fs/ext4/page-io.c - maze/linux - Git at Google

 /*
  * linux/fs/ext4/page-io.c
  *
  * This contains the new page_io functions for ext4
  *
  * Written by Theodore Ts'o, 2010.
  */

 #include <linux/fs.h>
 #include <linux/time.h>
 #include <linux/jbd2.h>
 #include <linux/highuid.h>
 #include <linux/pagemap.h>
 #include <linux/quotaops.h>
 #include <linux/string.h>
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include <linux/mpage.h>
 #include <linux/namei.h>
 #include <linux/aio.h>
 #include <linux/uio.h>
 #include <linux/bio.h>
 #include <linux/workqueue.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/ratelimit.h>

 #include "ext4_jbd2.h"
 #include "xattr.h"
 #include "acl.h"

 static struct kmem_cache *io_end_cachep;

 int __init ext4_init_pageio(void)
 {
 	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
 	if (io_end_cachep == NULL)
 		return -ENOMEM;
 	return 0;
 }

 void ext4_exit_pageio(void)
 {
 	kmem_cache_destroy(io_end_cachep);
 }

 /*
  * Print an buffer I/O error compatible with the fs/buffer.c.  This
  * provides compatibility with dmesg scrapers that look for a specific
  * buffer I/O error message.  We really need a unified error reporting
  * structure to userspace ala Digital Unix's uerf system, but it's
  * probably not going to happen in my lifetime, due to LKML politics...
  */
 static void buffer_io_error(struct buffer_head *bh)
 {
 	char b[BDEVNAME_SIZE];
 	printk_ratelimited(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
 			bdevname(bh->b_bdev, b),
 			(unsigned long long)bh->b_blocknr);
 }

 static void ext4_finish_bio(struct bio *bio)
 {
 	int i;
 	int error = !test_bit(BIO_UPTODATE, &bio->bi_flags);

 	for (i = 0; i < bio->bi_vcnt; i++) {
 		struct bio_vec *bvec = &bio->bi_io_vec[i];
 		struct page *page = bvec->bv_page;
 		struct buffer_head *bh, *head;
 		unsigned bio_start = bvec->bv_offset;
 		unsigned bio_end = bio_start + bvec->bv_len;
 		unsigned under_io = 0;
 		unsigned long flags;

 		if (!page)
 			continue;

 		if (error) {
 			SetPageError(page);
 			set_bit(AS_EIO, &page->mapping->flags);
 		}
 		bh = head = page_buffers(page);
 		/*
 		 * We check all buffers in the page under BH_Uptodate_Lock
 		 * to avoid races with other end io clearing async_write flags
 		 */
 		local_irq_save(flags);
 		bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
 		do {
 			if (bh_offset(bh) < bio_start ||
 			    bh_offset(bh) + bh->b_size > bio_end) {
 				if (buffer_async_write(bh))
 					under_io++;
 				continue;
 			}
 			clear_buffer_async_write(bh);
 			if (error)
 				buffer_io_error(bh);
 		} while ((bh = bh->b_this_page) != head);
 		bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
 		local_irq_restore(flags);
 		if (!under_io)
 			end_page_writeback(page);
 	}
 }

 static void ext4_release_io_end(ext4_io_end_t *io_end)
 {
 	struct bio *bio, *next_bio;

 	BUG_ON(!list_empty(&io_end->list));
 	BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
 	WARN_ON(io_end->handle);

 	if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
 		wake_up_all(ext4_ioend_wq(io_end->inode));

 	for (bio = io_end->bio; bio; bio = next_bio) {
 		next_bio = bio->bi_private;
 		ext4_finish_bio(bio);
 		bio_put(bio);
 	}
 	if (io_end->flag & EXT4_IO_END_DIRECT)
 		inode_dio_done(io_end->inode);
 	if (io_end->iocb)
 		aio_complete(io_end->iocb, io_end->result, 0);
 	kmem_cache_free(io_end_cachep, io_end);
 }

 static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
 {
 	struct inode *inode = io_end->inode;

 	io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
 	/* Wake up anyone waiting on unwritten extent conversion */
 	if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
 		wake_up_all(ext4_ioend_wq(inode));
 }

