On Thu, 2024-01-18 at 11:41 +0100, Miklos Szeredi wrote:
Add a check on each layer for the xwhiteout feature. This prevents unnecessary checking the overlay.whiteouts xattr when reading a directory if this feature is not enabled, i.e. most of the time.
Fixes: bc8df7a3dc03 ("ovl: Add an alternative type of whiteout") Cc: stable@vger.kernel.org # v6.7 Signed-off-by: Miklos Szeredi mszeredi@redhat.com
Hi Alex,
Can you please test this in your environment?
Interesting, I was just finishing a patch for this, and it is mostly identical. It works in my testing.
Reviewed-by: Alexander Larsson alexl@redhat.com
I xwhiteout test in xfstests needs this tweak:
--- a/tests/overlay/084 +++ b/tests/overlay/084 @@ -115,6 +115,7 @@ do_test_xwhiteout() mkdir -p $basedir/lower $basedir/upper $basedir/work touch $basedir/lower/regular $basedir/lower/hidden $basedir/upper/hidden
- setfattr -n $prefix.overlay.feature_xwhiteout -v "y"
$basedir/upper setfattr -n $prefix.overlay.whiteouts -v "y" $basedir/upper setfattr -n $prefix.overlay.whiteout -v "y" $basedir/upper/hidden
Also, I will need to update mkcomposefs to set this xattr and bump the image version.
Thanks, Miklos
fs/overlayfs/namei.c | 10 +++++++--- fs/overlayfs/overlayfs.h | 8 ++++++-- fs/overlayfs/ovl_entry.h | 2 ++ fs/overlayfs/readdir.c | 11 ++++++++--- fs/overlayfs/super.c | 13 ++++++++++++- fs/overlayfs/util.c | 9 ++++++++- 6 files changed, 43 insertions(+), 10 deletions(-)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index 03bc8d5dfa31..583cf56df66e 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -863,7 +863,8 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper, * Returns next layer in stack starting from top. * Returns -1 if this is the last layer. */ -int ovl_path_next(int idx, struct dentry *dentry, struct path *path) +int ovl_path_next(int idx, struct dentry *dentry, struct path *path,
const struct ovl_layer **layer){ struct ovl_entry *oe = OVL_E(dentry); struct ovl_path *lowerstack = ovl_lowerstack(oe); @@ -871,13 +872,16 @@ int ovl_path_next(int idx, struct dentry *dentry, struct path *path) BUG_ON(idx < 0); if (idx == 0) { ovl_path_upper(dentry, path);
if (path->dentry)
if (path->dentry) {*layer = &OVL_FS(dentry->d_sb)->layers[0];return ovl_numlower(oe) ? 1 : -1;
}idx++; } BUG_ON(idx > ovl_numlower(oe)); path->dentry = lowerstack[idx - 1].dentry;
- path->mnt = lowerstack[idx - 1].layer->mnt;
- *layer = lowerstack[idx - 1].layer;
- path->mnt = (*layer)->mnt;
return (idx < ovl_numlower(oe)) ? idx + 1 : -1; } diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 05c3dd597fa8..991eb5d5c66c 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -51,6 +51,7 @@ enum ovl_xattr { OVL_XATTR_PROTATTR, OVL_XATTR_XWHITEOUT, OVL_XATTR_XWHITEOUTS,
- OVL_XATTR_FEATURE_XWHITEOUT,
}; enum ovl_inode_flag { @@ -492,7 +493,9 @@ 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_path_check_xwhiteouts_xattr(struct ovl_fs *ofs,
const struct ovl_layer *layer,const struct path *path);bool ovl_init_uuid_xattr(struct super_block *sb, struct ovl_fs *ofs, const struct path *upperpath); @@ -674,7 +677,8 @@ int ovl_get_index_name(struct ovl_fs *ofs, struct dentry *origin, struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh); struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper, struct dentry *origin, bool verify); -int ovl_path_next(int idx, struct dentry *dentry, struct path *path); +int ovl_path_next(int idx, struct dentry *dentry, struct path *path,
const struct ovl_layer **layer);int ovl_verify_lowerdata(struct dentry *dentry); struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags); diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h index d82d2a043da2..51729e614f5a 100644 --- a/fs/overlayfs/ovl_entry.h +++ b/fs/overlayfs/ovl_entry.h @@ -40,6 +40,8 @@ struct ovl_layer { int idx; /* One fsid per unique underlying sb (upper fsid == 0) */ int fsid;
- /* xwhiteouts are enabled on this layer*/
- bool feature_xwhiteout;
