1 files changed, 144 insertions, 179 deletions

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 5981e17f46f0..d9d0833444f5 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
+#include <linux/task_io_accounting_ops.h>
 #include <linux/bio.h>
 #include <linux/wait.h>
 #include <linux/err.h>
@@ -121,8 +122,7 @@ struct dio {
 
 	/* BIO completion state */
 	spinlock_t bio_lock;		/* protects BIO fields below */
-	int bio_count;			/* nr bios to be completed */
-	int bios_in_flight;		/* nr bios in flight */
+	unsigned long refcount;		/* direct_io_worker() and bios */
 	struct bio *bio_list;		/* singly linked via bi_private */
 	struct task_struct *waiter;	/* waiting task (NULL if none) */
 
@@ -209,76 +209,55 @@ static struct page *dio_get_page(struct dio *dio)
 	return dio->pages[dio->head++];
 }
 
-/*
- * Called when all DIO BIO I/O has been completed - let the filesystem
- * know, if it registered an interest earlier via get_block.  Pass the
- * private field of the map buffer_head so that filesystems can use it
- * to hold additional state between get_block calls and dio_complete.
- */
-static void dio_complete(struct dio *dio, loff_t offset, ssize_t bytes)
-{
-	if (dio->end_io && dio->result)
-		dio->end_io(dio->iocb, offset, bytes, dio->map_bh.b_private);
-	if (dio->lock_type == DIO_LOCKING)
-		/* lockdep: non-owner release */
-		up_read_non_owner(&dio->inode->i_alloc_sem);
-}
-
-/*
- * Called when a BIO has been processed.  If the count goes to zero then IO is
- * complete and we can signal this to the AIO layer.
+/**
+ * dio_complete() - called when all DIO BIO I/O has been completed
+ * @offset: the byte offset in the file of the completed operation
+ *
+ * This releases locks as dictated by the locking type, lets interested parties
+ * know that a DIO operation has completed, and calculates the resulting return
+ * code for the operation.
+ *
+ * It lets the filesystem know if it registered an interest earlier via
+ * get_block.  Pass the private field of the map buffer_head so that
+ * filesystems can use it to hold additional state between get_block calls and
+ * dio_complete.
  */
-static void finished_one_bio(struct dio *dio)
+static int dio_complete(struct dio *dio, loff_t offset, int ret)
 {
-	unsigned long flags;
+	ssize_t transferred = 0;
 
-	spin_lock_irqsave(&dio->bio_lock, flags);
-	if (dio->bio_count == 1) {
-		if (dio->is_async) {
-			ssize_t transferred;
-			loff_t offset;
-
-			/*
-			 * Last reference to the dio is going away.
-			 * Drop spinlock and complete the DIO.
-			 */
-			spin_unlock_irqrestore(&dio->bio_lock, flags);
+	/*
+	 * AIO submission can race with bio completion to get here while
+	 * expecting to have the last io completed by bio completion.
+	 * In that case -EIOCBQUEUED is in fact not an error we want
+	 * to preserve through this call.
+	 */
+	if (ret == -EIOCBQUEUED)
+		ret = 0;
 
-			/* Check for short read case */
-			transferred = dio->result;
-			offset = dio->iocb->ki_pos;
+	if (dio->result) {
+		transferred = dio->result;
 
-			if ((dio->rw == READ) &&
-			    ((offset + transferred) > dio->i_size))
-				transferred = dio->i_size - offset;
+		/* Check for short read case */
+		if ((dio->rw == READ) && ((offset + transferred) > dio->i_size))
+			transferred = dio->i_size - offset;
+	}
 
-			/* check for error in completion path */
-			if (dio->io_error)
-				transferred = dio->io_error;
+	if (dio->end_io && dio->result)
+		dio->end_io(dio->iocb, offset, transferred,
+			    dio->map_bh.b_private);
+	if (dio->lock_type == DIO_LOCKING)
+		/* lockdep: non-owner release */
+		up_read_non_owner(&dio->inode->i_alloc_sem);
 
-			dio_complete(dio, offset, transferred);
+	if (ret == 0)
+		ret = dio->page_errors;
+	if (ret == 0)
+		ret = dio->io_error;
+	if (ret == 0)
+		ret = transferred;
 