 /*
  * Check a range of space and convert unwritten extents to written. Note that
  * we are protected from truncate touching same part of extent tree by the
  * fact that truncate code waits for all DIO to finish (thus exclusion from
  * direct IO is achieved) and also waits for PageWriteback bits. Thus we
  * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
  * completed (happens from ext4_free_ioend()).
  */
 static int ext4_end_io(ext4_io_end_t *io)
 {
 	struct inode *inode = io->inode;
 	loff_t offset = io->offset;
 	ssize_t size = io->size;
 	handle_t *handle = io->handle;
 	int ret = 0;

 	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);

 	io->handle = NULL;	/* Following call will use up the handle */
 	ret = ext4_convert_unwritten_extents(handle, inode, offset, size);
 	if (ret < 0) {
 		ext4_msg(inode->i_sb, KERN_EMERG,
 			 "failed to convert unwritten extents to written "
 			 "extents -- potential data loss!  "
 			 "(inode %lu, offset %llu, size %zd, error %d)",
 			 inode->i_ino, offset, size, ret);
 	}
 	ext4_clear_io_unwritten_flag(io);
 	ext4_release_io_end(io);
 	return ret;
 }

 static void dump_completed_IO(struct inode *inode, struct list_head *head)
 {
 #ifdef	EXT4FS_DEBUG
 	struct list_head *cur, *before, *after;
 	ext4_io_end_t *io, *io0, *io1;

 	if (list_empty(head))
 		return;

 	ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
 	list_for_each_entry(io, head, list) {
 		cur = &io->list;
 		before = cur->prev;
 		io0 = container_of(before, ext4_io_end_t, list);
 		after = cur->next;
 		io1 = container_of(after, ext4_io_end_t, list);

 		ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
 			    io, inode->i_ino, io0, io1);
 	}
 #endif
 }

 /* Add the io_end to per-inode completed end_io list. */
 static void ext4_add_complete_io(ext4_io_end_t *io_end)
 {
 	struct ext4_inode_info *ei = EXT4_I(io_end->inode);
 	struct workqueue_struct *wq;
 	unsigned long flags;

 	BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
 	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 	if (io_end->handle) {
 		wq = EXT4_SB(io_end->inode->i_sb)->rsv_conversion_wq;
 		if (list_empty(&ei->i_rsv_conversion_list))
 			queue_work(wq, &ei->i_rsv_conversion_work);
 		list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
 	} else {
 		wq = EXT4_SB(io_end->inode->i_sb)->unrsv_conversion_wq;
 		if (list_empty(&ei->i_unrsv_conversion_list))
 			queue_work(wq, &ei->i_unrsv_conversion_work);
 		list_add_tail(&io_end->list, &ei->i_unrsv_conversion_list);
 	}
 	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 }

 static int ext4_do_flush_completed_IO(struct inode *inode,
 				      struct list_head *head)
 {
 	ext4_io_end_t *io;
 	struct list_head unwritten;
 	unsigned long flags;
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	int err, ret = 0;

 	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 	dump_completed_IO(inode, head);
 	list_replace_init(head, &unwritten);
 	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

 	while (!list_empty(&unwritten)) {
 		io = list_entry(unwritten.next, ext4_io_end_t, list);
 		BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
 		list_del_init(&io->list);

 		err = ext4_end_io(io);
 		if (unlikely(!ret && err))
 			ret = err;
 	}
 	return ret;
 }

 /*
  * work on completed IO, to convert unwritten extents to extents
  */
 void ext4_end_io_rsv_work(struct work_struct *work)
 {
 	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
 						  i_rsv_conversion_work);
 	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
 }

 void ext4_end_io_unrsv_work(struct work_struct *work)
 {
 	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
 						  i_unrsv_conversion_work);
 	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_unrsv_conversion_list);
 }

 ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
 {
 	ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
 	if (io) {
 		atomic_inc(&EXT4_I(inode)->i_ioend_count);
 		io->inode = inode;
 		INIT_LIST_HEAD(&io->list);
 		atomic_set(&io->count, 1);
 	}
 	return io;
 }

 void ext4_put_io_end_defer(ext4_io_end_t *io_end)
 {
 	if (atomic_dec_and_test(&io_end->count)) {
 		if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
 			ext4_release_io_end(io_end);
 			return;
 		}
 		ext4_add_complete_io(io_end);
 	}
 }

 int ext4_put_io_end(ext4_io_end_t *io_end)
 {
 	int err = 0;

 	if (atomic_dec_and_test(&io_end->count)) {
 		if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
 			err = ext4_convert_unwritten_extents(io_end->handle,
 						io_end->inode, io_end->offset,
 						io_end->size);
 			io_end->handle = NULL;
 			ext4_clear_io_unwritten_flag(io_end);
 		}
 		ext4_release_io_end(io_end);
 	}
 	return err;
 }

 ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
 {
 	atomic_inc(&io_end->count);
 	return io_end;
 }

 /* BIO completion function for page writeback */
 static void ext4_end_bio(struct bio *bio, int error)
 {
 	ext4_io_end_t *io_end = bio->bi_private;
 	sector_t bi_sector = bio->bi_sector;

 	BUG_ON(!io_end);
 	bio->bi_end_io = NULL;
 	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 		error = 0;

 	if (error) {
 		struct inode *inode = io_end->inode;

 		ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
 			     "(offset %llu size %ld starting block %llu)",
 			     inode->i_ino,
 			     (unsigned long long) io_end->offset,
 			     (long) io_end->size,
 			     (unsigned long long)
 			     bi_sector >> (inode->i_blkbits - 9));
 	}

 	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
 		/*
 		 * Link bio into list hanging from io_end. We have to do it
 		 * atomically as bio completions can be racing against each
 		 * other.
 		 */
 		bio->bi_private = xchg(&io_end->bio, bio);
 		ext4_put_io_end_defer(io_end);
 	} else {
 		/*
 		 * Drop io_end reference early. Inode can get freed once
 		 * we finish the bio.
 		 */
 		ext4_put_io_end_defer(io_end);
 		ext4_finish_bio(bio);
 		bio_put(bio);
 	}
 }

 void ext4_io_submit(struct ext4_io_submit *io)
 {
 	struct bio *bio = io->io_bio;

 	if (bio) {
 		bio_get(io->io_bio);
 		submit_bio(io->io_op, io->io_bio);
 		BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
 		bio_put(io->io_bio);
 	}
 	io->io_bio = NULL;
 }

 void ext4_io_submit_init(struct ext4_io_submit *io,
 			 struct writeback_control *wbc)
 {
 	io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
 	io->io_bio = NULL;
 	io->io_end = NULL;
 }

 static int io_submit_init_bio(struct ext4_io_submit *io,
 			      struct buffer_head *bh)
 {
 	int nvecs = bio_get_nr_vecs(bh->b_bdev);
 	struct bio *bio;

 	bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
 	if (!bio)
 		return -ENOMEM;
 	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 	bio->bi_bdev = bh->b_bdev;
 	bio->bi_end_io = ext4_end_bio;
 	bio->bi_private = ext4_get_io_end(io->io_end);
 	io->io_bio = bio;
 	io->io_next_block = bh->b_blocknr;
 	return 0;
 }

 static int io_submit_add_bh(struct ext4_io_submit *io,
 			    struct inode *inode,
 			    struct buffer_head *bh)
 {
 	int ret;

 	if (io->io_bio && bh->b_blocknr != io->io_next_block) {
 submit_and_retry:
 		ext4_io_submit(io);
 	}
 	if (io->io_bio == NULL) {
 		ret = io_submit_init_bio(io, bh);
 		if (ret)
 			return ret;
 	}
 	ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
 	if (ret != bh->b_size)
 		goto submit_and_retry;
 	io->io_next_block++;
 	return 0;
 }

 int ext4_bio_write_page(struct ext4_io_submit *io,
 			struct page *page,
 			int len,
 			struct writeback_control *wbc)
 {
 	struct inode *inode = page->mapping->host;
 	unsigned block_start, blocksize;
 	struct buffer_head *bh, *head;
 	int ret = 0;
 	int nr_submitted = 0;

 	blocksize = 1 << inode->i_blkbits;

 	BUG_ON(!PageLocked(page));
 	BUG_ON(PageWriteback(page));

 	set_page_writeback(page);
 	ClearPageError(page);

