ext4: mechanical rename some of the direct I/O get_block's identifiers

This commit renames some of the direct I/O's block allocation flags,
variables, and functions introduced in Mingming's "Direct IO for holes
and fallocate" patches so that they can be used by ext4's buffered
write path as well.  Also changed the related function comments
accordingly to cover both direct write and buffered write cases.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 38 insertions, 46 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 427f469..28f116b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3468,7 +3468,7 @@ out:
 	return ret;
 }
 
-static int ext4_get_block_dio_write(struct inode *inode, sector_t iblock,
+static int ext4_get_block_write(struct inode *inode, sector_t iblock,
 		   struct buffer_head *bh_result, int create)
 {
 	handle_t *handle = NULL;
@@ -3476,28 +3476,14 @@ static int ext4_get_block_dio_write(struct inode *inode, sector_t iblock,
 	unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
 	int dio_credits;
 
-	ext4_debug("ext4_get_block_dio_write: inode %lu, create flag %d\n",
+	ext4_debug("ext4_get_block_write: inode %lu, create flag %d\n",
 		   inode->i_ino, create);
 	/*
-	 * DIO VFS code passes create = 0 flag for write to
-	 * the middle of file. It does this to avoid block
-	 * allocation for holes, to prevent expose stale data
-	 * out when there is parallel buffered read (which does
-	 * not hold the i_mutex lock) while direct IO write has
-	 * not completed. DIO request on holes finally falls back
-	 * to buffered IO for this reason.
-	 *
-	 * For ext4 extent based file, since we support fallocate,
-	 * new allocated extent as uninitialized, for holes, we
-	 * could fallocate blocks for holes, thus parallel
-	 * buffered IO read will zero out the page when read on
-	 * a hole while parallel DIO write to the hole has not completed.
-	 *
-	 * when we come here, we know it's a direct IO write to
-	 * to the middle of file (<i_size)
-	 * so it's safe to override the create flag from VFS.
+	 * ext4_get_block in prepare for a DIO write or buffer write.
+	 * We allocate an uinitialized extent if blocks haven't been allocated.
+	 * The extent will be converted to initialized after IO complete.
 	 */
-	create = EXT4_GET_BLOCKS_DIO_CREATE_EXT;
+	create = EXT4_GET_BLOCKS_IO_CREATE_EXT;
 
 	if (max_blocks > DIO_MAX_BLOCKS)
 		max_blocks = DIO_MAX_BLOCKS;
@@ -3524,19 +3510,20 @@ static void ext4_free_io_end(ext4_io_end_t *io)
 	iput(io->inode);
 	kfree(io);
 }
-static void dump_aio_dio_list(struct inode * inode)
+
+static void dump_completed_IO(struct inode * inode)
 {
 #ifdef	EXT4_DEBUG
 	struct list_head *cur, *before, *after;
 	ext4_io_end_t *io, *io0, *io1;
 
-	if (list_empty(&EXT4_I(inode)->i_aio_dio_complete_list)){
-		ext4_debug("inode %lu aio dio list is empty\n", inode->i_ino);
+	if (list_empty(&EXT4_I(inode)->i_completed_io_list)){
+		ext4_debug("inode %lu completed_io list is empty\n", inode->i_ino);
 		return;
 	}
 
-	ext4_debug("Dump inode %lu aio_dio_completed_IO list \n", inode->i_ino);
-	list_for_each_entry(io, &EXT4_I(inode)->i_aio_dio_complete_list, list){
+	ext4_debug("Dump inode %lu completed_io list \n", inode->i_ino);
+	list_for_each_entry(io, &EXT4_I(inode)->i_completed_io_list, list){
 		cur = &io->list;
 		before = cur->prev;
 		io0 = container_of(before, ext4_io_end_t, list);
@@ -3552,21 +3539,21 @@ static void dump_aio_dio_list(struct inode * inode)
 /*
  * check a range of space and convert unwritten extents to written.
  */
-static int ext4_end_aio_dio_nolock(ext4_io_end_t *io)
+static int ext4_end_io_nolock(ext4_io_end_t *io)
 {
 	struct inode *inode = io->inode;
 	loff_t offset = io->offset;
 	ssize_t size = io->size;
 	int ret = 0;
 
-	ext4_debug("end_aio_dio_onlock: io 0x%p from inode %lu,list->next 0x%p,"
+	ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
 		   "list->prev 0x%p\n",
 	           io, inode->i_ino, io->list.next, io->list.prev);
 
 	if (list_empty(&io->list))
 		return ret;
 
