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From: Jeff Layton <jlayton@kernel.org>
To: ceph-devel@vger.kernel.org, idryomov@gmail.com
Subject: [PATCH 2/3] ceph: clean up locking annotation for ceph_get_snap_realm and __lookup_snap_realm
Date: Thu,  3 Jun 2021 12:52:30 -0400	[thread overview]
Message-ID: <20210603165231.110559-3-jlayton@kernel.org> (raw)
In-Reply-To: <20210603165231.110559-1-jlayton@kernel.org>

They both say that the snap_rwsem must be held for write, but I don't
see any real reason for it, and it's not currently always called that
way.

The lookup is just walking the rbtree, so holding it for read should be
fine there. The "get" is bumping the refcount and (possibly) removing
it from the empty list. I see no need to hold the snap_rwsem for write
for that.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/snap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index bc6c33d485e6..f8cac2abab3f 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -60,12 +60,12 @@
 /*
  * increase ref count for the realm
  *
- * caller must hold snap_rwsem for write.
+ * caller must hold snap_rwsem.
  */
 void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
 			 struct ceph_snap_realm *realm)
 {
-	lockdep_assert_held_write(&mdsc->snap_rwsem);
+	lockdep_assert_held(&mdsc->snap_rwsem);
 
 	dout("get_realm %p %d -> %d\n", realm,
 	     atomic_read(&realm->nref), atomic_read(&realm->nref)+1);
@@ -139,7 +139,7 @@ static struct ceph_snap_realm *ceph_create_snap_realm(
 /*
  * lookup the realm rooted at @ino.
  *
- * caller must hold snap_rwsem for write.
+ * caller must hold snap_rwsem.
  */
 static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
 						   u64 ino)
@@ -147,7 +147,7 @@ static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
 	struct rb_node *n = mdsc->snap_realms.rb_node;
 	struct ceph_snap_realm *r;
 
-	lockdep_assert_held_write(&mdsc->snap_rwsem);
+	lockdep_assert_held(&mdsc->snap_rwsem);
 
 	while (n) {
 		r = rb_entry(n, struct ceph_snap_realm, node);
-- 
2.31.1


  parent reply	other threads:[~2021-06-03 16:52 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03 16:52 [PATCH 0/3] ceph: locking fixes for snaprealm handling Jeff Layton
2021-06-03 16:52 ` [PATCH 1/3] ceph: add some lockdep assertions around " Jeff Layton
2021-06-21 20:05   ` Ilya Dryomov
2021-06-21 20:51     ` Jeff Layton
2021-06-21 21:27       ` Ilya Dryomov
2021-06-03 16:52 ` Jeff Layton [this message]
2021-06-21 20:48   ` [PATCH 2/3] ceph: clean up locking annotation for ceph_get_snap_realm and __lookup_snap_realm Ilya Dryomov
2021-06-03 16:52 ` [PATCH 3/3] ceph: must hold snap_rwsem when filling inode for async create Jeff Layton
2021-06-21 19:45   ` Ilya Dryomov

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