +struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper); +bool ovl_dentry_is_opaque(struct dentry *dentry); +void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque); +bool ovl_is_whiteout(struct dentry *dentry); +void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry); +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, + unsigned int flags); +struct file *ovl_path_open(struct path *path, int flags); + +struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry, + struct kstat *stat, const char *link); + +/* readdir.c */ +extern const struct file_operations ovl_dir_operations; +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type); + +/* inode.c */ +int ovl_setattr(struct dentry *dentry, struct iattr *attr); +int ovl_permission(struct inode *inode, int mask); +int ovl_setxattr(struct dentry *dentry, const char *name, + const void *value, size_t size, int flags); +ssize_t ovl_getxattr(struct dentry *dentry, const char *name, + void *value, size_t size); +ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size); +int ovl_removexattr(struct dentry *dentry, const char *name); + +struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, + struct ovl_entry *oe); +static inline void ovl_copyattr(struct inode *from, struct inode *to) +{ + to->i_uid = from->i_uid; + to->i_gid = from->i_gid; +} + +/* dir.c */ +extern const struct inode_operations ovl_dir_inode_operations; + +/* copy_up.c */ +int ovl_copy_up(struct dentry *dentry); +int ovl_copy_up_truncate(struct dentry *dentry, loff_t size); --- /dev/null +++ b/fs/overlayfs/readdir.c @@ -0,0 +1,566 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/namei.h> +#include <linux/file.h> +#include <linux/xattr.h> +#include <linux/rbtree.h> +#include <linux/security.h> +#include <linux/cred.h> +#include "overlayfs.h" + +struct ovl_cache_entry { + const char *name; + unsigned int len; + unsigned int type; + u64 ino; + bool is_whiteout; + struct list_head l_node; + struct rb_node node; +}; + +struct ovl_readdir_data { + struct rb_root *root; + struct list_head *list; + struct list_head *middle; + struct dentry *dir; + int count; + int err; +}; + +struct ovl_dir_file { + bool is_real; + bool is_cached; + struct list_head cursor; + u64 cache_version; + struct list_head cache; + struct file *realfile; +}; + +static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n) +{ + return container_of(n, struct ovl_cache_entry, node); +} + +static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root, + const char *name, int len) +{ + struct rb_node *node = root->rb_node; + int cmp; + + while (node) { + struct ovl_cache_entry *p = ovl_cache_entry_from_node(node); + + cmp = strncmp(name, p->name, len); + if (cmp > 0) + node = p->node.rb_right; + else if (cmp < 0 || len < p->len) + node = p->node.rb_left; + else + return p; + } + + return NULL; +} + +static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len, + u64 ino, unsigned int d_type) +{ + struct ovl_cache_entry *p; + + p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL); + if (p) { + char *name_copy = (char *) (p + 1); + memcpy(name_copy, name, len); + name_copy[len] = '\0'; + p->name = name_copy; + p->len = len; + p->type = d_type; + p->ino = ino; + p->is_whiteout = false; + } + + return p; +} + +static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd, + const char *name, int len, u64 ino, + unsigned int d_type) +{ + struct rb_node **newp = &rdd->root->rb_node; + struct rb_node *parent = NULL; + struct ovl_cache_entry *p; + + while (*newp) { + int cmp; + struct ovl_cache_entry *tmp; + + parent = *newp; + tmp = ovl_cache_entry_from_node(*newp); + cmp = strncmp(name, tmp->name, len); + if (cmp > 0) + newp = &tmp->node.rb_right; + else if (cmp < 0 || len < tmp->len) + newp = &tmp->node.rb_left; + else + return 0; + } + + p = ovl_cache_entry_new(name, len, ino, d_type); + if (p == NULL) + return -ENOMEM; + + list_add_tail(&p->l_node, rdd->list); + rb_link_node(&p->node, parent, newp); + rb_insert_color(&p->node, rdd->root); + + return 0; +} + +static int ovl_fill_lower(void *buf, const char *name, int namelen, + loff_t offset, u64 ino, unsigned int d_type) +{ + struct ovl_readdir_data *rdd = buf; + struct ovl_cache_entry *p; + + rdd->count++; + p = ovl_cache_entry_find(rdd->root, name, namelen); + if (p) { + list_move_tail(&p->l_node, rdd->middle); + } else { + p = ovl_cache_entry_new(name, namelen, ino, d_type); + if (p == NULL) + rdd->err = -ENOMEM; + else + list_add_tail(&p->l_node, rdd->middle); + } + + return rdd->err; +} + +static void ovl_cache_free(struct list_head *list) +{ + struct ovl_cache_entry *p; + struct ovl_cache_entry *n; + + list_for_each_entry_safe(p, n, list, l_node) + kfree(p); + + INIT_LIST_HEAD(list); +} + +static int ovl_fill_upper(void *buf, const char *name, int namelen, + loff_t offset, u64 ino, unsigned int d_type) +{ + struct ovl_readdir_data *rdd = buf; + + rdd->count++; + return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type); +} + +static inline int ovl_dir_read(struct path *realpath, + struct ovl_readdir_data *rdd, filldir_t filler) +{ + struct file *realfile; + int err; + + realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY); + if (IS_ERR(realfile)) + return PTR_ERR(realfile); + + do { + rdd->count = 0; + rdd->err = 0; + err = vfs_readdir(realfile, filler, rdd); + if (err >= 0) + err = rdd->err; + } while (!err && rdd->count); + fput(realfile); + + return 0; +} + +static void ovl_dir_reset(struct file *file) +{ + struct ovl_dir_file *od = file->private_data; + enum ovl_path_type type = ovl_path_type(file->f_path.dentry); + + if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) { + list_del_init(&od->cursor); + ovl_cache_free(&od->cache); + od->is_cached = false; + } + WARN_ON(!od->is_real && type != OVL_PATH_MERGE); + if (od->is_real && type == OVL_PATH_MERGE) { + fput(od->realfile); + od->realfile = NULL; + od->is_real = false; + } +} + +static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd) +{ + struct ovl_cache_entry *p; + struct dentry *dentry; + const struct cred *old_cred; + struct cred *override_cred; + + override_cred = prepare_creds(); + if (!override_cred) { + ovl_cache_free(rdd->list); + return -ENOMEM; + } + + /* + * CAP_SYS_ADMIN for getxattr + * CAP_DAC_OVERRIDE for lookup + */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + old_cred = override_creds(override_cred); + + mutex_lock(&rdd->dir->d_inode->i_mutex); + list_for_each_entry(p, rdd->list, l_node) { + if (p->type != DT_LNK) + continue; + + dentry = lookup_one_len(p->name, rdd->dir, p->len); + if (IS_ERR(dentry)) + continue; + + p->is_whiteout = ovl_is_whiteout(dentry); + dput(dentry); + } + mutex_unlock(&rdd->dir->d_inode->i_mutex); + + revert_creds(old_cred); + put_cred(override_cred); + + return 0; +} + +static inline int ovl_dir_read_merged(struct path *upperpath, + struct path *lowerpath, + struct ovl_readdir_data *rdd) +{ + int err; + struct rb_root root = RB_ROOT; + struct list_head middle; + + rdd->root = &root; + if (upperpath->dentry) { + rdd->dir = upperpath->dentry; + err = ovl_dir_read(upperpath, rdd, ovl_fill_upper); + if (err) + goto out; + + err = ovl_dir_mark_whiteouts(rdd); + if (err) + goto out; + } + /* + * Insert lowerpath entries before upperpath ones, this allows + * offsets to be reasonably constant + */ + list_add(&middle, rdd->list); + rdd->middle = &middle; + err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower); + list_del(&middle); +out: + rdd->root = NULL; + + return err; +} + +static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos) +{ + struct list_head *l; + loff_t off; + + l = od->cache.next; + for (off = 0; off < pos; off++) { + if (l == &od->cache) + break; + l = l->next; + } + list_move_tail(&od->cursor, l); +} + +static int ovl_readdir(struct