On Fri, Jan 19, 2024 at 12:14 PM Miklos Szeredi mszeredi@redhat.com wrote:
Add a check on each lower 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.
Share the same xattr for the per-directory and the per-layer flag, which has the effect that if this is enabled for a layer, then the optimization to bypass checking of individual entries does not work on the root of the layer. This was deemed better, than having a separate xattr for the layer and the directory.
Fixes: bc8df7a3dc03 ("ovl: Add an alternative type of whiteout") Cc: stable@vger.kernel.org # v6.7 Signed-off-by: Miklos Szeredi mszeredi@redhat.com
v2:
- use overlay.whiteouts instead of overlay.feature_xwhiteout
- move initialization to ovl_get_layers()
- xwhiteouts can only be enabled on lower layer
fs/overlayfs/namei.c | 10 +++++++--- fs/overlayfs/overlayfs.h | 7 +++++-- fs/overlayfs/ovl_entry.h | 2 ++ fs/overlayfs/readdir.c | 11 ++++++++--- fs/overlayfs/super.c | 13 +++++++++++++ fs/overlayfs/util.c | 7 ++++++- 6 files changed, 41 insertions(+), 9 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..6359cf5c66ff 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -492,7 +492,9 @@ 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 +676,8 @@ 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..33fcd3d3af30 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 xwhiteouts;};
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;
Not needed since we do not support xwhiteouts on upper.
err = ovl_dir_read(&realpath, &rdd); if (err)diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index a0967bb25003..04588721eb2a 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1027,6 +1027,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, struct ovl_fs_context_layer *l = &ctx->lower[i]; struct vfsmount *mnt; struct inode *trap;
struct path root; int fsid; if (i < nr_merged_lower)@@ -1069,6 +1070,16 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, */ mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
/** Check if xwhiteout (xattr whiteout) support is enabled on* this layer.*/root.mnt = mnt;root.dentry = mnt->mnt_root;err = ovl_path_getxattr(ofs, &root, OVL_XATTR_XWHITEOUTS, NULL, 0);if (err >= 0)layers[ofs->numlayer].xwhiteouts = true;layers[ofs->numlayer].trap = trap; layers[ofs->numlayer].mnt = mnt; layers[ofs->numlayer].idx = ofs->numlayer;@@ -1079,6 +1090,8 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, l->name = NULL; ofs->numlayer++; ofs->fs[fsid].is_lower = true;
extra spaces.
} /*diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index c3f020ca13a8..6c6e6f5893ea 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->xwhiteouts)return false;/* xattr.whiteouts must be a directory */ if (!d_is_dir(dentry)) return false;-- 2.43.0
Do you want me to fix/test and send this to Linus?
Alex, can we add your RVB to v2?
Thanks, Amir.