 	/*
 	 * In the first loop we prepare and mark buffers to submit. We have to
 	 * mark all buffers in the page before submitting so that
 	 * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
 	 * on the first buffer finishes and we are still working on submitting
 	 * the second buffer.
 	 */
 	bh = head = page_buffers(page);
 	do {
 		block_start = bh_offset(bh);
 		if (block_start >= len) {
 			/*
 			 * Comments copied from block_write_full_page_endio:
 			 *
 			 * The page straddles i_size.  It must be zeroed out on
 			 * each and every writepage invocation because it may
 			 * be mmapped.  "A file is mapped in multiples of the
 			 * page size.  For a file that is not a multiple of
 			 * the  page size, the remaining memory is zeroed when
 			 * mapped, and writes to that region are not written
 			 * out to the file."
 			 */
 			zero_user_segment(page, block_start,
 					  block_start + blocksize);
 			clear_buffer_dirty(bh);
 			set_buffer_uptodate(bh);
 			continue;
 		}
 		if (!buffer_dirty(bh) || buffer_delay(bh) ||
 		    !buffer_mapped(bh) || buffer_unwritten(bh)) {
 			/* A hole? We can safely clear the dirty bit */
 			if (!buffer_mapped(bh))
 				clear_buffer_dirty(bh);
 			if (io->io_bio)
 				ext4_io_submit(io);
 			continue;
 		}
 		if (buffer_new(bh)) {
 			clear_buffer_new(bh);
 			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
 		}
 		set_buffer_async_write(bh);
 	} while ((bh = bh->b_this_page) != head);

 	/* Now submit buffers to write */
 	bh = head = page_buffers(page);
 	do {
 		if (!buffer_async_write(bh))
 			continue;
 		ret = io_submit_add_bh(io, inode, bh);
 		if (ret) {
 			/*
 			 * We only get here on ENOMEM.  Not much else
 			 * we can do but mark the page as dirty, and
 			 * better luck next time.
 			 */
 			redirty_page_for_writepage(wbc, page);
 			break;
 		}
 		nr_submitted++;
 		clear_buffer_dirty(bh);
 	} while ((bh = bh->b_this_page) != head);

 	/* Error stopped previous loop? Clean up buffers... */
 	if (ret) {
 		do {
 			clear_buffer_async_write(bh);
 			bh = bh->b_this_page;
 		} while (bh != head);
 	}
 	unlock_page(page);
 	/* Nothing submitted - we have to end page writeback */
 	if (!nr_submitted)
 		end_page_writeback(page);
 	return ret;
 }
	/*
	* linux/fs/ext4/page-io.c
	*
	* This contains the new page_io functions for ext4
	*
	* Written by Theodore Ts'o, 2010.
	*/

	#include <linux/fs.h>
	#include <linux/time.h>
	#include <linux/jbd2.h>
	#include <linux/highuid.h>
	#include <linux/pagemap.h>
	#include <linux/quotaops.h>
	#include <linux/string.h>
	#include <linux/buffer_head.h>
	#include <linux/writeback.h>
	#include <linux/pagevec.h>
	#include <linux/mpage.h>
	#include <linux/namei.h>
	#include <linux/aio.h>
	#include <linux/uio.h>
	#include <linux/bio.h>
	#include <linux/workqueue.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/mm.h>
	#include <linux/ratelimit.h>

	#include "ext4_jbd2.h"
	#include "xattr.h"
	#include "acl.h"

	static struct kmem_cache *io_end_cachep;

	int __init ext4_init_pageio(void)
	{
	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
	if (io_end_cachep == NULL)
	return -ENOMEM;
	return 0;
	}

	void ext4_exit_pageio(void)
	{
	kmem_cache_destroy(io_end_cachep);
	}

	/*
	* Print an buffer I/O error compatible with the fs/buffer.c. This
	* provides compatibility with dmesg scrapers that look for a specific
	* buffer I/O error message. We really need a unified error reporting
	* structure to userspace ala Digital Unix's uerf system, but it's
	* probably not going to happen in my lifetime, due to LKML politics...
	*/
	static void buffer_io_error(struct buffer_head *bh)
	{
	char b[BDEVNAME_SIZE];
	printk_ratelimited(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
	bdevname(bh->b_bdev, b),
	(unsigned long long)bh->b_blocknr);
	}

	static void ext4_finish_bio(struct bio *bio)
	{
	int i;
	int error = !test_bit(BIO_UPTODATE, &bio->bi_flags);

