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authorYan, Zheng <zyan@redhat.com>2017-07-06 11:12:21 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-07-27 15:10:21 -0700
commit6823b31afd1091dbf66311f7adc6f44fd53ea514 (patch)
parent3002c15f57be5e6cbcc8df55ee49964d9052ae4d (diff)
ceph: fix race in concurrent readdir
commit 84583cfb973c4313955c6231cc9cb3772d280b15 upstream. For a large directory, program needs to issue multiple readdir syscalls to get all dentries. When there are multiple programs read the directory concurrently. Following sequence of events can happen. - program calls readdir with pos = 2. ceph sends readdir request to mds. The reply contains N1 entries. ceph adds these N1 entries to readdir cache. - program calls readdir with pos = N1+2. The readdir is satisfied by the readdir cache, N2 entries are returned. (Other program calls readdir in the middle, which fills the cache) - program calls readdir with pos = N1+N2+2. ceph sends readdir request to mds. The reply contains N3 entries and it reaches directory end. ceph adds these N3 entries to the readdir cache and marks directory complete. The second readdir call does not update fi->readdir_cache_idx. ceph add the last N3 entries to wrong places. Signed-off-by: "Yan, Zheng" <zyan@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index e071d23f6148..ef7240ace576 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -271,6 +271,11 @@ out:
if (ret < 0)
err = ret;
+ /* last_name no longer match cache index */
+ if (fi->readdir_cache_idx >= 0) {
+ fi->readdir_cache_idx = -1;
+ fi->dir_release_count = 0;
+ }
return err;