virtio_blk: set the zone write granularitygrafted

virtblk_read_zoned_limits() reads the write granularity that the device
reports in virtio_blk_zoned_characteristics and assigns it to the
physical block size and to io_min, but never to the limit that is named
after it. queue_limits.zone_write_granularity is left at zero, so
blk_validate_zoned_limits() raises it to the logical block size:

	if (lim->zone_write_granularity < lim->logical_block_size)
		lim->zone_write_granularity = lim->logical_block_size;

A device that reports a granularity coarser than its logical block size,
which is what the field exists to express, therefore has it silently
reduced. A 512e host managed disk passed through to a guest reports a
logical block size of 512 and a write granularity of 4096, and the guest
ends up with a zone write granularity of 512.

bio_split_alignment() returns lim->zone_write_granularity if it is non-zero
and bio_split_io_at() may split a bio with as per bio_split_alignment().
This can real to the write getting rejected by the host drive, as the write
is not aligned to the physical block size.

zonefs also takes its block size from bdev_zone_write_granularity(), so it
would incorrectly use 512 on a disk that requires 4096.

sd_zbc_read_zones() sets the limit from the physical block size for the
same reason. NVMe ZNS and null_blk leave it unset, but the fallback
gives the right answer for them, as their write granularity is the
logical block size. virtio carries a separate value that may exceed it.

Set the zone write granularity from the value that the device reports.

Fixes: 95bfec41bd3d ("virtio-blk: add support for zoned block devices")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://patch.msgid.link/20260918140641.2031075-2-cassel@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 273 insertions, 0 deletions