	for (i = 0; i < bio->bi_vcnt; i++) {
	struct bio_vec *bvec = &bio->bi_io_vec[i];
	struct page *page = bvec->bv_page;
	struct buffer_head bh, head;
	unsigned bio_start = bvec->bv_offset;
	unsigned bio_end = bio_start + bvec->bv_len;
	unsigned under_io = 0;
	unsigned long flags;

	if (!page)
	continue;

	if (error) {
	SetPageError(page);
	set_bit(AS_EIO, &page->mapping->flags);
	}
	bh = head = page_buffers(page);
	/*
	* We check all buffers in the page under BH_Uptodate_Lock
	* to avoid races with other end io clearing async_write flags
	*/
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
	do {
	if (bh_offset(bh) < bio_start \|\|
	bh_offset(bh) + bh->b_size > bio_end) {
	if (buffer_async_write(bh))
	under_io++;
	continue;
	}
	clear_buffer_async_write(bh);
	if (error)
	buffer_io_error(bh);
	} while ((bh = bh->b_this_page) != head);
	bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
	local_irq_restore(flags);
	if (!under_io)
	end_page_writeback(page);
	}
	}

	static void ext4_release_io_end(ext4_io_end_t *io_end)
	{
	struct bio bio, next_bio;

	BUG_ON(!list_empty(&io_end->list));
	BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
	WARN_ON(io_end->handle);

	if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
	wake_up_all(ext4_ioend_wq(io_end->inode));

	for (bio = io_end->bio; bio; bio = next_bio) {
	next_bio = bio->bi_private;
	ext4_finish_bio(bio);
	bio_put(bio);
	}
	if (io_end->flag & EXT4_IO_END_DIRECT)
	inode_dio_done(io_end->inode);
	if (io_end->iocb)
	aio_complete(io_end->iocb, io_end->result, 0);
	kmem_cache_free(io_end_cachep, io_end);
	}

	static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
	{
	struct inode *inode = io_end->inode;

	io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
	/* Wake up anyone waiting on unwritten extent conversion */
	if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
	wake_up_all(ext4_ioend_wq(inode));
	}

	/*
	* Check a range of space and convert unwritten extents to written. Note that
	* we are protected from truncate touching same part of extent tree by the
	* fact that truncate code waits for all DIO to finish (thus exclusion from
	* direct IO is achieved) and also waits for PageWriteback bits. Thus we
	* cannot get to ext4_ext_truncate() before all IOs overlapping that range are
	* completed (happens from ext4_free_ioend()).
	*/
	static int ext4_end_io(ext4_io_end_t *io)
	{
	struct inode *inode = io->inode;
	loff_t offset = io->offset;
	ssize_t size = io->size;
	handle_t *handle = io->handle;
	int ret = 0;

	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);

	io->handle = NULL; /* Following call will use up the handle */
	ret = ext4_convert_unwritten_extents(handle, inode, offset, size);
	if (ret < 0) {
	ext4_msg(inode->i_sb, KERN_EMERG,
	"failed to convert unwritten extents to written "
	"extents -- potential data loss! "
	"(inode %lu, offset %llu, size %zd, error %d)",
	inode->i_ino, offset, size, ret);
	}
	ext4_clear_io_unwritten_flag(io);
	ext4_release_io_end(io);
	return ret;
	}

	static void dump_completed_IO(struct inode inode, struct list_head head)
	{
	#ifdef EXT4FS_DEBUG
	struct list_head cur, before, *after;
	ext4_io_end_t io, io0, *io1;

	if (list_empty(head))
	return;

	ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
	list_for_each_entry(io, head, list) {
	cur = &io->list;
	before = cur->prev;
	io0 = container_of(before, ext4_io_end_t, list);
	after = cur->next;
	io1 = container_of(after, ext4_io_end_t, list);

	ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
	io, inode->i_ino, io0, io1);
	}
	#endif
	}

	/* Add the io_end to per-inode completed end_io list. */
	static void ext4_add_complete_io(ext4_io_end_t *io_end)
	{
	struct ext4_inode_info *ei = EXT4_I(io_end->inode);
	struct workqueue_struct *wq;
	unsigned long flags;

	BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
	if (io_end->handle) {
	wq = EXT4_SB(io_end->inode->i_sb)->rsv_conversion_wq;
	if (list_empty(&ei->i_rsv_conversion_list))
	queue_work(wq, &ei->i_rsv_conversion_work);
	list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
	} else {
	wq = EXT4_SB(io_end->inode->i_sb)->unrsv_conversion_wq;
	if (list_empty(&ei->i_unrsv_conversion_list))
	queue_work(wq, &ei->i_unrsv_conversion_work);
	list_add_tail(&io_end->list, &ei->i_unrsv_conversion_list);
	}
	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
	}

	static int ext4_do_flush_completed_IO(struct inode *inode,
	struct list_head *head)
	{
	ext4_io_end_t *io;
	struct list_head unwritten;
	unsigned long flags;
	struct ext4_inode_info *ei = EXT4_I(inode);
	int err, ret = 0;

	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
	dump_completed_IO(inode, head);
	list_replace_init(head, &unwritten);
	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

	while (!list_empty(&unwritten)) {
	io = list_entry(unwritten.next, ext4_io_end_t, list);
	BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
	list_del_init(&io->list);

	err = ext4_end_io(io);
	if (unlikely(!ret && err))
	ret = err;
	}
	return ret;
	}

	/*
	* work on completed IO, to convert unwritten extents to extents
	*/
	void ext4_end_io_rsv_work(struct work_struct *work)
	{
	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
	i_rsv_conversion_work);
	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
	}

	void ext4_end_io_unrsv_work(struct work_struct *work)
	{
	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
	i_unrsv_conversion_work);
	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_unrsv_conversion_list);
	}

	ext4_io_end_t ext4_init_io_end(struct inode inode, gfp_t flags)
	{
	ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
	if (io) {
	atomic_inc(&EXT4_I(inode)->i_ioend_count);
	io->inode = inode;
	INIT_LIST_HEAD(&io->list);
	atomic_set(&io->count, 1);
	}
	return io;
	}

	void ext4_put_io_end_defer(ext4_io_end_t *io_end)
	{
	if (atomic_dec_and_test(&io_end->count)) {
	if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) \|\| !io_end->size) {
	ext4_release_io_end(io_end);
	return;
	}
	ext4_add_complete_io(io_end);
	}
	}

	int ext4_put_io_end(ext4_io_end_t *io_end)
	{
	int err = 0;

	if (atomic_dec_and_test(&io_end->count)) {
	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
	err = ext4_convert_unwritten_extents(io_end->handle,
	io_end->inode, io_end->offset,
	io_end->size);
	io_end->handle = NULL;
	ext4_clear_io_unwritten_flag(io_end);
	}
	ext4_release_io_end(io_end);
	}
	return err;
	}

	ext4_io_end_t ext4_get_io_end(ext4_io_end_t io_end)
	{
	atomic_inc(&io_end->count);
	return io_end;
	}

	/* BIO completion function for page writeback */
	static void ext4_end_bio(struct bio *bio, int error)
	{
	ext4_io_end_t *io_end = bio->bi_private;
	sector_t bi_sector = bio->bi_sector;

	BUG_ON(!io_end);
	bio->bi_end_io = NULL;
	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
	error = 0;

	if (error) {
	struct inode *inode = io_end->inode;

	ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
	"(offset %llu size %ld starting block %llu)",
	inode->i_ino,
	(unsigned long long) io_end->offset,
	(long) io_end->size,
	(unsigned long long)
	bi_sector >> (inode->i_blkbits - 9));
	}

	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
	/*
	* Link bio into list hanging from io_end. We have to do it
	* atomically as bio completions can be racing against each
	* other.
	*/
	bio->bi_private = xchg(&io_end->bio, bio);
	ext4_put_io_end_defer(io_end);
	} else {
	/*
	* Drop io_end reference early. Inode can get freed once
	* we finish the bio.
	*/
	ext4_put_io_end_defer(io_end);
	ext4_finish_bio(bio);
	bio_put(bio);
	}
	}

	void ext4_io_submit(struct ext4_io_submit *io)
	{
	struct bio *bio = io->io_bio;

	if (bio) {
	bio_get(io->io_bio);
	submit_bio(io->io_op, io->io_bio);
	BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
	bio_put(io->io_bio);
	}
	io->io_bio = NULL;
	}

