ext4: use bio layer instead of buffer layer in mpage_da_submit_io (bd2d0210) · Commits · e / devices / android_kernel_sony_msm8998

fs/ext4/Makefile

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -4,7 +4,7 @@

	obj-$(CONFIG_EXT4_FS) += ext4.o		obj-$(CONFIG_EXT4_FS) += ext4.o

	ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \		ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
	ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \		ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
	ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o		ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o

fs/ext4/ext4.h

+35 −1

Original line number	Original line	Diff line number	Diff line
	@@ -168,7 +168,20 @@ struct mpage_da_data {
	int pages_written;		int pages_written;
	int retval;		int retval;
	};		};
	#define EXT4_IO_UNWRITTEN 0x1
			/*
			* Flags for ext4_io_end->flags
			*/
			#define EXT4_IO_END_UNWRITTEN 0x0001
			#define EXT4_IO_END_ERROR 0x0002

			struct ext4_io_page {
			struct page *p_page;
			int p_count;
			};

			#define MAX_IO_PAGES 128

	typedef struct ext4_io_end {		typedef struct ext4_io_end {
	struct list_head list; /* per-file finished IO list */		struct list_head list; /* per-file finished IO list */
	struct inode inode; / file being written to */		struct inode inode; / file being written to */
	@@ -179,8 +192,18 @@ typedef struct ext4_io_end {
	struct work_struct work; /* data work queue */		struct work_struct work; /* data work queue */
	struct kiocb iocb; / iocb struct for AIO */		struct kiocb iocb; / iocb struct for AIO */
	int result; /* error value for AIO */		int result; /* error value for AIO */
			int num_io_pages;
			struct ext4_io_page *pages[MAX_IO_PAGES];
	} ext4_io_end_t;		} ext4_io_end_t;

			struct ext4_io_submit {
			int io_op;
			struct bio *io_bio;
			ext4_io_end_t *io_end;
			struct ext4_io_page *io_page;
			sector_t io_next_block;
			};

	/*		/*
	* Special inodes numbers		* Special inodes numbers
	*/		*/
	@@ -2044,6 +2067,17 @@ extern int ext4_move_extents(struct file o_filp, struct file d_filp,
	__u64 start_orig, __u64 start_donor,		__u64 start_orig, __u64 start_donor,
	__u64 len, __u64 *moved_len);		__u64 len, __u64 *moved_len);

			/* page-io.c */
			extern int __init init_ext4_pageio(void);
			extern void exit_ext4_pageio(void);
			extern void ext4_free_io_end(ext4_io_end_t *io);
			extern ext4_io_end_t ext4_init_io_end(struct inode inode, gfp_t flags);
			extern int ext4_end_io_nolock(ext4_io_end_t *io);
			extern void ext4_io_submit(struct ext4_io_submit *io);
			extern int ext4_bio_write_page(struct ext4_io_submit *io,
			struct page *page,
			int len,
			struct writeback_control *wbc);

	/* BH_Uninit flag: blocks are allocated but uninitialized on disk */		/* BH_Uninit flag: blocks are allocated but uninitialized on disk */
	enum ext4_state_bits {		enum ext4_state_bits {

fs/ext4/extents.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -3202,7 +3202,7 @@ ext4_ext_handle_uninitialized_extents(handle_t handle, struct inode inode,
	* completed		* completed
	*/		*/
	if (io)		if (io)
	io->flag = EXT4_IO_UNWRITTEN;		io->flag = EXT4_IO_END_UNWRITTEN;
	else		else
	ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);		ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
	if (ext4_should_dioread_nolock(inode))		if (ext4_should_dioread_nolock(inode))
	@@ -3494,7 +3494,7 @@ int ext4_ext_map_blocks(handle_t handle, struct inode inode,
	*/		*/
	if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {		if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
	if (io)		if (io)
	io->flag = EXT4_IO_UNWRITTEN;		io->flag = EXT4_IO_END_UNWRITTEN;
	else		else
	ext4_set_inode_state(inode,		ext4_set_inode_state(inode,
	EXT4_STATE_DIO_UNWRITTEN);		EXT4_STATE_DIO_UNWRITTEN);

