Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Mon 22 Sep 2014 12:41:59 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request: (59 commits)
  block: Always compile virtio-blk dataplane
  vring: Better error handling if num is too large
  virtio: Import virtio_vring.h
  async: aio_context_new(): Handle event_notifier_init failure
  block: vhdx - fix reading beyond pointer during image creation
  block: delete cow block driver
  block/archipelago: Fix typo in qemu_archipelago_truncate()
  ahci: Add test_identify case to ahci-test.
  ahci: Add test_hba_enable to ahci-test.
  ahci: Add test_hba_spec to ahci-test.
  ahci: properly shadow the TFD register
  ahci: add test_pci_enable to ahci-test.
  ahci: Add test_pci_spec to ahci-test.
  ahci: MSI capability should be at 0x80, not 0x50.
  ahci: Adding basic functionality qtest.
  layout: Add generators for refcount table and blocks
  fuzz: Add fuzzing functions for entries of refcount table and blocks
  docs: List all image elements currently supported by the fuzzer
  qapi/block-core: Add "new" qcow2 options
  qcow2: Add overlap-check.template option
  ...

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

19 files changed, 403 insertions, 676 deletions

diff --git a/block/Makefile.objs b/block/Makefile.objs
index c9c8bbb..a833ed5 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -1,4 +1,4 @@
-block-obj-y += raw_bsd.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat.o
+block-obj-y += raw_bsd.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat.o
 block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o
 block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
 block-obj-y += qed-check.o
@@ -9,6 +9,7 @@ block-obj-y += snapshot.o qapi.o
 block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
 block-obj-$(CONFIG_POSIX) += raw-posix.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
+block-obj-y += null.o
 
 block-obj-y += nbd.o nbd-client.o sheepdog.o
 block-obj-$(CONFIG_LIBISCSI) += iscsi.o
diff --git a/block/archipelago.c b/block/archipelago.c
index 93fb7c0..73d91a4 100644
--- a/block/archipelago.c
+++ b/block/archipelago.c
@@ -91,7 +91,6 @@ typedef struct ArchipelagoAIOCB {
     struct BDRVArchipelagoState *s;
     QEMUIOVector *qiov;
     ARCHIPCmd cmd;
-    bool cancelled;
     int status;
     int64_t size;
     int64_t ret;
@@ -318,9 +317,7 @@ static void qemu_archipelago_complete_aio(void *opaque)
     aio_cb->common.cb(aio_cb->common.opaque, aio_cb->ret);
     aio_cb->status = 0;
 
-    if (!aio_cb->cancelled) {
-        qemu_aio_release(aio_cb);
-    }
+    qemu_aio_unref(aio_cb);
     g_free(reqdata);
 }
 
@@ -725,19 +722,8 @@ static int qemu_archipelago_create(const char *filename,
     return ret;
 }
 
-static void qemu_archipelago_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    ArchipelagoAIOCB *aio_cb = (ArchipelagoAIOCB *) blockacb;
-    aio_cb->cancelled = true;
-    while (aio_cb->status == -EINPROGRESS) {
-        aio_poll(bdrv_get_aio_context(aio_cb->common.bs), true);
-    }
-    qemu_aio_release(aio_cb);
-}
-
 static const AIOCBInfo archipelago_aiocb_info = {
     .aiocb_size = sizeof(ArchipelagoAIOCB),
-    .cancel = qemu_archipelago_aio_cancel,
 };
 
 static int archipelago_submit_request(BDRVArchipelagoState *s,
@@ -889,7 +875,6 @@ static BlockDriverAIOCB *qemu_archipelago_aio_rw(BlockDriverState *bs,
 
     aio_cb->ret = 0;
     aio_cb->s = s;
-    aio_cb->cancelled = false;
     aio_cb->status = -EINPROGRESS;
 
     off = sector_num * BDRV_SECTOR_SIZE;
@@ -905,7 +890,7 @@ static BlockDriverAIOCB *qemu_archipelago_aio_rw(BlockDriverState *bs,
 
 err_exit:
     error_report("qemu_archipelago_aio_rw(): I/O Error\n");
-    qemu_aio_release(aio_cb);
+    qemu_aio_unref(aio_cb);
     return NULL;
 }
 
