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Subject[PATCH 3/4] map multiple blocks for mpage_readpages()
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This patch changes mpage_readpages() and get_block() to
get the disk mapping information for multiple blocks at the
same time.

b_size represents the amount of disk mapping that needs to
mapped. On the successful get_block() b_size indicates the
amount of disk mapping thats actually mapped. Only the
filesystems who care to use this information and provide multiple
disk blocks at a time can choose to do so.

No changes are needed for the filesystems who wants to ignore this.


This patch changes mpage_readpages() and get_block() to
get the disk mapping information for multiple blocks at the
same time.

b_size represents the amount of disk mapping that needs to
mapped. On the successful get_block() b_size indicates the
amount of disk mapping thats actually mapped. Only the
filesystems who care to use this information and provide multiple
disk blocks at a time can choose to do so.

No changes are needed for the filesystems who wants to ignore this.

Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>

fs/jfs/inode.c | 3 -
fs/mpage.c | 98 +++++++++++++++++++++++++++++++++++---------
fs/xfs/linux-2.6/xfs_aops.c | 4 -
3 files changed, 83 insertions(+), 22 deletions(-)
Index: linux-2.6.16-rc5/fs/mpage.c
===================================================================
--- linux-2.6.16-rc5.orig/fs/mpage.c 2006-02-27 08:22:45.000000000 -0800
+++ linux-2.6.16-rc5/fs/mpage.c 2006-02-27 08:22:56.000000000 -0800
@@ -165,7 +165,9 @@ map_buffer_to_page(struct page *page, st

static struct bio *
do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
- sector_t *last_block_in_bio, get_block_t get_block)
+ sector_t *last_block_in_bio, struct buffer_head *map_bh,
+ unsigned long *first_logical_block, int *map_valid,
+ get_block_t get_block)
{
struct inode *inode = page->mapping->host;
const unsigned blkbits = inode->i_blkbits;
@@ -173,34 +175,72 @@ do_mpage_readpage(struct bio *bio, struc
const unsigned blocksize = 1 << blkbits;
sector_t block_in_file;
sector_t last_block;
+ sector_t last_block_in_file;
sector_t blocks[MAX_BUF_PER_PAGE];
unsigned page_block;
unsigned first_hole = blocks_per_page;
struct block_device *bdev = NULL;
- struct buffer_head bh;
int length;
int fully_mapped = 1;
+ unsigned nblocks, i;

if (page_has_buffers(page))
goto confused;

block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
- last_block = (i_size_read(inode) + blocksize - 1) >> blkbits;
+ last_block = block_in_file + (nr_pages * blocks_per_page);
+ last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
+ if (last_block > last_block_in_file)
+ last_block = last_block_in_file;
+ page_block = 0;
+
+ /*
+ * Map blocks using the result from the last get_blocks call first.
+ */
+ nblocks = map_bh->b_size >> blkbits;
+ if (*map_valid &&
+ block_in_file > *first_logical_block &&
+ block_in_file < (*first_logical_block + nblocks)) {
+ unsigned map_offset = block_in_file - *first_logical_block;
+ unsigned last = nblocks - map_offset;
+
+ for (i = 0; ; i++) {
+ if (i == last) {
+ *map_valid = 0;
+ break;
+ }
+ if (page_block == blocks_per_page)
+ break;
+ blocks[page_block] = map_bh->b_blocknr + map_offset + i;
+ page_block++;
+ block_in_file++;
+ }
+ bdev = map_bh->b_bdev;
+ }
+
+ /*
+ * Then do more get_blocks calls until we are done with this page.
+ */
+ map_bh->b_page = page;
+ while (page_block < blocks_per_page) {
+ map_bh->b_state = 0;
+ map_bh->b_size = 0;

- bh.b_page = page;
- for (page_block = 0; page_block < blocks_per_page;
- page_block++, block_in_file++) {
- bh.b_state = 0;
if (block_in_file < last_block) {
- bh.b_size = blocksize;
- if (get_block(inode, block_in_file, &bh, 0))
+ map_bh->b_size = (last_block - block_in_file) << blkbits;
+ if (get_block(inode, block_in_file, map_bh, 0))
goto confused;
+ *first_logical_block = block_in_file;
+ *map_valid = 1;
}

- if (!buffer_mapped(&bh)) {
+ if (!buffer_mapped(map_bh)) {
fully_mapped = 0;
if (first_hole == blocks_per_page)
first_hole = page_block;
+ page_block++;
+ block_in_file++;
+ *map_valid = 0;
continue;
}