file *file, void *buf, filldir_t filler) +{ + struct ovl_dir_file *od = file->private_data; + int res; + + if (!file->f_pos) + ovl_dir_reset(file); + + if (od->is_real) { + res = vfs_readdir(od->realfile, filler, buf); + file->f_pos = od->realfile->f_pos; + + return res; + } + + if (!od->is_cached) { + struct path lowerpath; + struct path upperpath; + struct ovl_readdir_data rdd = { .list = &od->cache }; + + ovl_path_lower(file->f_path.dentry, &lowerpath); + ovl_path_upper(file->f_path.dentry, &upperpath); + + res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd); + if (res) { + ovl_cache_free(rdd.list); + return res; + } + + od->cache_version = ovl_dentry_version_get(file->f_path.dentry); + od->is_cached = true; + + ovl_seek_cursor(od, file->f_pos); + } + + while (od->cursor.next != &od->cache) { + int over; + loff_t off; + struct ovl_cache_entry *p; + + p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node); + off = file->f_pos; + if (!p->is_whiteout) { + over = filler(buf, p->name, p->len, off, p->ino, + p->type); + if (over) + break; + } + file->f_pos++; + list_move(&od->cursor, &p->l_node); + } + + return 0; +} + +static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin) +{ + loff_t res; + struct ovl_dir_file *od = file->private_data; + + mutex_lock(&file->f_dentry->d_inode->i_mutex); + if (!file->f_pos) + ovl_dir_reset(file); + + if (od->is_real) { + res = vfs_llseek(od->realfile, offset, origin); + file->f_pos = od->realfile->f_pos; + } else { + res = -EINVAL; + + switch (origin) { + case SEEK_CUR: + offset += file->f_pos; + break; + case SEEK_SET: + break; + default: + goto out_unlock; + } + if (offset < 0) + goto out_unlock; + + if (offset != file->f_pos) { + file->f_pos = offset; + if (od->is_cached) + ovl_seek_cursor(od, offset); + } + res = offset; + } +out_unlock: + mutex_unlock(&file->f_dentry->d_inode->i_mutex); + + return res; +} + +static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end, + int datasync) +{ + struct ovl_dir_file *od = file->private_data; + + /* May need to reopen directory if it got copied up */ + if (!od->realfile) { + struct path upperpath; + + ovl_path_upper(file->f_path.dentry, &upperpath); + od->realfile = ovl_path_open(&upperpath, O_RDONLY); + if (IS_ERR(od->realfile)) + return PTR_ERR(od->realfile); + } + + return vfs_fsync_range(od->realfile, start, end, datasync); +} + +static int ovl_dir_release(struct inode *inode, struct file *file) +{ + struct ovl_dir_file *od = file->private_data; + + list_del(&od->cursor); + ovl_cache_free(&od->cache); + if (od->realfile) + fput(od->realfile); + kfree(od); + + return 0; +} + +static int ovl_dir_open(struct inode *inode, struct file *file) +{ + struct path realpath; + struct file *realfile; + struct ovl_dir_file *od; + enum ovl_path_type type; + + od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL); + if (!od) + return -ENOMEM; + + type = ovl_path_real(file->f_path.dentry, &realpath); + realfile = ovl_path_open(&realpath, file->f_flags); + if (IS_ERR(realfile)) { + kfree(od); + return PTR_ERR(realfile); + } + INIT_LIST_HEAD(&od->cache); + INIT_LIST_HEAD(&od->cursor); + od->is_cached = false; + od->realfile = realfile; + od->is_real = (type != OVL_PATH_MERGE); + file->private_data = od; + + return 0; +} + +const struct file_operations ovl_dir_operations = { + .read = generic_read_dir, + .open = ovl_dir_open, + .readdir = ovl_readdir, + .llseek = ovl_dir_llseek, + .fsync = ovl_dir_fsync, + .release = ovl_dir_release, +}; + +static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list) +{ + int err; + struct path lowerpath; + struct path upperpath; + struct ovl_cache_entry *p; + struct ovl_readdir_data rdd = { .list = list }; + + ovl_path_upper(dentry, &upperpath); + ovl_path_lower(dentry, &lowerpath); + + err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd); + if (err) + return err; + + err = 