@@ -1008,7 +993,7 @@ static int qemu_archipelago_truncate(BlockDriverState *bs, int64_t offset)
     req = xseg_get_request(s->xseg, s->srcport, s->mportno, X_ALLOC);
     if (!req) {
         archipelagolog("Cannot get XSEG request\n");
-        return err_exit2;
+        goto err_exit2;
     }
 
     ret = xseg_prep_request(s->xseg, req, targetlen, 0);
diff --git a/block/blkdebug.c b/block/blkdebug.c
index 69b330e..ced0b60 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -52,11 +52,8 @@ typedef struct BlkdebugSuspendedReq {
     QLIST_ENTRY(BlkdebugSuspendedReq) next;
 } BlkdebugSuspendedReq;
 
-static void blkdebug_aio_cancel(BlockDriverAIOCB *blockacb);
-
 static const AIOCBInfo blkdebug_aiocb_info = {
-    .aiocb_size = sizeof(BlkdebugAIOCB),
-    .cancel     = blkdebug_aio_cancel,
+    .aiocb_size    = sizeof(BlkdebugAIOCB),
 };
 
 enum {
@@ -447,17 +444,7 @@ static void error_callback_bh(void *opaque)
     struct BlkdebugAIOCB *acb = opaque;
     qemu_bh_delete(acb->bh);
     acb->common.cb(acb->common.opaque, acb->ret);
-    qemu_aio_release(acb);
-}
-
-static void blkdebug_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    BlkdebugAIOCB *acb = container_of(blockacb, BlkdebugAIOCB, common);
-    if (acb->bh) {
-        qemu_bh_delete(acb->bh);
-        acb->bh = NULL;
-    }
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
 }
 
 static BlockDriverAIOCB *inject_error(BlockDriverState *bs,
diff --git a/block/blkverify.c b/block/blkverify.c
index 163064c..7d64a23 100644
--- a/block/blkverify.c
+++ b/block/blkverify.c
@@ -29,7 +29,6 @@ struct BlkverifyAIOCB {
 
     int ret;                    /* first completed request's result */
     unsigned int done;          /* completion counter */
-    bool *finished;             /* completion signal for cancel */
 
     QEMUIOVector *qiov;         /* user I/O vector */
     QEMUIOVector raw_qiov;      /* cloned I/O vector for raw file */
@@ -38,22 +37,8 @@ struct BlkverifyAIOCB {
     void (*verify)(BlkverifyAIOCB *acb);
 };
 
-static void blkverify_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    BlkverifyAIOCB *acb = (BlkverifyAIOCB *)blockacb;
-    AioContext *aio_context = bdrv_get_aio_context(blockacb->bs);
-    bool finished = false;
-
-    /* Wait until request completes, invokes its callback, and frees itself */
-    acb->finished = &finished;
-    while (!finished) {
-        aio_poll(aio_context, true);
-    }
-}
-
 static const AIOCBInfo blkverify_aiocb_info = {
     .aiocb_size         = sizeof(BlkverifyAIOCB),
-    .cancel             = blkverify_aio_cancel,
 };
 
 static void GCC_FMT_ATTR(2, 3) blkverify_err(BlkverifyAIOCB *acb,
@@ -194,7 +179,6 @@ static BlkverifyAIOCB *blkverify_aio_get(BlockDriverState *bs, bool is_write,
     acb->qiov = qiov;
     acb->buf = NULL;
     acb->verify = NULL;
-    acb->finished = NULL;
     return acb;
 }
 
