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authorVasily Tarasov <vtaras@openvz.org>2006-10-12 15:09:51 +0200
committerJens Axboe <jens.axboe@oracle.com>2006-10-12 15:09:51 +0200
commitd58cdfb89ce0c6bd5f81ae931a984ef298dbda20 (patch)
treef872c5b474411002f0905ebe702e752292f1cc21 /fs/ioprio.c
parentcea2885a2e989d1dc19af1fc991717b33b7d1456 (diff)
downloadlinux-d58cdfb89ce0c6bd5f81ae931a984ef298dbda20.tar.gz
[PATCH] block layer: ioprio_best function fix
Currently ioprio_best function first checks wethere aioprio or bioprio equals IOPRIO_CLASS_NONE (ioprio_valid() macros does that) and if it is so it returns bioprio/aioprio appropriately. Thus the next four lines, that set aclass/bclass to IOPRIO_CLASS_BE, if aclass/bclass == IOPRIO_CLASS_NONE, are never executed. The second problem: if aioprio from class IOPRIO_CLASS_NONE and bioprio from class IOPRIO_CLASS_IDLE are passed to ioprio_best function, it will return IOPRIO_CLASS_IDLE. It means that during __make_request we can merge two requests and set the priority of merged request to IDLE, while one of the initial requests originates from a process with NONE (default) priority. So we can get a situation when a process with default ioprio will experience IO starvation, while there is no process from real-time class in the system. Just removing ioprio_valid check should correct situation. Signed-off-by: Vasily Tarasov <vtaras@openvz.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'fs/ioprio.c')
-rw-r--r--fs/ioprio.c5
1 files changed, 0 insertions, 5 deletions
diff --git a/fs/ioprio.c b/fs/ioprio.c
index 6dc6721d9e8..89e8da112a7 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -150,11 +150,6 @@ int ioprio_best(unsigned short aprio, unsigned short bprio)
unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);
unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);
- if (!ioprio_valid(aprio))
- return bprio;
- if (!ioprio_valid(bprio))
- return aprio;
-
if (aclass == IOPRIO_CLASS_NONE)
aclass = IOPRIO_CLASS_BE;
if (bclass == IOPRIO_CLASS_NONE)