Commit 1874198 ("blk-mq: rework flush sequencing logic") switched ->flush_rq from being an embedded member of the request_queue structure to being dynamically allocated in blk_init_queue_node(). Request-based DM multipath doesn't use blk_init_queue_node(), instead it uses blk_alloc_queue_node() + blk_init_allocated_queue(). Because commit 1874198 placed the dynamic allocation of ->flush_rq in blk_init_queue_node() any flush issued to a dm-mpath device would crash with a NULL pointer, e.g.: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] blk_rq_init+0x1e/0xb0 PGD bb3c7067 PUD bb01d067 PMD 0 Oops: 0002 [#1] SMP ... CPU: 5 PID: 5028 Comm: dt Tainted: G W O 3.14.0-rc3.snitm+ #10 ... task: ffff88032fb270e0 ti: ffff880079564000 task.ti: ffff880079564000 RIP: 0010:[] [] blk_rq_init+0x1e/0xb0 RSP: 0018:ffff880079565c98 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000030 RDX: ffff880260c74048 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff880079565ca8 R08: ffff880260aa1e98 R09: 0000000000000001 R10: ffff88032fa78500 R11: 0000000000000246 R12: 0000000000000000 R13: ffff880260aa1de8 R14: 0000000000000650 R15: 0000000000000000 FS: 00007f8d36a2a700(0000) GS:ffff88033fca0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000079b36000 CR4: 00000000000007e0 Stack: 0000000000000000 ffff880260c74048 ffff880079565cd8 ffffffff81257a47 ffff880260aa1de8 ffff880260c74048 0000000000000001 0000000000000000 ffff880079565d08 ffffffff81257c2d 0000000000000000 ffff880260aa1de8 Call Trace: [] blk_flush_complete_seq+0x2d7/0x2e0 [] blk_insert_flush+0x1dd/0x210 [] __elv_add_request+0x1f9/0x320 [] ? blk_account_io_start+0x111/0x190 [] blk_queue_bio+0x25b/0x330 [] dm_request+0x35/0x40 [dm_mod] [] generic_make_request+0xc0/0x100 [] submit_bio+0x73/0x140 [] submit_bio_wait+0x5d/0x80 [] blkdev_issue_flush+0x78/0xa0 [] blkdev_fsync+0x3f/0x60 [] vfs_fsync_range+0x1e/0x20 [] vfs_fsync+0x1c/0x20 [] do_fsync+0x41/0x80 [] ? SyS_lseek+0x7e/0x80 [] SyS_fsync+0x10/0x20 [] system_call_fastpath+0x16/0x1b Fix this by moving the ->flush_rq allocation from blk_init_queue_node() to blk_init_allocated_queue(). blk_init_queue_node() also calls blk_init_allocated_queue() so this change is functionality equivalent for all blk_init_queue_node() callers. Reported-by: Hannes Reinecke Reported-by: Christoph Hellwig Signed-off-by: Mike Snitzer Signed-off-by: Jens Axboe --- block/blk-core.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 853f927..4cd5ffc 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -693,20 +693,11 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id) if (!uninit_q) return NULL; - uninit_q->flush_rq = kzalloc(sizeof(struct request), GFP_KERNEL); - if (!uninit_q->flush_rq) - goto out_cleanup_queue; - q = blk_init_allocated_queue(uninit_q, rfn, lock); if (!q) - goto out_free_flush_rq; - return q; + blk_cleanup_queue(uninit_q); -out_free_flush_rq: - kfree(uninit_q->flush_rq); -out_cleanup_queue: - blk_cleanup_queue(uninit_q); - return NULL; + return q; } EXPORT_SYMBOL(blk_init_queue_node); @@ -717,6 +708,10 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn, if (!q) return NULL; + q->flush_rq = kzalloc(sizeof(struct request), GFP_KERNEL); + if (!q->flush_rq) + return NULL; + if (blk_init_rl(&q->root_rl, q, GFP_KERNEL)) return NULL; -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/