Block layer patches

- Image creation: Honour pwrite_zeroes_alignment for zeroing first sector
 - block-backend: Fix race (causing a crash) when resuming queued requests
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Merge tag 'for-upstream' of https://repo.or.cz/qemu/kevin into staging

Block layer patches

- Image creation: Honour pwrite_zeroes_alignment for zeroing first sector
- block-backend: Fix race (causing a crash) when resuming queued requests

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* tag 'for-upstream' of https://repo.or.cz/qemu/kevin:
  iotests: add Linux loop device image creation test
  block: use pwrite_zeroes_alignment when writing first sector
  file-posix: populate pwrite_zeroes_alignment
  block-backend: Fix race when resuming queued requests

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

block.c

@@ -606,12 +606,13 @@ create_file_fallback_zero_first_sector(BlockBackend *blk,
                                        int64_t current_size,
                                        Error **errp)
 {
+    uint32_t alignment = blk_get_pwrite_zeroes_alignment(blk);
     int64_t bytes_to_clear;
     int ret;
 
     GLOBAL_STATE_CODE();
 
-    bytes_to_clear = MIN(current_size, BDRV_SECTOR_SIZE);
+    bytes_to_clear = MIN(current_size, MAX(BDRV_SECTOR_SIZE, alignment));
     if (bytes_to_clear) {
         ret = blk_co_pwrite_zeroes(blk, 0, bytes_to_clear, BDRV_REQ_MAY_UNMAP);
         if (ret < 0) {

block/block-backend.c

@@ -1318,9 +1318,9 @@ static void coroutine_fn blk_wait_while_drained(BlockBackend *blk)
          * section.
          */
         qemu_mutex_lock(&blk->queued_requests_lock);
+        /* blk_root_drained_end() has the corresponding blk_inc_in_flight() */
         blk_dec_in_flight(blk);
         qemu_co_queue_wait(&blk->queued_requests, &blk->queued_requests_lock);
-        blk_inc_in_flight(blk);
         qemu_mutex_unlock(&blk->queued_requests_lock);
     }
 }
@@ -2305,6 +2305,17 @@ uint32_t blk_get_request_alignment(BlockBackend *blk)
     return bs ? bs->bl.request_alignment : BDRV_SECTOR_SIZE;
 }
 
+/* Returns the optimal write zeroes alignment, in bytes; guaranteed nonzero */
+uint32_t blk_get_pwrite_zeroes_alignment(BlockBackend *blk)
+{
+    BlockDriverState *bs = blk_bs(blk);
+    IO_CODE();
+    if (!bs) {
+        return BDRV_SECTOR_SIZE;
+    }
+    return bs->bl.pwrite_zeroes_alignment ?: bs->bl.request_alignment;
+}
+
 /* Returns the maximum hardware transfer length, in bytes; guaranteed nonzero */
 uint64_t blk_get_max_hw_transfer(BlockBackend *blk)
 {
@@ -2767,9 +2778,11 @@ static void blk_root_drained_end(BdrvChild *child)
             blk->dev_ops->drained_end(blk->dev_opaque);
         }
         qemu_mutex_lock(&blk->queued_requests_lock);
-        while (qemu_co_enter_next(&blk->queued_requests,
-                                  &blk->queued_requests_lock)) {
+        while (!qemu_co_queue_empty(&blk->queued_requests)) {
             /* Resume all queued requests */
+            blk_inc_in_flight(blk);
+            qemu_co_enter_next(&blk->queued_requests,
+                               &blk->queued_requests_lock);
         }
         qemu_mutex_unlock(&blk->queued_requests_lock);
     }

block/file-posix.c

@@ -1611,6 +1611,22 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
 
             bs->bl.pdiscard_alignment = dalign;
         }
+
+#ifdef __linux__
+        /*
+         * Linux requires logical block size alignment for write zeroes even
+         * when normal reads/writes do not require alignment.
+         */
+        if (!s->needs_alignment) {
+            ret = probe_logical_blocksize(s->fd,
+                                          &bs->bl.pwrite_zeroes_alignment);
+            if (ret < 0) {
+                error_setg_errno(errp, -ret,
+                                 "Failed to probe logical block size");
+                return;
+            }
+        }
+#endif /* __linux__ */
     }
 
     raw_refresh_zoned_limits(bs, &st, errp);

include/system/block-backend-io.h

@@ -116,6 +116,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
                                   void *opaque, int ret);
 
 uint32_t blk_get_request_alignment(BlockBackend *blk);
+uint32_t blk_get_pwrite_zeroes_alignment(BlockBackend *blk);
 uint32_t blk_get_max_transfer(BlockBackend *blk);
 uint64_t blk_get_max_hw_transfer(BlockBackend *blk);
 

tests/qemu-iotests/tests/loop-create-file

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+# group: quick
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright Red Hat, Inc.
+#
+# Test Linux loop device image creation
+#
+# This test verifies #3127 "qemu-img create fails on loop device with sector size 4096"
+# https://gitlab.com/qemu-project/qemu/-/issues/3127
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+status=1	# failure is the default!
+
+_cleanup() {
+    if [ -n "$loopdev" ]; then
+        sudo losetup --detach "$loopdev"
+    fi
+
+    _cleanup_test_img
+}
+
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+cd ..
+. ./common.rc
+. ./common.filter
+
+_supported_fmt raw
+_supported_proto file
+_supported_os Linux
+
+if ! sudo -n losetup &>/dev/null; then
+    _notrun "sudo losetup not available"
+fi
+
+echo
+echo "=== Create image on a 4 KB sector size loop device ==="
+echo
+
+_make_test_img -f $IMGFMT 1M
+
+loopdev=$(sudo losetup --sector-size 4096 --find --show "$TEST_IMG")
+if [ -z "$loopdev" ]; then
+    _fail
+fi
+
+sudo $QEMU_IMG_PROG create -f raw "$loopdev" 1M | \
+    sed -e "s#/dev/loop[0-9]\\+#LOOPDEV#g"
+
+# success, all done
+echo
+echo '*** done'
+rm -f $seq.full
+status=0

tests/qemu-iotests/tests/loop-create-file.out

@@ -0,0 +1,8 @@
+QA output created by loop-create-file
+
+=== Create image on a 4 KB sector size loop device ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576
+Formatting 'LOOPDEV', fmt=raw size=1048576
+
+*** done