[PATCH] cfq-iosched: merging problem

ec8acb69 · Jens Axboe <[email protected]> · 2007-01-02 18:32:11 +01:00

Two issues:

- The final return 1 should be a return 0, otherwise comparing cfqq is
  a noop.

- bio_sync() only checks the sync flag, while rq_is_sync() checks both
  for READ and sync. The latter is what we want. Expand the bio check
  to include reads, and relax the restriction to allow merging of async
  io into sync requests.

In the future we want to clean up the SYNC logic, right now it means
both sync request (such as READ and O_DIRECT WRITE) and unplug-on-issue.
Leave that for later.

Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: ec8acb6904fabb8e741f741ec99bb1c18f2b3dee
Parents: dc3c3377

Changes

1 files changed · +3 −3

File	Status	Add	Del	Content
block/cfq-iosched.c	modified	+3	−3	View file

block/cfq-iosched.c

View file

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4b4217d..07b7062 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -577,9 +577,9 @@ static int cfq_allow_merge(request_queue_t *q, struct request *rq,
 	pid_t key;
 
 	/*
-	 * Disallow merge, if bio and rq aren't both sync or async
+	 * Disallow merge of a sync bio into an async request.
 	 */
-	if (!!bio_sync(bio) != !!rq_is_sync(rq))
+	if ((bio_data_dir(bio) == READ || bio_sync(bio)) && !rq_is_sync(rq))
 		return 0;
 
 	/*
@@ -592,7 +592,7 @@ static int cfq_allow_merge(request_queue_t *q, struct request *rq,
 	if (cfqq == RQ_CFQQ(rq))
 		return 1;
 
-	return 1;
+	return 0;
 }
 
 static inline void