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authorJens Axboe <jens.axboe@oracle.com>2006-12-20 11:04:12 +0100
committerJens Axboe <jens.axboe@oracle.com>2006-12-20 11:04:12 +0100
commitda775265021b61d5eb81df155e36cb0810f6df53 (patch)
treef7b28991b281a8c581bd3ab0bb470e158ae2206f /include
parent8e5cfc45e7527eb5c8a9a22d56a7b9227e7c0913 (diff)
[PATCH] cfq-iosched: don't allow sync merges across queues
Currently we allow any merge, even if the io originates from different processes. This can cause really bad starvation and unfairness, if those ios happen to be synchronous (reads or direct writes). So add a allow_merge hook to the io scheduler ops, so an io scheduler can help decide whether a bio/process combination may be merged with an existing request. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/elevator.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index a24931d2440..e88fcbc77f8 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -12,6 +12,8 @@ typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struc
typedef void (elevator_merged_fn) (request_queue_t *, struct request *, int);
+typedef int (elevator_allow_merge_fn) (request_queue_t *, struct request *, struct bio *);
+
typedef int (elevator_dispatch_fn) (request_queue_t *, int);
typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
@@ -33,6 +35,7 @@ struct elevator_ops
elevator_merge_fn *elevator_merge_fn;
elevator_merged_fn *elevator_merged_fn;
elevator_merge_req_fn *elevator_merge_req_fn;
+ elevator_allow_merge_fn *elevator_allow_merge_fn;
elevator_dispatch_fn *elevator_dispatch_fn;
elevator_add_req_fn *elevator_add_req_fn;