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ext4: dirty page has always buffers attached

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ext4_writepage(), write_cache_pages_da(), and mpage_da_submit_io()
doesn't have to deal with the case when page doesn't have buffers. We
attach buffers to a page in ->write_begin() and ->page_mkwrite() which
covers all places where a page can become dirty.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara 2013-01-28 12:55:08 -05:00 committed by Theodore Ts'o
parent 002bd7fa3a
commit f8bec37037
1 changed files with 38 additions and 109 deletions
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147
fs/ext4/inode.c
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@ -132,8 +132,6 @@ static inline int ext4_begin_ordered_truncate(struct inode *inode,
}
static void ext4_invalidatepage(struct page *page, unsigned long offset);
static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create);
static int __ext4_journalled_writepage(struct page *page, unsigned int len);
static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);
static int ext4_discard_partial_page_buffers_no_lock(handle_t *handle,
@ -1374,7 +1372,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
if (nr_pages == 0)
break;
for (i = 0; i < nr_pages; i++) {
int commit_write = 0, skip_page = 0;
int skip_page = 0;
struct page *page = pvec.pages[i];
index = page->index;
@ -1396,27 +1394,9 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
BUG_ON(!PageLocked(page));
BUG_ON(PageWriteback(page));
/*
* If the page does not have buffers (for
* whatever reason), try to create them using
* __block_write_begin. If this fails,
* skip the page and move on.
*/
if (!page_has_buffers(page)) {
if (__block_write_begin(page, 0, len,
noalloc_get_block_write)) {
skip_page:
unlock_page(page);
continue;
}
commit_write = 1;
}
bh = page_bufs = page_buffers(page);
block_start = 0;
do {
if (!bh)
goto skip_page;
if (map && (cur_logical >= map->m_lblk) &&
(cur_logical <= (map->m_lblk +
(map->m_len - 1)))) {
@ -1444,12 +1424,10 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
pblock++;
} while (bh != page_bufs);
if (skip_page)
goto skip_page;
if (commit_write)
/* mark the buffer_heads as dirty & uptodate */
block_commit_write(page, 0, len);
if (skip_page) {
unlock_page(page);
continue;
}
clear_page_dirty_for_io(page);
err = ext4_bio_write_page(&io_submit, page, len,
@ -1869,27 +1847,6 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
return 0;
}
/*
* This function is used as a standard get_block_t calback function when there
* is no desire to allocate any blocks. It is used as a callback function for
* block_write_begin(). These functions should only try to map a single block
* at a time.
*
* Since this function doesn't do block allocations even if the caller
* requests it by passing in create=1, it is critically important that
* any caller checks to make sure that any buffer heads are returned
* by this function are either all already mapped or marked for
* delayed allocation before calling ext4_bio_write_page(). Otherwise,
* b_blocknr could be left unitialized, and the page write functions will
* be taken by surprise.
*/
static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
return _ext4_get_block(inode, iblock, bh_result, 0);
}
static int bget_one(handle_t *handle, struct buffer_head *bh)
{
get_bh(bh);
@ -2014,7 +1971,7 @@ static int __ext4_journalled_writepage(struct page *page,
static int ext4_writepage(struct page *page,
struct writeback_control *wbc)
{
int ret = 0, commit_write = 0;
int ret = 0;
loff_t size;
unsigned int len;
struct buffer_head *page_bufs = NULL;
@ -2028,21 +1985,6 @@ static int ext4_writepage(struct page *page,
else
len = PAGE_CACHE_SIZE;
/*
* If the page does not have buffers (for whatever reason),
* try to create them using __block_write_begin. If this
* fails, redirty the page and move on.
*/
if (!page_has_buffers(page)) {
if (__block_write_begin(page, 0, len,
noalloc_get_block_write)) {
redirty_page:
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return 0;
}
commit_write = 1;
}
page_bufs = page_buffers(page);
if (ext4_walk_page_buffers(NULL, page_bufs, 0, len, NULL,
ext4_bh_delay_or_unwritten)) {
@ -2056,11 +1998,10 @@ static int ext4_writepage(struct page *page,
*/
WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
PF_MEMALLOC);
goto redirty_page;
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return 0;
}
if (commit_write)
/* now mark the buffer_heads as dirty and uptodate */
block_commit_write(page, 0, len);
if (PageChecked(page) && ext4_should_journal_data(inode))
/*
@ -2203,51 +2144,39 @@ static int write_cache_pages_da(handle_t *handle,
logical = (sector_t) page->index <<
(PAGE_CACHE_SHIFT - inode->i_blkbits);
if (!page_has_buffers(page)) {
mpage_add_bh_to_extent(mpd, logical,
PAGE_CACHE_SIZE,
(1 << BH_Dirty) | (1 << BH_Uptodate));
if (mpd->io_done)
goto ret_extent_tail;
} else {
/* Add all dirty buffers to mpd */
head = page_buffers(page);
bh = head;
do {
BUG_ON(buffer_locked(bh));
/*
* Page with regular buffer heads,
* just add all dirty ones
* We need to try to allocate unmapped blocks
* in the same page. Otherwise we won't make
* progress with the page in ext4_writepage
*/
head = page_buffers(page);
bh = head;
do {
BUG_ON(buffer_locked(bh));
if (ext4_bh_delay_or_unwritten(NULL, bh)) {
mpage_add_bh_to_extent(mpd, logical,
bh->b_size,
bh->b_state);
if (mpd->io_done)
goto ret_extent_tail;
} else if (buffer_dirty(bh) &&
buffer_mapped(bh)) {
/*
* We need to try to allocate
* unmapped blocks in the same page.
* Otherwise we won't make progress
* with the page in ext4_writepage
* mapped dirty buffer. We need to
* update the b_state because we look
* at b_state in mpage_da_map_blocks.
* We don't update b_size because if we
* find an unmapped buffer_head later
* we need to use the b_state flag of
* that buffer_head.
*/
if (ext4_bh_delay_or_unwritten(NULL, bh)) {
mpage_add_bh_to_extent(mpd, logical,
bh->b_size,
bh->b_state);
if (mpd->io_done)
goto ret_extent_tail;
} else if (buffer_dirty(bh) && (buffer_mapped(bh))) {
/*
* mapped dirty buffer. We need
* to update the b_state
* because we look at b_state
* in mpage_da_map_blocks. We
* don't update b_size because
* if we find an unmapped
* buffer_head later we need to
* use the b_state flag of that
* buffer_head.
*/
if (mpd->b_size == 0)
mpd->b_state = bh->b_state & BH_FLAGS;
}
logical++;
} while ((bh = bh->b_this_page) != head);
}
if (mpd->b_size == 0)
mpd->b_state =
bh->b_state & BH_FLAGS;
}
logical++;
} while ((bh = bh->b_this_page) != head);
if (nr_to_write > 0) {
nr_to_write--;