0; + + list_for_each_entry(p, list, l_node) { + if (p->is_whiteout) + continue; + + if (p->name[0] == '.') { + if (p->len == 1) + continue; + if (p->len == 2 && p->name[1] == '.') + continue; + } + err = -ENOTEMPTY; + break; + } + + return err; +} + +static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list) +{ + struct path upperpath; + struct dentry *upperdir; + struct ovl_cache_entry *p; + const struct cred *old_cred; + struct cred *override_cred; + int err; + + ovl_path_upper(dir, &upperpath); + upperdir = upperpath.dentry; + + override_cred = prepare_creds(); + if (!override_cred) + return -ENOMEM; + + /* + * CAP_DAC_OVERRIDE for lookup and unlink + * CAP_SYS_ADMIN for setxattr of "trusted" namespace + * CAP_FOWNER for unlink in sticky directory + */ + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_FOWNER); + old_cred = override_creds(override_cred); + + err = vfs_setxattr(upperdir, ovl_opaque_xattr, "y", 1, 0); + if (err) + goto out_revert_creds; + + mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT); + list_for_each_entry(p, list, l_node) { + struct dentry *dentry; + int ret; + + if (!p->is_whiteout) + continue; + + dentry = lookup_one_len(p->name, upperdir, p->len); + if (IS_ERR(dentry)) { + printk(KERN_WARNING + "overlayfs: failed to lookup whiteout %.*s: %li\n", + p->len, p->name, PTR_ERR(dentry)); + continue; + } + ret = vfs_unlink(upperdir->d_inode, dentry); + dput(dentry); + if (ret) + printk(KERN_WARNING + "overlayfs: failed to unlink whiteout %.*s: %i\n", + p->len, p->name, ret); + } + mutex_unlock(&upperdir->d_inode->i_mutex); + +out_revert_creds: + revert_creds(old_cred); + put_cred(override_cred); + + return err; +} + +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type) +{ + int err; + LIST_HEAD(list); + + err = ovl_check_empty_dir(dentry, &list); + if (!err && type == OVL_PATH_MERGE) + err = ovl_remove_whiteouts(dentry, &list); + + ovl_cache_free(&list); + + return err; +} --- /dev/null +++ b/fs/overlayfs/super.c @@ -0,0 +1,685 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/xattr.h> +#include <linux/security.h> +#include <linux/mount.h> +#include <linux/slab.h> +#include <linux/parser.h> +#include <linux/module.h> +#include <linux/cred.h> +#include <linux/sched.h> +#include <linux/statfs.h> +#include <linux/seq_file.h> +#include "overlayfs.h" + +MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); +MODULE_DESCRIPTION("Overlay filesystem"); +MODULE_LICENSE("GPL"); + +#define OVERLAYFS_SUPER_MAGIC 0x794c764f + +struct ovl_config { + char *lowerdir; + char *upperdir; +}; + +/* private information held for overlayfs's superblock */ +struct ovl_fs { + struct vfsmount *upper_mnt; + struct vfsmount *lower_mnt; + long lower_namelen; + /* pathnames of lower and upper dirs, for show_options */ + struct ovl_config config; +}; + +/* private information held for every overlayfs dentry */ +struct ovl_entry { + /* + * Keep "double reference" on upper dentries, so that + * d_delete() doesn't think it's OK to reset d_inode to NULL. + */ + struct dentry *__upperdentry; + struct dentry *lowerdentry; + union { + struct { + u64 version; + bool opaque; + }; + struct rcu_head rcu; + }; +}; + +const char *ovl_whiteout_xattr = "trusted.overlay.whiteout"; +const char *ovl_opaque_xattr = "trusted.overlay.opaque"; + + +enum ovl_path_type ovl_path_type(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + if (oe->__upperdentry) { + if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode)) + return OVL_PATH_MERGE; + else + return OVL_PATH_UPPER; + } else { + return OVL_PATH_LOWER; + } +} + +static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe) +{ + struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry); + smp_read_barrier_depends(); + return upperdentry; +} + +void ovl_path_upper(struct dentry *dentry, struct path *path) +{ + struct ovl_fs *ofs = dentry->d_sb->s_fs_info; + struct ovl_entry *oe = dentry->d_fsdata; + + path->mnt = ofs->upper_mnt; + path->dentry = ovl_upperdentry_dereference(oe); +} + +void ovl_path_lower(struct dentry *dentry, struct path *path) +{ + struct ovl_fs *ofs = dentry->d_sb->s_fs_info; + struct ovl_entry *oe = dentry->d_fsdata; + + path->mnt = ofs->lower_mnt; + path->dentry = oe->lowerdentry; +} + +enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path) +{ + + enum ovl_path_type type = ovl_path_type(dentry); + + if (type == OVL_PATH_LOWER) + ovl_path_lower(dentry, path); + else + ovl_path_upper(dentry, path); + + return type; +} + +struct dentry *ovl_dentry_upper(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + return ovl_upperdentry_dereference(oe); +} + +struct dentry *ovl_dentry_lower(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + return oe->lowerdentry; +} + +struct dentry *ovl_dentry_real(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + struct dentry *realdentry; + + realdentry = ovl_upperdentry_dereference(oe); + if (!realdentry) + realdentry = oe->lowerdentry; + + return realdentry; +} + +struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper) +{ + struct dentry *realdentry; + + realdentry = ovl_upperdentry_dereference(oe); + if (realdentry) { + *is_upper = true; + } else { + realdentry = oe->lowerdentry; + *is_upper = false; + } + return realdentry; +} + +bool ovl_dentry_is_opaque(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + return oe->opaque; +} + +void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque) +{ + struct ovl_entry *oe = dentry->d_fsdata; + oe->opaque = opaque; +} + +void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex)); + WARN_ON(oe->__upperdentry); + BUG_ON(!upperdentry->d_inode); + smp_wmb(); + oe->__upperdentry = dget(upperdentry); +} + +void ovl_dentry_version_inc(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); + oe->version++; +} + +u64 ovl_dentry_version_get(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); + return oe->version; +} + +bool ovl_is_whiteout(struct dentry *dentry) +{ + int res; + char val; + + if (!dentry) + return false; + if (!dentry->d_inode) + return false; + if (!S_ISLNK(dentry->d_inode->i_mode)) + return false; + + res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1); + if (res == 1 && val == 'y') + return true; + + return false; +} + +static bool ovl_is_opaquedir(struct dentry *dentry) +{ + int res; + char val; + + if (!S_ISDIR(dentry->d_inode->i_mode)) + return false; + + res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1); + if (res == 1 && val == 'y') + return true; + + return false; +} + +static void ovl_entry_free(struct rcu_head *head) +{ + struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu); + kfree(oe); +} + +static void ovl_dentry_release(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + if (oe) { + dput(oe->__upperdentry); + dput(oe->__upperdentry); + dput(oe->lowerdentry); + call_rcu(&oe->rcu, ovl_entry_free); + } +} + +const struct dentry_operations ovl_dentry_operations = { + .d_release = ovl_dentry_release, +}; + +static struct ovl_entry *ovl_alloc_entry(void) +{ + return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL); +} + +static inline struct dentry *ovl_lookup_real(struct dentry *dir, + struct qstr *name) +{ + struct dentry *dentry; + + mutex_lock(&dir->d_inode->i_mutex); + dentry = lookup_one_len(name->name, dir, name->len); + mutex_unlock(&dir->d_inode->i_mutex); + + if (IS_ERR(dentry)) { + if (PTR_ERR(dentry) == -ENOENT) + dentry = NULL; + } else if (!dentry->d_inode) { + dput(dentry); + dentry = NULL; + } + return dentry; +} + +static int ovl_do_lookup(struct dentry *dentry) +{ + struct ovl_entry *oe; + struct dentry *upperdir; + struct dentry *lowerdir; + struct dentry *upperdentry = NULL; + struct dentry *lowerdentry = NULL; + struct inode *inode = NULL; + int err; + + err = -ENOMEM; + oe = ovl_alloc_entry(); + if (!oe) + goto