[net-next-2.6.git] / fs / ext4 / page-io.c

/*
 * 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 ext4_init_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 ext4_exit_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;
}
Commit	Line	Data
bd2d0210 TT	1	/*
	2	* linux/fs/ext4/page-io.c
	3	*
	4	* This contains the new page_io functions for ext4
	5	*
	6	* Written by Theodore Ts'o, 2010.
	7	*/
	8
	9	#include <linux/module.h>
	10	#include <linux/fs.h>
	11	#include <linux/time.h>
	12	#include <linux/jbd2.h>
	13	#include <linux/highuid.h>
	14	#include <linux/pagemap.h>
	15	#include <linux/quotaops.h>
	16	#include <linux/string.h>
	17	#include <linux/buffer_head.h>
	18	#include <linux/writeback.h>
	19	#include <linux/pagevec.h>
	20	#include <linux/mpage.h>
	21	#include <linux/namei.h>
	22	#include <linux/uio.h>
	23	#include <linux/bio.h>
	24	#include <linux/workqueue.h>
	25	#include <linux/kernel.h>
	26	#include <linux/slab.h>
	27
	28	#include "ext4_jbd2.h"
	29	#include "xattr.h"
	30	#include "acl.h"
	31	#include "ext4_extents.h"
	32
	33	static struct kmem_cache io_page_cachep, io_end_cachep;
	34
5dabfc78	35	int __init ext4_init_pageio(void)
bd2d0210 TT	36	{
	37	io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT);
	38	if (io_page_cachep == NULL)
	39	return -ENOMEM;
	40	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
	41	if (io_page_cachep == NULL) {
	42	kmem_cache_destroy(io_page_cachep);
	43	return -ENOMEM;
	44	}
	45
	46	return 0;
	47	}
	48
5dabfc78	49	void ext4_exit_pageio(void)
bd2d0210 TT	50	{
	51	kmem_cache_destroy(io_end_cachep);
	52	kmem_cache_destroy(io_page_cachep);
	53	}
	54
	55	void ext4_free_io_end(ext4_io_end_t *io)
	56	{
	57	int i;
	58
	59	BUG_ON(!io);
	60	if (io->page)
	61	put_page(io->page);
	62	for (i = 0; i < io->num_io_pages; i++) {
	63	if (--io->pages[i]->p_count == 0) {
	64	struct page *page = io->pages[i]->p_page;
	65
	66	end_page_writeback(page);
	67	put_page(page);
	68	kmem_cache_free(io_page_cachep, io->pages[i]);
	69	}
	70	}
	71	io->num_io_pages = 0;
	72	iput(io->inode);
	73	kmem_cache_free(io_end_cachep, io);
	74	}
	75
	76	/*
	77	* check a range of space and convert unwritten extents to written.
	78	*/
	79	int ext4_end_io_nolock(ext4_io_end_t *io)
	80	{
	81	struct inode *inode = io->inode;
	82	loff_t offset = io->offset;
	83	ssize_t size = io->size;
	84	int ret = 0;
	85
	86	ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
	87	"list->prev 0x%p\n",
	88	io, inode->i_ino, io->list.next, io->list.prev);
	89
	90	if (list_empty(&io->list))
	91	return ret;
	92
	93	if (!(io->flag & EXT4_IO_END_UNWRITTEN))
	94	return ret;
	95
	96	ret = ext4_convert_unwritten_extents(inode, offset, size);
	97	if (ret < 0) {
	98	printk(KERN_EMERG "%s: failed to convert unwritten "
	99	"extents to written extents, error is %d "
	100	"io is still on inode %lu aio dio list\n",
	101	__func__, ret, inode->i_ino);
	102	return ret;
	103	}
	104
	105	if (io->iocb)
	106	aio_complete(io->iocb, io->result, 0);
	107	/* clear the DIO AIO unwritten flag */
	108	io->flag &= ~EXT4_IO_END_UNWRITTEN;
	109	return ret;
	110	}
	111
	112	/*
	113	* work on completed aio dio IO, to convert unwritten extents to extents
114	*/
115	static void ext4_end_io_work(struct work_struct *work)
116	{
117	ext4_io_end_t *io = container_of(work, ext4_io_end_t, work);
118	struct inode *inode = io->inode;
119	struct ext4_inode_info *ei = EXT4_I(inode);
120	unsigned long flags;
121	int ret;
122
123	mutex_lock(&inode->i_mutex);
124	ret = ext4_end_io_nolock(io);
125	if (ret < 0) {
126	mutex_unlock(&inode->i_mutex);
127	return;
128	}
129
130	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
131	if (!list_empty(&io->list))
132	list_del_init(&io->list);
133	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
134	mutex_unlock(&inode->i_mutex);
135	ext4_free_io_end(io);
136	}
137
138	ext4_io_end_t ext4_init_io_end(struct inode inode, gfp_t flags)
139	{
140	ext4_io_end_t *io = NULL;
141
142	io = kmem_cache_alloc(io_end_cachep, flags);
143	if (io) {
144	memset(io, 0, sizeof(*io));
145	io->inode = igrab(inode);
146	BUG_ON(!io->inode);
147	INIT_WORK(&io->work, ext4_end_io_work);
148	INIT_LIST_HEAD(&io->list);
149	}
150	return io;
151	}
152
153	/*
154	* Print an buffer I/O error compatible with the fs/buffer.c. This
155	* provides compatibility with dmesg scrapers that look for a specific
156	* buffer I/O error message. We really need a unified error reporting
157	* structure to userspace ala Digital Unix's uerf system, but it's
158	* probably not going to happen in my lifetime, due to LKML politics...
