Merge tag 'ceph-for-6.11-rc2' of https://github.com/ceph/ceph-client

Pull ceph fix from Ilya Dryomov:
 "A fix for a potential hang in the MDS when cap revocation races with
  the client releasing the caps in question, marked for stable"

* tag 'ceph-for-6.11-rc2' of https://github.com/ceph/ceph-client:
  ceph: force sending a cap update msg back to MDS for revoke op

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 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags)
 	}
 
 	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 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags)
 	     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 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags)
 				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);
 }
 
 /*

fs/ceph/super.h

@@ -203,6 +203,7 @@ struct ceph_cap {
 #define CHECK_CAPS_AUTHONLY     1  /* only check auth cap */
 #define CHECK_CAPS_FLUSH        2  /* flush any dirty caps */
 #define CHECK_CAPS_NOINVAL      4  /* don't invalidate pagecache */
+#define CHECK_CAPS_FLUSH_FORCE  8  /* force flush any caps */
 
 struct ceph_cap_flush {
 	u64 tid;