[PATCH] map multiple blocks for mpage_readpages()
Badari Pulavarty [Sun, 26 Mar 2006 09:38:01 +0000 (01:38 -0800)]
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>

fs/jfs/inode.c
fs/mpage.c
fs/xfs/linux-2.6/xfs_aops.c

index 51a5fed..7239ef3 100644 (file)
@@ -258,7 +258,8 @@ jfs_get_blocks(struct inode *ip, sector_t lblock, unsigned long max_blocks,
 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 7903b74..9bf2eb3 100644 (file)
@@ -163,9 +163,19 @@ map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
        } 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 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
        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;
+
+       /*
+        * 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;
 
-       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;
                }
 
-               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 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
                 * 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 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
                        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 @@ 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];
@@ -332,7 +390,10 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
        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 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
                                        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 @@ int mpage_readpage(struct page *page, get_block_t get_block)
 {
        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;
index 4f2476f..a79b84f 100644 (file)
@@ -1310,8 +1310,9 @@ xfs_get_block(
        struct buffer_head      *bh_result,
        int                     create)
 {
-       return __xfs_get_block(inode, iblock, 0, bh_result,
-                                       create, 0, BMAPI_WRITE);
+       return __xfs_get_block(inode, iblock,
+                               bh_result->b_size >> inode->i_blkbits,
+                               bh_result, create, 0, BMAPI_WRITE);
 }
 
 STATIC int