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| author | Alexander Larsson <alexl@redhat.com> | 2023-08-23 17:33:42 +0300 |
|---|---|---|
| committer | Amir Goldstein <amir73il@gmail.com> | 2023-10-31 01:12:59 +0300 |
| commit | bc8df7a3dc035903426a17ea3027f55817de13a8 (patch) | |
| tree | 7a10810e897acf2f76f601d52214d3b12fffbdb5 /fs/overlayfs/overlayfs.h | |
| parent | dad02fad84cbce30f317b69a4f2391f90045f79d (diff) | |
| download | linux-bc8df7a3dc035903426a17ea3027f55817de13a8.tar.xz | |
ovl: Add an alternative type of whiteout
An xattr whiteout (called "xwhiteout" in the code) is a reguar file of
zero size with the "overlay.whiteout" xattr set. A file like this in a
directory with the "overlay.whiteouts" xattrs set will be treated the
same way as a regular whiteout.
The "overlay.whiteouts" directory xattr is used in order to
efficiently handle overlay checks in readdir(), as we only need to
checks xattrs in affected directories.
The advantage of this kind of whiteout is that they can be escaped
using the standard overlay xattr escaping mechanism. So, a file with a
"overlay.overlay.whiteout" xattr would be unescaped to
"overlay.whiteout", which could then be consumed by another overlayfs
as a whiteout.
Overlayfs itself doesn't create whiteouts like this, but a userspace
mechanism could use this alternative mechanism to convert images that
may contain whiteouts to be used with overlayfs.
To work as a whiteout for both regular overlayfs mounts as well as
userxattr mounts both the "user.overlay.whiteout*" and the
"trusted.overlay.whiteout*" xattrs will need to be created.
Signed-off-by: Alexander Larsson <alexl@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Diffstat (limited to 'fs/overlayfs/overlayfs.h')
| -rw-r--r-- | fs/overlayfs/overlayfs.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 393c6ba9bffa..ca88b2636a57 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -49,6 +49,8 @@ enum ovl_xattr { OVL_XATTR_UUID, OVL_XATTR_METACOPY, OVL_XATTR_PROTATTR, + OVL_XATTR_XWHITEOUT, + OVL_XATTR_XWHITEOUTS, }; enum ovl_inode_flag { @@ -473,6 +475,7 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry); void ovl_dir_modified(struct dentry *dentry, bool impurity); u64 ovl_inode_version_get(struct inode *inode); bool ovl_is_whiteout(struct dentry *dentry); +bool ovl_path_is_whiteout(struct ovl_fs *ofs, const struct path *path); struct file *ovl_path_open(const struct path *path, int flags); int ovl_copy_up_start(struct dentry *dentry, int flags); void ovl_copy_up_end(struct dentry *dentry); @@ -480,9 +483,21 @@ bool ovl_already_copied_up(struct dentry *dentry, int flags); bool ovl_path_check_dir_xattr(struct ovl_fs *ofs, const struct path *path, enum ovl_xattr ox); bool ovl_path_check_origin_xattr(struct ovl_fs *ofs, const struct path *path); +bool ovl_path_check_xwhiteout_xattr(struct ovl_fs *ofs, const struct path *path); +bool ovl_path_check_xwhiteouts_xattr(struct ovl_fs *ofs, const struct path *path); bool ovl_init_uuid_xattr(struct super_block *sb, struct ovl_fs *ofs, const struct path *upperpath); +static inline bool ovl_upper_is_whiteout(struct ovl_fs *ofs, + struct dentry *upperdentry) +{ + struct path upperpath = { + .dentry = upperdentry, + .mnt = ovl_upper_mnt(ofs), + }; + return ovl_path_is_whiteout(ofs, &upperpath); +} + static inline bool ovl_check_origin_xattr(struct ovl_fs *ofs, struct dentry *upperdentry) { |