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Re: [dm-devel] Ext4 and xfs problems in dm-thin on allocation and discard



On 06/19/12 15:30, Mike Snitzer wrote:
I don't recall Spelic saying anything about EOPNOTSUPP. So what has made you zero in on an -EOPNOTSUPP return (which should not be happening)?

Exactly: I do not know if EOPNOTSUPP is being returned or not.

If this helps, I have configured dm-thin via lvm2
  LVM version:     2.02.95(2) (2012-03-06)
  Library version: 1.02.74 (2012-03-06)
  Driver version:  4.22.0

from dmsetup table I only see one option : "skip_block_zeroing", if and only if I configure it with -Zn . I do not see anything regarding ignore_discard

vg1-pooltry1-tpool: 0 20971520 thin-pool 252:1 252:2 2048 0 1 skip_block_zeroing
     vg1-pooltry1_tdata: 0 20971520 linear 9:20 62922752
     vg1-pooltry1_tmeta: 0 8192 linear 9:20 83894272
     vg1-thinlv1: 0 31457280 thin 252:3 1


and in dmesg:
[ 33.685200] device-mapper: thin: Discard unsupported by data device (dm-2): Disabling discard passdown. [ 33.709586] device-mapper: thin: Discard unsupported by data device (dm-6): Disabling discard passdown.


I do not know what is the mechanism for which xfs cannot unmap blocks from dm-thin, but it really can't. If anyone has dm-thin installed he can try. This is 100% reproducible for me.



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