[PATCH 4/6] ovl: generalize the lower_fs[] array

Amir Goldstein
2019-11-17T15:43:47Z

Rename lower_fs[] array to fs[], extend its size by one and initialize
fs[0] with upper fs values. fsid 0 is already reserved even with lower
only overlay, so fs[0] remains uninitialized in this case as well.

Rename numlowerfs to maxfsid and use index 0..maxfsid to access the
fs[] array.

This gets rid of special casing upper layer in ovl_map_dev_ino().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/inode.c | 31 +++++++++----------
fs/overlayfs/ovl_entry.h | 5 ++-
fs/overlayfs/super.c | 66 +++++++++++++++++++++-------------------
3 files changed, 51 insertions(+), 51 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 717337f2b3fb..9e894f5e19b4 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -75,8 +75,7 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
return err;
}

-static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat,
- struct ovl_layer *lower_layer)
+static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
{
bool samefs = ovl_same_fs(dentry->d_sb);
unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
@@ -103,9 +102,7 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat,
pr_warn_ratelimited("overlayfs: inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
dentry, stat->ino, xinobits);
} else {
- if (lower_layer)
- stat->ino |= ((u64)lower_layer->fsid) << shift;
-
+ stat->ino |= ((u64)fsid) << shift;
stat->dev = dentry->d_sb->s_dev;
return 0;
}
@@ -124,15 +121,15 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat,
*/
stat->dev = dentry->d_sb->s_dev;
stat->ino = dentry->d_inode->i_ino;
- } else if (lower_layer && lower_layer->fsid) {
+ } else {
/*
* For non-samefs setup, if we cannot map all layers st_ino
* to a unified address space, we need to make sure that st_dev
- * is unique per lower fs. Upper layer uses real st_dev and
- * lower layers use the unique anonymous bdev assigned to the
- * lower fs.
+ * is unique per lower fs. Layers that are on the same fs as
+ * upper layer use real upper st_dev and other lower layers use
+ * the unique anonymous bdev assigned to the lower fs.
*/
- stat->dev = lower_layer->fs->pseudo_dev;
+ stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;
}

return 0;
@@ -146,7 +143,7 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
struct path realpath;
const struct cred *old_cred;
bool is_dir = S_ISDIR(dentry->d_inode->i_mode);
- struct ovl_layer *lower_layer = NULL;
+ int fsid;
int err;
bool metacopy_blocks = false;

@@ -168,9 +165,8 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
* persistent st_ino across mount cycle.
*/
if (!is_dir || ovl_same_dev(dentry->d_sb)) {
- if (!OVL_TYPE_UPPER(type)) {
- lower_layer = ovl_dentry_layer(dentry);
- } else if (OVL_TYPE_ORIGIN(type)) {
+ fsid = ovl_dentry_layer(dentry)->fsid;
+ if (OVL_TYPE_ORIGIN(type)) {
struct kstat lowerstat;
u32 lowermask = STATX_INO | STATX_BLOCKS |
(!is_dir ? STATX_NLINK : 0);
@@ -199,14 +195,15 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||
(!ovl_verify_lower(dentry->d_sb) &&
(is_dir || lowerstat.nlink == 1))) {
- lower_layer = ovl_dentry_layer(dentry);
/*
* Cannot use origin st_dev;st_ino because
* origin inode content may differ from overlay
* inode content.
*/
- if (samefs || lower_layer->fsid)
+ if (samefs || fsid)
stat->ino = lowerstat.ino;
+ } else {
+ fsid = 0;
}

/*
@@ -240,7 +237,7 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
}
}

- err = ovl_map_dev_ino(dentry, stat, lower_layer);
+ err = ovl_map_dev_ino(dentry, stat, fsid);
if (err)
goto out;

diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index ef05817d8d89..93e9fd5fba9d 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -46,10 +46,9 @@ struct ovl_path {
struct ovl_fs {
struct vfsmount *upper_mnt;
unsigned int numlower;
- /* Number of unique lower sb that differ from upper sb */
- unsigned int numlowerfs;
+ unsigned int maxfsid;
struct ovl_layer *layers;
- struct ovl_sb *lower_fs;
+ struct ovl_sb *fs;
/* workbasedir is the path at workdir= mount option */
struct dentry *workbasedir;
/* workdir is the 'work' directory under workbasedir */
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ae22c3363c33..09e53780d9bc 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -228,10 +228,13 @@ static void ovl_free_fs(struct ovl_fs *ofs)
iput(ofs->layers[i].trap);
mntput(ofs->layers[i].mnt);
}
- for (i = 0; i < ofs->numlowerfs; i++)
- free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
kfree(ofs->layers);
- kfree(ofs->lower_fs);
+ if (ofs->fs) {
+ /* fs[0].pseudo_dev is either null or real upper st_dev */
+ for (i = 1; i <= ofs->maxfsid; i++)
+ free_anon_bdev(ofs->fs[i].pseudo_dev);
+ kfree(ofs->fs);
+ }

kfree(ofs->config.lowerdir);
kfree(ofs->config.upperdir);
@@ -1253,7 +1256,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
if (!ofs->config.nfs_export && !ofs->upper_mnt)
return true;

