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    Subject[PATCH 4.18 137/171] gfs2: Fix metadata read-ahead during truncate (2)
    Date
    4.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andreas Gruenbacher <agruenba@redhat.com>

    commit e7445ceddfc220c1aede6d42758a5acb8844e9c3 upstream.

    The previous attempt to fix for metadata read-ahead during truncate was
    incorrect: for files with a height > 2 (1006989312 bytes with a block
    size of 4096 bytes), read-ahead requests were not being issued for some
    of the indirect blocks discovered while walking the metadata tree,
    leading to significant slow-downs when deleting large files. Fix that.

    In addition, only issue read-ahead requests in the first pass through
    the meta-data tree, while deallocating data blocks.

    Fixes: c3ce5aa9b0 ("gfs2: Fix metadata read-ahead during truncate")
    Cc: stable@vger.kernel.org # v4.16+
    Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/gfs2/bmap.c | 14 ++++++++++----
    1 file changed, 10 insertions(+), 4 deletions(-)

    --- a/fs/gfs2/bmap.c
    +++ b/fs/gfs2/bmap.c
    @@ -1652,10 +1652,16 @@ static int punch_hole(struct gfs2_inode
    if (ret < 0)
    goto out;

    - /* issue read-ahead on metadata */
    - if (mp.mp_aheight > 1) {
    - for (; ret > 1; ret--) {
    - metapointer_range(&mp, mp.mp_aheight - ret,
    + /* On the first pass, issue read-ahead on metadata. */
    + if (mp.mp_aheight > 1 && strip_h == ip->i_height - 1) {
    + unsigned int height = mp.mp_aheight - 1;
    +
    + /* No read-ahead for data blocks. */
    + if (mp.mp_aheight - 1 == strip_h)
    + height--;
    +
    + for (; height >= mp.mp_aheight - ret; height--) {
    + metapointer_range(&mp, height,
    start_list, start_aligned,
    end_list, end_aligned,
    &start, &end);

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