159	*/
160	static void buffer_io_error(struct buffer_head *bh)
161	{
162	char b[BDEVNAME_SIZE];
163	printk(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
164	bdevname(bh->b_bdev, b),
165	(unsigned long long)bh->b_blocknr);
166	}
167
168	static void ext4_end_bio(struct bio *bio, int error)
169	{
170	ext4_io_end_t *io_end = bio->bi_private;
171	struct workqueue_struct *wq;
172	struct inode *inode;
173	unsigned long flags;
174	ext4_fsblk_t err_block;
175	int i;
176
177	BUG_ON(!io_end);
178	inode = io_end->inode;
179	bio->bi_private = NULL;
180	bio->bi_end_io = NULL;
181	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
182	error = 0;
183	err_block = bio->bi_sector >> (inode->i_blkbits - 9);
184	bio_put(bio);
185
186	if (!(inode->i_sb->s_flags & MS_ACTIVE)) {
187	pr_err("sb umounted, discard end_io request for inode %lu\n",
188	io_end->inode->i_ino);
189	ext4_free_io_end(io_end);
190	return;
191	}
192
193	if (error) {
194	io_end->flag \|= EXT4_IO_END_ERROR;
195	ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
196	"(offset %llu size %ld starting block %llu)",
197	inode->i_ino,
198	(unsigned long long) io_end->offset,
199	(long) io_end->size,
200	(unsigned long long) err_block);
201	}
202
203	for (i = 0; i < io_end->num_io_pages; i++) {
204	struct page *page = io_end->pages[i]->p_page;
205	struct buffer_head bh, head;
206	int partial_write = 0;
207
208	head = page_buffers(page);
209	if (error)
210	SetPageError(page);
211	BUG_ON(!head);
212	if (head->b_size == PAGE_CACHE_SIZE)
213	clear_buffer_dirty(head);
214	else {
215	loff_t offset;
216	loff_t io_end_offset = io_end->offset + io_end->size;
217
218	offset = (sector_t) page->index << PAGE_CACHE_SHIFT;
219	bh = head;
220	do {
221	if ((offset >= io_end->offset) &&
222	(offset+bh->b_size <= io_end_offset)) {
223	if (error)
224	buffer_io_error(bh);
225
226	clear_buffer_dirty(bh);
227	}
228	if (buffer_delay(bh))
229	partial_write = 1;
230	else if (!buffer_mapped(bh))
231	clear_buffer_dirty(bh);
232	else if (buffer_dirty(bh))
233	partial_write = 1;
234	offset += bh->b_size;
235	bh = bh->b_this_page;
236	} while (bh != head);
237	}
238
239	if (--io_end->pages[i]->p_count == 0) {
240	struct page *page = io_end->pages[i]->p_page;
241
242	end_page_writeback(page);
243	put_page(page);
244	kmem_cache_free(io_page_cachep, io_end->pages[i]);
245	}
246
247	/*
248	* If this is a partial write which happened to make
249	* all buffers uptodate then we can optimize away a
250	* bogus readpage() for the next read(). Here we
251	* 'discover' whether the page went uptodate as a
252	* result of this (potentially partial) write.