fs/ext4/inode.c

+14 −104

Original line number	Original line	Diff line number	Diff line
	@@ -2016,8 +2016,10 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
	struct buffer_head bh, page_bufs = NULL;		struct buffer_head bh, page_bufs = NULL;
	int journal_data = ext4_should_journal_data(inode);		int journal_data = ext4_should_journal_data(inode);
	sector_t pblock = 0, cur_logical = 0;		sector_t pblock = 0, cur_logical = 0;
			struct ext4_io_submit io_submit;

	BUG_ON(mpd->next_page <= mpd->first_page);		BUG_ON(mpd->next_page <= mpd->first_page);
			memset(&io_submit, 0, sizeof(io_submit));
	/*		/*
	* We need to start from the first_page to the next_page - 1		* We need to start from the first_page to the next_page - 1
	* to make sure we also write the mapped dirty buffer_heads.		* to make sure we also write the mapped dirty buffer_heads.
	@@ -2109,16 +2111,16 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
	/* mark the buffer_heads as dirty & uptodate */		/* mark the buffer_heads as dirty & uptodate */
	block_commit_write(page, 0, len);		block_commit_write(page, 0, len);

	if (journal_data && PageChecked(page))		/*
			* Delalloc doesn't support data journalling,
			* but eventually maybe we'll lift this
			* restriction.
			*/
			if (unlikely(journal_data && PageChecked(page)))
	err = __ext4_journalled_writepage(page, len);		err = __ext4_journalled_writepage(page, len);
	else if (buffer_uninit(page_bufs)) {		else
	ext4_set_bh_endio(page_bufs, inode);		err = ext4_bio_write_page(&io_submit, page,
	err = block_write_full_page_endio(page,		len, mpd->wbc);
	noalloc_get_block_write,
	mpd->wbc, ext4_end_io_buffer_write);
	} else
	err = block_write_full_page(page,
	noalloc_get_block_write, mpd->wbc);

	if (!err)		if (!err)
	mpd->pages_written++;		mpd->pages_written++;
	@@ -2131,6 +2133,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
	}		}
	pagevec_release(&pvec);		pagevec_release(&pvec);
	}		}
			ext4_io_submit(&io_submit);
	return ret;		return ret;
	}		}

	@@ -3426,15 +3429,6 @@ ext4_readpages(struct file file, struct address_space mapping,
	return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);		return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);
	}		}

	static void ext4_free_io_end(ext4_io_end_t *io)
	{
	BUG_ON(!io);
	if (io->page)
	put_page(io->page);
	iput(io->inode);
	kfree(io);
	}

	static void ext4_invalidatepage_free_endio(struct page *page, unsigned long offset)		static void ext4_invalidatepage_free_endio(struct page *page, unsigned long offset)
	{		{
	struct buffer_head head, bh;		struct buffer_head head, bh;
	@@ -3639,68 +3633,6 @@ static void dump_completed_IO(struct inode * inode)
	#endif		#endif
	}		}

	/*
	* check a range of space and convert unwritten extents to written.
	*/
	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("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 != EXT4_IO_UNWRITTEN)
	return ret;

	ret = ext4_convert_unwritten_extents(inode, offset, size);
	if (ret < 0) {
	printk(KERN_EMERG "%s: failed to convert unwritten"
	"extents to written extents, error is %d"
	" io is still on inode %lu aio dio list\n",
	__func__, ret, inode->i_ino);
	return ret;
	}

	if (io->iocb)
	aio_complete(io->iocb, io->result, 0);
	/* clear the DIO AIO unwritten flag */
	io->flag = 0;
	return ret;
	}

	/*
	* work on completed aio dio IO, to convert unwritten extents to extents
	*/
	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;
	struct ext4_inode_info *ei = EXT4_I(inode);
	unsigned long flags;
	int ret;

	mutex_lock(&inode->i_mutex);
	ret = ext4_end_io_nolock(io);
	if (ret < 0) {
	mutex_unlock(&inode->i_mutex);
	return;
	}

