ceph: force sending a cap update msg back to MDS for revoke op

If a client sends out a cap update dropping caps with the prior 'seq'
just before an incoming cap revoke request, then the client may drop
the revoke because it believes it's already released the requested
capabilities.

This causes the MDS to wait indefinitely for the client to respond
to the revoke. It's therefore always a good idea to ack the cap
revoke request with the bumped up 'seq'.

Currently if the cap->issued equals to the newcaps the check_caps()
will do nothing, we should force flush the caps.

Cc: stable@vger.kernel.org
Link: https://tracker.ceph.com/issues/61782
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 24 insertions, 11 deletions

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index e98aa8219303..808c9c048276 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2016,6 +2016,8 @@ bool __ceph_should_report_size(struct ceph_inode_info *ci)
  *  CHECK_CAPS_AUTHONLY - we should only check the auth cap
  *  CHECK_CAPS_FLUSH - we should flush any dirty caps immediately, without
  *    further delay.
+ *  CHECK_CAPS_FLUSH_FORCE - we should flush any caps immediately, without
+ *    further delay.
  */
 void ceph_check_caps(struct ceph_inode_info *ci, int flags)
 {
@@ -2097,7 +2099,7 @@ retry:
 	}
 
 	doutc(cl, "%p %llx.%llx file_want %s used %s dirty %s "
-	      "flushing %s issued %s revoking %s retain %s %s%s%s\n",
+	      "flushing %s issued %s revoking %s retain %s %s%s%s%s\n",
 	     inode, ceph_vinop(inode), ceph_cap_string(file_wanted),
 	     ceph_cap_string(used), ceph_cap_string(ci->i_dirty_caps),
 	     ceph_cap_string(ci->i_flushing_caps),
@@ -2105,7 +2107,8 @@ retry:
 	     ceph_cap_string(retain),
 	     (flags & CHECK_CAPS_AUTHONLY) ? " AUTHONLY" : "",
 	     (flags & CHECK_CAPS_FLUSH) ? " FLUSH" : "",
-	     (flags & CHECK_CAPS_NOINVAL) ? " NOINVAL" : "");
+	     (flags & CHECK_CAPS_NOINVAL) ? " NOINVAL" : "",
+	     (flags & CHECK_CAPS_FLUSH_FORCE) ? " FLUSH_FORCE" : "");
 
 	/*
 	 * If we no longer need to hold onto old our caps, and we may
@@ -2180,6 +2183,11 @@ retry:
 				queue_writeback = true;
 		}
 
+		if (flags & CHECK_CAPS_FLUSH_FORCE) {
+			doutc(cl, "force to flush caps\n");
+			goto ack;
+		}
+
 		if (cap == ci->i_auth_cap &&
 		    (cap->issued & CEPH_CAP_FILE_WR)) {
 			/* request larger max_size from MDS? */
@@ -3510,6 +3518,8 @@ static void handle_cap_grant(struct inode *inode,
 	bool queue_invalidate = false;
 	bool deleted_inode = false;
 	bool fill_inline = false;
+	bool revoke_wait = false;
+	int flags = 0;
 
 	/*
 	 * If there is at least one crypto block then we'll trust
@@ -3705,16 +3715,18 @@ static void handle_cap_grant(struct inode *inode,
 		      ceph_cap_string(cap->issued), ceph_cap_string(newcaps),
 		      ceph_cap_string(revoking));
 		if (S_ISREG(inode->i_mode) &&
-		    (revoking & used & CEPH_CAP_FILE_BUFFER))
+		    (revoking & used & CEPH_CAP_FILE_BUFFER)) {
 			writeback = true;  /* initiate writeback; will delay ack */
-		else if (queue_invalidate &&
+			revoke_wait = true;
+		} else if (queue_invalidate &&
 			 revoking == CEPH_CAP_FILE_CACHE &&
-			 (newcaps & CEPH_CAP_FILE_LAZYIO) == 0)
-			; /* do nothing yet, invalidation will be queued */
-		else if (cap == ci->i_auth_cap)
+			 (newcaps & CEPH_CAP_FILE_LAZYIO) == 0) {
+			revoke_wait = true; /* do nothing yet, invalidation will be queued */
+		} else if (cap == ci->i_auth_cap) {
 			check_caps = 1; /* check auth cap only */
-		else
+		} else {
 			check_caps = 2; /* check all caps */
+		}
 		/* If there is new caps, try to wake up the waiters */
 		if (~cap->issued & newcaps)
 			wake = true;
@@ -3741,8 +3753,9 @@ static void handle_cap_grant(struct inode *inode,
 	BUG_ON(cap->issued & ~cap->implemented);
 
 	/* don't let check_caps skip sending a response to MDS for revoke msgs */
-	if (le32_to_cpu(grant->op) == CEPH_CAP_OP_REVOKE) {
+	if (!revoke_wait && le32_to_cpu(grant->op) == CEPH_CAP_OP_REVOKE) {
 		cap->mds_wanted = 0;
+		flags |= CHECK_CAPS_FLUSH_FORCE;
 		if (cap == ci->i_auth_cap)
 			check_caps = 1; /* check auth cap only */
 		else
@@ -3798,9 +3811,9 @@ static void handle_cap_grant(struct inode *inode,
 
 	mutex_unlock(&session->s_mutex);
 	if (check_caps == 1)
-		ceph_check_caps(ci, CHECK_CAPS_AUTHONLY | CHECK_CAPS_NOINVAL);
+		ceph_check_caps(ci, flags | CHECK_CAPS_AUTHONLY | CHECK_CAPS_NOINVAL);
 	else if (check_caps == 2)
-		ceph_check_caps(ci, CHECK_CAPS_NOINVAL);
+		ceph_check_caps(ci, flags | CHECK_CAPS_NOINVAL);
 }
 
 /*