From: Mikulas Patocka <mpatocka@redhat.com>
Date: Thu, 10 Dec 2009 23:52:34 +0000 (+0000)
Subject: dm snapshot: trigger exceptions in remaining snapshots during merge
X-Git-Tag: v2.6.33-rc1~75^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=73dfd078cf8bfee4018fb22f1e2a24f2e05b69dc;p=pandora-kernel.git

dm snapshot: trigger exceptions in remaining snapshots during merge

When there is one merging snapshot and other non-merging snapshots,
snapshot_merge_process() must make exceptions in the non-merging
snapshots.

Use a sequence count to resolve the race between I/O to chunks that are
about to be merged.  The count increases each time an exception
reallocation finishes.  Use wait_event() to wait until the count
changes.

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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