Block layer patches:

- qcow2 cache option default changes (Linux: 32 MB maximum, limited by
   whatever cache size can be made use of with the specific image;
   default cache-clean-interval of 10 minutes)
 - reopen: Allow specifying unchanged child node references, and changing
   a few generic options (discard, detect-zeroes)
 - Fix werror/rerror defaults for -device drive=<node-name>
 - Test case fixes
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Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- qcow2 cache option default changes (Linux: 32 MB maximum, limited by
  whatever cache size can be made use of with the specific image;
  default cache-clean-interval of 10 minutes)
- reopen: Allow specifying unchanged child node references, and changing
  a few generic options (discard, detect-zeroes)
- Fix werror/rerror defaults for -device drive=<node-name>
- Test case fixes

# gpg: Signature made Mon 01 Oct 2018 18:17:35 BST
# gpg:                using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (23 commits)
  tests/test-bdrv-drain: Fix too late qemu_event_reset()
  test-replication: Lock AioContext around blk_unref()
  qcow2: Fix cache-clean-interval documentation
  block-backend: Set werror/rerror defaults in blk_new()
  qcow2: Explicit number replaced by a constant
  qcow2: Set the default cache-clean-interval to 10 minutes
  qcow2: Resize the cache upon image resizing
  qcow2: Increase the default upper limit on the L2 cache size
  qcow2: Assign the L2 cache relatively to the image size
  qcow2: Avoid duplication in setting the refcount cache size
  qcow2: Make sizes more humanly readable
  include: Add a lookup table of sizes
  qcow2: Options' documentation fixes
  block: Allow changing 'detect-zeroes' on reopen
  block: Allow changing 'discard' on reopen
  file-posix: Forbid trying to change unsupported options during reopen
  block: Forbid trying to change unsupported options during reopen
  block: Allow child references on reopen
  block: Don't look for child references in append_open_options()
  block: Remove child references from bs->{options,explicit_options}
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

block.c

@@ -764,6 +764,31 @@ static void bdrv_join_options(BlockDriverState *bs, QDict *options,
     }
 }
 
+static BlockdevDetectZeroesOptions bdrv_parse_detect_zeroes(QemuOpts *opts,
+                                                            int open_flags,
+                                                            Error **errp)
+{
+    Error *local_err = NULL;
+    char *value = qemu_opt_get_del(opts, "detect-zeroes");
+    BlockdevDetectZeroesOptions detect_zeroes =
+        qapi_enum_parse(&BlockdevDetectZeroesOptions_lookup, value,
+                        BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF, &local_err);
+    g_free(value);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return detect_zeroes;
+    }
+
+    if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
+        !(open_flags & BDRV_O_UNMAP))
+    {
+        error_setg(errp, "setting detect-zeroes to unmap is not allowed "
+                   "without setting discard operation to unmap");
+    }
+
+    return detect_zeroes;
+}
+
 /**
  * Set open flags for a given discard mode
  *
@@ -1094,19 +1119,19 @@ static void update_flags_from_options(int *flags, QemuOpts *opts)
     *flags &= ~BDRV_O_CACHE_MASK;
 
     assert(qemu_opt_find(opts, BDRV_OPT_CACHE_NO_FLUSH));
-    if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_NO_FLUSH, false)) {
+    if (qemu_opt_get_bool_del(opts, BDRV_OPT_CACHE_NO_FLUSH, false)) {
         *flags |= BDRV_O_NO_FLUSH;
     }
 
     assert(qemu_opt_find(opts, BDRV_OPT_CACHE_DIRECT));
-    if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_DIRECT, false)) {
+    if (qemu_opt_get_bool_del(opts, BDRV_OPT_CACHE_DIRECT, false)) {
         *flags |= BDRV_O_NOCACHE;
     }
 
     *flags &= ~BDRV_O_RDWR;
 
     assert(qemu_opt_find(opts, BDRV_OPT_READ_ONLY));
-    if (!qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false)) {
+    if (!qemu_opt_get_bool_del(opts, BDRV_OPT_READ_ONLY, false)) {
         *flags |= BDRV_O_RDWR;
     }
 
@@ -1328,7 +1353,6 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
     const char *driver_name = NULL;
     const char *node_name = NULL;
     const char *discard;
-    const char *detect_zeroes;
     QemuOpts *opts;
     BlockDriver *drv;
     Error *local_err = NULL;
@@ -1417,29 +1441,12 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
         }
     }
 
-    detect_zeroes = qemu_opt_get(opts, "detect-zeroes");
+    bs->detect_zeroes =
-    if (detect_zeroes) {
+        bdrv_parse_detect_zeroes(opts, bs->open_flags, &local_err);
-        BlockdevDetectZeroesOptions value =
+    if (local_err) {
-            qapi_enum_parse(&BlockdevDetectZeroesOptions_lookup,
+        error_propagate(errp, local_err);
-                            detect_zeroes,
+        ret = -EINVAL;
-                            BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF,
+        goto fail_opts;
-                            &local_err);
-        if (local_err) {
-            error_propagate(errp, local_err);
-            ret = -EINVAL;
-            goto fail_opts;
-        }
-
-        if (value == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
-            !(bs->open_flags & BDRV_O_UNMAP))
-        {
-            error_setg(errp, "setting detect-zeroes to unmap is not allowed "
-                             "without setting discard operation to unmap");
-            ret = -EINVAL;
-            goto fail_opts;
-        }
-
-        bs->detect_zeroes = value;
     }
 
     if (filename != NULL) {
@@ -2763,12 +2770,15 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
         }
     }
 
