Because blkcg_exit_queue() is now called from inside blk_cleanup_queue()
it is no longer safe to access cgroup information during or after the
blk_cleanup_queue() call. Hence protect the generic_make_request_checks()
call with blk_queue_enter() / blk_queue_exit().
Reported-by: Ming Lei <ming....@redhat.com>
Fixes: a063057d7c73 ("block: Fix a race between request queue removal and the
block cgroup controller")
Signed-off-by: Bart Van Assche <bart.vanass...@wdc.com>
Cc: Ming Lei <ming....@redhat.com>
Cc: Joseph Qi <joseph...@linux.alibaba.com>
---
Changes compared to v2: converted two ternary expressions into if-statements.
Changes compared to v1: guarded the blk_queue_exit() inside the loop with "if
(q)".
block/blk-core.c | 35 +++++++++++++++++++++++++++++------
1 file changed, 29 insertions(+), 6 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 34e2f2227fd9..39308e874ffa 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2386,8 +2386,20 @@ blk_qc_t generic_make_request(struct bio *bio)
* yet.
*/
struct bio_list bio_list_on_stack[2];
+ blk_mq_req_flags_t flags = 0;
+ struct request_queue *q = bio->bi_disk->queue;
blk_qc_t ret = BLK_QC_T_NONE;
+ if (bio->bi_opf & REQ_NOWAIT)
+ flags = BLK_MQ_REQ_NOWAIT;
+ if (blk_queue_enter(q, flags) < 0) {
+ if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT))
+ bio_wouldblock_error(bio);
+ else
+ bio_io_error(bio);
+ return ret;
+ }
+
if (!generic_make_request_checks(bio))
goto out;
@@ -2424,11 +2436,22 @@ blk_qc_t generic_make_request(struct bio *bio)
bio_list_init(&bio_list_on_stack[0]);
current->bio_list = bio_list_on_stack;
do {
- struct request_queue *q = bio->bi_disk->queue;
- blk_mq_req_flags_t flags = bio->bi_opf & REQ_NOWAIT ?
- BLK_MQ_REQ_NOWAIT : 0;
+ bool enter_succeeded = true;
+
+ if (unlikely(q != bio->bi_disk->queue)) {
+ if (q)
+ blk_queue_exit(q);
+ q = bio->bi_disk->queue;
+ flags = 0;
+ if (bio->bi_opf & REQ_NOWAIT)
+ flags = BLK_MQ_REQ_NOWAIT;
+ if (blk_queue_enter(q, flags) < 0) {
+ enter_succeeded = false;
+ q = NULL;
+ }
+ }
- if (likely(blk_queue_enter(q, flags) == 0)) {
+ if (enter_succeeded) {
struct bio_list lower, same;
/* Create a fresh bio_list for all subordinate requests
*/
@@ -2436,8 +2459,6 @@ blk_qc_t generic_make_request(struct bio *bio)
bio_list_init(&bio_list_on_stack[0]);
ret = q->make_request_fn(q, bio);
- blk_queue_exit(q);
-
/* sort new bios into those for a lower level
* and those for the same level
*/
@@ -2464,6 +2485,8 @@ blk_qc_t generic_make_request(struct bio *bio)
current->bio_list = NULL; /* deactivate */
out:
+ if (q)
+ blk_queue_exit(q);
return ret;
}
EXPORT_SYMBOL(generic_make_request);
--
2.16.2
