From 8a22efa15b46d524577cac79da63cebca8e8307f Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 9 Mar 2018 15:51:02 +0200 Subject: 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 Signed-off-by: Miklos Szeredi --- fs/exportfs/expfs.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'fs/exportfs') 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. -- cgit v1.2.3