-    /* Remove all children options from bs->options and bs->explicit_options */
+    /* Remove all children options and references
+     * from bs->options and bs->explicit_options */
     QLIST_FOREACH(child, &bs->children, next) {
         char *child_key_dot;
         child_key_dot = g_strdup_printf("%s.", child->name);
         qdict_extract_subqdict(bs->explicit_options, NULL, child_key_dot);
         qdict_extract_subqdict(bs->options, NULL, child_key_dot);
+        qdict_del(bs->explicit_options, child->name);
+        qdict_del(bs->options, child->name);
         g_free(child_key_dot);
     }
 
@@ -3153,7 +3163,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
     BlockDriver *drv;
     QemuOpts *opts;
     QDict *orig_reopen_opts;
-    const char *value;
+    char *discard = NULL;
     bool read_only;
 
     assert(reopen_state != NULL);
@@ -3176,18 +3186,28 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
 
     update_flags_from_options(&reopen_state->flags, opts);
 
-    /* node-name and driver must be unchanged. Put them back into the QDict, so
+    discard = qemu_opt_get_del(opts, "discard");
-     * that they are checked at the end of this function. */
+    if (discard != NULL) {
-    value = qemu_opt_get(opts, "node-name");
+        if (bdrv_parse_discard_flags(discard, &reopen_state->flags) != 0) {
-    if (value) {
+            error_setg(errp, "Invalid discard option");
-        qdict_put_str(reopen_state->options, "node-name", value);
+            ret = -EINVAL;
+            goto error;
+        }
     }
 
-    value = qemu_opt_get(opts, "driver");
+    reopen_state->detect_zeroes =
-    if (value) {
+        bdrv_parse_detect_zeroes(opts, reopen_state->flags, &local_err);
-        qdict_put_str(reopen_state->options, "driver", value);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto error;
     }
 
+    /* All other options (including node-name and driver) must be unchanged.
+     * Put them back into the QDict, so that they are checked at the end
+     * of this function. */
+    qemu_opts_to_qdict(opts, reopen_state->options);
+
     /* If we are to stay read-only, do not allow permission change
      * to r/w. Attempting to set to r/w may fail if either BDRV_O_ALLOW_RDWR is
      * not set, or if the BDS still has copy_on_read enabled */
@@ -3239,6 +3259,24 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
             QObject *new = entry->value;
             QObject *old = qdict_get(reopen_state->bs->options, entry->key);
 
+            /* Allow child references (child_name=node_name) as long as they
+             * point to the current child (i.e. everything stays the same). */
+            if (qobject_type(new) == QTYPE_QSTRING) {
+                BdrvChild *child;
+                QLIST_FOREACH(child, &reopen_state->bs->children, next) {
+                    if (!strcmp(child->name, entry->key)) {
+                        break;
+                    }
+                }
+
+                if (child) {
+                    const char *str = qobject_get_try_str(new);
+                    if (!strcmp(child->bs->node_name, str)) {
+                        continue; /* Found child with this name, skip option */
+                    }
+                }
+            }
+
             /*
              * TODO: When using -drive to specify blockdev options, all values
              * will be strings; however, when using -blockdev, blockdev-add or
@@ -3278,6 +3316,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
 error:
     qemu_opts_del(opts);
     qobject_unref(orig_reopen_opts);
+    g_free(discard);
     return ret;
 }
 
@@ -3290,6 +3329,7 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
 {
     BlockDriver *drv;
     BlockDriverState *bs;
+    BdrvChild *child;
     bool old_can_write, new_can_write;
 
     assert(reopen_state != NULL);
@@ -3313,6 +3353,14 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     bs->options            = reopen_state->options;
     bs->open_flags         = reopen_state->flags;
     bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
+    bs->detect_zeroes      = reopen_state->detect_zeroes;
+
+    /* Remove child references from bs->options and bs->explicit_options.
+     * Child options were already removed in bdrv_reopen_queue_child() */
+    QLIST_FOREACH(child, &bs->children, next) {
+        qdict_del(bs->explicit_options, child->name);
+        qdict_del(bs->options, child->name);
+    }
 
     bdrv_refresh_limits(bs, NULL);
 
