On Tue, Nov 12, 2019 at 10:03:18AM +0100, Hannes Reinecke wrote:
> On 11/12/19 9:46 AM, Ming Lei wrote:
> > 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>
> >
> Oh f**k.
> That is the bug I've been hunting for years now.
The bad commit is merged in Feb. 2019, just wondering why you have hunt
it for years? :-)
--
Ming
