From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 10 Jul 2013 22:41:18 +0000 (+0100)
Subject: dm: optimize use SRCU and RCU
X-Git-Tag: v3.11-rc1~20^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=83d5e5b0af907d46d241a86d9e44003b3f0accbd;p=pandora-kernel.git

dm: optimize use SRCU and RCU

This patch removes "io_lock" and "map_lock" in struct mapped_device and
"holders" in struct dm_table and replaces these mechanisms with
sleepable-rcu.

Previously, the code would call "dm_get_live_table" and "dm_table_put" to
get and release table. Now, the code is changed to call "dm_get_live_table"
and "dm_put_live_table". dm_get_live_table locks sleepable-rcu and
dm_put_live_table unlocks it.

dm_get_live_table_fast/dm_put_live_table_fast can be used instead of
dm_get_live_table/dm_put_live_table. These *_fast functions use
non-sleepable RCU, so the caller must not block between them.

If the code changes active or inactive dm table, it must call
dm_sync_table before destroying the old table.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---

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