Commit 0ea97180 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
Browse files

consolidate generic_writepages and mpage_writepages 



Clean up massive code duplication between mpage_writepages() and
generic_writepages().

The new generic function, write_cache_pages() takes a function pointer
argument, which will be called for each page to be written.

Maybe cifs_writepages() too can use this infrastructure, but I'm not
touching that with a ten-foot pole.

The upcoming page writeback support in fuse will also want this.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Acked-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e10cc1df

fs/mpage.c

+45 −129
Original line number Diff line number Diff line
@@ -454,11 +454,18 @@ EXPORT_SYMBOL(mpage_readpage); 
 * written, so it can intelligently allocate a suitably-sized BIO.  For now,

 * just allocate full-size (16-page) BIOs.

 */

static struct bio *

__mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,

	sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc,

	writepage_t writepage_fn)

struct mpage_data {

	struct bio *bio;

	sector_t last_block_in_bio;

	get_block_t *get_block;

	unsigned use_writepage;

};



static int __mpage_writepage(struct page *page, struct writeback_control *wbc,

			     void *data)

{

	struct mpage_data *mpd = data;

	struct bio *bio = mpd->bio;

	struct address_space *mapping = page->mapping;

	struct inode *inode = page->mapping->host;

	const unsigned blkbits = inode->i_blkbits;
@@ -476,6 +483,7 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block, 
	int length;

	struct buffer_head map_bh;

	loff_t i_size = i_size_read(inode);

	int ret = 0;



	if (page_has_buffers(page)) {

		struct buffer_head *head = page_buffers(page);
@@ -538,7 +546,7 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block, 


		map_bh.b_state = 0;

		map_bh.b_size = 1 << blkbits;

		if (get_block(inode, block_in_file, &map_bh, 1))

		if (mpd->get_block(inode, block_in_file, &map_bh, 1))

			goto confused;

		if (buffer_new(&map_bh))

			unmap_underlying_metadata(map_bh.b_bdev,
@@ -584,7 +592,7 @@ page_is_mapped: 
	/*

	 * This page will go to BIO.  Do we need to send this BIO off first?

	 */

	if (bio && *last_block_in_bio != blocks[0] - 1)

	if (bio && mpd->last_block_in_bio != blocks[0] - 1)

		bio = mpage_bio_submit(WRITE, bio);



alloc_new:
@@ -641,7 +649,7 @@ alloc_new: 
					boundary_block, 1 << blkbits);

		}

	} else {

		*last_block_in_bio = blocks[blocks_per_page - 1];

		mpd->last_block_in_bio = blocks[blocks_per_page - 1];

	}

	goto out;
@@ -649,18 +657,19 @@ confused: 
	if (bio)

		bio = mpage_bio_submit(WRITE, bio);



	if (writepage_fn) {

		*ret = (*writepage_fn)(page, wbc);

	if (mpd->use_writepage) {

		ret = mapping->a_ops->writepage(page, wbc);

	} else {

		*ret = -EAGAIN;

		ret = -EAGAIN;

		goto out;

	}

	/*

	 * The caller has a ref on the inode, so *mapping is stable

	 */

	mapping_set_error(mapping, *ret);

	mapping_set_error(mapping, ret);

out:

	return bio;

	mpd->bio = bio;

	return ret;

}



/**
@@ -683,120 +692,27 @@ out: 
 * the call was made get new I/O started against them.  If wbc->sync_mode is

 * WB_SYNC_ALL then we were called for data integrity and we must wait for

 * existing IO to complete.

 *

 * If you fix this you should check generic_writepages() also!