	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
	if (!list_empty(&io->list))
	list_del_init(&io->list);
	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
	mutex_unlock(&inode->i_mutex);
	ext4_free_io_end(io);
	}

	/*		/*
	* This function is called from ext4_sync_file().		* This function is called from ext4_sync_file().
	*		*
	@@ -3756,28 +3688,6 @@ int flush_completed_IO(struct inode *inode)
	return (ret2 < 0) ? ret2 : 0;		return (ret2 < 0) ? ret2 : 0;
	}		}

	static ext4_io_end_t ext4_init_io_end (struct inode inode, gfp_t flags)
	{
	ext4_io_end_t *io = NULL;

	io = kmalloc(sizeof(*io), flags);

	if (io) {
	igrab(inode);
	io->inode = inode;
	io->flag = 0;
	io->offset = 0;
	io->size = 0;
	io->page = NULL;
	io->iocb = NULL;
	io->result = 0;
	INIT_WORK(&io->work, ext4_end_io_work);
	INIT_LIST_HEAD(&io->list);
	}

	return io;
	}

	static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,		static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
	ssize_t size, void *private, int ret,		ssize_t size, void *private, int ret,
	bool is_async)		bool is_async)
	@@ -3797,7 +3707,7 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
	size);		size);

	/* if not aio dio with unwritten extents, just free io and return */		/* if not aio dio with unwritten extents, just free io and return */
	if (io_end->flag != EXT4_IO_UNWRITTEN){		if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
	ext4_free_io_end(io_end);		ext4_free_io_end(io_end);
	iocb->private = NULL;		iocb->private = NULL;
	out:		out:
	@@ -3842,7 +3752,7 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate)
	goto out;		goto out;
	}		}

	io_end->flag = EXT4_IO_UNWRITTEN;		io_end->flag = EXT4_IO_END_UNWRITTEN;
	inode = io_end->inode;		inode = io_end->inode;

	/* Add the io_end to per-inode completed io list*/		/* Add the io_end to per-inode completed io list*/

fs/ext4/page-io.c

0 → 100644

+430 −0

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

			#include <linux/module.h>
			#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/uio.h>
			#include <linux/bio.h>
			#include <linux/workqueue.h>
			#include <linux/kernel.h>
			#include <linux/slab.h>

			#include "ext4_jbd2.h"
			#include "xattr.h"
			#include "acl.h"
			#include "ext4_extents.h"

			static struct kmem_cache io_page_cachep, io_end_cachep;

			int __init init_ext4_pageio(void)
			{
			io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT);
			if (io_page_cachep == NULL)
			return -ENOMEM;
			io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
			if (io_page_cachep == NULL) {
			kmem_cache_destroy(io_page_cachep);
			return -ENOMEM;
			}

			return 0;
			}

			void exit_ext4_pageio(void)
			{
			kmem_cache_destroy(io_end_cachep);
			kmem_cache_destroy(io_page_cachep);
			}

			void ext4_free_io_end(ext4_io_end_t *io)
			{
			int i;

			BUG_ON(!io);
			if (io->page)
			put_page(io->page);
			for (i = 0; i < io->num_io_pages; i++) {
			if (--io->pages[i]->p_count == 0) {
			struct page *page = io->pages[i]->p_page;

			end_page_writeback(page);
			put_page(page);
			kmem_cache_free(io_page_cachep, io->pages[i]);
			}
			}
			io->num_io_pages = 0;
			iput(io->inode);
			kmem_cache_free(io_end_cachep, io);
			}

			/*
			* check a range of space and convert unwritten extents to written.
			*/
			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("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 & EXT4_IO_END_UNWRITTEN))
			return ret;

			ret = ext4_convert_unwritten_extents(inode, offset, size);
			if (ret < 0) {
			printk(KERN_EMERG "%s: failed to convert unwritten "
			"extents to written extents, error is %d "
			"io is still on inode %lu aio dio list\n",
			__func__, ret, inode->i_ino);
			return ret;
			}

			if (io->iocb)
			aio_complete(io->iocb, io->result, 0);
			/* clear the DIO AIO unwritten flag */
			io->flag &= ~EXT4_IO_END_UNWRITTEN;
			return ret;
			}

