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Message-Id: <1465826958-19398-13-git-send-email-philipp.reisner@linbit.com>
Date: Mon, 13 Jun 2016 16:09:00 +0200
From: Philipp Reisner <philipp.reisner@...bit.com>
To: Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org
Cc: drbd-dev@...ts.linbit.com
Subject: [PATCH 12/30] drbd: possibly disable discard support, if backend has discard_zeroes_data=0
From: Lars Ellenberg <lars.ellenberg@...bit.com>
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@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
---
drivers/block/drbd/drbd_nl.c | 80 ++++++++++++++++++++++++++++++--------------
1 file changed, 55 insertions(+), 25 deletions(-)
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 8d757d6..12e9b31 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -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)
--
2.7.4
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