 */

int

mpage_writepages(struct address_space *mapping,

		struct writeback_control *wbc, get_block_t get_block)

{

	struct backing_dev_info *bdi = mapping->backing_dev_info;

	struct bio *bio = NULL;

	sector_t last_block_in_bio = 0;

	int ret = 0;

	int done = 0;

	int (*writepage)(struct page *page, struct writeback_control *wbc);

	struct pagevec pvec;

	int nr_pages;

	pgoff_t index;

	pgoff_t end;		/* Inclusive */

	int scanned = 0;

	int range_whole = 0;



	if (wbc->nonblocking && bdi_write_congested(bdi)) {

		wbc->encountered_congestion = 1;

		return 0;

	int ret;



	if (!get_block)

		ret = generic_writepages(mapping, wbc);

	else {

		struct mpage_data mpd = {

			.bio = NULL,

			.last_block_in_bio = 0,

			.get_block = get_block,

			.use_writepage = 1,

		};



		ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);

		if (mpd.bio)

			mpage_bio_submit(WRITE, mpd.bio);

	}



	writepage = NULL;

	if (get_block == NULL)

		writepage = mapping->a_ops->writepage;



	pagevec_init(&pvec, 0);

	if (wbc->range_cyclic) {

		index = mapping->writeback_index; /* Start from prev offset */

		end = -1;

	} else {

		index = wbc->range_start >> PAGE_CACHE_SHIFT;

		end = wbc->range_end >> PAGE_CACHE_SHIFT;

		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)

			range_whole = 1;

		scanned = 1;

	}

retry:

	while (!done && (index <= end) &&

			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,

			PAGECACHE_TAG_DIRTY,

			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {

		unsigned i;



		scanned = 1;

		for (i = 0; i < nr_pages; i++) {

			struct page *page = pvec.pages[i];



			/*

			 * At this point we hold neither mapping->tree_lock nor

			 * lock on the page itself: the page may be truncated or

			 * invalidated (changing page->mapping to NULL), or even

			 * swizzled back from swapper_space to tmpfs file

			 * mapping

			 */



			lock_page(page);



			if (unlikely(page->mapping != mapping)) {

				unlock_page(page);

				continue;

			}



			if (!wbc->range_cyclic && page->index > end) {

				done = 1;

				unlock_page(page);

				continue;

			}



			if (wbc->sync_mode != WB_SYNC_NONE)

				wait_on_page_writeback(page);



			if (PageWriteback(page) ||

					!clear_page_dirty_for_io(page)) {

				unlock_page(page);

				continue;

			}



			if (writepage) {

				ret = (*writepage)(page, wbc);

				mapping_set_error(mapping, ret);

			} else {

				bio = __mpage_writepage(bio, page, get_block,

						&last_block_in_bio, &ret, wbc,

						page->mapping->a_ops->writepage);

			}

			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))

				unlock_page(page);

			if (ret || (--(wbc->nr_to_write) <= 0))

				done = 1;

			if (wbc->nonblocking && bdi_write_congested(bdi)) {

				wbc->encountered_congestion = 1;

				done = 1;

			}

		}

		pagevec_release(&pvec);

		cond_resched();

	}

	if (!scanned && !done) {

		/*

		 * We hit the last page and there is more work to be done: wrap

		 * back to the start of the file

		 */

		scanned = 1;

		index = 0;

		goto retry;

	}

	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))

		mapping->writeback_index = index;

	if (bio)

		mpage_bio_submit(WRITE, bio);

	return ret;

}

EXPORT_SYMBOL(mpage_writepages);
@@ -804,15 +720,15 @@ EXPORT_SYMBOL(mpage_writepages); 
int mpage_writepage(struct page *page, get_block_t get_block,

	struct writeback_control *wbc)

{

	int ret = 0;

	struct bio *bio;

	sector_t last_block_in_bio = 0;



	bio = __mpage_writepage(NULL, page, get_block,

			&last_block_in_bio, &ret, wbc, NULL);

	if (bio)

		mpage_bio_submit(WRITE, bio);



	struct mpage_data mpd = {

		.bio = NULL,

		.last_block_in_bio = 0,

		.get_block = get_block,

		.use_writepage = 0,

	};

	int ret = __mpage_writepage(page, wbc, &mpd);

	if (mpd.bio)

		mpage_bio_submit(WRITE, mpd.bio);

	return ret;

