On Tue, Nov 12, 2019 at 07:19:58AM +0000, Junichi Nomura wrote:
> __bio_try_merge_page() may merge a page to bio without bio_full() check
> and cause bi_size overflow.
>
> The overflow typically ends up with sd_init_command() warning on zero
> segment request with call trace like this:
>
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 1986 at drivers/scsi/scsi_lib.c:1025 scsi_init_io+0x156/0x180
> CPU: 2 PID: 1986 Comm: kworker/2:1H Kdump: loaded Not tainted 5.4.0-rc7 #1
> Workqueue: kblockd blk_mq_run_work_fn
> RIP: 0010:scsi_init_io+0x156/0x180
> RSP: 0018:ffffa11487663bf0 EFLAGS: 00010246
> RAX: 00000000002be0a0 RBX: ffff8e6e9ff30118 RCX: 0000000000000000
> RDX: 00000000ffffffe1 RSI: 0000000000000000 RDI: ffff8e6e9ff30118
> RBP: ffffa11487663c18 R08: ffffa11487663d28 R09: ffff8e6e9ff30150
> R10: 0000000000000001 R11: 0000000000000000 R12: ffff8e6e9ff30000
> R13: 0000000000000001 R14: ffff8e74a1cf1800 R15: ffff8e6e9ff30000
> FS: 0000000000000000(0000) GS:ffff8e6ea7680000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fff18cf0fe8 CR3: 0000000659f0a001 CR4: 00000000001606e0
> Call Trace:
> sd_init_command+0x326/0xb40 [sd_mod]
> scsi_queue_rq+0x502/0xaa0
> ? blk_mq_get_driver_tag+0xe7/0x120
> blk_mq_dispatch_rq_list+0x256/0x5a0
> ? elv_rb_del+0x24/0x30
> ? deadline_remove_request+0x7b/0xc0
> blk_mq_do_dispatch_sched+0xa3/0x140
> blk_mq_sched_dispatch_requests+0xfb/0x170
> __blk_mq_run_hw_queue+0x81/0x130
> blk_mq_run_work_fn+0x1b/0x20
> process_one_work+0x179/0x390
> worker_thread+0x4f/0x3e0
> kthread+0x105/0x140
> ? max_active_store+0x80/0x80
> ? kthread_bind+0x20/0x20
> ret_from_fork+0x35/0x40
> ---[ end trace f9036abf5af4a4d3 ]---
> blk_update_request: I/O error, dev sdd, sector 2875552 op 0x1:(WRITE) flags 0x0 phys_seg 0 prio class 0
> XFS (sdd1): writeback error on sector 2875552
>
> __bio_try_merge_page() should check the overflow before actually doing
> merge.
>
> Fixes: 07173c3ec276c ("block: enable multipage bvecs")
> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
>
> diff --git a/block/bio.c b/block/bio.c
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -751,7 +751,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
> if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
> return false;
>
> - if (bio->bi_vcnt > 0) {
> + if (bio->bi_vcnt > 0 && !bio_full(bio, len)) {
> struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
>
> if (page_is_mergeable(bv, page, len, off, same_page)) {
>
Looks fine:
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
--
Ming
