dm snapshot: avoid allocating exceptions in merge

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The snapshot-merge target should not allocate new exceptions because the
intent is to merge all of its exceptions as quickly and safely as
possible.

This patch introduces the snapshot-merge mapping function and updates
__origin_write() so that it doesn't allocate exceptions on any snapshots
that are being merged.

If a write request to a merging snapshot device is to be dispatched
directly to the origin (because the chunk is not remapped or was already
merged), snapshot_merge_map() must make exceptions in other snapshots so
calls do_origin().

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

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This commit is contained in:

Mikulas Patocka 2009-12-10 23:52:31 +00:00 • committed by Alasdair G Kergon

parent 515ad66cc4

commit 3452c2a1eb

1 changed files with 56 additions and 1 deletions

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drivers/md/dm-snap.c

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