[PATCH 2/8] aio: disable retry

[Zach Brown <zach.brown@oracle.com>]

This patch ensures that aio ops won't be retried.  Code that uses EIOCBRETRY
will fail to build and modules that reference kick_iocb() won't load.

This simplifies an upcoming patch by ensuring that it doesn't have to support
aio ops that retry.  Further patches could remove much more of fs/aio.c if we
chose to remove retry-based aio support.

Signed-off-by: Zach Brown <zach.brown@oracle.com>
---
 fs/aio.c              |   82 +-----------------------------------------------
 fs/ocfs2/dlmglue.c    |    2 +-
 fs/read_write.c       |   34 ++------------------
 include/linux/aio.h   |   11 ------
 include/linux/errno.h |    1 -
 5 files changed, 6 insertions(+), 124 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 02a2c93..2406981 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -697,37 +697,12 @@ static ssize_t aio_run_iocb(struct kiocb *iocb)
 	 */
 	ret = retry(iocb);
 
-	if (ret != -EIOCBRETRY && ret != -EIOCBQUEUED) {
+	if (ret != -EIOCBQUEUED) {
 		BUG_ON(!list_empty(&iocb->ki_wait.task_list));
 		aio_complete(iocb, ret, 0);
 	}
 out:
 	spin_lock_irq(&ctx->ctx_lock);
-
-	if (-EIOCBRETRY == ret) {
-		/*
-		 * OK, now that we are done with this iteration
-		 * and know that there is more left to go,
-		 * this is where we let go so that a subsequent
-		 * "kick" can start the next iteration
-		 */
-
-		/* will make __queue_kicked_iocb succeed from here on */
-		INIT_LIST_HEAD(&iocb->ki_run_list);
-		/* we must queue the next iteration ourselves, if it
-		 * has already been kicked */
-		if (kiocbIsKicked(iocb)) {
-			__queue_kicked_iocb(iocb);
-
-			/*
-			 * __queue_kicked_iocb will always return 1 here, because
-			 * iocb->ki_run_list is empty at this point so it should
-			 * be safe to unconditionally queue the context into the
-			 * work queue.
-			 */
-			aio_queue_work(ctx);
-		}
-	}
 	return ret;
 }
 
@@ -840,56 +815,6 @@ static void aio_kick_handler(struct work_struct *work)
 		queue_delayed_work(aio_wq, &ctx->wq, 0);
 }
 
-
-/*
- * Called by kick_iocb to queue the kiocb for retry
- * and if required activate the aio work queue to process
- * it
- */
-static void try_queue_kicked_iocb(struct kiocb *iocb)
-{
- 	struct kioctx	*ctx = iocb->ki_ctx;
-	unsigned long flags;
-	int run = 0;
-
-	/* We're supposed to be the only path putting the iocb back on the run
-	 * list.  If we find that the iocb is *back* on a wait queue already
-	 * than retry has happened before we could queue the iocb.  This also
-	 * means that the retry could have completed and freed our iocb, no
-	 * good. */
-	BUG_ON((!list_empty(&iocb->ki_wait.task_list)));
-
-	spin_lock_irqsave(&ctx->ctx_lock, flags);
-	/* set this inside the lock so that we can't race with aio_run_iocb()
-	 * testing it and putting the iocb on the run list under the lock */
-	if (!kiocbTryKick(iocb))
-		run = __queue_kicked_iocb(iocb);
-	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
-	if (run)
-		aio_queue_work(ctx);
-}
-
-/*
- * kick_iocb:
- *      Called typically from a wait queue callback context
- *      (aio_wake_function) to trigger a retry of the iocb.
- *      The retry is usually executed by aio workqueue
- *      threads (See aio_kick_handler).
- */
-void kick_iocb(struct kiocb *iocb)
-{
-	/* sync iocbs are easy: they can only ever be executing from a 
-	 * single context. */
-	if (is_sync_kiocb(iocb)) {
-		kiocbSetKicked(iocb);
-	        wake_up_process(iocb->ki_obj.tsk);
-		return;
-	}
-
-	try_queue_kicked_iocb(iocb);
-}
-EXPORT_SYMBOL(kick_iocb);
-
 /* aio_complete
  *	Called when the io request on the given iocb is complete.
  *	Returns true if this is the last user of the request.  The 
@@ -1352,7 +1277,7 @@ static ssize_t aio_rw_vect_retry(struct kiocb *iocb)
 	/* If we managed to write some out we return that, rather than
 	 * the eventual error. */
 	if (opcode == IOCB_CMD_PWRITEV
-	    && ret < 0 && ret != -EIOCBQUEUED && ret != -EIOCBRETRY
+	    && ret < 0 && ret != -EIOCBQUEUED
 	    && iocb->ki_nbytes - iocb->ki_left)
 		ret = iocb->ki_nbytes - iocb->ki_left;
 