@@ -5139,23 +5187,12 @@ static bool append_open_options(QDict *d, BlockDriverState *bs)
 {
     const QDictEntry *entry;
     QemuOptDesc *desc;
-    BdrvChild *child;
     bool found_any = false;
 
     for (entry = qdict_first(bs->options); entry;
          entry = qdict_next(bs->options, entry))
     {
-        /* Exclude node-name references to children */
+        /* Exclude all non-driver-specific options */
-        QLIST_FOREACH(child, &bs->children, next) {
-            if (!strcmp(entry->key, child->name)) {
-                break;
-            }
-        }
-        if (child) {
-            continue;
-        }
-
-        /* And exclude all non-driver-specific options */
         for (desc = bdrv_runtime_opts.desc; desc->name; desc++) {
             if (!strcmp(qdict_entry_key(entry), desc->name)) {
                 break;

block/block-backend.c

@@ -325,6 +325,9 @@ BlockBackend *blk_new(uint64_t perm, uint64_t shared_perm)
     blk->shared_perm = shared_perm;
     blk_set_enable_write_cache(blk, true);
 
+    blk->on_read_error = BLOCKDEV_ON_ERROR_REPORT;
+    blk->on_write_error = BLOCKDEV_ON_ERROR_ENOSPC;
+
     block_acct_init(&blk->stats);
 
     notifier_list_init(&blk->remove_bs_notifiers);

block/file-posix.c

@@ -741,8 +741,6 @@ static int raw_check_lock_bytes(int fd, uint64_t perm, uint64_t shared_perm,
                            "Failed to get \"%s\" lock",
                            perm_name);
                 g_free(perm_name);
-                error_append_hint(errp,
-                                  "Is another process using the image?\n");
                 return ret;
             }
         }
@@ -758,8 +756,6 @@ static int raw_check_lock_bytes(int fd, uint64_t perm, uint64_t shared_perm,
                            "Failed to get shared \"%s\" lock",
                            perm_name);
                 g_free(perm_name);
-                error_append_hint(errp,
-                                  "Is another process using the image?\n");
                 return ret;
             }
         }
@@ -796,6 +792,9 @@ static int raw_handle_perm_lock(BlockDriverState *bs,
             if (!ret) {
                 return 0;
             }
+            error_append_hint(errp,
+                              "Is another process using the image [%s]?\n",
+                              bs->filename);
         }
         op = RAW_PL_ABORT;
         /* fall through to unlock bytes. */
@@ -850,8 +849,13 @@ static int raw_reopen_prepare(BDRVReopenState *state,
         goto out;
     }
 
-    rs->check_cache_dropped = qemu_opt_get_bool(opts, "x-check-cache-dropped",
+    rs->check_cache_dropped =
-                                                s->check_cache_dropped);
+        qemu_opt_get_bool_del(opts, "x-check-cache-dropped", false);
+
+    /* This driver's reopen function doesn't currently allow changing
+     * other options, so let's put them back in the original QDict and
+     * bdrv_reopen_prepare() will detect changes and complain. */
+    qemu_opts_to_qdict(opts, state->options);
 
     if (s->type == FTYPE_CD) {
         rs->open_flags |= O_NONBLOCK;
@@ -2217,6 +2221,9 @@ raw_co_create(BlockdevCreateOptions *options, Error **errp)
     /* Step two: Check that nobody else has taken conflicting locks */
     result = raw_check_lock_bytes(fd, perm, shared, errp);
     if (result < 0) {
+        error_append_hint(errp,
+                          "Is another process using the image [%s]?\n",
+                          file_opts->filename);
         goto out_unlock;
     }
 

block/qcow2.c

@@ -777,29 +777,35 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
                              uint64_t *refcount_cache_size, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t combined_cache_size;
+    uint64_t combined_cache_size, l2_cache_max_setting;
     bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set;
     int min_refcount_cache = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;
+    uint64_t virtual_disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
+    uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size / 8);
 
     combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE);
     l2_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_L2_CACHE_SIZE);
     refcount_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_REFCOUNT_CACHE_SIZE);
 
     combined_cache_size = qemu_opt_get_size(opts, QCOW2_OPT_CACHE_SIZE, 0);
-    *l2_cache_size = qemu_opt_get_size(opts, QCOW2_OPT_L2_CACHE_SIZE, 0);
+    l2_cache_max_setting = qemu_opt_get_size(opts, QCOW2_OPT_L2_CACHE_SIZE,
+                                             DEFAULT_L2_CACHE_MAX_SIZE);
     *refcount_cache_size = qemu_opt_get_size(opts,
                                              QCOW2_OPT_REFCOUNT_CACHE_SIZE, 0);
 
     *l2_cache_entry_size = qemu_opt_get_size(
         opts, QCOW2_OPT_L2_CACHE_ENTRY_SIZE, s->cluster_size);
 
