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ext4: move mpage_put_bnr_to_bhs()'s functionality to mpage_da_submit_…
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…io()

This massively simplifies the ext4_da_writepages() code path by
completely removing mpage_put_bnr_bhs(), which is almost 100 lines of
code iterating over a set of pages using pagevec_lookup(), and folds
that functionality into mpage_da_submit_io()'s existing
pagevec_lookup() loop.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Theodore Ts'o committed Oct 28, 2010
1 parent 3ecdb3a commit 1de3e3d
Showing 1 changed file with 38 additions and 101 deletions.
139 changes: 38 additions & 101 deletions fs/ext4/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2003,7 +2003,8 @@ static void ext4_da_page_release_reservation(struct page *page,
*
* As pages are already locked by write_cache_pages(), we can't use it
*/
static int mpage_da_submit_io(struct mpage_da_data *mpd)
static int mpage_da_submit_io(struct mpage_da_data *mpd,
struct ext4_map_blocks *map)
{
struct pagevec pvec;
unsigned long index, end;
Expand All @@ -2014,6 +2015,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
unsigned int len, block_start;
struct buffer_head *bh, *page_bufs = NULL;
int journal_data = ext4_should_journal_data(inode);
sector_t pblock = 0, cur_logical = 0;

BUG_ON(mpd->next_page <= mpd->first_page);
/*
Expand All @@ -2031,7 +2033,7 @@ 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;
int commit_write = 0, redirty_page = 0;
struct page *page = pvec.pages[i];

index = page->index;
Expand All @@ -2042,6 +2044,12 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
len = size & ~PAGE_CACHE_MASK;
else
len = PAGE_CACHE_SIZE;
if (map) {
cur_logical = index << (PAGE_CACHE_SHIFT -
inode->i_blkbits);
pblock = map->m_pblk + (cur_logical -
map->m_lblk);
}
index++;

BUG_ON(!PageLocked(page));
Expand All @@ -2068,13 +2076,34 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
bh = page_bufs = page_buffers(page);
block_start = 0;
do {
/* redirty page if block allocation undone */
if (!bh || buffer_delay(bh) ||
buffer_unwritten(bh))
if (!bh)
goto redirty_page;
if (map && (cur_logical >= map->m_lblk) &&
(cur_logical <= (map->m_lblk +
(map->m_len - 1)))) {
if (buffer_delay(bh)) {
clear_buffer_delay(bh);
bh->b_blocknr = pblock;
}
if (buffer_unwritten(bh) ||
buffer_mapped(bh))
BUG_ON(bh->b_blocknr != pblock);
if (map->m_flags & EXT4_MAP_UNINIT)
set_buffer_uninit(bh);
clear_buffer_unwritten(bh);
}

/* redirty page if block allocation undone */
if (buffer_delay(bh) || buffer_unwritten(bh))
redirty_page = 1;
bh = bh->b_this_page;
block_start += bh->b_size;
} while ((bh != page_bufs) && (block_start < len));
cur_logical++;
pblock++;
} while (bh != page_bufs);

if (redirty_page)
goto redirty_page;

if (commit_write)
/* mark the buffer_heads as dirty & uptodate */
Expand Down Expand Up @@ -2105,91 +2134,6 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
return ret;
}

/*
* mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
*
* the function goes through all passed space and put actual disk
* block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
*/
static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd,
struct ext4_map_blocks *map)
{
struct inode *inode = mpd->inode;
struct address_space *mapping = inode->i_mapping;
int blocks = map->m_len;
sector_t pblock = map->m_pblk, cur_logical;
struct buffer_head *head, *bh;
pgoff_t index, end;
struct pagevec pvec;
int nr_pages, i;

index = map->m_lblk >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
end = (map->m_lblk + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);

pagevec_init(&pvec, 0);

while (index <= end) {
/* XXX: optimize tail */
nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
if (nr_pages == 0)
break;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];

index = page->index;
if (index > end)
break;
index++;

BUG_ON(!PageLocked(page));
BUG_ON(PageWriteback(page));
BUG_ON(!page_has_buffers(page));

bh = page_buffers(page);
head = bh;

/* skip blocks out of the range */
do {
if (cur_logical >= map->m_lblk)
break;
cur_logical++;
} while ((bh = bh->b_this_page) != head);

do {
if (cur_logical > map->m_lblk + (blocks - 1))
break;

if (buffer_delay(bh) || buffer_unwritten(bh)) {

BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);

if (buffer_delay(bh)) {
clear_buffer_delay(bh);
bh->b_blocknr = pblock;
} else {
/*
* unwritten already should have
* blocknr assigned. Verify that
*/
clear_buffer_unwritten(bh);
BUG_ON(bh->b_blocknr != pblock);
}

} else if (buffer_mapped(bh))
BUG_ON(bh->b_blocknr != pblock);

if (map->m_flags & EXT4_MAP_UNINIT)
set_buffer_uninit(bh);
cur_logical++;
pblock++;
} while ((bh = bh->b_this_page) != head);
}
pagevec_release(&pvec);
}
}


static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
sector_t logical, long blk_cnt)
{
Expand Down Expand Up @@ -2252,7 +2196,7 @@ static void ext4_print_free_blocks(struct inode *inode)
static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
{
int err, blks, get_blocks_flags;
struct ext4_map_blocks map;
struct ext4_map_blocks map, *mapp = NULL;
sector_t next = mpd->b_blocknr;
unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
Expand Down Expand Up @@ -2343,6 +2287,7 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
}
BUG_ON(blks == 0);

mapp = &map;
if (map.m_flags & EXT4_MAP_NEW) {
struct block_device *bdev = mpd->inode->i_sb->s_bdev;
int i;
Expand All @@ -2351,14 +2296,6 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
unmap_underlying_metadata(bdev, map.m_pblk + i);
}

/*
* If blocks are delayed marked, we need to
* put actual blocknr and drop delayed bit
*/
if ((mpd->b_state & (1 << BH_Delay)) ||
(mpd->b_state & (1 << BH_Unwritten)))
mpage_put_bnr_to_bhs(mpd, &map);

if (ext4_should_order_data(mpd->inode)) {
err = ext4_jbd2_file_inode(handle, mpd->inode);
if (err)
Expand All @@ -2382,7 +2319,7 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
}

submit_io:
mpage_da_submit_io(mpd);
mpage_da_submit_io(mpd, mapp);
mpd->io_done = 1;
}

Expand Down

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