Dne 3.4.2018 v 06:07 Dennis Yang napsal(a):
Hi,
Recently we have came across an issue that dm-thin pool will be
switched to READ_ONLY mode because dm_pool_alloc_data_block() returns
-ENOSPC. AFAIK, this should not happen since alloc_data_block() will
check if there is any free space (and commit metadata if it first
reports no free space) before it allocates pool block. In addition,
total virtual space of all thin volumes is smaller than the pool
physical space in my testing environment which makes pool impossible
to run out of space.
Hi
Which kernel has been used during testing - was this upstream ?
(4.16??)
This issue could be easily reproduced by the following steps.
1) Create a thin pool and a slightly smaller thin volume
sudo dmsetup create meta --table "0 40000000 linear /dev/sdf 0"
maximum metadadata size is only ~16G (... 33161216 blocks or so)
sudo dmsetup create data --table "0 10240000 linear /dev/md125 0"
sudo dd if=/dev/zero of=/dev/mapper/meta bs=1M count=1
sudo dmsetup create pool --table "0 10240000 thin-pool /dev/mapper/meta /dev/mapper/data 1024 0 2 skip_block_zeroing error_if_no_space"
sudo dmsetup message pool 0 "create_thin 0"
sudo dmsetup create thin --table "0 10238976 thin /dev/mapper/pool 0"
I've tried to reproduce with smaller LVs - but haven't managed yet:
vg-LV1: 0 102384 thin 253:4 1
vg-pool: 0 102400 linear 253:4 0
vg-pool-tpool: 0 102400 thin-pool 253:2 253:3 128 0 2 skip_block_zeroing
error_if_no_space
vg-pool_tdata: 0 102400 linear 253:0 10240
vg-pool_tmeta: 0 8192 linear 253:1 2048
Regards
Zdenek
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