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

From: NeilBrown
Date: Sun May 18 2008 - 21:11:34 EST

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@xxxxxxx>

### 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


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

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