	void ext4_io_submit_init(struct ext4_io_submit *io,
	struct writeback_control *wbc)
	{
	io->io_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
	io->io_bio = NULL;
	io->io_end = NULL;
	}

	static int io_submit_init_bio(struct ext4_io_submit *io,
	struct buffer_head *bh)
	{
	int nvecs = bio_get_nr_vecs(bh->b_bdev);
	struct bio *bio;

	bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
	if (!bio)
	return -ENOMEM;
	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
	bio->bi_bdev = bh->b_bdev;
	bio->bi_end_io = ext4_end_bio;
	bio->bi_private = ext4_get_io_end(io->io_end);
	io->io_bio = bio;
	io->io_next_block = bh->b_blocknr;
	return 0;
	}

	static int io_submit_add_bh(struct ext4_io_submit *io,
	struct inode *inode,
	struct buffer_head *bh)
	{
	int ret;

	if (io->io_bio && bh->b_blocknr != io->io_next_block) {
	submit_and_retry:
	ext4_io_submit(io);
	}
	if (io->io_bio == NULL) {
	ret = io_submit_init_bio(io, bh);
	if (ret)
	return ret;
	}
	ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
	if (ret != bh->b_size)
	goto submit_and_retry;
	io->io_next_block++;
	return 0;
	}

	int ext4_bio_write_page(struct ext4_io_submit *io,
	struct page *page,
	int len,
	struct writeback_control *wbc)
	{
	struct inode *inode = page->mapping->host;
	unsigned block_start, blocksize;
	struct buffer_head bh, head;
	int ret = 0;
	int nr_submitted = 0;

	blocksize = 1 << inode->i_blkbits;

	BUG_ON(!PageLocked(page));
	BUG_ON(PageWriteback(page));

	set_page_writeback(page);
	ClearPageError(page);

	/*
	* In the first loop we prepare and mark buffers to submit. We have to
	* mark all buffers in the page before submitting so that
	* end_page_writeback() cannot be called from ext4_bio_end_io() when IO
	* on the first buffer finishes and we are still working on submitting
	* the second buffer.
	*/
	bh = head = page_buffers(page);
	do {
	block_start = bh_offset(bh);
	if (block_start >= len) {
	/*
	* Comments copied from block_write_full_page_endio:
	*
	* The page straddles i_size. It must be zeroed out on
	* each and every writepage invocation because it may
	* be mmapped. "A file is mapped in multiples of the
	* page size. For a file that is not a multiple of
	* the page size, the remaining memory is zeroed when
	* mapped, and writes to that region are not written
	* out to the file."
	*/
	zero_user_segment(page, block_start,
	block_start + blocksize);
	clear_buffer_dirty(bh);
	set_buffer_uptodate(bh);
	continue;
	}
	if (!buffer_dirty(bh) \|\| buffer_delay(bh) \|\|
	!buffer_mapped(bh) \|\| buffer_unwritten(bh)) {
	/* A hole? We can safely clear the dirty bit */
	if (!buffer_mapped(bh))
	clear_buffer_dirty(bh);
	if (io->io_bio)
	ext4_io_submit(io);
	continue;
	}
	if (buffer_new(bh)) {
	clear_buffer_new(bh);
	unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
	}
	set_buffer_async_write(bh);
	} while ((bh = bh->b_this_page) != head);

	/* Now submit buffers to write */
	bh = head = page_buffers(page);
	do {
	if (!buffer_async_write(bh))
	continue;
	ret = io_submit_add_bh(io, inode, bh);
	if (ret) {
	/*
	* We only get here on ENOMEM. Not much else
	* we can do but mark the page as dirty, and
	* better luck next time.
	*/
	redirty_page_for_writepage(wbc, page);
	break;
	}
	nr_submitted++;
	clear_buffer_dirty(bh);
	} while ((bh = bh->b_this_page) != head);

	/* Error stopped previous loop? Clean up buffers... */
	if (ret) {
	do {
	clear_buffer_async_write(bh);
	bh = bh->b_this_page;
	} while (bh != head);
	}
	unlock_page(page);
	/* Nothing submitted - we have to end page writeback */
	if (!nr_submitted)
	end_page_writeback(page);
	return ret;
	}