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Subject[PATCH AUTOSEL 4.9 05/23] ceph: don't skip updating wanted caps when cap is stale
Date
From: "Yan, Zheng" <zyan@redhat.com>

[ Upstream commit 0aa971b6fd3f92afef6afe24ef78d9bb14471519 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 f5d9835264aa1..617e9ae67f506 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1764,8 +1764,12 @@ 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 &&
--
2.20.1
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