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drbd: keep max-bio size during detach/attach on disconnected primary 

We want to store in persistent meta data what the peer DRBD can handle,
which, due to spreading requests to multiple bios,
may be more than its backing device can handle.

Otherwise, if a disconnected Primary temporarily loses access to its local data
as well, we may accidentally shrink the max-bio setting, portentially causing
already assembled, but not yet processed, application bios to be spuriously
failed due to device limits.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Lars Ellenberg 2014-04-28 18:43:27 +02:00 committed by Jens Axboe
parent 074f4afeb2
commit fa090e708a
1 changed files with 7 additions and 1 deletions
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8
drivers/block/drbd/drbd_nl.c
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@ -1194,8 +1194,14 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
peer = DRBD_MAX_BIO_SIZE_P95; /* drbd 8.3.8 onwards, before 8.4.0 */
else
peer = DRBD_MAX_BIO_SIZE;
}
/* We may later detach and re-attach on a disconnected Primary.
* Avoid this setting to jump back in that case.
* We want to store what we know the peer DRBD can handle,
* not what the peer IO backend can handle. */
if (peer > device->peer_max_bio_size)
device->peer_max_bio_size = peer;
}
new = min(local, peer);
if (device->state.role == R_PRIMARY && new < now)