253	*/
254	if (!partial_write)
255	SetPageUptodate(page);
256	}
257
258	io_end->num_io_pages = 0;
259
260	/* Add the io_end to per-inode completed io list*/
261	spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
262	list_add_tail(&io_end->list, &EXT4_I(inode)->i_completed_io_list);
263	spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);
264
265	wq = EXT4_SB(inode->i_sb)->dio_unwritten_wq;
266	/* queue the work to convert unwritten extents to written */
267	queue_work(wq, &io_end->work);
268	}
269
270	void ext4_io_submit(struct ext4_io_submit *io)
271	{
272	struct bio *bio = io->io_bio;
273
274	if (bio) {
275	bio_get(io->io_bio);
276	submit_bio(io->io_op, io->io_bio);
277	BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
278	bio_put(io->io_bio);
279	}
280	io->io_bio = 0;
281	io->io_op = 0;
282	io->io_end = 0;
283	}
284
285	static int io_submit_init(struct ext4_io_submit *io,
286	struct inode *inode,
287	struct writeback_control *wbc,
288	struct buffer_head *bh)
289	{
290	ext4_io_end_t *io_end;
291	struct page *page = bh->b_page;
292	int nvecs = bio_get_nr_vecs(bh->b_bdev);
293	struct bio *bio;
294
295	io_end = ext4_init_io_end(inode, GFP_NOFS);
296	if (!io_end)
297	return -ENOMEM;
298	do {
299	bio = bio_alloc(GFP_NOIO, nvecs);
300	nvecs >>= 1;
301	} while (bio == NULL);
302
303	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
304	bio->bi_bdev = bh->b_bdev;
305	bio->bi_private = io->io_end = io_end;
306	bio->bi_end_io = ext4_end_bio;
307
308	io_end->inode = inode;
309	io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);
310
311	io->io_bio = bio;
312	io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?
313	WRITE_SYNC_PLUG : WRITE);
314	io->io_next_block = bh->b_blocknr;
315	return 0;
316	}
317
318	static int io_submit_add_bh(struct ext4_io_submit *io,
319	struct ext4_io_page *io_page,
320	struct inode *inode,
321	struct writeback_control *wbc,
322	struct buffer_head *bh)
323	{
324	ext4_io_end_t *io_end;
325	int ret;
326
327	if (buffer_new(bh)) {
328	clear_buffer_new(bh);
329	unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
330	}
331
332	if (!buffer_mapped(bh) \|\| buffer_delay(bh)) {
333	if (!buffer_mapped(bh))
334	clear_buffer_dirty(bh);
335	if (io->io_bio)
336	ext4_io_submit(io);
337	return 0;
338	}
339
340	if (io->io_bio && bh->b_blocknr != io->io_next_block) {
341	submit_and_retry:
342	ext4_io_submit(io);
343	}
344	if (io->io_bio == NULL) {
345	ret = io_submit_init(io, inode, wbc, bh);
346	if (ret)
347	return ret;
348	}
349	io_end = io->io_end;
350	if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
351	(io_end->pages[io_end->num_io_pages-1] != io_page))
352	goto submit_and_retry;
353	if (buffer_uninit(bh))
354	io->io_end->flag \|= EXT4_IO_END_UNWRITTEN;
355	io->io_end->size += bh->b_size;
356	io->io_next_block++;
357	ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
358	if (ret != bh->b_size)
359	goto submit_and_retry;
360	if ((io_end->num_io_pages == 0) \|\|
361	(io_end->pages[io_end->num_io_pages-1] != io_page)) {
362	io_end->pages[io_end->num_io_pages++] = io_page;
363	io_page->p_count++;
364	}
365	return 0;
366	}
367
368	int ext4_bio_write_page(struct ext4_io_submit *io,
369	struct page *page,
370	int len,
371	struct writeback_control *wbc)
372	{
373	struct inode *inode = page->mapping->host;
374	unsigned block_start, block_end, blocksize;
375	struct ext4_io_page *io_page;
376	struct buffer_head bh, head;
377	int ret = 0;
378
379	blocksize = 1 << inode->i_blkbits;
380
381	BUG_ON(PageWriteback(page));
382	set_page_writeback(page);
383	ClearPageError(page);
384
385	io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
386	if (!io_page) {
387	set_page_dirty(page);
388	unlock_page(page);
389	return -ENOMEM;
390	}
391	io_page->p_page = page;
392	io_page->p_count = 0;
393	get_page(page);
394
395	for (bh = head = page_buffers(page), block_start = 0;
396	bh != head \|\| !block_start;
397	block_start = block_end, bh = bh->b_this_page) {
398	block_end = block_start + blocksize;
399	if (block_start >= len) {
400	clear_buffer_dirty(bh);
401	set_buffer_uptodate(bh);
402	continue;
403	}
404	ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
405	if (ret) {
406	/*
407	* We only get here on ENOMEM. Not much else
408	* we can do but mark the page as dirty, and
409	* better luck next time.
410	*/
411	set_page_dirty(page);
412	break;
413	}
414	}
415	unlock_page(page);
416	/*
417	* If the page was truncated before we could do the writeback,
418	* or we had a memory allocation error while trying to write
419	* the first buffer head, we won't have submitted any pages for
420	* I/O. In that case we need to make sure we've cleared the
421	* PageWriteback bit from the page to prevent the system from
422	* wedging later on.
423	*/
424	if (io_page->p_count == 0) {
425	put_page(page);
426	end_page_writeback(page);
427	kmem_cache_free(io_page_cachep, io_page);
428	}
429	return ret;
430	}