-			/* Complete AIO later if falling back to buffered i/o */
-			if (dio->result == dio->size ||
-				((dio->rw == READ) && dio->result)) {
-				aio_complete(dio->iocb, transferred, 0);
-				kfree(dio);
-				return;
-			} else {
-				/*
-				 * Falling back to buffered
-				 */
-				spin_lock_irqsave(&dio->bio_lock, flags);
-				dio->bio_count--;
-				if (dio->waiter)
-					wake_up_process(dio->waiter);
-				spin_unlock_irqrestore(&dio->bio_lock, flags);
-				return;
-			}
-		}
-	}
-	dio->bio_count--;
-	spin_unlock_irqrestore(&dio->bio_lock, flags);
+	return ret;
 }
 
 static int dio_bio_complete(struct dio *dio, struct bio *bio);
@@ -288,12 +267,27 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio);
 static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error)
 {
 	struct dio *dio = bio->bi_private;
+	unsigned long remaining;
+	unsigned long flags;
 
 	if (bio->bi_size)
 		return 1;
 
 	/* cleanup the bio */
 	dio_bio_complete(dio, bio);
+
+	spin_lock_irqsave(&dio->bio_lock, flags);
+	remaining = --dio->refcount;
+	if (remaining == 1 && dio->waiter)
+		wake_up_process(dio->waiter);
+	spin_unlock_irqrestore(&dio->bio_lock, flags);
+
+	if (remaining == 0) {
+		int ret = dio_complete(dio, dio->iocb->ki_pos, 0);
+		aio_complete(dio->iocb, ret, 0);
+		kfree(dio);
+	}
+
 	return 0;
 }
 
@@ -315,8 +309,7 @@ static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error)
 	spin_lock_irqsave(&dio->bio_lock, flags);
 	bio->bi_private = dio->bio_list;
 	dio->bio_list = bio;
-	dio->bios_in_flight--;
-	if (dio->waiter && dio->bios_in_flight == 0)
+	if (--dio->refcount == 1 && dio->waiter)
 		wake_up_process(dio->waiter);
 	spin_unlock_irqrestore(&dio->bio_lock, flags);
 	return 0;
@@ -347,6 +340,8 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev,
  * In the AIO read case we speculatively dirty the pages before starting IO.
  * During IO completion, any of these pages which happen to have been written
  * back will be redirtied by bio_check_pages_dirty().
+ *
+ * bios hold a dio reference between submit_bio and ->end_io.
  */
 static void dio_bio_submit(struct dio *dio)
 {
@@ -354,12 +349,14 @@ static void dio_bio_submit(struct dio *dio)
 	unsigned long flags;
 
 	bio->bi_private = dio;
+
 	spin_lock_irqsave(&dio->bio_lock, flags);
-	dio->bio_count++;
-	dio->bios_in_flight++;
+	dio->refcount++;
 	spin_unlock_irqrestore(&dio->bio_lock, flags);
+
 	if (dio->is_async && dio->rw == READ)
 		bio_set_pages_dirty(bio);
+
 	submit_bio(dio->rw, bio);
 
 	dio->bio = NULL;
@@ -376,28 +373,37 @@ static void dio_cleanup(struct dio *dio)
 }
 
 /*
- * Wait for the next BIO to complete.  Remove it and return it.
+ * Wait for the next BIO to complete.  Remove it and return it.  NULL is
+ * returned once all BIOs have been completed.  This must only be called once
+ * all bios have been issued so that dio->refcount can only decrease.  This
+ * requires that that the caller hold a reference on the dio.
  */
 static struct bio *dio_await_one(struct dio *dio)
 {
 	unsigned long flags;
-	struct bio *bio;
+	struct bio *bio = NULL;
 
