ovl_whiteout() relies on the workdir i_rwsem to provide exclusive access
to ofs->whiteout which it manipulates. Rather than depending on this,
add a new mutex, "whiteout_lock" to explicitly provide the required
locking. Use guard(mutex) for this so that we can return without
needing to explicitly unlock.
Then take the lock on workdir only when needed - to lookup the temp name
and to do the whiteout or link.
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
fs/overlayfs/dir.c | 44 ++++++++++++++++++++++------------------
fs/overlayfs/ovl_entry.h | 1 +
fs/overlayfs/params.c | 2 ++
3 files changed, 27 insertions(+), 20 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 6a70faeee6fa..7eb806a4e5f8 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -84,41 +84,45 @@ static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
struct dentry *workdir = ofs->workdir;
struct inode *wdir = workdir->d_inode;
- inode_lock_nested(wdir, I_MUTEX_PARENT);
+ guard(mutex)(&ofs->whiteout_lock);
+
if (!ofs->whiteout) {
+ inode_lock_nested(wdir, I_MUTEX_PARENT);
whiteout = ovl_lookup_temp(ofs, workdir);
- if (IS_ERR(whiteout))
- goto out;
-
- err = ovl_do_whiteout(ofs, wdir, whiteout);
- if (err) {
- dput(whiteout);
- whiteout = ERR_PTR(err);
- goto out;
+ if (!IS_ERR(whiteout)) {
+ err = ovl_do_whiteout(ofs, wdir, whiteout);
+ if (err) {
+ dput(whiteout);
+ whiteout = ERR_PTR(err);
+ }
}
+ inode_unlock(wdir);
+ if (IS_ERR(whiteout))
+ return whiteout;
ofs->whiteout = whiteout;
}
if (!ofs->no_shared_whiteout) {
+ inode_lock_nested(wdir, I_MUTEX_PARENT);
whiteout = ovl_lookup_temp(ofs, workdir);
- if (IS_ERR(whiteout))
- goto out;
-
- err = ovl_do_link(ofs, ofs->whiteout, wdir, whiteout);
- if (!err)
- goto out;
-
- if (err != -EMLINK) {
+ if (!IS_ERR(whiteout)) {
+ err = ovl_do_link(ofs, ofs->whiteout, wdir, whiteout);
+ if (err) {
+ dput(whiteout);
+ whiteout = ERR_PTR(err);
+ }
+ }
+ inode_unlock(wdir);
+ if (!IS_ERR(whiteout))
+ return whiteout;
+ if (PTR_ERR(whiteout) != -EMLINK) {
pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
ofs->whiteout->d_inode->i_nlink, err);
ofs->no_shared_whiteout = true;
}
- dput(whiteout);
}
whiteout = ofs->whiteout;
ofs->whiteout = NULL;
-out:
- inode_unlock(wdir);
return whiteout;
}
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index afb7762f873f..4c1bae935ced 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -88,6 +88,7 @@ struct ovl_fs {
/* Shared whiteout cache */
struct dentry *whiteout;
bool no_shared_whiteout;
+ struct mutex whiteout_lock;
/* r/o snapshot of upperdir sb's only taken on volatile mounts */
errseq_t errseq;
};
diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index f42488c01957..cb1a17c066cd 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -797,6 +797,8 @@ int ovl_init_fs_context(struct fs_context *fc)
fc->s_fs_info = ofs;
fc->fs_private = ctx;
fc->ops = &ovl_context_ops;
+
+ mutex_init(&ofs->whiteout_lock);
return 0;
out_err:
--
2.49.0
