From: "Yan, Zheng" <zyan@redhat.com>
Date: Tue, 10 Mar 2020 19:34:20 +0800
Subject: ceph: don't skip updating wanted caps when cap is stale
Git-commit: 0aa971b6fd3f92afef6afe24ef78d9bb14471519
Patch-mainline: v5.7-rc1
References: bsc#1205905

1. try_get_cap_refs() fails to get caps and finds that mds_wanted
   does not include what it wants. It returns -ESTALE.
2. ceph_get_caps() calls ceph_renew_caps(). ceph_renew_caps() finds
   that inode has cap, so it calls ceph_check_caps().
3. ceph_check_caps() finds that issued caps (without checking if it's
   stale) already includes caps wanted by open file, so it skips
   updating wanted caps.

Above events can cause an infinite loop inside ceph_get_caps().

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>

---
 fs/ceph/caps.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 086bb3adc08a..be1ae4b92cfd 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2008,8 +2008,12 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,
 		}
 
 		/* want more caps from mds? */
-		if (want & ~(cap->mds_wanted | cap->issued))
-			goto ack;
+		if (want & ~cap->mds_wanted) {
+			if (want & ~(cap->mds_wanted | cap->issued))
+				goto ack;
+			if (!__cap_is_valid(cap))
+				goto ack;
+		}
 
 		/* things we might delay */
 		if ((cap->issued & ~retain) == 0)