+    *l2_cache_size = MIN(max_l2_cache, l2_cache_max_setting);
+
     if (combined_cache_size_set) {
         if (l2_cache_size_set && refcount_cache_size_set) {
             error_setg(errp, QCOW2_OPT_CACHE_SIZE ", " QCOW2_OPT_L2_CACHE_SIZE
                        " and " QCOW2_OPT_REFCOUNT_CACHE_SIZE " may not be set "
                        "at the same time");
             return;
-        } else if (*l2_cache_size > combined_cache_size) {
+        } else if (l2_cache_size_set &&
+                   (l2_cache_max_setting > combined_cache_size)) {
             error_setg(errp, QCOW2_OPT_L2_CACHE_SIZE " may not exceed "
                        QCOW2_OPT_CACHE_SIZE);
             return;
@@ -814,9 +820,6 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
         } else if (refcount_cache_size_set) {
             *l2_cache_size = combined_cache_size - *refcount_cache_size;
         } else {
-            uint64_t virtual_disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
-            uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size / 8);
-
             /* Assign as much memory as possible to the L2 cache, and
              * use the remainder for the refcount cache */
             if (combined_cache_size >= max_l2_cache + min_refcount_cache) {
@@ -828,16 +831,9 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
                 *l2_cache_size = combined_cache_size - *refcount_cache_size;
             }
         }
-    } else {
-        if (!l2_cache_size_set) {
-            *l2_cache_size = MAX(DEFAULT_L2_CACHE_BYTE_SIZE,
-                                 (uint64_t)DEFAULT_L2_CACHE_CLUSTERS
-                                 * s->cluster_size);
-        }
-        if (!refcount_cache_size_set) {
-            *refcount_cache_size = min_refcount_cache;
-        }
     }
+    /* l2_cache_size and refcount_cache_size are ensured to have at least
+     * their minimum values in qcow2_update_options_prepare() */
 
     if (*l2_cache_entry_size < (1 << MIN_CLUSTER_BITS) ||
         *l2_cache_entry_size > s->cluster_size ||
@@ -948,7 +944,7 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
     /* New interval for cache cleanup timer */
     r->cache_clean_interval =
         qemu_opt_get_number(opts, QCOW2_OPT_CACHE_CLEAN_INTERVAL,
-                            s->cache_clean_interval);
+                            DEFAULT_CACHE_CLEAN_INTERVAL);
 #ifndef CONFIG_LINUX
     if (r->cache_clean_interval != 0) {
         error_setg(errp, QCOW2_OPT_CACHE_CLEAN_INTERVAL
@@ -1328,7 +1324,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
     /* 2^(s->refcount_order - 3) is the refcount width in bytes */
     s->refcount_block_bits = s->cluster_bits - (s->refcount_order - 3);
     s->refcount_block_size = 1 << s->refcount_block_bits;
-    bs->total_sectors = header.size / 512;
+    bs->total_sectors = header.size / BDRV_SECTOR_SIZE;
     s->csize_shift = (62 - (s->cluster_bits - 8));
     s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
     s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
@@ -3422,6 +3418,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
     uint64_t old_length;
     int64_t new_l1_size;
     int ret;
+    QDict *options;
 
     if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA &&
         prealloc != PREALLOC_MODE_FALLOC && prealloc != PREALLOC_MODE_FULL)
@@ -3453,7 +3450,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
         goto fail;
     }
 
-    old_length = bs->total_sectors * 512;
+    old_length = bs->total_sectors * BDRV_SECTOR_SIZE;
     new_l1_size = size_to_l1(s, offset);
 
     if (offset < old_length) {
@@ -3646,6 +3643,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
         }
     }
 
+    bs->total_sectors = offset / BDRV_SECTOR_SIZE;
+
     /* write updated header.size */
     offset = cpu_to_be64(offset);
     ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, size),
@@ -3656,6 +3655,14 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
     }
 
     s->l1_vm_state_index = new_l1_size;
+
+    /* Update cache sizes */
+    options = qdict_clone_shallow(bs->options);
+    ret = qcow2_update_options(bs, options, s->flags, errp);
+    qobject_unref(options);
+    if (ret < 0) {
+        goto fail;
+    }
     ret = 0;
 fail:
     qemu_co_mutex_unlock(&s->lock);

block/qcow2.h

@@ -27,6 +27,7 @@
 
 #include "crypto/block.h"
 #include "qemu/coroutine.h"
+#include "qemu/units.h"
 
 //#define DEBUG_ALLOC
 //#define DEBUG_ALLOC2
@@ -43,11 +44,11 @@
 
 /* 8 MB refcount table is enough for 2 PB images at 64k cluster size
  * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
-#define QCOW_MAX_REFTABLE_SIZE 0x800000
+#define QCOW_MAX_REFTABLE_SIZE S_8MiB
 
 /* 32 MB L1 table is enough for 2 PB images at 64k cluster size
  * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
-#define QCOW_MAX_L1_SIZE 0x2000000
+#define QCOW_MAX_L1_SIZE S_32MiB
 
 /* Allow for an average of 1k per snapshot table entry, should be plenty of
  * space for snapshot names and IDs */
@@ -73,12 +74,16 @@
 /* Must be at least 4 to cover all cases of refcount table growth */
 #define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */
 