			/*
			* work on completed aio dio IO, to convert unwritten extents to extents
			*/
			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;
			struct ext4_inode_info *ei = EXT4_I(inode);
			unsigned long flags;
			int ret;

			mutex_lock(&inode->i_mutex);
			ret = ext4_end_io_nolock(io);
			if (ret < 0) {
			mutex_unlock(&inode->i_mutex);
			return;
			}

			spin_lock_irqsave(&ei->i_completed_io_lock, flags);
			if (!list_empty(&io->list))
			list_del_init(&io->list);
			spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
			mutex_unlock(&inode->i_mutex);
			ext4_free_io_end(io);
			}

			ext4_io_end_t ext4_init_io_end(struct inode inode, gfp_t flags)
			{
			ext4_io_end_t *io = NULL;

			io = kmem_cache_alloc(io_end_cachep, flags);
			if (io) {
			memset(io, 0, sizeof(*io));
			io->inode = igrab(inode);
			BUG_ON(!io->inode);
			INIT_WORK(&io->work, ext4_end_io_work);
			INIT_LIST_HEAD(&io->list);
			}
			return io;
			}

			/*
			* 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(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_end_bio(struct bio *bio, int error)
			{
			ext4_io_end_t *io_end = bio->bi_private;
			struct workqueue_struct *wq;
			struct inode *inode;
			unsigned long flags;
			ext4_fsblk_t err_block;
			int i;

			BUG_ON(!io_end);
			inode = io_end->inode;
			bio->bi_private = NULL;
			bio->bi_end_io = NULL;
			if (test_bit(BIO_UPTODATE, &bio->bi_flags))
			error = 0;
			err_block = bio->bi_sector >> (inode->i_blkbits - 9);
			bio_put(bio);

			if (!(inode->i_sb->s_flags & MS_ACTIVE)) {
			pr_err("sb umounted, discard end_io request for inode %lu\n",
			io_end->inode->i_ino);
			ext4_free_io_end(io_end);
			return;
			}

			if (error) {
			io_end->flag \|= EXT4_IO_END_ERROR;
			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) err_block);
			}

			for (i = 0; i < io_end->num_io_pages; i++) {
			struct page *page = io_end->pages[i]->p_page;
			struct buffer_head bh, head;
			int partial_write = 0;

			head = page_buffers(page);
			if (error)
			SetPageError(page);
			BUG_ON(!head);
			if (head->b_size == PAGE_CACHE_SIZE)
			clear_buffer_dirty(head);
			else {
			loff_t offset;
			loff_t io_end_offset = io_end->offset + io_end->size;

			offset = (sector_t) page->index << PAGE_CACHE_SHIFT;
			bh = head;
			do {
			if ((offset >= io_end->offset) &&
			(offset+bh->b_size <= io_end_offset)) {
			if (error)
			buffer_io_error(bh);

			clear_buffer_dirty(bh);
			}
			if (buffer_delay(bh))
			partial_write = 1;
			else if (!buffer_mapped(bh))
			clear_buffer_dirty(bh);
			else if (buffer_dirty(bh))
			partial_write = 1;
			offset += bh->b_size;
			bh = bh->b_this_page;
			} while (bh != head);
			}

			if (--io_end->pages[i]->p_count == 0) {
			struct page *page = io_end->pages[i]->p_page;

			end_page_writeback(page);
			put_page(page);
			kmem_cache_free(io_page_cachep, io_end->pages[i]);
			}

			/*
			* If this is a partial write which happened to make
			* all buffers uptodate then we can optimize away a
			* bogus readpage() for the next read(). Here we
			* 'discover' whether the page went uptodate as a
			* result of this (potentially partial) write.
			*/
			if (!partial_write)
			SetPageUptodate(page);
			}

			io_end->num_io_pages = 0;

