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Commit 650d2a06 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Alasdair G Kergon
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dm thin: do not send discards to shared blocks



When process_discard receives a partial discard that doesn't cover a
full block, it sends this discard down to that block. Unfortunately, the
block can be shared and the discard would corrupt the other snapshots
sharing this block.

This patch detects block sharing and ends the discard with success when
sending it to the shared block.

The above change means that if the device supports discard it can't be
guaranteed that a discard request zeroes data. Therefore, we set
ti->discard_zeroes_data_unsupported.

Thin target discard support with this bug arrived in commit
104655fd (dm thin: support discards).

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Cc: stable@kernel.org
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 751f188d
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