 	spin_lock_irqsave(&dio->bio_lock, flags);
-	while (dio->bio_list == NULL) {
-		set_current_state(TASK_UNINTERRUPTIBLE);
-		if (dio->bio_list == NULL) {
-			dio->waiter = current;
-			spin_unlock_irqrestore(&dio->bio_lock, flags);
-			blk_run_address_space(dio->inode->i_mapping);
-			io_schedule();
-			spin_lock_irqsave(&dio->bio_lock, flags);
-			dio->waiter = NULL;
-		}
-		set_current_state(TASK_RUNNING);
+
+	/*
+	 * Wait as long as the list is empty and there are bios in flight.  bio
+	 * completion drops the count, maybe adds to the list, and wakes while
+	 * holding the bio_lock so we don't need set_current_state()'s barrier
+	 * and can call it after testing our condition.
+	 */
+	while (dio->refcount > 1 && dio->bio_list == NULL) {
+		__set_current_state(TASK_UNINTERRUPTIBLE);
+		dio->waiter = current;
+		spin_unlock_irqrestore(&dio->bio_lock, flags);
+		io_schedule();
+		/* wake up sets us TASK_RUNNING */
+		spin_lock_irqsave(&dio->bio_lock, flags);
+		dio->waiter = NULL;
+	}
+	if (dio->bio_list) {
+		bio = dio->bio_list;
+		dio->bio_list = bio->bi_private;
 	}
-	bio = dio->bio_list;
-	dio->bio_list = bio->bi_private;
 	spin_unlock_irqrestore(&dio->bio_lock, flags);
 	return bio;
 }
@@ -426,34 +432,24 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
 		}
 		bio_put(bio);
 	}
-	finished_one_bio(dio);
 	return uptodate ? 0 : -EIO;
 }
 
 /*
- * Wait on and process all in-flight BIOs.
+ * Wait on and process all in-flight BIOs.  This must only be called once
+ * all bios have been issued so that the refcount can only decrease.
+ * This just waits for all bios to make it through dio_bio_complete.  IO
+ * errors are propogated through dio->io_error and should be propogated via
+ * dio_complete().
  */
-static int dio_await_completion(struct dio *dio)
+static void dio_await_completion(struct dio *dio)
 {
-	int ret = 0;
-
-	if (dio->bio)
-		dio_bio_submit(dio);
-
-	/*
-	 * The bio_lock is not held for the read of bio_count.
-	 * This is ok since it is the dio_bio_complete() that changes
-	 * bio_count.
-	 */
-	while (dio->bio_count) {
-		struct bio *bio = dio_await_one(dio);
-		int ret2;
-
-		ret2 = dio_bio_complete(dio, bio);
-		if (ret == 0)
-			ret = ret2;
-	}
-	return ret;
+	struct bio *bio;
+	do {
+		bio = dio_await_one(dio);
+		if (bio)
+			dio_bio_complete(dio, bio);
+	} while (bio);
 }
 
 /*
@@ -675,6 +671,13 @@ submit_page_section(struct dio *dio, struct page *page,
 {
 	int ret = 0;
 
+	if (dio->rw & WRITE) {
+		/*
+		 * Read accounting is performed in submit_bio()
+		 */
+		task_io_account_write(len);
+	}
+
 	/*
 	 * Can we just grow the current page's presence in the dio?
 	 */
@@ -953,6 +956,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	struct dio *dio)
 {
 	unsigned long user_addr; 
+	unsigned long flags;
 	int seg;
 	ssize_t ret = 0;
 	ssize_t ret2;
@@ -983,17 +987,8 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	dio->iocb = iocb;
 	dio->i_size = i_size_read(inode);
 
-	/*
-	 * BIO completion state.
-	 *
-	 * ->bio_count starts out at one, and we decrement it to zero after all
-	 * BIOs are submitted.  This to avoid the situation where a really fast
-	 * (or synchronous) device could take the count to zero while we're
-	 * still submitting BIOs.
-	 */
-	dio->bio_count = 1;
-	dio->bios_in_flight = 0;
 	spin_lock_init(&dio->bio_lock);
+	dio->refcount = 1;
 	dio->bio_list = NULL;
 	dio->waiter = NULL;
 
@@ -1069,6 +1064,9 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	if (dio->bio)
 		dio_bio_submit(dio);
 
