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authorAmir Goldstein <amir73il@gmail.com>2018-03-09 14:51:02 +0100
committerMiklos Szeredi <mszeredi@redhat.com>2018-04-12 12:04:49 +0200
commit8a22efa15b46d524577cac79da63cebca8e8307f (patch)
treed6c87569edb074ddd6edb3b88eb3105abefb3d6b /fs/exportfs
parentovl: disambiguate ovl_encode_fh() (diff)
downloadlinux-8a22efa15b46d524577cac79da63cebca8e8307f.tar.xz
linux-8a22efa15b46d524577cac79da63cebca8e8307f.zip
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>
Diffstat (limited to 'fs/exportfs')
-rw-r--r--fs/exportfs/expfs.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 329a5d103846..645158dc33f1 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -435,6 +435,15 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
if (IS_ERR_OR_NULL(result))
return ERR_PTR(-ESTALE);
+ /*
+ * If no acceptance criteria was specified by caller, a disconnected
+ * dentry is also accepatable. Callers may use this mode to query if
+ * file handle is stale or to get a reference to an inode without
+ * risking the high overhead caused by directory reconnect.
+ */
+ if (!acceptable)
+ return result;
+
if (d_is_dir(result)) {
/*
* This request is for a directory.