linux-ext4 - Re: [dm-devel] do not disable ext4 discards on first discard failure? [was: Re: dm snapshot: ignore discards issued to the snapshot-origin target]

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Message-ID: <alpine.LFD.2.00.1105021631590.3778@dhcp-27-109.brq.redhat.com>
Date:	Mon, 2 May 2011 16:39:31 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
cc:	Lukas Czerner <lczerner@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	device-mapper development <dm-devel@...hat.com>,
	Alasdair G Kergon <agk@...hat.com>, sandeen@...hat.com,
	Mike Snitzer <snitzer@...hat.com>, DarkNovaNick@...il.com,
	linux-lvm@...hat.com, linux-ext4@...r.kernel.org
Subject: Re: [dm-devel] do not disable ext4 discards on first discard failure?
 [was: Re: dm snapshot: ignore discards issued to the snapshot-origin
 target]

On Mon, 2 May 2011, Martin K. Petersen wrote:

> >>>>> "Lukas" == Lukas Czerner <lczerner@...hat.com> writes:
> 
> Lukas> So I gave it a try. First of all the device composed of SSD and
> Lukas> spinning disk does export discard_support information properly,
> Lukas> however it also advertise discard_zeroes_data which is wrong and
> Lukas> possibly dangerous and should be fixed!
> 
> I can't reproduce this here. If I mix discard and non-discard devices
> things work correctly. discard_zeroes_data also gets cleared if I mix
> discard-capable drives where one zeroes and one doesn't.
> 
> 

[root@...m ~]# hdparm -I /dev/sdb | grep -i trim
[root@...m ~]# cat /sys/block/sdb/queue/discard_zeroes_data
0
[root@...m ~]# hdparm -I /dev/sdd | grep -i trim
           *    Data Set Management TRIM supported
           *    Deterministic read after TRIM
[root@...m ~]# cat /sys/block/sdd/queue/discard_zeroes_data 
1
[root@...m ~]# pvcreate /dev/sdd1 
  Physical volume "/dev/sdd1" successfully created
[root@...m ~]# pvcreate /dev/sdb3 
  Physical volume "/dev/sdb3" successfully created
[root@...m ~]# vgcreate vg_test /dev/sdd1 /dev/sdb3 
  Volume group "vg_test" successfully created
[root@...m ~]# lvcreate -L 3500M vg_test
  Logical volume "lvol0" created
[root@...m ~]# ls -lah /dev/mapper/vg_test-lvol0 
lrwxrwxrwx. 1 root root 7  2. kvě 10.30 /dev/mapper/vg_test-lvol0 -> ../dm-0
[root@...m ~]# cat /sys/block/dm-0/queue/discard_zeroes_data 
1
[root@...m ~]# uname -r
2.6.39-rc5-blkdev+
[root@...m ~]# cat /proc/partitions
   8       19    1951897 sdb3
   8       49    1951866 sdd1
 253        0    3584000 dm-0



So I assume it got fixes just recently ?. I'll give it a try with the
up-to-date kernel.

Thanks!
-Lukas