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drbd: Fix a potential race that could case data inconsistency 

When we have a write request and a state change C_WF_BITMAP_S -> C_SYNC_SOURCE
at the same time, and it happens that the line

    remote = remote && drbd_should_do_remote(s);

stills sees C_WF_BITMAP_S, and

     send_oos = rw == WRITE && drbd_should_send_oos(s);

already sees C_SYNC_SOURCE both are 0.

This causes the write to not be mirrored, but marked as out-of-sync on the
Sync_Source node.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2012-03-26 15:09:44 +02:00 committed by Philipp Reisner
parent 38a05c16b8
commit 81f448629a
1 changed files with 4 additions and 2 deletions
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6
drivers/block/drbd/drbd_req.c
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@ -822,6 +822,7 @@ int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long s
int local, remote, send_oos = 0;
int err;
int ret = 0;
union drbd_dev_state s;
/* allocate outside of all locks; */
req = drbd_req_new(mdev, bio);
@ -884,8 +885,9 @@ int __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long s
drbd_al_begin_io(mdev, &req->i);
}
remote = remote && drbd_should_do_remote(mdev->state);
send_oos = rw == WRITE && drbd_should_send_out_of_sync(mdev->state);
s = mdev->state;
remote = remote && drbd_should_do_remote(s);
send_oos = rw == WRITE && drbd_should_send_out_of_sync(s);
D_ASSERT(!(remote && send_oos));
if (!(local || remote) && !drbd_suspended(mdev)) {