ovl: do not try to reconnect a disconnected origin dentry
On lookup of non directory, we try to decode the origin file handle
stored in upper inode. The origin file handle is supposed to be decoded
to a disconnected non-dir dentry, which is fine, because we only need
the lower inode of a copy up origin.
However, if the origin file handle somehow turns out to be a directory
we pay the expensive cost of reconnecting the directory dentry, only to
get a mismatch file type and drop the dentry.
Optimize this case by explicitly opting out of reconnecting the dentry.
Opting-out of reconnect is done by passing a NULL acceptable callback
to exportfs_decode_fh().
While the case described above is a strange corner case that does not
really need to be optimized, the API added for this optimization will
be used by a following patch to optimize a more common case of decoding
an overlayfs file handle.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index e688cf0..1541135 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -685,7 +685,7 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
if (!ofs->upper_mnt)
return ERR_PTR(-EACCES);
- upper = ovl_decode_real_fh(fh, ofs->upper_mnt);
+ upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);
if (IS_ERR_OR_NULL(upper))
return upper;
@@ -735,7 +735,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
}
/* Then lookup origin by fh */
- err = ovl_check_origin_fh(ofs, fh, NULL, &stack);
+ err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack);
if (err) {
goto out_err;
} else if (index) {
