• Markus Stockhausen's avatar
    readahead: stricter check for bdi io_pages · d3949a0a
    Markus Stockhausen authored
    commit dc30b96a upstream.
    
    ondemand_readahead() checks bdi->io_pages to cap the maximum pages
    that need to be processed. This works until the readit section. If
    we would do an async only readahead (async size = sync size) and
    target is at beginning of window we expand the pages by another
    get_next_ra_size() pages. Btrace for large reads shows that kernel
    always issues a doubled size read at the beginning of processing.
    Add an additional check for io_pages in the lower part of the func.
    The fix helps devices that hard limit bio pages and rely on proper
    handling of max_hw_read_sectors (e.g. older FusionIO cards). For
    that reason it could qualify for stable.
    
    Fixes: 9491ae4a ("mm: don't cap request size based on read-ahead setting")
    Cc: stable@vger.kernel.org
    Signed-off-by: Markus Stockhausen stockhausen@collogia.de
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    d3949a0a