- for (i = 0; i < ofs->numlowerfs; i++) {
+ for (i = 1; i <= ofs->maxfsid; i++) {
/*
* We use uuid to associate an overlay lower file handle with a
* lower layer, so we can accept lower fs with null uuid as long
@@ -1261,8 +1264,8 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
* if we detect multiple lower fs with the same uuid, we
* disable lower file handle decoding on all of them.
*/
- if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) {
- ofs->lower_fs[i].bad_uuid = true;
+ if (uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
+ ofs->fs[i].bad_uuid = true;
return false;
}
}
@@ -1278,13 +1281,9 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
int err;
bool bad_uuid = false;

- /* fsid 0 is reserved for upper fs even with non upper overlay */
- if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
- return 0;
-
- for (i = 0; i < ofs->numlowerfs; i++) {
- if (ofs->lower_fs[i].sb == sb)
- return i + 1;
+ for (i = 0; i <= ofs->maxfsid; i++) {
+ if (ofs->fs[i].sb == sb)
+ return i;
}

if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
@@ -1305,12 +1304,12 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
return err;
}

- ofs->lower_fs[ofs->numlowerfs].sb = sb;
- ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
- ofs->lower_fs[ofs->numlowerfs].bad_uuid = bad_uuid;
- ofs->numlowerfs++;
+ ofs->maxfsid++;
+ ofs->fs[ofs->maxfsid].sb = sb;
+ ofs->fs[ofs->maxfsid].pseudo_dev = dev;
+ ofs->fs[ofs->maxfsid].bad_uuid = bad_uuid;

- return ofs->numlowerfs;
+ return ofs->maxfsid;
}

static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
@@ -1325,16 +1324,24 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
if (ofs->layers == NULL)
goto out;

- ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
- GFP_KERNEL);
- if (ofs->lower_fs == NULL)
+ ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
+ if (ofs->fs == NULL)
goto out;

- /* idx 0 is reserved for upper fs even with lower only overlay */
+ /* idx/fsid 0 are reserved for upper fs even with lower only overlay */
ofs->layers[0].mnt = ofs->upper_mnt;
ofs->layers[0].idx = 0;
ofs->layers[0].fsid = 0;

+ /*
+ * All lower layers that share the same fs as upper layer, use the real
+ * upper st_dev.
+ */
+ if (ofs->upper_mnt) {
+ ofs->fs[0].sb = ofs->upper_mnt->mnt_sb;
+ ofs->fs[0].pseudo_dev = ofs->upper_mnt->mnt_sb->s_dev;
+ }
+
for (i = 0; i < numlower; i++) {
struct vfsmount *mnt;
struct inode *trap;
@@ -1373,10 +1380,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
ofs->layers[ofs->numlower].mnt = mnt;
ofs->layers[ofs->numlower].idx = ofs->numlower;
ofs->layers[ofs->numlower].fsid = fsid;
- if (fsid) {
- ofs->layers[ofs->numlower].fs =
- &ofs->lower_fs[fsid - 1];
- }
+ ofs->layers[ofs->numlower].fs = &ofs->fs[fsid];
}

/*
@@ -1387,19 +1391,19 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
* bits reserved for fsid, it emits a warning and uses the original
* inode number.
*/
- if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
+ if (ofs->maxfsid == 0 || (ofs->maxfsid == 1 && !ofs->upper_mnt)) {
if (ofs->config.xino == OVL_XINO_ON)
pr_info("overlayfs: \"xino=on\" is useless with all layers on same fs, ignore.\n");
ofs->xino_bits = 0;
ofs->config.xino = OVL_XINO_SAME_FS;
} else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
/*
- * This is a roundup of number of bits needed for numlowerfs+1
- * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
- * upper fs even with non upper overlay.
+ * This is a roundup of number of bits needed for encoding
+ * fsid, where fsid 0 is reserved for upper fs even with
+ * lower only overlay.
*/
BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
- ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
+ ofs->xino_bits = ilog2(ofs->maxfsid) + 1;
}

if (ofs->xino_bits) {
--
2.17.1