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authorIlya Dryomov <idryomov@gmail.com>2023-09-20 19:01:03 +0200
committerIlya Dryomov <idryomov@gmail.com>2023-09-26 10:33:19 +0200
commit0b207d02bd9ab8dcc31b262ca9f60dbc1822500d (patch)
tree24fff1b6985a84033e2f5131a684c5c873615c8d /drivers/block
parentc10311776f0a8ddea2276df96e255625b07045a8 (diff)
rbd: take header_rwsem in rbd_dev_refresh() only when updating
rbd_dev_refresh() has been holding header_rwsem across header and parent info read-in unnecessarily for ages. With commit 870611e4877e ("rbd: get snapshot context after exclusive lock is ensured to be held"), the potential for deadlocks became much more real owning to a) header_rwsem now nesting inside lock_rwsem and b) rw_semaphores not allowing new readers after a writer is registered. For example, assuming that I/O request 1, I/O request 2 and header read-in request all target the same OSD: 1. I/O request 1 comes in and gets submitted 2. watch error occurs 3. rbd_watch_errcb() takes lock_rwsem for write, clears owner_cid and releases lock_rwsem 4. after reestablishing the watch, rbd_reregister_watch() calls rbd_dev_refresh() which takes header_rwsem for write and submits a header read-in request 5. I/O request 2 comes in: after taking lock_rwsem for read in __rbd_img_handle_request(), it blocks trying to take header_rwsem for read in rbd_img_object_requests() 6. another watch error occurs 7. rbd_watch_errcb() blocks trying to take lock_rwsem for write 8. I/O request 1 completion is received by the messenger but can't be processed because lock_rwsem won't be granted anymore 9. header read-in request completion can't be received, let alone processed, because the messenger is stranded Change rbd_dev_refresh() to take header_rwsem only for actually updating rbd_dev->header. Header and parent info read-in don't need any locking. Cc: stable@vger.kernel.org # 0b035401c570: rbd: move rbd_dev_refresh() definition Cc: stable@vger.kernel.org # 510a7330c82a: rbd: decouple header read-in from updating rbd_dev->header Cc: stable@vger.kernel.org # c10311776f0a: rbd: decouple parent info read-in from updating rbd_dev Cc: stable@vger.kernel.org Fixes: 870611e4877e ("rbd: get snapshot context after exclusive lock is ensured to be held") Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/rbd.c22
1 files changed, 11 insertions, 11 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index d62a0298c890..a999b698b131 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -6986,7 +6986,14 @@ static void rbd_dev_update_header(struct rbd_device *rbd_dev,
rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
rbd_assert(rbd_dev->header.object_prefix); /* !first_time */
- rbd_dev->header.image_size = header->image_size;
+ if (rbd_dev->header.image_size != header->image_size) {
+ rbd_dev->header.image_size = header->image_size;
+
+ if (!rbd_is_snap(rbd_dev)) {
+ rbd_dev->mapping.size = header->image_size;
+ rbd_dev_update_size(rbd_dev);
+ }
+ }
ceph_put_snap_context(rbd_dev->header.snapc);
rbd_dev->header.snapc = header->snapc;
@@ -7044,11 +7051,9 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
{
struct rbd_image_header header = { 0 };
struct parent_image_info pii = { 0 };
- u64 mapping_size;
int ret;
- down_write(&rbd_dev->header_rwsem);
- mapping_size = rbd_dev->mapping.size;
+ dout("%s rbd_dev %p\n", __func__, rbd_dev);
ret = rbd_dev_header_info(rbd_dev, &header, false);
if (ret)
@@ -7064,18 +7069,13 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
goto out;
}
+ down_write(&rbd_dev->header_rwsem);
rbd_dev_update_header(rbd_dev, &header);
if (rbd_dev->parent)
rbd_dev_update_parent(rbd_dev, &pii);
-
- rbd_assert(!rbd_is_snap(rbd_dev));
- rbd_dev->mapping.size = rbd_dev->header.image_size;
-
-out:
up_write(&rbd_dev->header_rwsem);
- if (!ret && mapping_size != rbd_dev->mapping.size)
- rbd_dev_update_size(rbd_dev);
+out:
rbd_parent_info_cleanup(&pii);
rbd_image_header_cleanup(&header);
return ret;