From: Kiyoshi Ueda Date: Thu, 10 Dec 2009 23:52:16 +0000 (+0000) Subject: dm: simplify request based suspend X-Git-Tag: v2.6.33-rc1~75^2~36 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9f518b27cf682dd5155a4c1679d52cd4b5be82f2;p=pandora-kernel.git dm: simplify request based suspend The semantics of bio-based dm were changed recently in the case of suspend with "--nolockfs" but without "--noflush". Before 2.6.30, I/Os submitted before the suspend invocation were always flushed. From 2.6.30 onwards, I/Os submitted before the suspend invocation might not be flushed. (For details, see http://marc.info/?t=123994433400003&r=1&w=2) This patch brings the behaviour of request-based dm into line with bio-based dm, simplifying the code and preparing for a subsequent patch that will wait for all in_flight I/Os to complete without stopping request_queue and use dm_wait_for_completion() for it. This change in semantics simplifies the suspend code as follows: o Suspend is implemented as stopping request_queue in request-based dm, and all I/Os are queued in the request_queue even after suspend is invoked. o In the old semantics, we had to track whether I/Os were queued before or after the suspend invocation, so a special barrier-like request called 'suspend marker' was introduced. o With the new semantics, we don't need to flush any I/O so we can remove the marker and the code related to the marker handling and I/O flushing. After removing this codes, the suspend sequence is now: 1. Flush all I/Os by lock_fs() if needed. 2. Stop dispatching any I/O by stopping the request_queue. 3. Wait for all in-flight I/Os to be completed or requeued. Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon --- Reading git-diff-tree failed