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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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      Last update: 2006-02-27 22:25    [W:0.031 / U:4.704 seconds]
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