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drbd: possibly disable discard support, if backend has discard_zeroes_data=0

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Now that we have the discard_zeroes_if_aligned setting, we should also
check it when setting up our queue parameters on the primary,
not only on the receiving side.

We announce discard support,
UNLESS

 * we are connected to a peer that does not support TRIM
   on the DRBD protocol level.  Otherwise, it would either discard, or
   do a fallback to zero-out, depending on its backend and configuration.

 * our local backend does not support discards,
   or (discard_zeroes_data=0 AND discard_zeroes_if_aligned=no).

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 2016-06-14 00:26:21 +02:00 committed by Jens Axboe
parent dd4f699da6
commit 69ba1ee936
1 changed files with 55 additions and 25 deletions
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80
drivers/block/drbd/drbd_nl.c
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@ -1154,6 +1154,59 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
return 0;
}
static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
{
q->limits.discard_granularity = granularity;
}
static void decide_on_discard_support(struct drbd_device *device,
struct request_queue *q,
struct request_queue *b,
bool discard_zeroes_if_aligned)
{
/* q = drbd device queue (device->rq_queue)
* b = backing device queue (device->ldev->backing_bdev->bd_disk->queue),
* or NULL if diskless
*/
struct drbd_connection *connection = first_peer_device(device)->connection;
bool can_do = b ? blk_queue_discard(b) : true;
if (can_do && b && !b->limits.discard_zeroes_data && !discard_zeroes_if_aligned) {
can_do = false;
drbd_info(device, "discard_zeroes_data=0 and discard_zeroes_if_aligned=no: disabling discards\n");
}
if (can_do && connection->cstate >= C_CONNECTED && !(connection->agreed_features & FF_TRIM)) {
can_do = false;
drbd_info(connection, "peer DRBD too old, does not support TRIM: disabling discards\n");
}
if (can_do) {
/* We don't care for the granularity, really.
* Stacking limits below should fix it for the local
* device. Whether or not it is a suitable granularity
* on the remote device is not our problem, really. If
* you care, you need to use devices with similar
* topology on all peers. */
blk_queue_discard_granularity(q, 512);
q->limits.max_discard_sectors = DRBD_MAX_DISCARD_SECTORS;
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
} else {
queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
blk_queue_discard_granularity(q, 0);
q->limits.max_discard_sectors = 0;
}
}
static void fixup_discard_if_not_supported(struct request_queue *q)
{
/* To avoid confusion, if this queue does not support discard, clear
* max_discard_sectors, which is what lsblk -D reports to the user.
* Older kernels got this wrong in "stack limits".
* */
if (!blk_queue_discard(q)) {
blk_queue_max_discard_sectors(q, 0);
blk_queue_discard_granularity(q, 0);
}
}
static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
unsigned int max_bio_size)
{
@ -1183,26 +1236,8 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi
/* This is the workaround for "bio would need to, but cannot, be split" */
blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
blk_queue_segment_boundary(q, PAGE_SIZE-1);
decide_on_discard_support(device, q, b, discard_zeroes_if_aligned);
if (b) {
struct drbd_connection *connection = first_peer_device(device)->connection;
blk_queue_max_discard_sectors(q, DRBD_MAX_DISCARD_SECTORS);
if (blk_queue_discard(b) && (b->limits.discard_zeroes_data || discard_zeroes_if_aligned) &&
(connection->cstate < C_CONNECTED || connection->agreed_features & FF_TRIM)) {
/* We don't care, stacking below should fix it for the local device.
* Whether or not it is a suitable granularity on the remote device
* is not our problem, really. If you care, you need to
* use devices with similar topology on all peers. */
q->limits.discard_granularity = 512;
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
} else {
blk_queue_max_discard_sectors(q, 0);
queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
q->limits.discard_granularity = 0;
}
blk_queue_stack_limits(q, b);
if (q->backing_dev_info.ra_pages != b->backing_dev_info.ra_pages) {
@ -1212,12 +1247,7 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi
q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;
}
}
/* To avoid confusion, if this queue does not support discard, clear
* max_discard_sectors, which is what lsblk -D reports to the user. */
if (!blk_queue_discard(q)) {
blk_queue_max_discard_sectors(q, 0);
q->limits.discard_granularity = 0;
}
fixup_discard_if_not_supported(q);
}
void drbd_reconsider_queue_parameters(struct drbd_device *device, struct drbd_backing_dev *bdev)