On Tue, 22 Nov 2011 01:50:37 +0100 Michał Mirosław <mirq-linux@xxxxxxxxxxxx> wrote: > On Mon, Nov 21, 2011 at 07:27:45PM +1100, NeilBrown wrote: > > On Mon, 21 Nov 2011 08:04:30 +0100 James Bottomley > > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > On Mon, 2011-11-21 at 12:37 +1100, NeilBrown wrote: > > > > Thank for the report. > > > > However as this crash is clearly in the SCSI layer it makes sense to reported > > > > it to linux-scsi - so I have cc:ed this reply there. > > > > > > > > On Sat, 19 Nov 2011 14:41:39 +0100 Michał Mirosław <mirq-linux@xxxxxxxxxxxx> > > > > wrote: > > > > > I get following BUG_ON tripped while booting, before rootfs is mounted by > > > > > Debian's initrd. This started to happen for kernels since sometime > > > > > during 3.1-rcX. > > > > > > > > > > [ 6.246170] ------------[ cut here ]------------ > > > > > [ 6.246246] kernel BUG at /mnt/src-tmp/jaja/git/qmqm/drivers/scsi/scsi_lib.c:1153! > > > > > > I can tell you what it is: > > > > > > /* > > > * Filesystem requests must transfer data. > > > */ > > > BUG_ON(!req->nr_phys_segments); > > > > > > But the fault is in the layer above SCSI. It means something sent a > > > request with REQ_TYPE_FS but no actual data attached ... this is > > > supposed to be impossible, hence the bug on. > > > > Thanks.... that sounds strangely familiar, but I cannot be sure and google > > doesn't help. > > > > Michał: what are you using on the RAID1 - some filesystem (which one)or swap or something else? > > The whole stack is: ext4 over lvm over dm-crypt over md-raid1 over SATA > drives. The boot doesn't survive to the point where the initrd script asks > for md-crypt's key password. > That gives us lots of room for pointing the finger of blame, doesn't it? I think it is -> his problem. :-) From the md part of the stack trace it looks most like a write request. It could be a retried read, but that is extremely unlike that early in boot. So presumably it is some sort of zero-length REQ_FLUSH or something like that. md/raid1 will just pass those unchanged down. My guess is that ext4 is generating this and something in the stack is stripping the REQ_FLUSH .... though why it even tries before asking for a password is beyond me. Maybe someone of dm-devel can help? If not we might need to try a debugging patch like this: diff --git a/block/blk-core.c b/block/blk-core.c index f43c8a5..59cb2ad 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1560,7 +1560,7 @@ generic_make_request_checks(struct bio *bio) goto end_io; } } - + WARN_ON(((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && nr_sectors == 0); if ((bio->bi_rw & REQ_DISCARD) && (!blk_queue_discard(q) || ((bio->bi_rw & REQ_SECURE) && NeilBrown
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