Comment 5 for bug 1082325

Description of problem:

If user enables issue_discards=1 and runs PV move command, and underlaying devices supports discard he will loose data from move chunks.

Here is short log of what is going on:
(chunk is release and discarded prior it's move)

#metadata/lv_manip.c:3013 Creating logical volume pvmove0
#metadata/lv_manip.c:3938 Inserting layer pvmove0 for segments of lvol0 on /dev/loop0
#metadata/lv_manip.c:3852 Matched PE range /dev/loop0:0-126 against /dev/loop0 0 len 1
#metadata/lv_manip.c:3798 Inserting /dev/loop0:0-0 of test/lvol0
#libdm-config.c:853 Setting devices/issue_discards to 1
#device/device.c:428 Device /dev/loop0 queue/discard_max_bytes is 4294966784 bytes.
#device/device.c:428 Device /dev/loop0 queue/discard_granularity is 4096 bytes.
#metadata/pv_manip.c:223 Discarding 1 extents offset 2048 sectors on /dev/loop0.
#device/dev-io.c:577 Closed /dev/loop0
#device/dev-io.c:524 Opened /dev/loop0 RW O_DIRECT
#device/dev-io.c:318 Discarding 4194304 bytes offset 1048576 bytes on /dev/loop0.
#metadata/lv_manip.c:432 Stack lvol0:0[0] on LV pvmove0:0
#metadata/lv_manip.c:86 Adding lvol0:0 as an user of pvmove0
#pvmove.c:164 Moving 1 extents of logical volume test/lvol0
#mm/pool-fast.c:59 Created fast mempool allocation at 0x16f1810
#libdm-config.c:866 allocation/mirror_logs_require_separate_pvs not found in config: defaulting to 0
#libdm-config.c:866 allocation/maximise_cling not found in config: defaulting to 1
#metadata/pv_map.c:55 Allowing allocation on /dev/loop1 start PE 0 length 127
#metadata/lv_manip.c:967 Parallel PVs at LE 0 length 1: /dev/loop0
#metadata/lv_manip.c:2023 Trying allocation using contiguous policy.
#metadata/lv_manip.c:1635 Still need 1 total extents:
#metadata/lv_manip.c:1638 1 (1 data/0 parity) parallel areas of 1 extents each
#metadata/lv_manip.c:1640 0 mirror logs of 0 extents each
#metadata/lv_manip.c:1329 Considering allocation area 0 as /dev/loop1 start PE 0 length 1 leaving 126.
#metadata/lv_manip.c:1112 Allocating parallel area 0 on /dev/loop1 start PE 0 length 1.

Version-Release number of selected component (if applicable):
lvm 2.02.96

How reproducible:

Steps to Reproduce:
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Actual results:

Expected results:

Additional info:

As a workaround - set issue_discards=0