@@ -210,8 +250,8 @@ do_mpage_readpage(struct bio *bio, struc
* we just collected from get_block into the page's buffers
* so readpage doesn't have to repeat the get_block call
*/
- if (buffer_uptodate(&bh)) {
- map_buffer_to_page(page, &bh, page_block);
+ if (buffer_uptodate(map_bh)) {
+ map_buffer_to_page(page, map_bh, page_block);
goto confused;
}

@@ -219,10 +259,20 @@ do_mpage_readpage(struct bio *bio, struc
goto confused; /* hole -> non-hole */

/* Contiguous blocks? */
- if (page_block && blocks[page_block-1] != bh.b_blocknr-1)
+ if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
goto confused;
- blocks[page_block] = bh.b_blocknr;
- bdev = bh.b_bdev;
+ nblocks = map_bh->b_size >> blkbits;
+ for (i = 0; ; i++) {
+ if (i == nblocks) {
+ *map_valid = 0;
+ break;
+ } else if (page_block == blocks_per_page)
+ break;
+ blocks[page_block] = map_bh->b_blocknr + i;
+ page_block++;
+ block_in_file++;
+ }
+ bdev = map_bh->b_bdev;
}

if (first_hole != blocks_per_page) {
@@ -261,7 +311,7 @@ alloc_new:
goto alloc_new;
}

- if (buffer_boundary(&bh) || (first_hole != blocks_per_page))
+ if (buffer_boundary(map_bh) || (first_hole != blocks_per_page))
bio = mpage_bio_submit(READ, bio);
else
*last_block_in_bio = blocks[blocks_per_page - 1];
@@ -332,6 +382,9 @@ mpage_readpages(struct address_space *ma
unsigned page_idx;
sector_t last_block_in_bio = 0;
struct pagevec lru_pvec;
+ struct buffer_head map_bh;
+ unsigned long first_logical_block = 0;
+ int map_valid = 0;

pagevec_init(&lru_pvec, 0);
for (page_idx = 0; page_idx < nr_pages; page_idx++) {
@@ -343,7 +396,9 @@ mpage_readpages(struct address_space *ma
page->index, GFP_KERNEL)) {
bio = do_mpage_readpage(bio, page,
nr_pages - page_idx,
- &last_block_in_bio, get_block);
+ &last_block_in_bio, &map_bh,
+ &first_logical_block,
+ &map_valid, get_block);
if (!pagevec_add(&lru_pvec, page))
__pagevec_lru_add(&lru_pvec);
} else {
@@ -365,9 +420,14 @@ int mpage_readpage(struct page *page, ge
{
struct bio *bio = NULL;
sector_t last_block_in_bio = 0;
+ struct buffer_head map_bh;
+ unsigned long first_logical_block = 0;
+ int map_valid = 0;
+

- bio = do_mpage_readpage(bio, page, 1,
- &last_block_in_bio, get_block);
+ bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
+ &map_bh, &first_logical_block, &map_valid,
+ get_block);
if (bio)
mpage_bio_submit(READ, bio);
return 0;
Index: linux-2.6.16-rc5/fs/jfs/inode.c
===================================================================
--- linux-2.6.16-rc5.orig/fs/jfs/inode.c 2006-02-26 21:09:35.000000000 -0800
+++ linux-2.6.16-rc5/fs/jfs/inode.c 2006-02-27 08:22:56.000000000 -0800
@@ -257,7 +257,8 @@ jfs_get_blocks(struct inode *ip, sector_
static int jfs_get_block(struct inode *ip, sector_t lblock,
struct buffer_head *bh_result, int create)
{
- return jfs_get_blocks(ip, lblock, 1, bh_result, create);
+ return jfs_get_blocks(ip, lblock, bh_result->b_size >> ip->i_blkbits,
+ bh_result, create);
}

static int jfs_writepage(struct page *page, struct writeback_control *wbc)
Index: linux-2.6.16-rc5/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
--- linux-2.6.16-rc5.orig/fs/xfs/linux-2.6/xfs_aops.c 2006-02-26 21:09:35.000000000 -0800
+++ linux-2.6.16-rc5/fs/xfs/linux-2.6/xfs_aops.c 2006-02-27 08:22:56.000000000 -0800
@@ -1136,8 +1136,8 @@ linvfs_get_block(
struct buffer_head *bh_result,
int create)
{
- return __linvfs_get_block(inode, iblock, 0, bh_result,
- create, 0, BMAPI_WRITE);
+ return __linvfs_get_block(inode, iblock, bh_result->b_size >> inode->i_blkbits,
+ bh_result, create, 0, BMAPI_WRITE);
}

STATIC int
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