}; struct ovl_path { diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c index a490fc47c3e7..c2597075e3f8 100644 --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -305,8 +305,6 @@ static inline int ovl_dir_read(const struct path *realpath, if (IS_ERR(realfile)) return PTR_ERR(realfile);
- rdd->in_xwhiteouts_dir = rdd->dentry &&
ovl_path_check_xwhiteouts_xattr(OVL_FS(rdd->dentry-d_sb), realpath);
rdd->first_maybe_whiteout = NULL; rdd->ctx.pos = 0; do { @@ -359,10 +357,14 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list, .is_lowest = false, }; int idx, next;
- struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
- const struct ovl_layer *layer;
for (idx = 0; idx != -1; idx = next) {
next = ovl_path_next(idx, dentry, &realpath);
next = ovl_path_next(idx, dentry, &realpath,&layer); rdd.is_upper = ovl_dentry_upper(dentry) == realpath.dentry;
if (ovl_path_check_xwhiteouts_xattr(ofs, layer,&realpath))
rdd.in_xwhiteouts_dir = true;if (next != -1) { err = ovl_dir_read(&realpath, &rdd); @@ -568,6 +570,7 @@ static int ovl_dir_read_impure(const struct path *path, struct list_head *list, int err; struct path realpath; struct ovl_cache_entry *p, *n;
- struct ovl_fs *ofs = OVL_FS(path->dentry->d_sb);
struct ovl_readdir_data rdd = { .ctx.actor = ovl_fill_plain, .list = list, @@ -577,6 +580,8 @@ static int ovl_dir_read_impure(const struct path *path, struct list_head *list, INIT_LIST_HEAD(list); *root = RB_ROOT; ovl_path_upper(path->dentry, &realpath);
- if (ovl_path_check_xwhiteouts_xattr(ofs, &ofs->layers[0],
&realpath))
rdd.in_xwhiteouts_dir = true;
I'm not sure exactly how impure dirs work, but I don't think this is needed. When we hit the read_impure() codepath, we never then actually look at the p->is_whiteout information.
err = ovl_dir_read(&realpath, &rdd); if (err) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index a0967bb25003..4e507ab780f3 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1291,7 +1291,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) struct ovl_entry *oe; struct ovl_layer *layers; struct cred *cred;
- int err;
- int err, i;
err = -EIO; if (WARN_ON(fc->user_ns != current_user_ns())) @@ -1414,6 +1414,17 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) if (err) goto out_free_oe;
- for (i = 0; i < ofs->numlayer; i++) {
struct path path = { .mnt = layers[i].mnt };if (path.mnt) {path.dentry = path.mnt->mnt_root;err = ovl_path_getxattr(ofs, &path,OVL_XATTR_FEATURE_XWHITEOUT, NULL, 0);
if (err >= 0)layers[i].feature_xwhiteout = true;}- }
/* Show index=off in /proc/mounts for forced r/o mount */ if (!ofs->indexdir) { ofs->config.index = false; diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index c3f020ca13a8..cae8219618e3 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -739,11 +739,16 @@ bool ovl_path_check_xwhiteout_xattr(struct ovl_fs *ofs, const struct path *path) return res >= 0; } -bool ovl_path_check_xwhiteouts_xattr(struct ovl_fs *ofs, const struct path *path) +bool ovl_path_check_xwhiteouts_xattr(struct ovl_fs *ofs,
const struct ovl_layer *layer,const struct path *path){ struct dentry *dentry = path->dentry; int res;
- if (!layer->feature_xwhiteout)
return false;/* xattr.whiteouts must be a directory */ if (!d_is_dir(dentry)) return false; @@ -838,6 +843,7 @@ bool ovl_path_check_dir_xattr(struct ovl_fs *ofs, const struct path *path, #define OVL_XATTR_PROTATTR_POSTFIX "protattr" #define OVL_XATTR_XWHITEOUT_POSTFIX "whiteout" #define OVL_XATTR_XWHITEOUTS_POSTFIX "whiteouts" +#define OVL_XATTR_FEATURE_XWHITEOUT_POSTFIX "feature_xwhiteout" #define OVL_XATTR_TAB_ENTRY(x) \ [x] = { [false] = OVL_XATTR_TRUSTED_PREFIX x ## _POSTFIX, \ @@ -855,6 +861,7 @@ const char *const ovl_xattr_table[][2] = { OVL_XATTR_TAB_ENTRY(OVL_XATTR_PROTATTR), OVL_XATTR_TAB_ENTRY(OVL_XATTR_XWHITEOUT), OVL_XATTR_TAB_ENTRY(OVL_XATTR_XWHITEOUTS),
- OVL_XATTR_TAB_ENTRY(OVL_XATTR_FEATURE_XWHITEOUT),
}; int ovl_check_setxattr(struct ovl_fs *ofs, struct dentry *upperdentry,