[PATCH] map multiple blocks for mpage_readpages()
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.
[akpm@osdl.org: cleanups]
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/mpage.c b/fs/mpage.c
index 7903b74..9bf2eb3 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -163,9 +163,19 @@
} while (page_bh != head);
}
+/*
+ * This is the worker routine which does all the work of mapping the disk
+ * blocks and constructs largest possible bios, submits them for IO if the
+ * blocks are not contiguous on the disk.
+ *
+ * We pass a buffer_head back and forth and use its buffer_mapped() flag to
+ * represent the validity of its disk mapping and to decide when to do the next
+ * get_block() call.
+ */
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, get_block_t get_block)
{
struct inode *inode = page->mapping->host;
const unsigned blkbits = inode->i_blkbits;
@@ -173,34 +183,72 @@
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;
+ unsigned relative_block;
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;
- bh.b_page = page;
- for (page_block = 0; page_block < blocks_per_page;
- page_block++, block_in_file++) {
- bh.b_state = 0;
+ /*
+ * Map blocks using the result from the previous get_blocks call first.
+ */
+ nblocks = map_bh->b_size >> blkbits;
+ if (buffer_mapped(map_bh) && 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 (relative_block = 0; ; relative_block++) {
+ if (relative_block == last) {
+ clear_buffer_mapped(map_bh);
+ break;
+ }
+ if (page_block == blocks_per_page)
+ break;
+ blocks[page_block] = map_bh->b_blocknr + map_offset +
+ relative_block;
+ 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;
+
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;
}
- 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++;
+ clear_buffer_mapped(map_bh);
continue;
}
@@ -210,8 +258,8 @@
* 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 +267,20 @@
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 (relative_block = 0; ; relative_block++) {
+ if (relative_block == nblocks) {
+ clear_buffer_mapped(map_bh);
+ break;
+ } else if (page_block == blocks_per_page)
+ break;
+ blocks[page_block] = map_bh->b_blocknr+relative_block;
+ page_block++;
+ block_in_file++;
+ }
+ bdev = map_bh->b_bdev;
}
if (first_hole != blocks_per_page) {
@@ -261,7 +319,7 @@
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];
@@ -332,7 +390,10 @@
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;
+ clear_buffer_mapped(&map_bh);
pagevec_init(&lru_pvec, 0);
for (page_idx = 0; page_idx < nr_pages; page_idx++) {
struct page *page = list_entry(pages->prev, struct page, lru);
@@ -343,7 +404,9 @@
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,
+ get_block);
if (!pagevec_add(&lru_pvec, page))
__pagevec_lru_add(&lru_pvec);
} else {
@@ -365,9 +428,12 @@
{
struct bio *bio = NULL;
sector_t last_block_in_bio = 0;
+ struct buffer_head map_bh;
+ unsigned long first_logical_block = 0;
- bio = do_mpage_readpage(bio, page, 1,
- &last_block_in_bio, get_block);
+ clear_buffer_mapped(&map_bh);
+ bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
+ &map_bh, &first_logical_block, get_block);
if (bio)
mpage_bio_submit(READ, bio);
return 0;