• Damien Le Moal's avatar
    block: Fix __blkdev_issue_zeroout loop · 615d22a5
    Damien Le Moal authored
    The BIO issuing loop in __blkdev_issue_zeroout() is allocating BIOs
    with a maximum number of bvec (pages) equal to
    
    min(nr_sects, (sector_t)BIO_MAX_PAGES)
    
    This works since the requested number of bvecs will always be limited
    to the absolute maximum number supported (BIO_MAX_PAGES), but this is
    ineficient as too many bvec entries may be requested due to the
    different units being used in the min() operation (number of sectors vs
    number of pages).
    To fix this, introduce the helper __blkdev_sectors_to_bio_pages() to
    correctly calculate the number of bvecs for zeroout BIOs as the issuing
    loop progresses. The calculation is done using consistent units and
    makes sure that the number of pages return is at least 1 (for cases
    where the number of sectors is less that the number of sectors in
    a page).
    
    Also remove a trailing space after the bit shift in the internal loop
    min() call.
    Signed-off-by: default avatarDamien Le Moal <damien.lemoal@wdc.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    615d22a5
blk-lib.c 9.82 KB