@@ -208,10 +192,7 @@ static void blkverify_aio_bh(void *opaque)
         qemu_vfree(acb->buf);
     }
     acb->common.cb(acb->common.opaque, acb->ret);
-    if (acb->finished) {
-        *acb->finished = true;
-    }
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
 }
 
 static void blkverify_aio_cb(void *opaque, int ret)
diff --git a/block/cow.c b/block/cow.c
deleted file mode 100644
index c3769fe..0000000
--- a/block/cow.c
+++ /dev/null
@@ -1,433 +0,0 @@
-/*
- * Block driver for the COW format
- *
- * Copyright (c) 2004 Fabrice Bellard
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
- * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-#include "qemu-common.h"
-#include "block/block_int.h"
-#include "qemu/module.h"
-
-/**************************************************************/
-/* COW block driver using file system holes */
-
-/* user mode linux compatible COW file */
-#define COW_MAGIC 0x4f4f4f4d  /* MOOO */
-#define COW_VERSION 2
-
-struct cow_header_v2 {
-    uint32_t magic;
-    uint32_t version;
-    char backing_file[1024];
-    int32_t mtime;
-    uint64_t size;
-    uint32_t sectorsize;
-};
-
-typedef struct BDRVCowState {
-    CoMutex lock;
-    int64_t cow_sectors_offset;
-} BDRVCowState;
-
-static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
-{
-    const struct cow_header_v2 *cow_header = (const void *)buf;
-
-    if (buf_size >= sizeof(struct cow_header_v2) &&
-        be32_to_cpu(cow_header->magic) == COW_MAGIC &&
-        be32_to_cpu(cow_header->version) == COW_VERSION)
-        return 100;
-    else
-        return 0;
-}
-
-static int cow_open(BlockDriverState *bs, QDict *options, int flags,
-                    Error **errp)
-{
-    BDRVCowState *s = bs->opaque;
-    struct cow_header_v2 cow_header;
-    int bitmap_size;
-    int64_t size;
-    int ret;
-
-    /* see if it is a cow image */
-    ret = bdrv_pread(bs->file, 0, &cow_header, sizeof(cow_header));
-    if (ret < 0) {
-        goto fail;
-    }
-
-    if (be32_to_cpu(cow_header.magic) != COW_MAGIC) {
-        error_setg(errp, "Image not in COW format");
-        ret = -EINVAL;
-        goto fail;
-    }
-
-    if (be32_to_cpu(cow_header.version) != COW_VERSION) {
-        char version[64];
-        snprintf(version, sizeof(version),
-               "COW version %" PRIu32, cow_header.version);
-        error_set(errp, QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
-            bs->device_name, "cow", version);
-        ret = -ENOTSUP;
-        goto fail;
-    }
-
-    /* cow image found */
-    size = be64_to_cpu(cow_header.size);
-    bs->total_sectors = size / 512;
-
-    pstrcpy(bs->backing_file, sizeof(bs->backing_file),
-            cow_header.backing_file);
-
-    bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
-    s->cow_sectors_offset = (bitmap_size + 511) & ~511;
-    qemu_co_mutex_init(&s->lock);
-    return 0;
- fail:
-    return ret;
-}
-
-static inline void cow_set_bits(uint8_t *bitmap, int start, int64_t nb_sectors)
-{
-    int64_t bitnum = start, last = start + nb_sectors;
-    while (bitnum < last) {
-        if ((bitnum & 7) == 0 && bitnum + 8 <= last) {
-            bitmap[bitnum / 8] = 0xFF;
-            bitnum += 8;
-            continue;
-        }
-        bitmap[bitnum/8] |= (1 << (bitnum % 8));
-        bitnum++;
-    }
-}
-
-#define BITS_PER_BITMAP_SECTOR (512 * 8)
-
-/* Cannot use bitmap.c on big-endian machines.  */
-static int cow_test_bit(int64_t bitnum, const uint8_t *bitmap)
-{
-    return (bitmap[bitnum / 8] & (1 << (bitnum & 7))) != 0;
-}
-
-static int cow_find_streak(const uint8_t *bitmap, int value, int start, int nb_sectors)
-{
-    int streak_value = value ? 0xFF : 0;
-    int last = MIN(start + nb_sectors, BITS_PER_BITMAP_SECTOR);
-    int bitnum = start;
-    while (bitnum < last) {
-        if ((bitnum & 7) == 0 && bitmap[bitnum / 8] == streak_value) {
-            bitnum += 8;
-            continue;
-        }
-        if (cow_test_bit(bitnum, bitmap) == value) {
-            bitnum++;
-            continue;
-        }
-        break;
-    }
-    return MIN(bitnum, last) - start;
-}
-
-/* Return true if first block has been changed (ie. current version is
- * in COW file).  Set the number of continuous blocks for which that
- * is true. */