-	if (io->flag != DIO_AIO_UNWRITTEN)
+	if (io->flag != EXT4_IO_UNWRITTEN)
 		return ret;
 
 	if (offset + size <= i_size_read(inode))
@@ -3584,17 +3571,18 @@ static int ext4_end_aio_dio_nolock(ext4_io_end_t *io)
 	io->flag = 0;
 	return ret;
 }
+
 /*
  * work on completed aio dio IO, to convert unwritten extents to extents
  */
-static void ext4_end_aio_dio_work(struct work_struct *work)
+static void ext4_end_io_work(struct work_struct *work)
 {
 	ext4_io_end_t *io  = container_of(work, ext4_io_end_t, work);
 	struct inode *inode = io->inode;
 	int ret = 0;
 
 	mutex_lock(&inode->i_mutex);
-	ret = ext4_end_aio_dio_nolock(io);
+	ret = ext4_end_io_nolock(io);
 	if (ret >= 0) {
 		if (!list_empty(&io->list))
 			list_del_init(&io->list);
@@ -3602,32 +3590,35 @@ static void ext4_end_aio_dio_work(struct work_struct *work)
 	}
 	mutex_unlock(&inode->i_mutex);
 }
+
 /*
  * This function is called from ext4_sync_file().
  *
- * When AIO DIO IO is completed, the work to convert unwritten
- * extents to written is queued on workqueue but may not get immediately
+ * When IO is completed, the work to convert unwritten extents to
+ * written is queued on workqueue but may not get immediately
  * scheduled. When fsync is called, we need to ensure the
  * conversion is complete before fsync returns.
- * The inode keeps track of a list of completed AIO from DIO path
- * that might needs to do the conversion. This function walks through
- * the list and convert the related unwritten extents to written.
+ * The inode keeps track of a list of pending/completed IO that
+ * might needs to do the conversion. This function walks through
+ * the list and convert the related unwritten extents for completed IO
+ * to written.
+ * The function return the number of pending IOs on success.
  */
-int flush_aio_dio_completed_IO(struct inode *inode)
+int flush_completed_IO(struct inode *inode)
 {
 	ext4_io_end_t *io;
 	int ret = 0;
 	int ret2 = 0;
 
-	if (list_empty(&EXT4_I(inode)->i_aio_dio_complete_list))
+	if (list_empty(&EXT4_I(inode)->i_completed_io_list))
 		return ret;
 
-	dump_aio_dio_list(inode);
-	while (!list_empty(&EXT4_I(inode)->i_aio_dio_complete_list)){
-		io = list_entry(EXT4_I(inode)->i_aio_dio_complete_list.next,
+	dump_completed_IO(inode);
+	while (!list_empty(&EXT4_I(inode)->i_completed_io_list)){
+		io = list_entry(EXT4_I(inode)->i_completed_io_list.next,
 				ext4_io_end_t, list);
 		/*
-		 * Calling ext4_end_aio_dio_nolock() to convert completed
+		 * Calling ext4_end_io_nolock() to convert completed
 		 * IO to written.
 		 *
 		 * When ext4_sync_file() is called, run_queue() may already
@@ -3640,7 +3631,7 @@ int flush_aio_dio_completed_IO(struct inode *inode)
 		 * avoid double converting from both fsync and background work
 		 * queue work.
 		 */
-		ret = ext4_end_aio_dio_nolock(io);
+		ret = ext4_end_io_nolock(io);
 		if (ret < 0)
 			ret2 = ret;
 		else
@@ -3662,7 +3653,7 @@ static ext4_io_end_t *ext4_init_io_end (struct inode *inode)
 		io->offset = 0;
 		io->size = 0;
 		io->error = 0;
-		INIT_WORK(&io->work, ext4_end_aio_dio_work);
+		INIT_WORK(&io->work, ext4_end_io_work);
 		INIT_LIST_HEAD(&io->list);
 	}
 
@@ -3685,7 +3676,7 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
 		  size);
 
 	/* if not aio dio with unwritten extents, just free io and return */
-	if (io_end->flag != DIO_AIO_UNWRITTEN){
+	if (io_end->flag != EXT4_IO_UNWRITTEN){
 		ext4_free_io_end(io_end);
 		iocb->private = NULL;
 		return;
@@ -3700,9 +3691,10 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
 
 	/* Add the io_end to per-inode completed aio dio list*/
 	list_add_tail(&io_end->list,
-		 &EXT4_I(io_end->inode)->i_aio_dio_complete_list);
+		 &EXT4_I(io_end->inode)->i_completed_io_list);
 	iocb->private = NULL;
 }
+
 /*
  * For ext4 extent files, ext4 will do direct-io write to holes,
  * preallocated extents, and those write extend the file, no need to
@@ -3772,7 +3764,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
 		ret = blockdev_direct_IO(rw, iocb, inode,
 					 inode->i_sb->s_bdev, iov,
 					 offset, nr_segs,
-					 ext4_get_block_dio_write,
+					 ext4_get_block_write,
 					 ext4_end_io_dio);
 		if (iocb->private)
 			EXT4_I(inode)->cur_aio_dio = NULL;