On Fri, 21 Sep 2012 10:24:45 +0800 "Jianpeng Ma" <majianpeng@xxxxxxxxx> wrote: > On 2012-09-20 11:24 NeilBrown <neilb@xxxxxxx> Wrote: > >On Thu, 20 Sep 2012 11:04:46 +0800 "Jianpeng Ma" <majianpeng@xxxxxxxxx> wrote: > > > >> On 2012-09-20 10:51 NeilBrown <neilb@xxxxxxx> Wrote: > >> >On Sat, 15 Sep 2012 10:20:35 +0800 "Jianpeng Ma" <majianpeng@xxxxxxxxx> wrote: > >> > > >> >> In func 'ops_run_bio' if you read the dev which the last reading > >> >> of this dev didn't return,it will destrory the req/rreq'source of rdev. > >> >> It may call hung-task. > >> >> For example, for badsector or other reasons, read-operation only used > >> >> stripe instead of chunk_aligned_read. > >> >> First:stripe 0;second: stripe 8;third:stripe 16.At the block-layer,three > >> >> bios merged. > >> >> Because media error of sector from 0 to 7, the request retried. > >> >> At this time, raid5d readed stripe0 again.But it will set 'bio->next = > >> >> NULL'.So the stripe 8 and 16 didn't return. > >> >> > >> >> Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx> > >> > > >> >Hi, > >> > I'm really trying, but I cannot understand what you are saying. > >> > > >> Sorry for my bad english. > >> >I think the situation that you are describing involves a 24 sector request. > >> >This is attached to 3 stripe_heads - 8 sectors each - at address 0, 8, 16. > >> > > >> >So 'toread' on the first device of each stripe points to this bio, and > >> >bi_next is NULL. > >> > > >> >The "req" bio for each device is filled out to read one page and these three > >> >'req' bios are submitted. The block layer merges these into a single request. > >> > > >> >This request reports an error because there is a read error somewhere in the > >> >first 8 sectors. > >> > > >> Yes, > >> >So one, or maybe all, of the 'req' bios return with an error? > >> From my test, when req did not return and at the same time, the bio(stripe 0) send. > >> So this operation will set bi_next is NULL. > > > >Are you saying that we send another bio before the first one has returned? > >That shouldn't be possible as sh->count will prevent it from happening. > >While there is an outstanding request, sh->count will be >0, and until > >sh->count is 0, we won't try to send any more requests. > > > >So I still don't understand. Please try to provide as much detail as > >possible. If it is easier, write in your own language and use > >translate.google.com to convert to english. ?? > > > >Thanks, > >NeilBrown > > Hi, > i wrote a shell-script can reproduct this bug. > Note: mdadm -V > mdadm - v3.3-pre - Unreleased > > > #!/bin/bash > > declare -i count > declare -i sector > count=0 > sector=2048 > while true > do > hdparm --make-bad-sector $sector --yes-i-know-what-i-am-doing /dev/sdc > /dev/null > hdparm --make-bad-sector $sector --yes-i-know-what-i-am-doing /dev/sdd > /dev/null > hdparm --make-bad-sector $sector --yes-i-know-what-i-am-doing /dev/sde > /dev/null > let count++ > let sector+=$count*8 > if (($count == 40));then > break > fi > done > > while true > do > mdadm -S /dev/md0 > mdadm -CR /dev/md0 -l5 -c4 -n4 missing /dev/sd[cde] > dd if=/dev/md0 of=/dev/null bs=10M count=1 iflag=direct > sleep 1 > done > > > Thanks Thanks a lot! I'll try this out and see what I find. NeilBrown
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