-static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *num_same)
-{
-    int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8;
-    uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE;
-    bool first = true;
-    int changed = 0, same = 0;
-
-    do {
-        int ret;
-        uint8_t bitmap[BDRV_SECTOR_SIZE];
-
-        bitnum &= BITS_PER_BITMAP_SECTOR - 1;
-        int sector_bits = MIN(nb_sectors, BITS_PER_BITMAP_SECTOR - bitnum);
-
-        ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
-        if (ret < 0) {
-            return ret;
-        }
-
-        if (first) {
-            changed = cow_test_bit(bitnum, bitmap);
-            first = false;
-        }
-
-        same += cow_find_streak(bitmap, changed, bitnum, nb_sectors);
-
-        bitnum += sector_bits;
-        nb_sectors -= sector_bits;
-        offset += BDRV_SECTOR_SIZE;
-    } while (nb_sectors);
-
-    *num_same = same;
-    return changed;
-}
-
-static int64_t coroutine_fn cow_co_get_block_status(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, int *num_same)
-{
-    BDRVCowState *s = bs->opaque;
-    int ret = cow_co_is_allocated(bs, sector_num, nb_sectors, num_same);
-    int64_t offset = s->cow_sectors_offset + (sector_num << BDRV_SECTOR_BITS);
-    if (ret < 0) {
-        return ret;
-    }
-    return (ret ? BDRV_BLOCK_DATA : 0) | offset | BDRV_BLOCK_OFFSET_VALID;
-}
-
-static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
-        int nb_sectors)
-{
-    int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8;
-    uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE;
-    bool first = true;
-    int sector_bits;
-
-    for ( ; nb_sectors;
-            bitnum += sector_bits,
-            nb_sectors -= sector_bits,
-            offset += BDRV_SECTOR_SIZE) {
-        int ret, set;
-        uint8_t bitmap[BDRV_SECTOR_SIZE];
-
-        bitnum &= BITS_PER_BITMAP_SECTOR - 1;
-        sector_bits = MIN(nb_sectors, BITS_PER_BITMAP_SECTOR - bitnum);
-
-        ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
-        if (ret < 0) {
-            return ret;
-        }
-
-        /* Skip over any already set bits */
-        set = cow_find_streak(bitmap, 1, bitnum, sector_bits);
-        bitnum += set;
-        sector_bits -= set;
-        nb_sectors -= set;
-        if (!sector_bits) {
-            continue;
-        }
-
-        if (first) {
-            ret = bdrv_flush(bs->file);
-            if (ret < 0) {
-                return ret;
-            }
-            first = false;
-        }
-
-        cow_set_bits(bitmap, bitnum, sector_bits);
-
-        ret = bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap));
-        if (ret < 0) {
-            return ret;
-        }
-    }
-
-    return 0;
-}
-
-static int coroutine_fn cow_read(BlockDriverState *bs, int64_t sector_num,
-                                 uint8_t *buf, int nb_sectors)
-{
-    BDRVCowState *s = bs->opaque;
-    int ret, n;
-
-    while (nb_sectors > 0) {
-        ret = cow_co_is_allocated(bs, sector_num, nb_sectors, &n);
-        if (ret < 0) {
-            return ret;
-        }
-        if (ret) {
-            ret = bdrv_pread(bs->file,
-                        s->cow_sectors_offset + sector_num * 512,
-                        buf, n * 512);
-            if (ret < 0) {
-                return ret;
-            }
-        } else {
-            if (bs->backing_hd) {
-                /* read from the base image */
-                ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
-                if (ret < 0) {
-                    return ret;
-                }
-            } else {
-                memset(buf, 0, n * 512);
-            }
-        }
-        nb_sectors -= n;
-        sector_num += n;
-        buf += n * 512;
-    }
-    return 0;
-}
-
-static coroutine_fn int cow_co_read(BlockDriverState *bs, int64_t sector_num,
-                                    uint8_t *buf, int nb_sectors)
-{
-    int ret;
-    BDRVCowState *s = bs->opaque;
-    qemu_co_mutex_lock(&s->lock);
-    ret = cow_read(bs, sector_num, buf, nb_sectors);
-    qemu_co_mutex_unlock(&s->lock);
-    return ret;
-}
-
-static int cow_write(BlockDriverState *bs, int64_t sector_num,
-                     const uint8_t *buf, int nb_sectors)
-{
-    BDRVCowState *s = bs->opaque;
-    int ret;
-