+	/* All IO is now issued, send it on its way */
+	blk_run_address_space(inode->i_mapping);
+
 	/*
 	 * It is possible that, we return short IO due to end of file.
 	 * In that case, we need to release all the pages we got hold on.
@@ -1084,74 +1082,41 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 		mutex_unlock(&dio->inode->i_mutex);
 
 	/*
-	 * OK, all BIOs are submitted, so we can decrement bio_count to truly
-	 * reflect the number of to-be-processed BIOs.
+	 * The only time we want to leave bios in flight is when a successful
+	 * partial aio read or full aio write have been setup.  In that case
+	 * bio completion will call aio_complete.  The only time it's safe to
+	 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
+	 * This had *better* be the only place that raises -EIOCBQUEUED.
 	 */
-	if (dio->is_async) {
-		int should_wait = 0;
+	BUG_ON(ret == -EIOCBQUEUED);
+	if (dio->is_async && ret == 0 && dio->result &&
+	    ((rw & READ) || (dio->result == dio->size)))
+		ret = -EIOCBQUEUED;
 
-		if (dio->result < dio->size && (rw & WRITE)) {
-			dio->waiter = current;
-			should_wait = 1;
-		}
-		if (ret == 0)
-			ret = dio->result;
-		finished_one_bio(dio);		/* This can free the dio */
-		blk_run_address_space(inode->i_mapping);
-		if (should_wait) {
-			unsigned long flags;
-			/*
-			 * Wait for already issued I/O to drain out and
-			 * release its references to user-space pages
-			 * before returning to fallback on buffered I/O
-			 */
-
-			spin_lock_irqsave(&dio->bio_lock, flags);
-			set_current_state(TASK_UNINTERRUPTIBLE);
-			while (dio->bio_count) {
-				spin_unlock_irqrestore(&dio->bio_lock, flags);
-				io_schedule();
-				spin_lock_irqsave(&dio->bio_lock, flags);
-				set_current_state(TASK_UNINTERRUPTIBLE);
-			}
-			spin_unlock_irqrestore(&dio->bio_lock, flags);
-			set_current_state(TASK_RUNNING);
-			kfree(dio);
-		}
-	} else {
-		ssize_t transferred = 0;
-
-		finished_one_bio(dio);
-		ret2 = dio_await_completion(dio);
-		if (ret == 0)
-			ret = ret2;
-		if (ret == 0)
-			ret = dio->page_errors;
-		if (dio->result) {
-			loff_t i_size = i_size_read(inode);
-
-			transferred = dio->result;
-			/*
-			 * Adjust the return value if the read crossed a
-			 * non-block-aligned EOF.
-			 */
-			if (rw == READ && (offset + transferred > i_size))
-				transferred = i_size - offset;
-		}
-		dio_complete(dio, offset, transferred);
-		if (ret == 0)
-			ret = transferred;
+	if (ret != -EIOCBQUEUED)
+		dio_await_completion(dio);
 
-		/* We could have also come here on an AIO file extend */
-		if (!is_sync_kiocb(iocb) && (rw & WRITE) &&
-		    ret >= 0 && dio->result == dio->size)
-			/*
-			 * For AIO writes where we have completed the
-			 * i/o, we have to mark the the aio complete.
-			 */
-			aio_complete(iocb, ret, 0);
+	/*
+	 * Sync will always be dropping the final ref and completing the
+	 * operation.  AIO can if it was a broken operation described above or
+	 * in fact if all the bios race to complete before we get here.  In
+	 * that case dio_complete() translates the EIOCBQUEUED into the proper
+	 * return code that the caller will hand to aio_complete().
+	 *
+	 * This is managed by the bio_lock instead of being an atomic_t so that
+	 * completion paths can drop their ref and use the remaining count to
+	 * decide to wake the submission path atomically.
+	 */
+	spin_lock_irqsave(&dio->bio_lock, flags);
+	ret2 = --dio->refcount;
+	spin_unlock_irqrestore(&dio->bio_lock, flags);
+	BUG_ON(!dio->is_async && ret2 != 0);
+	if (ret2 == 0) {
+		ret = dio_complete(dio, offset, ret);
 		kfree(dio);
-	}
+	} else
+		BUG_ON(ret != -EIOCBQUEUED);
+
 	return ret;
 }