diff options
| author | Christoph Böhmwalder <christoph.boehmwalder@linbit.com> | 2026-02-05 18:39:29 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2026-02-11 10:35:56 -0700 |
| commit | 2ebc8d600fb907fa6b1e7095c0b6d84fc47e91ea (patch) | |
| tree | 0b2f231ef362b701f07a13826d69d0b85f1617c7 /drivers/block/drbd | |
| parent | 192c0159402e6bfbe13de6f8379546943297783d (diff) | |
drbd: always set BLK_FEAT_STABLE_WRITES
DRBD requires stable pages because it may read the same bio data
multiple times for local disk I/O and network transmission, and in
some cases for calculating checksums.
The BLK_FEAT_STABLE_WRITES flag is set when the device is first
created, but blk_set_stacking_limits() clears it whenever a
backing device is attached. In some cases the flag may be
inherited from the backing device, but we want it to be enabled
at all times.
Unconditionally re-enable BLK_FEAT_STABLE_WRITES in
drbd_reconsider_queue_parameters() after the queue parameter
negotiations.
Also, document why we want this flag enabled in the first place.
Fixes: 1a02f3a73f8c ("block: move the stable_writes flag to queue_limits")
Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block/drbd')
| -rw-r--r-- | drivers/block/drbd/drbd_main.c | 3 | ||||
| -rw-r--r-- | drivers/block/drbd/drbd_nl.c | 20 |
2 files changed, 19 insertions, 4 deletions
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c index c73376886e7a..1f6ac9202b66 100644 --- a/drivers/block/drbd/drbd_main.c +++ b/drivers/block/drbd/drbd_main.c @@ -2659,9 +2659,6 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig * connect. */ .max_hw_sectors = DRBD_MAX_BIO_SIZE_SAFE >> 8, - .features = BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA | - BLK_FEAT_ROTATIONAL | - BLK_FEAT_STABLE_WRITES, }; device = minor_to_device(minor); diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c index 91f3b8afb63c..b502038be0a9 100644 --- a/drivers/block/drbd/drbd_nl.c +++ b/drivers/block/drbd/drbd_nl.c @@ -1296,6 +1296,8 @@ void drbd_reconsider_queue_parameters(struct drbd_device *device, lim.max_segments = drbd_backing_dev_max_segments(device); } else { lim.max_segments = BLK_MAX_SEGMENTS; + lim.features = BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA | + BLK_FEAT_ROTATIONAL | BLK_FEAT_STABLE_WRITES; } lim.max_hw_sectors = new >> SECTOR_SHIFT; @@ -1318,8 +1320,24 @@ void drbd_reconsider_queue_parameters(struct drbd_device *device, lim.max_hw_discard_sectors = 0; } - if (bdev) + if (bdev) { blk_stack_limits(&lim, &b->limits, 0); + /* + * blk_set_stacking_limits() cleared the features, and + * blk_stack_limits() may or may not have inherited + * BLK_FEAT_STABLE_WRITES from the backing device. + * + * DRBD always requires stable writes because: + * 1. The same bio data is read for both local disk I/O and + * network transmission. If the page changes mid-flight, + * the local and remote copies could diverge. + * 2. When data integrity is enabled, DRBD calculates a + * checksum before sending the data. If the page changes + * between checksum calculation and transmission, the + * receiver will detect a checksum mismatch. + */ + lim.features |= BLK_FEAT_STABLE_WRITES; + } /* * If we can handle "zeroes" efficiently on the protocol, we want to do |