From: "Yan, Zheng" <zyan@redhat.com>

Date: Thu, 22 Nov 2018 15:26:01 +0800

Subject: ceph: skip updating 'wanted' caps if caps are already issued

Git-commit: fdac94fab7995ebc52ff9c5b6247133c67a7564a

Patch-mainline: v5.0-rc1

References: bsc#1122215

When reading cached inode that already has Fscr caps, this can avoid

two cap messages (one updats 'wanted' caps, one clears 'wanted' caps).

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Acked-by: Luis Henriques <lhenriques@suse.com>

---

 fs/ceph/caps.c |   27 +++++++++++++++++----------

 1 file changed, 17 insertions(+), 10 deletions(-)

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

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

@@ -1970,8 +1970,7 @@ retry_locked:

 			goto ack;

 		/* things we might delay */

-		if ((cap->issued & ~retain) == 0 &&

-		    cap->mds_wanted == want)

+		if ((cap->issued & ~retain) == 0)

 			continue;     /* nope, all good */

 		if (no_delay)

@@ -3047,7 +3046,8 @@ static void handle_cap_grant(struct inod

 	int used, wanted, dirty;

 	u64 size = le64_to_cpu(grant->size);

 	u64 max_size = le64_to_cpu(grant->max_size);

-	int check_caps = 0;

+	unsigned char check_caps = 0;

+	bool was_stale = cap->cap_gen < session->s_cap_gen;

 	bool wake = false;

 	bool writeback = false;

 	bool queue_trunc = false;

@@ -3199,13 +3199,20 @@ static void handle_cap_grant(struct inod

 	     ceph_cap_string(wanted),

 	     ceph_cap_string(used),

 	     ceph_cap_string(dirty));

-	if (wanted != le32_to_cpu(grant->wanted)) {

-		dout("mds wanted %s -> %s\n",

-		     ceph_cap_string(le32_to_cpu(grant->wanted)),

-		     ceph_cap_string(wanted));

-		/* imported cap may not have correct mds_wanted */

-		if (le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT)

-			check_caps = 1;

+

+	if ((was_stale || le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT) &&

+	    (wanted & ~(cap->mds_wanted | newcaps))) {

+		/*

+		 * If mds is importing cap, prior cap messages that update

+		 * 'wanted' may get dropped by mds (migrate seq mismatch).

+		 *

+		 * We don't send cap message to update 'wanted' if what we

+		 * want are already issued. If mds revokes caps, cap message

+		 * that releases caps also tells mds what we want. But if

+		 * caps got revoked by mds forcedly (session stale). We may

+		 * haven't told mds what we want.

+		 */

+		check_caps = 1;

 	}

 	/* revocation, grant, or no-op? */