-    ret = bdrv_pwrite(bs->file, s->cow_sectors_offset + sector_num * 512,
-                      buf, nb_sectors * 512);
-    if (ret < 0) {
-        return ret;
-    }
-
-    return cow_update_bitmap(bs, sector_num, nb_sectors);
-}
-
-static coroutine_fn int cow_co_write(BlockDriverState *bs, int64_t sector_num,
-                                     const uint8_t *buf, int nb_sectors)
-{
-    int ret;
-    BDRVCowState *s = bs->opaque;
-    qemu_co_mutex_lock(&s->lock);
-    ret = cow_write(bs, sector_num, buf, nb_sectors);
-    qemu_co_mutex_unlock(&s->lock);
-    return ret;
-}
-
-static void cow_close(BlockDriverState *bs)
-{
-}
-
-static int cow_create(const char *filename, QemuOpts *opts, Error **errp)
-{
-    struct cow_header_v2 cow_header;
-    struct stat st;
-    int64_t image_sectors = 0;
-    char *image_filename = NULL;
-    Error *local_err = NULL;
-    int ret;
-    BlockDriverState *cow_bs = NULL;
-
-    /* Read out options */
-    image_sectors = DIV_ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
-                                 BDRV_SECTOR_SIZE);
-    image_filename = qemu_opt_get_del(opts, BLOCK_OPT_BACKING_FILE);
-
-    ret = bdrv_create_file(filename, opts, &local_err);
-    if (ret < 0) {
-        error_propagate(errp, local_err);
-        goto exit;
-    }
-
-    ret = bdrv_open(&cow_bs, filename, NULL, NULL,
-                    BDRV_O_RDWR | BDRV_O_PROTOCOL, NULL, &local_err);
-    if (ret < 0) {
-        error_propagate(errp, local_err);
-        goto exit;
-    }
-
-    memset(&cow_header, 0, sizeof(cow_header));
-    cow_header.magic = cpu_to_be32(COW_MAGIC);
-    cow_header.version = cpu_to_be32(COW_VERSION);
-    if (image_filename) {
-        /* Note: if no file, we put a dummy mtime */
-        cow_header.mtime = cpu_to_be32(0);
-
-        if (stat(image_filename, &st) != 0) {
-            goto mtime_fail;
-        }
-        cow_header.mtime = cpu_to_be32(st.st_mtime);
-    mtime_fail:
-        pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
-                image_filename);
-    }
-    cow_header.sectorsize = cpu_to_be32(512);
-    cow_header.size = cpu_to_be64(image_sectors * 512);
-    ret = bdrv_pwrite(cow_bs, 0, &cow_header, sizeof(cow_header));
-    if (ret < 0) {
-        goto exit;
-    }
-
-    /* resize to include at least all the bitmap */
-    ret = bdrv_truncate(cow_bs,
-        sizeof(cow_header) + ((image_sectors + 7) >> 3));
-    if (ret < 0) {
-        goto exit;
-    }
-
-exit:
-    g_free(image_filename);
-    if (cow_bs) {
-        bdrv_unref(cow_bs);
-    }
-    return ret;
-}
-
-static QemuOptsList cow_create_opts = {
-    .name = "cow-create-opts",
-    .head = QTAILQ_HEAD_INITIALIZER(cow_create_opts.head),
-    .desc = {
-        {
-            .name = BLOCK_OPT_SIZE,
-            .type = QEMU_OPT_SIZE,
-            .help = "Virtual disk size"
-        },
-        {
-            .name = BLOCK_OPT_BACKING_FILE,
-            .type = QEMU_OPT_STRING,
-            .help = "File name of a base image"
-        },
-        { /* end of list */ }
-    }
-};
-
-static BlockDriver bdrv_cow = {
-    .format_name    = "cow",
-    .instance_size  = sizeof(BDRVCowState),
-
-    .bdrv_probe     = cow_probe,
-    .bdrv_open      = cow_open,
-    .bdrv_close     = cow_close,
-    .bdrv_create    = cow_create,
-    .bdrv_has_zero_init     = bdrv_has_zero_init_1,
-    .supports_backing       = true,
-
-    .bdrv_read              = cow_co_read,
-    .bdrv_write             = cow_co_write,
-    .bdrv_co_get_block_status   = cow_co_get_block_status,
-
-    .create_opts    = &cow_create_opts,
-};
-
-static void bdrv_cow_init(void)
-{
-    bdrv_register(&bdrv_cow);
-}
-
-block_init(bdrv_cow_init);
diff --git a/block/curl.c b/block/curl.c
index 938f9d9..225407c 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -212,7 +212,7 @@ static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
             qemu_iovec_from_buf(acb->qiov, 0, s->orig_buf + acb->start,
                                 acb->end - acb->start);
             acb->common.cb(acb->common.opaque, 0);
-            qemu_aio_release(acb);
+            qemu_aio_unref(acb);
             s->acb[i] = NULL;
         }
     }
@@ -304,7 +304,7 @@ static void curl_multi_check_completion(BDRVCURLState *s)
                     }
 
