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author | Ilya Dryomov <idryomov@gmail.com> | 2023-09-20 19:01:03 +0200 |
---|---|---|
committer | Ilya Dryomov <idryomov@gmail.com> | 2023-09-26 10:33:19 +0200 |
commit | 0b207d02bd9ab8dcc31b262ca9f60dbc1822500d (patch) | |
tree | 24fff1b6985a84033e2f5131a684c5c873615c8d /drivers/block | |
parent | rbd: decouple parent info read-in from updating rbd_dev (diff) | |
download | linux-0b207d02bd9ab8dcc31b262ca9f60dbc1822500d.tar.xz linux-0b207d02bd9ab8dcc31b262ca9f60dbc1822500d.zip |
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.c | 22 |
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; |