@@ -1524,10 +1449,7 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb)
 static int aio_wake_function(wait_queue_t *wait, unsigned mode,
 			     int sync, void *key)
 {
-	struct kiocb *iocb = container_of(wait, struct kiocb, ki_wait);
-
 	list_del_init(&wait->task_list);
-	kick_iocb(iocb);
 	return 1;
 }
 
diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 0d38d67..fb7bb85 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -2282,7 +2282,7 @@ int ocfs2_inode_lock_full_nested(struct inode *inode,
 	status = __ocfs2_cluster_lock(osb, lockres, level, dlm_flags,
 				      arg_flags, subclass, _RET_IP_);
 	if (status < 0) {
-		if (status != -EAGAIN && status != -EIOCBRETRY)
+		if (status != -EAGAIN)
 			mlog_errno(status);
 		goto bail;
 	}
diff --git a/fs/read_write.c b/fs/read_write.c
index 3ac2898..a6d1b45 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -239,16 +239,6 @@ int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count
 	return count > MAX_RW_COUNT ? MAX_RW_COUNT : count;
 }
 
-static void wait_on_retry_sync_kiocb(struct kiocb *iocb)
-{
-	set_current_state(TASK_UNINTERRUPTIBLE);
-	if (!kiocbIsKicked(iocb))
-		schedule();
-	else
-		kiocbClearKicked(iocb);
-	__set_current_state(TASK_RUNNING);
-}
-
 ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 {
 	struct iovec iov = { .iov_base = buf, .iov_len = len };
@@ -259,13 +249,7 @@ ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *pp
 	kiocb.ki_pos = *ppos;
 	kiocb.ki_left = len;
 
-	for (;;) {
-		ret = filp->f_op->aio_read(&kiocb, &iov, 1, kiocb.ki_pos);
-		if (ret != -EIOCBRETRY)
-			break;
-		wait_on_retry_sync_kiocb(&kiocb);
-	}
-
+	ret = filp->f_op->aio_read(&kiocb, &iov, 1, kiocb.ki_pos);
 	if (-EIOCBQUEUED == ret)
 		ret = wait_on_sync_kiocb(&kiocb);
 	*ppos = kiocb.ki_pos;
@@ -314,13 +298,7 @@ ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, lof
 	kiocb.ki_pos = *ppos;
 	kiocb.ki_left = len;
 
-	for (;;) {
-		ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);
-		if (ret != -EIOCBRETRY)
-			break;
-		wait_on_retry_sync_kiocb(&kiocb);
-	}
-
+	ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);
 	if (-EIOCBQUEUED == ret)
 		ret = wait_on_sync_kiocb(&kiocb);
 	*ppos = kiocb.ki_pos;
@@ -494,13 +472,7 @@ ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
 	kiocb.ki_left = len;
 	kiocb.ki_nbytes = len;
 
-	for (;;) {
-		ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);
-		if (ret != -EIOCBRETRY)
-			break;
-		wait_on_retry_sync_kiocb(&kiocb);
-	}
-
+	ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);
 	if (ret == -EIOCBQUEUED)
 		ret = wait_on_sync_kiocb(&kiocb);
 	*ppos = kiocb.ki_pos;
diff --git a/include/linux/aio.h b/include/linux/aio.h
index aea219d..4f88ec2 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -74,15 +74,6 @@ struct kioctx;
  * not ask the method again -- ki_retry must ensure forward progress.
  * aio_complete() must be called once and only once in the future, multiple
  * calls may result in undefined behaviour.
- *
- * If ki_retry returns -EIOCBRETRY it has made a promise that kick_iocb()
- * will be called on the kiocb pointer in the future.  This may happen
- * through generic helpers that associate kiocb->ki_wait with a wait
- * queue head that ki_retry uses via current->io_wait.  It can also happen
- * with custom tracking and manual calls to kick_iocb(), though that is
- * discouraged.  In either case, kick_iocb() must be called once and only
- * once.  ki_retry must ensure forward progress, the AIO core will wait
- * indefinitely for kick_iocb() to be called.
  */
 struct kiocb {
 	struct list_head	ki_run_list;
@@ -210,14 +201,12 @@ extern unsigned aio_max_size;
 #ifdef CONFIG_AIO
 extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb);
 extern int aio_put_req(struct kiocb *iocb);
-extern void kick_iocb(struct kiocb *iocb);
 extern int aio_complete(struct kiocb *iocb, long res, long res2);
 struct mm_struct;
 extern void exit_aio(struct mm_struct *mm);
 #else
 static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
 static inline int aio_put_req(struct kiocb *iocb) { return 0; }
-static inline void kick_iocb(struct kiocb *iocb) { }
 static inline int aio_complete(struct kiocb *iocb, long res, long res2) { return 0; }
 struct mm_struct;
 static inline void exit_aio(struct mm_struct *mm) { }
diff --git a/include/linux/errno.h b/include/linux/errno.h
index 4668583..63a1f15 100644
--- a/include/linux/errno.h
+++ b/include/linux/errno.h
@@ -27,7 +27,6 @@
 #define EBADTYPE	527	/* Type not supported by server */
 #define EJUKEBOX	528	/* Request initiated, but will not complete before timeout */
 #define EIOCBQUEUED	529	/* iocb queued, will get completion event */
-#define EIOCBRETRY	530	/* iocb queued, will trigger a retry */
 
 #endif
 
-- 
1.6.2.5