-/* Whichever is more */
+#ifdef CONFIG_LINUX
-#define DEFAULT_L2_CACHE_CLUSTERS 8 /* clusters */
+#define DEFAULT_L2_CACHE_MAX_SIZE S_32MiB
-#define DEFAULT_L2_CACHE_BYTE_SIZE 1048576 /* bytes */
+#define DEFAULT_CACHE_CLEAN_INTERVAL 600  /* seconds */
-
+#else
-#define DEFAULT_CLUSTER_SIZE 65536
+#define DEFAULT_L2_CACHE_MAX_SIZE S_8MiB
+/* Cache clean interval is currently available only on Linux, so must be 0 */
+#define DEFAULT_CACHE_CLEAN_INTERVAL 0
+#endif
 
+#define DEFAULT_CLUSTER_SIZE S_64KiB
 
 #define QCOW2_OPT_LAZY_REFCOUNTS "lazy-refcounts"
 #define QCOW2_OPT_DISCARD_REQUEST "pass-discard-request"

docs/qcow2-cache.txt

@@ -79,14 +79,14 @@ Choosing the right cache sizes
 In order to choose the cache sizes we need to know how they relate to
 the amount of allocated space.
 
-The amount of virtual disk that can be mapped by the L2 and refcount
+The part of the virtual disk that can be mapped by the L2 and refcount
 caches (in bytes) is:
 
    disk_size = l2_cache_size * cluster_size / 8
    disk_size = refcount_cache_size * cluster_size * 8 / refcount_bits
 
 With the default values for cluster_size (64KB) and refcount_bits
-(16), that is
+(16), this becomes:
 
    disk_size = l2_cache_size * 8192
    disk_size = refcount_cache_size * 32768
@@ -97,12 +97,16 @@ need:
    l2_cache_size = disk_size_GB * 131072
    refcount_cache_size = disk_size_GB * 32768
 
-QEMU has a default L2 cache of 1MB (1048576 bytes) and a refcount
+For example, 1MB of L2 cache is needed to cover every 8 GB of the virtual
-cache of 256KB (262144 bytes), so using the formulas we've just seen
+image size (given that the default cluster size is used):
-we have
 
-   1048576 / 131072 = 8 GB of virtual disk covered by that cache
+   8 GB / 8192 = 1 MB
-    262144 /  32768 = 8 GB
+
+The refcount cache is 4 times the cluster size by default. With the default
+cluster size of 64 KB, it is 256 KB (262144 bytes). This is sufficient for
+8 GB of image size:
+
+   262144 * 32768 = 8 GB
 
 
 How to configure the cache sizes
@@ -121,8 +125,15 @@ There are a few things that need to be taken into account:
  - Both caches must have a size that is a multiple of the cluster size
    (or the cache entry size: see "Using smaller cache sizes" below).
 
- - The default L2 cache size is 8 clusters or 1MB (whichever is more),
+ - The maximum L2 cache size is 32 MB by default on Linux platforms (enough
-   and the minimum is 2 clusters (or 2 cache entries, see below).
+   for full coverage of 256 GB images, with the default cluster size). This
+   value can be modified using the "l2-cache-size" option. QEMU will not use
+   more memory than needed to hold all of the image's L2 tables, regardless
+   of this max. value.
+   On non-Linux platforms the maximal value is smaller by default (8 MB) and
+   this difference stems from the fact that on Linux the cache can be cleared
+   periodically if needed, using the "cache-clean-interval" option (see below).
+   The minimal L2 cache size is 2 clusters (or 2 cache entries, see below).
 
  - The default (and minimum) refcount cache size is 4 clusters.
 
@@ -130,6 +141,9 @@ There are a few things that need to be taken into account:
    memory as possible to the L2 cache before increasing the refcount
    cache size.
 
+ - At most two of "l2-cache-size", "refcount-cache-size", and "cache-size"
+   can be set simultaneously.
+
 Unlike L2 tables, refcount blocks are not used during normal I/O but
 only during allocations and internal snapshots. In most cases they are
 accessed sequentially (even during random guest I/O) so increasing the
@@ -177,9 +191,10 @@ Some things to take into account:
    always uses the cluster size as the entry size.
 
  - If the L2 cache is big enough to hold all of the image's L2 tables
-   (as explained in the "Choosing the right cache sizes" section
+   (as explained in the "Choosing the right cache sizes" and "How to
-   earlier in this document) then none of this is necessary and you
+   configure the cache sizes" sections in this document) then none of
-   can omit the "l2-cache-entry-size" parameter altogether.
+   this is necessary and you can omit the "l2-cache-entry-size"
+   parameter altogether.
 
 
 Reducing the memory usage
@@ -187,18 +202,18 @@ Reducing the memory usage
 It is possible to clean unused cache entries in order to reduce the
 memory usage during periods of low I/O activity.
 
-The parameter "cache-clean-interval" defines an interval (in seconds).
+The parameter "cache-clean-interval" defines an interval (in seconds),
-All cache entries that haven't been accessed during that interval are
+after which all the cache entries that haven't been accessed during the
-removed from memory.
+interval are removed from memory. Setting this parameter to 0 disables this
+feature.
 
