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    Subject[07/11] ext4: Use tag dirty lookup during mpage_da_submit_io
    From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Date: Tue Oct 14 09:20:19 2008 -0400
    Subject: ext4: Use tag dirty lookup during mpage_da_submit_io

    commit af6f029d3836eb7264cd3fbb13a6baf0e5fdb5ea upstream.

    This enables us to drop the range_cont writeback mode
    use from ext4_da_writepages.

    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: Jayson R. King <dev@jaysonking.com>

    ---
    fs/ext4/inode.c | 30 +++++++++++++-----------------
    1 file changed, 13 insertions(+), 17 deletions(-)

    diff -urNp linux-2.6.27.orig/fs/ext4/inode.c linux-2.6.27/fs/ext4/inode.c
    --- linux-2.6.27.orig/fs/ext4/inode.c 2010-02-26 14:24:53.269252744 -0600
    +++ linux-2.6.27/fs/ext4/inode.c 2010-02-26 14:25:01.277252724 -0600
    @@ -1699,17 +1699,23 @@ static int mpage_da_submit_io(struct mpa

    pagevec_init(&pvec, 0);
    while (index <= end) {
    - nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
    + /*
    + * We can use PAGECACHE_TAG_DIRTY lookup here because
    + * even though we have cleared the dirty flag on the page
    + * We still keep the page in the radix tree with tag
    + * PAGECACHE_TAG_DIRTY. See clear_page_dirty_for_io.
    + * The PAGECACHE_TAG_DIRTY is cleared in set_page_writeback
    + * which is called via the below writepage callback.
    + */
    + nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
    + PAGECACHE_TAG_DIRTY,
    + min(end - index,
    + (pgoff_t)PAGEVEC_SIZE-1) + 1);
    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));

    @@ -2442,7 +2448,6 @@ static int ext4_da_writepages(struct add
    struct writeback_control *wbc)
    {
    handle_t *handle = NULL;
    - loff_t range_start = 0;
    struct mpage_da_data mpd;
    struct inode *inode = mapping->host;
    int needed_blocks, ret = 0, nr_to_writebump = 0;
    @@ -2481,14 +2486,7 @@ static int ext4_da_writepages(struct add
    wbc->nr_to_write = sbi->s_mb_stream_request;
    }

    - if (!wbc->range_cyclic)
    - /*
    - * If range_cyclic is not set force range_cont
    - * and save the old writeback_index
    - */
    - wbc->range_cont = 1;

    - range_start = wbc->range_start;
    pages_skipped = wbc->pages_skipped;

    mpd.wbc = wbc;
    @@ -2559,9 +2557,8 @@ restart_loop:
    wbc->nr_to_write = to_write;
    }

    - if (wbc->range_cont && (pages_skipped != wbc->pages_skipped)) {
    + if (!wbc->range_cyclic && (pages_skipped != wbc->pages_skipped)) {
    /* We skipped pages in this loop */
    - wbc->range_start = range_start;
    wbc->nr_to_write = to_write +
    wbc->pages_skipped - pages_skipped;
    wbc->pages_skipped = pages_skipped;
    @@ -2570,7 +2567,6 @@ restart_loop:

    out_writepages:
    wbc->nr_to_write = to_write - nr_to_writebump;
    - wbc->range_start = range_start;
    return ret;
    }


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