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Commit ac0b1bc1 authored by Benjamin LaHaise's avatar Benjamin LaHaise Committed by Linus Torvalds
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[PATCH] aio: kiocb locking to serialise retry and cancel 



Implement a per-kiocb lock to serialise retry operations and cancel.  This
is done using wait_on_bit_lock() on the KIF_LOCKED bit of kiocb->ki_flags.
Also, make the cancellation path lock the kiocb and subsequently release
all references to it if the cancel was successful.  This version includes a
fix for the deadlock with __aio_run_iocbs.

Signed-off-by: default avatarBenjamin LaHaise <bcrl@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8f58202b

fs/aio.c

+25 −4
Original line number Diff line number Diff line
@@ -546,6 +546,24 @@ struct kioctx *lookup_ioctx(unsigned long ctx_id) 
	return ioctx;

}



static int lock_kiocb_action(void *param)

{

	schedule();

	return 0;

}



static inline void lock_kiocb(struct kiocb *iocb)

{

	wait_on_bit_lock(&iocb->ki_flags, KIF_LOCKED, lock_kiocb_action,

			 TASK_UNINTERRUPTIBLE);

}



static inline void unlock_kiocb(struct kiocb *iocb)

{

	kiocbClearLocked(iocb);

	wake_up_bit(&iocb->ki_flags, KIF_LOCKED);

}



/*

 * use_mm

 *	Makes the calling kernel thread take on the specified
@@ -786,7 +804,9 @@ static int __aio_run_iocbs(struct kioctx *ctx) 
		 * Hold an extra reference while retrying i/o.

		 */

		iocb->ki_users++;       /* grab extra reference */

		lock_kiocb(iocb);

		aio_run_iocb(iocb);

		unlock_kiocb(iocb);

		if (__aio_put_req(ctx, iocb))  /* drop extra ref */

			put_ioctx(ctx);

 	}
@@ -1527,10 +1547,9 @@ int fastcall io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, 
		goto out_put_req;



	spin_lock_irq(&ctx->ctx_lock);

	if (likely(list_empty(&ctx->run_list))) {

	aio_run_iocb(req);

	} else {

		list_add_tail(&req->ki_run_list, &ctx->run_list);

	unlock_kiocb(req);

	if (!list_empty(&ctx->run_list)) {

		/* drain the run list */

		while (__aio_run_iocbs(ctx))

			;
@@ -1661,6 +1680,7 @@ asmlinkage long sys_io_cancel(aio_context_t ctx_id, struct iocb __user *iocb, 
	if (NULL != cancel) {

		struct io_event tmp;

		pr_debug("calling cancel\n");

		lock_kiocb(kiocb);

		memset(&tmp, 0, sizeof(tmp));

		tmp.obj = (u64)(unsigned long)kiocb->ki_obj.user;

		tmp.data = kiocb->ki_user_data;
@@ -1672,6 +1692,7 @@ asmlinkage long sys_io_cancel(aio_context_t ctx_id, struct iocb __user *iocb, 
			if (copy_to_user(result, &tmp, sizeof(tmp)))

				ret = -EFAULT;

		}

		unlock_kiocb(kiocb);

	} else

		ret = -EINVAL;