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[PATCH] Fix current_io_context() vs set_task_ioprio() race

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I know nothing about io scheduler, but I suspect set_task_ioprio() is not safe.

current_io_context() initializes "struct io_context", then sets ->io_context.
set_task_ioprio() running on another cpu may see the changes out of order, so
->set_ioprio(ioc) may use io_context which was not initialized properly.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Oleg Nesterov 2006-08-21 08:34:15 +02:00 committed by Jens Axboe
parent 78bd4d484f
commit 9f83e45eb5
2 changed files with 5 additions and 0 deletions
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2
block/ll_rw_blk.c
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@ -3628,6 +3628,8 @@ struct io_context *current_io_context(gfp_t gfp_flags)
ret->nr_batch_requests = 0; /* because this is 0 */
ret->aic = NULL;
ret->cic_root.rb_node = NULL;
/* make sure set_task_ioprio() sees the settings above */
smp_wmb();
tsk->io_context = ret;
}

3
fs/ioprio.c
View File

@ -44,6 +44,9 @@ static int set_task_ioprio(struct task_struct *task, int ioprio)
task->ioprio = ioprio;
ioc = task->io_context;
/* see wmb() in current_io_context() */
smp_read_barrier_depends();
if (ioc && ioc->set_ioprio)
ioc->set_ioprio(ioc, ioprio);