}

EXPORT_SYMBOL(mpage_writepage);

include/linux/mpage.h

+0 −1
Original line number Diff line number Diff line
@@ -12,7 +12,6 @@ 
#ifdef CONFIG_BLOCK



struct writeback_control;

typedef int (writepage_t)(struct page *page, struct writeback_control *wbc);



int mpage_readpages(struct address_space *mapping, struct list_head *pages,

				unsigned nr_pages, get_block_t get_block);

include/linux/writeback.h

+8 −2
Original line number Diff line number Diff line
@@ -111,9 +111,15 @@ balance_dirty_pages_ratelimited(struct address_space *mapping) 
	balance_dirty_pages_ratelimited_nr(mapping, 1);

}



typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,

				void *data);



int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);

extern int generic_writepages(struct address_space *mapping,

int generic_writepages(struct address_space *mapping,

		       struct writeback_control *wbc);

int write_cache_pages(struct address_space *mapping,

		      struct writeback_control *wbc, writepage_t writepage,

		      void *data);

int do_writepages(struct address_space *mapping, struct writeback_control *wbc);

int sync_page_range(struct inode *inode, struct address_space *mapping,

			loff_t pos, loff_t count);

mm/page-writeback.c

+40 −19
Original line number Diff line number Diff line
@@ -588,31 +588,27 @@ void __init page_writeback_init(void) 
}



/**

 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.

 * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.

 * @mapping: address space structure to write

 * @wbc: subtract the number of written pages from *@wbc->nr_to_write

 * @writepage: function called for each page

 * @data: data passed to writepage function

 *

 * This is a library function, which implements the writepages()

 * address_space_operation.

 *

 * If a page is already under I/O, generic_writepages() skips it, even

 * If a page is already under I/O, write_cache_pages() skips it, even

 * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,

 * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()

 * and msync() need to guarantee that all the data which was dirty at the time

 * the call was made get new I/O started against them.  If wbc->sync_mode is

 * WB_SYNC_ALL then we were called for data integrity and we must wait for

 * existing IO to complete.

 *

 * Derived from mpage_writepages() - if you fix this you should check that

 * also!

 */

int generic_writepages(struct address_space *mapping,

		       struct writeback_control *wbc)

int write_cache_pages(struct address_space *mapping,

		      struct writeback_control *wbc, writepage_t writepage,

		      void *data)

{

	struct backing_dev_info *bdi = mapping->backing_dev_info;

	int ret = 0;

	int done = 0;

	int (*writepage)(struct page *page, struct writeback_control *wbc);

	struct pagevec pvec;

	int nr_pages;

	pgoff_t index;
@@ -625,12 +621,6 @@ int generic_writepages(struct address_space *mapping, 
		return 0;

	}



	writepage = mapping->a_ops->writepage;



	/* deal with chardevs and other special file */

	if (!writepage)

		return 0;



	pagevec_init(&pvec, 0);

	if (wbc->range_cyclic) {

		index = mapping->writeback_index; /* Start from prev offset */
@@ -682,8 +672,7 @@ retry: 
				continue;

			}



			ret = (*writepage)(page, wbc);

			mapping_set_error(mapping, ret);

			ret = (*writepage)(page, wbc, data);



			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))

				unlock_page(page);
@@ -710,6 +699,38 @@ retry: 
		mapping->writeback_index = index;

	return ret;

}

EXPORT_SYMBOL(write_cache_pages);



/*

 * Function used by generic_writepages to call the real writepage

 * function and set the mapping flags on error

 */

static int __writepage(struct page *page, struct writeback_control *wbc,

		       void *data)

{

	struct address_space *mapping = data;

	int ret = mapping->a_ops->writepage(page, wbc);

	mapping_set_error(mapping, ret);

	return ret;

}



/**

 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.

 * @mapping: address space structure to write

 * @wbc: subtract the number of written pages from *@wbc->nr_to_write

 *

 * This is a library function, which implements the writepages()

 * address_space_operation.

 */

int generic_writepages(struct address_space *mapping,

		       struct writeback_control *wbc)

{

	/* deal with chardevs and other special file */

	if (!mapping->a_ops->writepage)

		return 0;



	return write_cache_pages(mapping, wbc, __writepage, mapping);

}



EXPORT_SYMBOL(generic_writepages);

CRA Git | Maintained and supported by SUSTech CRA and CCSE