-This example removes all unused cache entries every 15 minutes:
+The following example removes all unused cache entries every 15 minutes:
 
    -drive file=hd.qcow2,cache-clean-interval=900
 
-If unset, the default value for this parameter is 0 and it disables
+If unset, the default value for this parameter is 600 on platforms which
-this feature.
+support this functionality, and is 0 (disabled) on other platforms.
 
-Note that this functionality currently relies on the MADV_DONTNEED
+This functionality currently relies on the MADV_DONTNEED argument for
-argument for madvise() to actually free the memory. This is a
+madvise() to actually free the memory. This is a Linux-specific feature,
-Linux-specific feature, so cache-clean-interval is not supported in
+so cache-clean-interval is not supported on other systems.
-other systems.

include/block/block.h

@@ -184,6 +184,7 @@ typedef QSIMPLEQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue;
 typedef struct BDRVReopenState {
     BlockDriverState *bs;
     int flags;
+    BlockdevDetectZeroesOptions detect_zeroes;
     uint64_t perm, shared_perm;
     QDict *options;
     QDict *explicit_options;

include/qemu/units.h

@@ -17,4 +17,59 @@
 #define PiB     (INT64_C(1) << 50)
 #define EiB     (INT64_C(1) << 60)
 
+#define S_1KiB                  1024
+#define S_2KiB                  2048
+#define S_4KiB                  4096
+#define S_8KiB                  8192
+#define S_16KiB                16384
+#define S_32KiB                32768
+#define S_64KiB                65536
+#define S_128KiB              131072
+#define S_256KiB              262144
+#define S_512KiB              524288
+#define S_1MiB               1048576
+#define S_2MiB               2097152
+#define S_4MiB               4194304
+#define S_8MiB               8388608
+#define S_16MiB             16777216
+#define S_32MiB             33554432
+#define S_64MiB             67108864
+#define S_128MiB           134217728
+#define S_256MiB           268435456
+#define S_512MiB           536870912
+#define S_1GiB            1073741824
+#define S_2GiB            2147483648
+#define S_4GiB            4294967296
+#define S_8GiB            8589934592
+#define S_16GiB          17179869184
+#define S_32GiB          34359738368
+#define S_64GiB          68719476736
+#define S_128GiB        137438953472
+#define S_256GiB        274877906944
+#define S_512GiB        549755813888
+#define S_1TiB         1099511627776
+#define S_2TiB         2199023255552
+#define S_4TiB         4398046511104
+#define S_8TiB         8796093022208
+#define S_16TiB       17592186044416
+#define S_32TiB       35184372088832
+#define S_64TiB       70368744177664
+#define S_128TiB     140737488355328
+#define S_256TiB     281474976710656
+#define S_512TiB     562949953421312
+#define S_1PiB      1125899906842624
+#define S_2PiB      2251799813685248
+#define S_4PiB      4503599627370496
+#define S_8PiB      9007199254740992
+#define S_16PiB    18014398509481984
+#define S_32PiB    36028797018963968
+#define S_64PiB    72057594037927936
+#define S_128PiB  144115188075855872
+#define S_256PiB  288230376151711744
+#define S_512PiB  576460752303423488
+#define S_1EiB   1152921504606846976
+#define S_2EiB   2305843009213693952
+#define S_4EiB   4611686018427387904
+#define S_8EiB   9223372036854775808
+
 #endif

qapi/block-core.json

@@ -2897,7 +2897,9 @@
 #
 # @cache-clean-interval:  clean unused entries in the L2 and refcount
 #                         caches. The interval is in seconds. The default value
-#                         is 0 and it disables this feature (since 2.5)
+#                         is 600 on supporting platforms, and 0 on other
+#                         platforms. 0 disables this feature. (since 2.5)
+#
 # @encrypt:               Image decryption options. Mandatory for
 #                         encrypted images, except when doing a metadata-only
 #                         probe of the image. (since 2.10)

qemu-io-cmds.c

@@ -2025,7 +2025,7 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
         return -EINVAL;
     }
 
-    if (writethrough != blk_enable_write_cache(blk) &&
+    if (!writethrough != blk_enable_write_cache(blk) &&
         blk_get_attached_dev(blk))
     {
         error_report("Cannot change cache.writeback: Device attached");

qemu-options.hx

@@ -732,19 +732,23 @@ image file)
 
 @item cache-size
 The maximum total size of the L2 table and refcount block caches in bytes
-(default: 1048576 bytes or 8 clusters, whichever is larger)
+(default: the sum of l2-cache-size and refcount-cache-size)
 
 @item l2-cache-size
 The maximum size of the L2 table cache in bytes
-(default: 4/5 of the total cache size)
+(default: if cache-size is not specified - 32M on Linux platforms, and 8M on
+non-Linux platforms; otherwise, as large as possible within the cache-size,
+while permitting the requested or the minimal refcount cache size)
 
 @item refcount-cache-size
 The maximum size of the refcount block cache in bytes
-(default: 1/5 of the total cache size)
+(default: 4 times the cluster size; or if cache-size is specified, the part of
+it which is not used for the L2 cache)
 
 @item cache-clean-interval
 Clean unused entries in the L2 and refcount caches. The interval is in seconds.
-The default value is 0 and it disables this feature.
+The default value is 600 on supporting platforms, and 0 on other platforms.
+Setting it to 0 disables this feature.
 