			/* Add the io_end to per-inode completed io list*/
			spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
			list_add_tail(&io_end->list, &EXT4_I(inode)->i_completed_io_list);
			spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);

			wq = EXT4_SB(inode->i_sb)->dio_unwritten_wq;
			/* queue the work to convert unwritten extents to written */
			queue_work(wq, &io_end->work);
			}

			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 = 0;
			io->io_op = 0;
			io->io_end = 0;
			}

			static int io_submit_init(struct ext4_io_submit *io,
			struct inode *inode,
			struct writeback_control *wbc,
			struct buffer_head *bh)
			{
			ext4_io_end_t *io_end;
			struct page *page = bh->b_page;
			int nvecs = bio_get_nr_vecs(bh->b_bdev);
			struct bio *bio;

			io_end = ext4_init_io_end(inode, GFP_NOFS);
			if (!io_end)
			return -ENOMEM;
			do {
			bio = bio_alloc(GFP_NOIO, nvecs);
			nvecs >>= 1;
			} while (bio == NULL);

			bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
			bio->bi_bdev = bh->b_bdev;
			bio->bi_private = io->io_end = io_end;
			bio->bi_end_io = ext4_end_bio;

			io_end->inode = inode;
			io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);

			io->io_bio = bio;
			io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?
			WRITE_SYNC_PLUG : WRITE);
			io->io_next_block = bh->b_blocknr;
			return 0;
			}

			static int io_submit_add_bh(struct ext4_io_submit *io,
			struct ext4_io_page *io_page,
			struct inode *inode,
			struct writeback_control *wbc,
			struct buffer_head *bh)
			{
			ext4_io_end_t *io_end;
			int ret;

			if (buffer_new(bh)) {
			clear_buffer_new(bh);
			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
			}

			if (!buffer_mapped(bh) \|\| buffer_delay(bh)) {
			if (!buffer_mapped(bh))
			clear_buffer_dirty(bh);
			if (io->io_bio)
			ext4_io_submit(io);
			return 0;
			}

			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(io, inode, wbc, bh);
			if (ret)
			return ret;
			}
			io_end = io->io_end;
			if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
			(io_end->pages[io_end->num_io_pages-1] != io_page))
			goto submit_and_retry;
			if (buffer_uninit(bh))
			io->io_end->flag \|= EXT4_IO_END_UNWRITTEN;
			io->io_end->size += bh->b_size;
			io->io_next_block++;
			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;
			if ((io_end->num_io_pages == 0) \|\|
			(io_end->pages[io_end->num_io_pages-1] != io_page)) {
			io_end->pages[io_end->num_io_pages++] = io_page;
			io_page->p_count++;
			}
			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, block_end, blocksize;
			struct ext4_io_page *io_page;
			struct buffer_head bh, head;
			int ret = 0;

			blocksize = 1 << inode->i_blkbits;

			BUG_ON(PageWriteback(page));
			set_page_writeback(page);
			ClearPageError(page);

			io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
			if (!io_page) {
			set_page_dirty(page);
			unlock_page(page);
			return -ENOMEM;
			}
			io_page->p_page = page;
			io_page->p_count = 0;
			get_page(page);

			for (bh = head = page_buffers(page), block_start = 0;
			bh != head \|\| !block_start;
			block_start = block_end, bh = bh->b_this_page) {
			block_end = block_start + blocksize;
			if (block_start >= len) {
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
			continue;
			}
			ret = io_submit_add_bh(io, io_page, inode, wbc, 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.
			*/
			set_page_dirty(page);
			break;
			}
			}
			unlock_page(page);
			/*
			* If the page was truncated before we could do the writeback,
			* or we had a memory allocation error while trying to write
			* the first buffer head, we won't have submitted any pages for
			* I/O. In that case we need to make sure we've cleared the
			* PageWriteback bit from the page to prevent the system from
			* wedging later on.
			*/
			if (io_page->p_count == 0) {
			put_page(page);
			end_page_writeback(page);
			kmem_cache_free(io_page_cachep, io_page);
			}
			return ret;
			}