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consolidate generic_writepages and mpage_writepages
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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: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Miklos Szeredi authored and Linus Torvalds committed May 11, 2007
1 parent e10cc1d commit 0ea9718
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Showing 4 changed files with 93 additions and 151 deletions.
174 changes: 45 additions & 129 deletions fs/mpage.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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);
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -584,7 +592,7 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
/*
* 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:
Expand Down Expand Up @@ -641,26 +649,27 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
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;

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;
}

/**
Expand All @@ -683,136 +692,43 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
* 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;
}

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;
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);
}
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);

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);
1 change: 0 additions & 1 deletion include/linux/mpage.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down
10 changes: 8 additions & 2 deletions include/linux/writeback.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
struct writeback_control *wbc);
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);
Expand Down
59 changes: 40 additions & 19 deletions mm/page-writeback.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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 */
Expand Down Expand Up @@ -682,8 +672,7 @@ int generic_writepages(struct address_space *mapping,
continue;
}

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

if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))
unlock_page(page);
Expand All @@ -710,6 +699,38 @@ int generic_writepages(struct address_space *mapping,
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);

Expand Down

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