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| author | Amir Goldstein <amir73il@gmail.com> | 2023-06-26 16:34:25 +0300 |
|---|---|---|
| committer | Amir Goldstein <amir73il@gmail.com> | 2023-08-12 19:02:50 +0300 |
| commit | b0504bfe1b8acdcfb5ef466581d930835ef3c49e (patch) | |
| tree | 69074291700ec64db7789139faca31b5f5d05f58 /fs/overlayfs/super.c | |
| parent | 16aac5ad1fa94894b798dd522c5c3a6a0628d7f0 (diff) | |
| download | linux-b0504bfe1b8acdcfb5ef466581d930835ef3c49e.tar.xz | |
ovl: add support for unique fsid per instance
The legacy behavior of ovl_statfs() reports the f_fsid filled by
underlying upper fs. This fsid is not unique among overlayfs instances
on the same upper fs.
With mount option uuid=on, generate a non-persistent uuid per overlayfs
instance and use it as the seed for f_fsid, similar to tmpfs.
This is useful for reporting fanotify events with fid info from different
instances of overlayfs over the same upper fs.
The old behavior of null uuid and upper fs fsid is retained with the
mount option uuid=null, which is the default.
The mount option uuid=off that disables uuid checks in underlying layers
also retains the legacy behavior.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Diffstat (limited to 'fs/overlayfs/super.c')
| -rw-r--r-- | fs/overlayfs/super.c | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index e56108ffe8aa..c2bab6106e98 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -242,8 +242,9 @@ static int ovl_sync_fs(struct super_block *sb, int wait) */ 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 super_block *sb = dentry->d_sb; + struct ovl_fs *ofs = OVL_FS(sb); + struct dentry *root_dentry = sb->s_root; struct path path; int err; @@ -253,6 +254,8 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) if (!err) { buf->f_namelen = ofs->namelen; buf->f_type = OVERLAYFS_SUPER_MAGIC; + if (ovl_has_fsid(ofs)) + buf->f_fsid = uuid_to_fsid(sb->s_uuid.b); } return err; @@ -1421,9 +1424,12 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) if (!ovl_upper_mnt(ofs)) sb->s_flags |= SB_RDONLY; - if (!ofs->config.uuid && ofs->numfs > 1) { - pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=on.\n"); - ofs->config.uuid = true; + if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) { + pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n"); + ofs->config.uuid = OVL_UUID_NULL; + } else if (ovl_has_fsid(ofs)) { + /* Use per instance uuid/fsid */ + uuid_gen(&sb->s_uuid); } if (!ovl_force_readonly(ofs) && ofs->config.index) { |