diff --git a/include/net/codel_impl.h b/include/net/codel_impl.h
new file mode 100644
index 000000000..2c1f0ec30
--- /dev/null
+++ b/include/net/codel_impl.h
@@ -0,0 +1,273 @@
+#ifndef __NET_SCHED_CODEL_IMPL_H
+#define __NET_SCHED_CODEL_IMPL_H
+
+/*
+ * Codel - The Controlled-Delay Active Queue Management algorithm
+ *
+ *  Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
+ *  Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
+ *  Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
+ *  Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions, and the following disclaimer,
+ *    without modification.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The names of the authors may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * Alternatively, provided that this notice is retained in full, this
+ * software may be distributed under the terms of the GNU General
+ * Public License ("GPL") version 2, in which case the provisions of the
+ * GPL apply INSTEAD OF those given above.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ */
+
+/* Controlling Queue Delay (CoDel) algorithm
+ * =========================================
+ * Source : Kathleen Nichols and Van Jacobson
+ * http://queue.acm.org/detail.cfm?id=2209336
+ *
+ * Implemented on linux by Dave Taht and Eric Dumazet
+ */
+
+#include <net/inet_ecn.h>
+
+static void codel_params_init(struct codel_params *params)
+{
+	params->interval = MS2TIME(100);
+	params->target = MS2TIME(5);
+	params->ce_threshold = CODEL_DISABLED_THRESHOLD;
+	params->ce_threshold_mask = 0;
+	params->ce_threshold_selector = 0;
+	params->ecn = false;
+}
+
+static void codel_vars_init(struct codel_vars *vars)
+{
+	memset(vars, 0, sizeof(*vars));
+}
+
+static void codel_stats_init(struct codel_stats *stats)
+{
+	stats->maxpacket = 0;
+}
+
+/*
+ * http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
+ * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
+ *
+ * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
+ */
+static void codel_Newton_step(struct codel_vars *vars)
+{
+	u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
+	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
+	u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);
+
+	val >>= 2; /* avoid overflow in following multiply */
+	val = (val * invsqrt) >> (32 - 2 + 1);
+
+	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
+}
+
+/*
+ * CoDel control_law is t + interval/sqrt(count)
+ * We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
+ * both sqrt() and divide operation.
+ */
+static codel_time_t codel_control_law(codel_time_t t,
+				      codel_time_t interval,
+				      u32 rec_inv_sqrt)
+{
+	return t + reciprocal_scale(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
+}
+
+static bool codel_should_drop(const struct sk_buff *skb,
+			      void *ctx,
+			      struct codel_vars *vars,
+			      struct codel_params *params,
+			      struct codel_stats *stats,
+			      codel_skb_len_t skb_len_func,
+			      codel_skb_time_t skb_time_func,
+			      u32 *backlog,
+			      codel_time_t now)
+{
+	bool ok_to_drop;
+	u32 skb_len;
+
+	if (!skb) {
+		vars->first_above_time = 0;
+		return false;
+	}
+
+	skb_len = skb_len_func(skb);
+	WRITE_ONCE(vars->ldelay, now - skb_time_func(skb));
+
+	if (unlikely(skb_len > stats->maxpacket))
+		WRITE_ONCE(stats->maxpacket, skb_len);
+
+	if (codel_time_before(vars->ldelay, params->target) ||
+	    *backlog <= params->mtu) {
+		/* went below - stay below for at least interval */
+		vars->first_above_time = 0;
+		return false;
+	}
+	ok_to_drop = false;
+	if (vars->first_above_time == 0) {
+		/* just went above from below. If we stay above
+		 * for at least interval we'll say it's ok to drop
+		 */
+		vars->first_above_time = now + params->interval;
+	} else if (codel_time_after(now, vars->first_above_time)) {
+		ok_to_drop = true;
+	}
+	return ok_to_drop;
+}
+
+static struct sk_buff *codel_dequeue(void *ctx,
+				     u32 *backlog,
+				     struct codel_params *params,
+				     struct codel_vars *vars,
+				     struct codel_stats *stats,
+				     codel_skb_len_t skb_len_func,
+				     codel_skb_time_t skb_time_func,
+				     codel_skb_drop_t drop_func,
+				     codel_skb_dequeue_t dequeue_func)
+{
+	struct sk_buff *skb = dequeue_func(vars, ctx);
+	codel_time_t now;
+	bool drop;
+
+	if (!skb) {
+		vars->first_above_time = 0;
+		WRITE_ONCE(vars->dropping, false);
+		return skb;
+	}
+	now = codel_get_time();
+	drop = codel_should_drop(skb, ctx, vars, params, stats,
+				 skb_len_func, skb_time_func, backlog, now);
+	if (vars->dropping) {
+		if (!drop) {
+			/* sojourn time below target - leave dropping state */
+			WRITE_ONCE(vars->dropping, false);
+		} else if (codel_time_after_eq(now, vars->drop_next)) {
+			/* It's time for the next drop. Drop the current
+			 * packet and dequeue the next. The dequeue might
+			 * take us out of dropping state.
+			 * If not, schedule the next drop.
+			 * A large backlog might result in drop rates so high
+			 * that the next drop should happen now,
+			 * hence the while loop.
+			 */
+			while (vars->dropping &&
+			       codel_time_after_eq(now, vars->drop_next)) {
+				/* dont care of possible wrap
+				 * since there is no more divide.
+				 */
+				WRITE_ONCE(vars->count, vars->count + 1);
+				codel_Newton_step(vars);
+				if (params->ecn && INET_ECN_set_ce(skb)) {
+					WRITE_ONCE(stats->ecn_mark,
+						   stats->ecn_mark + 1);
+					WRITE_ONCE(vars->drop_next,
+						codel_control_law(vars->drop_next,
+								  params->interval,
+								  vars->rec_inv_sqrt));
+					goto end;
+				}
+				stats->drop_len += skb_len_func(skb);
+				drop_func(skb, ctx);
+				stats->drop_count++;
+				skb = dequeue_func(vars, ctx);
+				if (!codel_should_drop(skb, ctx,
+						       vars, params, stats,
+						       skb_len_func,
+						       skb_time_func,
+						       backlog, now)) {
+					/* leave dropping state */
+					WRITE_ONCE(vars->dropping, false);
+				} else {
+					/* and schedule the next drop */
+					WRITE_ONCE(vars->drop_next,
+						codel_control_law(vars->drop_next,
+								  params->interval,
+								  vars->rec_inv_sqrt));
+				}
+			}
+		}
+	} else if (drop) {
+		u32 delta;
+
+		if (params->ecn && INET_ECN_set_ce(skb)) {
+			WRITE_ONCE(stats->ecn_mark, stats->ecn_mark + 1);
+		} else {
+			stats->drop_len += skb_len_func(skb);
+			drop_func(skb, ctx);
+			stats->drop_count++;
+
+			skb = dequeue_func(vars, ctx);
+			drop = codel_should_drop(skb, ctx, vars, params,
+						 stats, skb_len_func,
+						 skb_time_func, backlog, now);
+		}
+		WRITE_ONCE(vars->dropping, true);
+		/* if min went above target close to when we last went below it
+		 * assume that the drop rate that controlled the queue on the
+		 * last cycle is a good starting point to control it now.
+		 */
+		delta = vars->count - vars->lastcount;
+		if (delta > 1 &&
+		    codel_time_before(now - vars->drop_next,
+				      16 * params->interval)) {
+			WRITE_ONCE(vars->count, delta);
+			/* we dont care if rec_inv_sqrt approximation
+			 * is not very precise :
+			 * Next Newton steps will correct it quadratically.
+			 */
+			codel_Newton_step(vars);
+		} else {
+			WRITE_ONCE(vars->count, 1);
+			vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
+		}
+		WRITE_ONCE(vars->lastcount, vars->count);
+		WRITE_ONCE(vars->drop_next,
+			   codel_control_law(now, params->interval,
+					     vars->rec_inv_sqrt));
+	}
+end:
+	if (skb && codel_time_after(vars->ldelay, params->ce_threshold)) {
+		bool set_ce = true;
+
+		if (params->ce_threshold_mask) {
+			int dsfield = skb_get_dsfield(skb);
+
+			set_ce = (dsfield >= 0 &&
+				  (((u8)dsfield & params->ce_threshold_mask) ==
+				   params->ce_threshold_selector));
+		}
+		if (set_ce && INET_ECN_set_ce(skb))
+			WRITE_ONCE(stats->ce_mark, stats->ce_mark + 1);
+	}
+	return skb;
+}
+
+#endif