This prevents a race between requests with a given snap context and
header updates that free it. The osd client was already expecting the
snap context to be reference counted, since it get()s it in
ceph_osdc_build_request and put()s it when the request completes.
Also remove the second down_read()/up_read() on header_rwsem in
rbd_do_request, which wasn't actually preventing this race or
protecting any other data.
Signed-off-by: Josh Durgin <josh.durgin@xxxxxxxxxxxxx>
Reviewed-by: Alex Elder <elder@xxxxxxxxxxx>
---
drivers/block/rbd.c | 36 ++++++++++++++++++------------------
1 files changed, 18 insertions(+), 18 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index a6bbda2..988f944 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -626,7 +626,7 @@ static void rbd_header_free(struct rbd_image_header
*header)
kfree(header->object_prefix);
kfree(header->snap_sizes);
kfree(header->snap_names);
- kfree(header->snapc);
+ ceph_put_snap_context(header->snapc);
}
/*
@@ -902,13 +902,10 @@ static int rbd_do_request(struct request *rq,
dout("rbd_do_request object_name=%s ofs=%lld len=%lld\n",
object_name, len, ofs);
- down_read(&rbd_dev->header_rwsem);
-
osdc = &rbd_dev->rbd_client->client->osdc;
req = ceph_osdc_alloc_request(osdc, flags, snapc, ops,
false, GFP_NOIO, pages, bio);
if (!req) {
- up_read(&rbd_dev->header_rwsem);
ret = -ENOMEM;
goto done_pages;
}
@@ -942,7 +939,6 @@ static int rbd_do_request(struct request *rq,
snapc,
&mtime,
req->r_oid, req->r_oid_len);
- up_read(&rbd_dev->header_rwsem);
if (linger_req) {
ceph_osdc_set_request_linger(osdc, req);
@@ -1448,6 +1444,7 @@ static void rbd_rq_fn(struct request_queue *q)
u64 ofs;
int num_segs, cur_seg = 0;
struct rbd_req_coll *coll;
+ struct ceph_snap_context *snapc;
/* peek at request from block layer */
if (!rq)
@@ -1474,21 +1471,20 @@ static void rbd_rq_fn(struct request_queue *q)
spin_unlock_irq(q->queue_lock);
- if (rbd_dev->snap_id != CEPH_NOSNAP) {
- bool snap_exists;
+ down_read(&rbd_dev->header_rwsem);
- down_read(&rbd_dev->header_rwsem);
- snap_exists = rbd_dev->snap_exists;
+ if (rbd_dev->snap_id != CEPH_NOSNAP && !rbd_dev->snap_exists) {
up_read(&rbd_dev->header_rwsem);
-
- if (!snap_exists) {
- dout("request for non-existent snapshot");
- spin_lock_irq(q->queue_lock);
- __blk_end_request_all(rq, -ENXIO);
- continue;
- }
+ dout("request for non-existent snapshot");
+ spin_lock_irq(q->queue_lock);
+ __blk_end_request_all(rq, -ENXIO);
+ continue;
}
+ snapc = ceph_get_snap_context(rbd_dev->header.snapc);
+
+ up_read(&rbd_dev->header_rwsem);
+
dout("%s 0x%x bytes at 0x%llx\n",
do_write ? "write" : "read",
size, blk_rq_pos(rq) * SECTOR_SIZE);
@@ -1498,6 +1494,7 @@ static void rbd_rq_fn(struct request_queue *q)
if (!coll) {
spin_lock_irq(q->queue_lock);
__blk_end_request_all(rq, -ENOMEM);
+ ceph_put_snap_context(snapc);
continue;
}
@@ -1521,7 +1518,7 @@ static void rbd_rq_fn(struct request_queue *q)
/* init OSD command: write or read */
if (do_write)
rbd_req_write(rq, rbd_dev,
- rbd_dev->header.snapc,
+ snapc,
ofs,
op_size, bio,
coll, cur_seg);
@@ -1544,6 +1541,8 @@ next_seg:
if (bp)
bio_pair_release(bp);
spin_lock_irq(q->queue_lock);
+
+ ceph_put_snap_context(snapc);
}
}
@@ -1744,7 +1743,8 @@ static int __rbd_refresh_header(struct rbd_device
*rbd_dev)
/* rbd_dev->header.object_prefix shouldn't change */
kfree(rbd_dev->header.snap_sizes);
kfree(rbd_dev->header.snap_names);
- kfree(rbd_dev->header.snapc);
+ /* osd requests may still refer to snapc */
+ ceph_put_snap_context(rbd_dev->header.snapc);
rbd_dev->header.image_size = h.image_size;
rbd_dev->header.total_snaps = h.total_snaps;
--
1.7.5.4
--
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