 @item pass-discard-request
 Whether discard requests to the qcow2 device should be forwarded to the data

tests/qemu-iotests/067.out

@@ -385,6 +385,7 @@ Testing: -device virtio-scsi -device scsi-cd,id=cd0
 {
     "return": [
         {
+            "io-status": "ok",
             "device": "",
             "locked": false,
             "removable": true,

tests/qemu-iotests/137

@@ -109,7 +109,6 @@ $QEMU_IO \
     -c "reopen -o cache-size=1M,l2-cache-size=64k,refcount-cache-size=64k" \
     -c "reopen -o cache-size=1M,l2-cache-size=2M" \
     -c "reopen -o cache-size=1M,refcount-cache-size=2M" \
-    -c "reopen -o l2-cache-size=256T" \
     -c "reopen -o l2-cache-entry-size=33k" \
     -c "reopen -o l2-cache-entry-size=128k" \
     -c "reopen -o refcount-cache-size=256T" \
@@ -119,6 +118,13 @@ $QEMU_IO \
     -c "reopen -o cache-clean-interval=-1" \
     "$TEST_IMG" | _filter_qemu_io
 
+IMGOPTS="cluster_size=256k" _make_test_img 32P
+$QEMU_IO \
+    -c "reopen -o l2-cache-entry-size=512,l2-cache-size=1T" \
+    "$TEST_IMG" | _filter_qemu_io
+
+_make_test_img 64M
+
 echo
 echo === Test transaction semantics ===
 echo

tests/qemu-iotests/137.out

@@ -19,7 +19,6 @@ Parameter 'lazy-refcounts' expects 'on' or 'off'
 cache-size, l2-cache-size and refcount-cache-size may not be set at the same time
 l2-cache-size may not exceed cache-size
 refcount-cache-size may not exceed cache-size
-L2 cache size too big
 L2 cache entry size must be a power of two between 512 and the cluster size (65536)
 L2 cache entry size must be a power of two between 512 and the cluster size (65536)
 Refcount cache size too big
@@ -27,6 +26,9 @@ Conflicting values for qcow2 options 'overlap-check' ('constant') and 'overlap-c
 Unsupported value 'blubb' for qcow2 option 'overlap-check'. Allowed are any of the following: none, constant, cached, all
 Unsupported value 'blubb' for qcow2 option 'overlap-check'. Allowed are any of the following: none, constant, cached, all
 Cache clean interval too big
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=36028797018963968
+L2 cache size too big
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 
 === Test transaction semantics ===
 

tests/qemu-iotests/153.out

@@ -12,11 +12,11 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t
 
 == Launching another QEMU, opts: '' ==
 QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=none,: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Launching another QEMU, opts: 'read-only=on' ==
 QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=none,read-only=on: Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Launching another QEMU, opts: 'read-only=on,force-share=on' ==
 
@@ -24,77 +24,77 @@ Is another process using the image?
 
 _qemu_io_wrapper -c read 0 512 TEST_DIR/t.qcow2
 can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_io_wrapper -r -c read 0 512 TEST_DIR/t.qcow2
 can't open device TEST_DIR/t.qcow2: Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_io_wrapper -c open  TEST_DIR/t.qcow2 -c read 0 512
 can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 no file open, try 'help open'
 
 _qemu_io_wrapper -c open -r  TEST_DIR/t.qcow2 -c read 0 512
 can't open device TEST_DIR/t.qcow2: Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 no file open, try 'help open'
 
 _qemu_img_wrapper info TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper check TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper compare TEST_DIR/t.qcow2 TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper map TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper amend -o  TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper commit TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper resize TEST_DIR/t.qcow2 32M
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper snapshot -l TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper convert TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.convert
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper dd if=TEST_DIR/t.qcow2 of=TEST_DIR/t.qcow2.convert bs=512 count=1
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper bench -c 1 TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper bench -w -c 1 TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
 qemu-img: TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 file format: IMGFMT
 
 == Running utility commands -U ==
@@ -132,7 +132,7 @@ Try 'qemu-img --help' for more information
 
 _qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper snapshot -l -U TEST_DIR/t.qcow2
 
@@ -157,7 +157,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t
 
 == Launching another QEMU, opts: '' ==
 QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=none,: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Launching another QEMU, opts: 'read-only=on' ==
 
@@ -167,13 +167,13 @@ Is another process using the image?
 
