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    Subject[PATCH 001 of 10] md: Fix possible oops when removing a bitmap from an active array

    It is possible to add a write-intent bitmap to an active array, or remove
    the bitmap that is there.
    When we do with the 'quiesce' the array, which causes make_request to
    block in "wait_barrier()".
    However we are sampling the value of "mddev->bitmap" before the
    wait_barrier call, and using it afterwards. This can result in
    using a bitmap structure that has been freed.

    Signed-off-by: Neil Brown <neilb@suse.de>

    ### Diffstat output
    ./drivers/md/raid1.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
    --- .prev/drivers/md/raid1.c 2008-05-19 11:02:04.000000000 +1000
    +++ ./drivers/md/raid1.c 2008-05-19 11:02:15.000000000 +1000
    @@ -773,7 +773,7 @@ static int make_request(struct request_q
    r1bio_t *r1_bio;
    struct bio *read_bio;
    int i, targets = 0, disks;
    - struct bitmap *bitmap = mddev->bitmap;
    + struct bitmap *bitmap;
    unsigned long flags;
    struct bio_list bl;
    struct page **behind_pages = NULL;
    @@ -802,6 +802,8 @@ static int make_request(struct request_q

    wait_barrier(conf);

    + bitmap = mddev->bitmap;
    +
    disk_stat_inc(mddev->gendisk, ios[rw]);
    disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));


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