out; + + upperdir = ovl_dentry_upper(dentry->d_parent); + lowerdir = ovl_dentry_lower(dentry->d_parent); + + if (upperdir) { + upperdentry = ovl_lookup_real(upperdir, &dentry->d_name); + err = PTR_ERR(upperdentry); + if (IS_ERR(upperdentry)) + goto out_put_dir; + + if (lowerdir && upperdentry && + (S_ISLNK(upperdentry->d_inode->i_mode) || + S_ISDIR(upperdentry->d_inode->i_mode))) { + const struct cred *old_cred; + struct cred *override_cred; + + err = -ENOMEM; + override_cred = prepare_creds(); + if (!override_cred) + goto out_dput_upper; + + /* CAP_SYS_ADMIN needed for getxattr */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + old_cred = override_creds(override_cred); + + if (ovl_is_opaquedir(upperdentry)) { + oe->opaque = true; + } else if (ovl_is_whiteout(upperdentry)) { + dput(upperdentry); + upperdentry = NULL; + oe->opaque = true; + } + revert_creds(old_cred); + put_cred(override_cred); + } + } + if (lowerdir && !oe->opaque) { + lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name); + err = PTR_ERR(lowerdentry); + if (IS_ERR(lowerdentry)) + goto out_dput_upper; + } + + if (lowerdentry && upperdentry && + (!S_ISDIR(upperdentry->d_inode->i_mode) || + !S_ISDIR(lowerdentry->d_inode->i_mode))) { + dput(lowerdentry); + lowerdentry = NULL; + oe->opaque = true; + } + + if (lowerdentry || upperdentry) { + struct dentry *realdentry; + + realdentry = upperdentry ? upperdentry : lowerdentry; + err = -ENOMEM; + inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, + oe); + if (!inode) + goto out_dput; + ovl_copyattr(realdentry->d_inode, inode); + } + + if (upperdentry) + oe->__upperdentry = dget(upperdentry); + + if (lowerdentry) + oe->lowerdentry = lowerdentry; + + dentry->d_fsdata = oe; + dentry->d_op = &ovl_dentry_operations; + d_add(dentry, inode); + + return 0; + +out_dput: + dput(lowerdentry); +out_dput_upper: + dput(upperdentry); +out_put_dir: + kfree(oe); +out: + return err; +} + +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, + unsigned int flags) +{ + int err = ovl_do_lookup(dentry); + + if (err) + return ERR_PTR(err); + + return NULL; +} + +struct file *ovl_path_open(struct path *path, int flags) +{ + path_get(path); + return dentry_open(path, flags, current_cred()); +} + +static void ovl_put_super(struct super_block *sb) +{ + struct ovl_fs *ufs = sb->s_fs_info; + + if (!(sb->s_flags & MS_RDONLY)) + mnt_drop_write(ufs->upper_mnt); + + mntput(ufs->upper_mnt); + mntput(ufs->lower_mnt); + + kfree(ufs->config.lowerdir); + kfree(ufs->config.upperdir); + kfree(ufs); +} + +static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data) +{ + int flags = *flagsp; + struct ovl_fs *ufs = sb->s_fs_info; + + /* When remounting rw or ro, we need to adjust the write access to the + * upper fs. + */ + if (((flags ^ sb->s_flags) & MS_RDONLY) == 0) + /* No change to readonly status */ + return 0; + + if (flags & MS_RDONLY) { + mnt_drop_write(ufs->upper_mnt); + return 0; + } else + return mnt_want_write(ufs->upper_mnt); +} + +/** + * ovl_statfs + * @sb: The overlayfs super block + * @buf: The struct kstatfs to fill in with stats + * + * Get the filesystem statistics. As writes always target the upper layer + * filesystem pass the statfs to the same filesystem. + */ +static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) +{ + struct ovl_fs *ofs = dentry->d_sb->s_fs_info; + struct dentry *root_dentry = dentry->d_sb->s_root; + struct path path; + int err; + + ovl_path_upper(root_dentry, &path); + + err = vfs_statfs(&path, buf); + if (!err) { + buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen); + buf->f_type = OVERLAYFS_SUPER_MAGIC; + } + + return err; +} + +/** + * ovl_show_options + * + * Prints the mount options for a given superblock. + * Returns zero; does not fail. + */ +static int ovl_show_options(struct seq_file *m, struct dentry *dentry) +{ + struct super_block *sb = dentry->d_sb; + struct ovl_fs *ufs = sb->s_fs_info; + + seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir); + seq_printf(m, ",upperdir=%s", ufs->config.upperdir); + return 0; +} + +static const struct super_operations ovl_super_operations = { + .put_super = ovl_put_super, + .remount_fs = ovl_remount_fs, + .statfs = ovl_statfs, + .show_options = ovl_show_options, +}; + +enum { + Opt_lowerdir, + Opt_upperdir, + Opt_err, +}; + +static const match_table_t ovl_tokens = { + {Opt_lowerdir, "lowerdir=%s"}, + {Opt_upperdir, "upperdir=%s"}, + {Opt_err, NULL} +}; + +static int ovl_parse_opt(char *opt, struct ovl_config *config) +{ + char *p; + + config->upperdir = NULL; + config->lowerdir = NULL; + + while ((p = strsep(&opt, ",")) != NULL) { + int token; + substring_t args[MAX_OPT_ARGS]; + + if (!*p) + continue; + + token = match_token(p, ovl_tokens, args); + switch (token) { + case Opt_upperdir: + kfree(config->upperdir); + config->upperdir = match_strdup(&args[0]); + if (!config->upperdir) + return -ENOMEM; + break; + + case Opt_lowerdir: + kfree(config->lowerdir); + config->lowerdir = match_strdup(&args[0]); + if (!config->lowerdir) + return -ENOMEM; + break; + + default: + return -EINVAL; + } + } + return 0; +} + +static int ovl_fill_super(struct super_block *sb, void *data, int silent) +{ + struct path lowerpath; + struct path upperpath; + struct inode *root_inode; + struct dentry *root_dentry; + struct ovl_entry *oe; + struct ovl_fs *ufs; + struct kstatfs statfs; + int err; + + err = -ENOMEM; + ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL); + if (!ufs) + goto out; + + err = ovl_parse_opt((char *) data, &ufs->config); + if (err) + goto out_free_ufs; + + err = -EINVAL; + if (!ufs->config.upperdir || !ufs->config.lowerdir) { + printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n"); + goto out_free_config; + } + + oe = ovl_alloc_entry(); + if (oe == NULL) + goto out_free_config; + + err = kern_path(ufs->config.upperdir, LOOKUP_FOLLOW, &upperpath); + if (err) + goto out_free_oe; + + err = kern_path(ufs->config.lowerdir, LOOKUP_FOLLOW, &lowerpath); + if (err) + goto out_put_upperpath; + + err = -ENOTDIR; + if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) || + !S_ISDIR(lowerpath.dentry->d_inode->i_mode)) + goto out_put_lowerpath; + + err = vfs_statfs(&lowerpath, &statfs); + if (err) { + printk(KERN_ERR "overlayfs: statfs failed on lowerpath\n"); + goto out_put_lowerpath; + } + ufs->lower_namelen = statfs.f_namelen; + + sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth, + lowerpath.mnt->mnt_sb->s_stack_depth) + 1; + + err = -EINVAL; + if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { + printk(KERN_ERR "overlayfs: maximum fs stacking depth exceeded\n"); + goto out_put_lowerpath; + } + + + ufs->upper_mnt = clone_private_mount(&upperpath); + err = PTR_ERR(ufs->upper_mnt); + if (IS_ERR(ufs->upper_mnt)) { + printk(KERN_ERR "overlayfs: failed to clone upperpath\n"); + goto out_put_lowerpath; + } + + ufs->lower_mnt = clone_private_mount(&lowerpath); + err = PTR_ERR(ufs->lower_mnt); + if (IS_ERR(ufs->lower_mnt)) { + printk(KERN_ERR "overlayfs: failed to clone lowerpath\n"); + goto out_put_upper_mnt; + } + + /* + * Make lower_mnt R/O. That way fchmod/fchown on lower file + * will fail instead of modifying lower fs. + */ + ufs->lower_mnt->mnt_flags |= MNT_READONLY; + + /* If the upper fs is r/o, we mark overlayfs r/o too */ + if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY) + sb->s_flags |= MS_RDONLY; + + if (!(sb->s_flags & MS_RDONLY)) { + err = mnt_want_write(ufs->upper_mnt); + if (err) + goto out_put_lower_mnt; + } + + err = -ENOMEM; + root_inode = ovl_new_inode(sb, S_IFDIR, oe); + if (!root_inode) + goto out_drop_write; + + root_dentry = d_make_root(root_inode); + if (!root_dentry) + goto out_drop_write; + + mntput(upperpath.mnt); + mntput(lowerpath.mnt); + + oe->__upperdentry = dget(upperpath.dentry); + oe->lowerdentry = lowerpath.dentry; + + root_dentry->d_fsdata = oe; + root_dentry->d_op = &ovl_dentry_operations; + + sb->s_magic = OVERLAYFS_SUPER_MAGIC; + sb->s_op = &ovl_super_operations; + sb->s_root = root_dentry; + sb->s_fs_info = ufs; + + return 0; + +out_drop_write: + if (!