 _qemu_io_wrapper -c read 0 512 TEST_DIR/t.qcow2
 can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_io_wrapper -r -c read 0 512 TEST_DIR/t.qcow2
 
 _qemu_io_wrapper -c open  TEST_DIR/t.qcow2 -c read 0 512
 can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 no file open, try 'help open'
 
 _qemu_io_wrapper -c open -r  TEST_DIR/t.qcow2 -c read 0 512
@@ -188,19 +188,19 @@ _qemu_img_wrapper map TEST_DIR/t.qcow2
 
 _qemu_img_wrapper amend -o  TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper commit TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper resize TEST_DIR/t.qcow2 32M
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper snapshot -l TEST_DIR/t.qcow2
 
@@ -212,11 +212,11 @@ _qemu_img_wrapper bench -c 1 TEST_DIR/t.qcow2
 
 _qemu_img_wrapper bench -w -c 1 TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
 qemu-img: TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 file format: IMGFMT
 
 == Running utility commands -U ==
@@ -254,7 +254,7 @@ Try 'qemu-img --help' for more information
 
 _qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 _qemu_img_wrapper snapshot -l -U TEST_DIR/t.qcow2
 
@@ -372,17 +372,17 @@ Round done
 
 == Two devices with the same image (read-only=off - read-only=off) ==
 QEMU_PROG: -drive if=none,file=TEST_DIR/t.qcow2,read-only=off: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Two devices with the same image (read-only=off - read-only=on) ==
 QEMU_PROG: -drive if=none,file=TEST_DIR/t.qcow2,read-only=on: Failed to get shared "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Two devices with the same image (read-only=off - read-only=on,force-share=on) ==
 
 == Two devices with the same image (read-only=on - read-only=off) ==
 QEMU_PROG: -drive if=none,file=TEST_DIR/t.qcow2,read-only=off: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Two devices with the same image (read-only=on - read-only=on) ==
 
@@ -403,13 +403,13 @@ Formatting 'TEST_DIR/t.IMGFMT.c', fmt=IMGFMT size=33554432 backing_file=TEST_DIR
 
 == Backing image also as an active device ==
 QEMU_PROG: -drive if=none,file=TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Backing image also as an active device (ro) ==
 
 == Symbolic link ==
 QEMU_PROG: -drive if=none,file=TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 
 == Active commit to intermediate layer should work when base in use ==
 {"return": {}}
@@ -420,7 +420,7 @@ Adding drive
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512
 can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 Creating overlay with qemu-img when the guest is running should be allowed
 
 _qemu_img_wrapper create -f qcow2 -b TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.overlay
@@ -433,7 +433,7 @@ _qemu_img_wrapper info TEST_DIR/t.qcow2
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512
 can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 Closing the other
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512

tests/qemu-iotests/182.out

@@ -4,5 +4,5 @@ Starting QEMU
 
 Starting a second QEMU using the same image should fail
 QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=none,id=drive0,file.locking=on: Failed to get "write" lock
-Is another process using the image?
+Is another process using the image [TEST_DIR/t.qcow2]?
 *** done

tests/test-bdrv-drain.c

@@ -694,6 +694,8 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
     s->bh_indirection_ctx = ctx_b;
 
     aio_ret = -EINPROGRESS;
+    qemu_event_reset(&done_event);
+
     if (drain_thread == 0) {
         acb = blk_aio_preadv(blk, 0, &qiov, 0, test_iothread_aio_cb, &aio_ret);
     } else {
@@ -723,7 +725,6 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
          * but the drain in this thread can continue immediately after
          * bdrv_dec_in_flight() and aio_ret might be assigned only slightly
          * later. */
-        qemu_event_reset(&done_event);
         do_drain_begin(drain_type, bs);
         g_assert_cmpint(bs->in_flight, ==, 0);
 
@@ -743,7 +744,6 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
         }
         break;
     case 1:
-        qemu_event_reset(&done_event);
         aio_bh_schedule_oneshot(ctx_a, test_iothread_drain_entry, &data);
         qemu_event_wait(&done_event);
         break;

tests/test-replication.c

@@ -207,13 +207,17 @@ static BlockBackend *start_primary(void)
 static void teardown_primary(void)
 {
     BlockBackend *blk;
+    AioContext *ctx;
 
     /* remove P_ID */
     blk = blk_by_name(P_ID);
     assert(blk);
 
+    ctx = blk_get_aio_context(blk);
+    aio_context_acquire(ctx);
     monitor_remove_blk(blk);
     blk_unref(blk);
+    aio_context_release(ctx);
 }
 
 static void test_primary_read(void)
@@ -365,20 +369,27 @@ static void teardown_secondary(void)
 {
     /* only need to destroy two BBs */
     BlockBackend *blk;
+    AioContext *ctx;
 
     /* remove S_LOCAL_DISK_ID */
     blk = blk_by_name(S_LOCAL_DISK_ID);
     assert(blk);
 
+    ctx = blk_get_aio_context(blk);
+    aio_context_acquire(ctx);
     monitor_remove_blk(blk);
     blk_unref(blk);
+    aio_context_release(ctx);
 
     /* remove S_ID */
     blk = blk_by_name(S_ID);
     assert(blk);
 
+    ctx = blk_get_aio_context(blk);
+    aio_context_acquire(ctx);
     monitor_remove_blk(blk);
     blk_unref(blk);
+    aio_context_release(ctx);
 }
 
 static void test_secondary_read(void)