From: Xiubo Li <xiubli@redhat.com>

Date: Wed, 27 Apr 2022 14:14:41 +0800

Subject: ceph: try to queue a writeback if revoking fails

Git-commit: a74379543d229a3fb1af8cd44cbd19844a7bb1bc

Patch-mainline: v5.19-rc1

References: jsc#SES-1880

If the pagecaches writeback just finished and the i_wrbuffer_ref

reaches zero it will try to trigger ceph_check_caps(). But if just

before ceph_check_caps() the i_wrbuffer_ref could be increased

again by mmap/cache write, then the Fwb revoke will fail.

We need to try to queue a writeback in this case instead of

triggering the writeback by BDI's delayed work per 5 seconds.

URL: https://tracker.ceph.com/issues/46904

URL: https://tracker.ceph.com/issues/55377

Signed-off-by: Xiubo Li <xiubli@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 | 28 ++++++++++++++++++++++++----

 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c

index a051e6e4d7ca..bf2e94005598 100644

--- a/fs/ceph/caps.c

+++ b/fs/ceph/caps.c

@@ -1911,6 +1911,7 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,

 	struct rb_node *p;

 	bool queue_invalidate = false;

 	bool tried_invalidate = false;

+	bool queue_writeback = false;

 	if (session)

 		ceph_get_mds_session(session);

@@ -2063,10 +2064,27 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,

 		}

 		/* completed revocation? going down and there are no caps? */

-		if (revoking && (revoking & cap_used) == 0) {

-			dout("completed revocation of %s\n",

-			     ceph_cap_string(cap->implemented & ~cap->issued));

-			goto ack;

+		if (revoking) {

+			if ((revoking & cap_used) == 0) {

+				dout("completed revocation of %s\n",

+				      ceph_cap_string(cap->implemented & ~cap->issued));

+				goto ack;

+			}

+

+			/*

+			 * If the "i_wrbuffer_ref" was increased by mmap or generic

+			 * cache write just before the ceph_check_caps() is called,

+			 * the Fb capability revoking will fail this time. Then we

+			 * must wait for the BDI's delayed work to flush the dirty

+			 * pages and to release the "i_wrbuffer_ref", which will cost

+			 * at most 5 seconds. That means the MDS needs to wait at

+			 * most 5 seconds to finished the Fb capability's revocation.

+			 *

+			 * Let's queue a writeback for it.

+			 */

+			if (S_ISREG(inode->i_mode) && ci->i_wrbuffer_ref &&

+			    (revoking & CEPH_CAP_FILE_BUFFER))

+				queue_writeback = true;

 		}

 		/* want more caps from mds? */

@@ -2136,6 +2154,8 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,

 	spin_unlock(&ci->i_ceph_lock);

 	ceph_put_mds_session(session);

+	if (queue_writeback)

+		ceph_queue_writeback(inode);

 	if (queue_invalidate)

 		ceph_queue_invalidate(inode);

 }