(sb->s_flags & MS_RDONLY)) + mnt_drop_write(ufs->upper_mnt); +out_put_lower_mnt: + mntput(ufs->lower_mnt); +out_put_upper_mnt: + mntput(ufs->upper_mnt); +out_put_lowerpath: + path_put(&lowerpath); +out_put_upperpath: + path_put(&upperpath); +out_free_oe: + kfree(oe); +out_free_config: + kfree(ufs->config.lowerdir); + kfree(ufs->config.upperdir); +out_free_ufs: + kfree(ufs); +out: + return err; +} + +static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags, + const char *dev_name, void *raw_data) +{ + return mount_nodev(fs_type, flags, raw_data, ovl_fill_super); +} + +static struct file_system_type ovl_fs_type = { + .owner = THIS_MODULE, + .name = "overlayfs", + .mount = ovl_mount, + .kill_sb = kill_anon_super, +}; + +static int __init ovl_init(void) +{ + return register_filesystem(&ovl_fs_type); +} + +static void __exit ovl_exit(void) +{ + unregister_filesystem(&ovl_fs_type); +} + +module_init(ovl_init); +module_exit(ovl_exit); --- a/fs/splice.c +++ b/fs/splice.c @@ -1307,6 +1307,7 @@ long do_splice_direct(struct file *in, l return ret; } +EXPORT_SYMBOL(do_splice_direct); static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, struct pipe_inode_info *opipe, --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -244,6 +244,12 @@ struct iattr { */ #include <linux/quota.h> +/* + * Maximum number of layers of fs stack. Needs to be limited to + * prevent kernel stack overflow + */ +#define FILESYSTEM_MAX_STACK_DEPTH 2 + /** * enum positive_aop_returns - aop return codes with specific semantics * @@ -1320,6 +1326,11 @@ struct super_block { /* Being remounted read-only */ int s_readonly_remount; + + /* + * Indicates how deep in a filesystem stack this SB is + */ + int s_stack_depth; }; /* superblock cache pruning functions */ @@ -1573,6 +1584,7 @@ struct inode_operations { int (*atomic_open)(struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode, int *opened); + int (*dentry_open)(struct dentry *, struct file *, const struct cred *); } ____cacheline_aligned; ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector, @@ -2005,6 +2017,7 @@ extern struct file *file_open_name(struc extern struct file *filp_open(const char *, int, umode_t); extern struct file *file_open_root(struct dentry *, struct vfsmount *, const char *, int); +extern int vfs_open(const struct path *, struct file *, const struct cred *); extern struct file * dentry_open(const struct path *, int, const struct cred *); extern int filp_close(struct file *, fl_owner_t id); @@ -2210,6 +2223,7 @@ extern sector_t bmap(struct inode *, sec #endif extern int notify_change(struct dentry *, struct iattr *); extern int inode_permission(struct inode *, int); +extern int __inode_permission(struct inode *, int); extern int generic_permission(struct inode *, int); static inline bool execute_ok(struct inode *inode) --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -68,6 +68,9 @@ extern void mnt_pin(struct vfsmount *mnt extern void mnt_unpin(struct vfsmount *mnt); extern int __mnt_is_readonly(struct vfsmount *mnt); +struct path; +extern struct vfsmount *clone_private_mount(struct path *path); + struct file_system_type; extern struct vfsmount *vfs_kern_mount(struct file_system_type *type, int flags, const char *name, --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5666,6 +5666,13 @@ F: drivers/scsi/osd/ F: include/scsi/osd_* F: fs/exofs/ +OVERLAYFS FILESYSTEM +M: Miklos Szeredi <miklos@szeredi.hu> +L: linux-fsdevel@vger.kernel.org +S: Supported +F: fs/overlayfs/* +F: Documentation/filesystems/overlayfs.txt + P54 WIRELESS DRIVER M: Christian Lamparter <chunkeey@googlemail.com> L: linux-wireless@vger.kernel.org