• NeilBrown's avatar
    Fix over-zealous flush_disk when changing device size. · 93b270f7
    NeilBrown authored
    There are two cases when we call flush_disk.
    In one, the device has disappeared (check_disk_change) so any
    data will hold becomes irrelevant.
    In the oter, the device has changed size (check_disk_size_change)
    so data we hold may be irrelevant.
    In both cases it makes sense to discard any 'clean' buffers,
    so they will be read back from the device if needed.
    In the former case it makes sense to discard 'dirty' buffers
    as there will never be anywhere safe to write the data.  In the
    second case it *does*not* make sense to discard dirty buffers
    as that will lead to file system corruption when you simply enlarge
    the containing devices.
    flush_disk calls __invalidate_devices.
    __invalidate_device calls both invalidate_inodes and invalidate_bdev.
    invalidate_inodes *does* discard I_DIRTY inodes and this does lead
    to fs corruption.
    invalidate_bev *does*not* discard dirty pages, but I don't really care
    about that at present.
    So this patch adds a flag to __invalidate_device (calling it
    __invalidate_device2) to indicate whether dirty buffers should be
    killed, and this is passed to invalidate_inodes which can choose to
    skip dirty inodes.
    flusk_disk then passes true from check_disk_change and false from
    dm avoids tripping over this problem by calling i_size_write directly
    rathher than using check_disk_size_change.
    md does use check_disk_size_change and so is affected.
    This regression was introduced by commit 608aeef1 which causes
    check_disk_size_change to call flush_disk, so it is suitable for any
    kernel since 2.6.27.
    Cc: stable@kernel.org
    Acked-by: default avatarJeff Moyer <jmoyer@redhat.com>
    Cc: Andrew Patterson <andrew.patterson@hp.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: default avatarNeilBrown <neilb@suse.de>
inode.c 44.4 KB