                     acb->common.cb(acb->common.opaque, -EIO);
-                    qemu_aio_release(acb);
+                    qemu_aio_unref(acb);
                     state->acb[i] = NULL;
                 }
             }
@@ -613,14 +613,8 @@ out_noclean:
     return -EINVAL;
 }
 
-static void curl_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    // Do we have to implement canceling? Seems to work without...
-}
-
 static const AIOCBInfo curl_aiocb_info = {
     .aiocb_size         = sizeof(CURLAIOCB),
-    .cancel             = curl_aio_cancel,
 };
 
 
@@ -642,7 +636,7 @@ static void curl_readv_bh_cb(void *p)
     // we can just call the callback and be done.
     switch (curl_find_buf(s, start, acb->nb_sectors * SECTOR_SIZE, acb)) {
         case FIND_RET_OK:
-            qemu_aio_release(acb);
+            qemu_aio_unref(acb);
             // fall through
         case FIND_RET_WAIT:
             return;
@@ -654,7 +648,7 @@ static void curl_readv_bh_cb(void *p)
     state = curl_init_state(acb->common.bs, s);
     if (!state) {
         acb->common.cb(acb->common.opaque, -EIO);
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return;
     }
 
@@ -670,7 +664,7 @@ static void curl_readv_bh_cb(void *p)
     if (state->buf_len && state->orig_buf == NULL) {
         curl_clean_state(state);
         acb->common.cb(acb->common.opaque, -ENOMEM);
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return;
     }
     state->acb[0] = acb;
diff --git a/block/iscsi.c b/block/iscsi.c
index 84bcae8..3c1b416 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -88,7 +88,6 @@ typedef struct IscsiAIOCB {
     struct scsi_task *task;
     uint8_t *buf;
     int status;
-    int canceled;
     int64_t sector_num;
     int nb_sectors;
 #ifdef __linux__
@@ -120,16 +119,14 @@ iscsi_bh_cb(void *p)
     g_free(acb->buf);
     acb->buf = NULL;
 
-    if (acb->canceled == 0) {
-        acb->common.cb(acb->common.opaque, acb->status);
-    }
+    acb->common.cb(acb->common.opaque, acb->status);
 
     if (acb->task != NULL) {
         scsi_free_scsi_task(acb->task);
         acb->task = NULL;
     }
 
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
 }
 
 static void
@@ -240,20 +237,15 @@ iscsi_aio_cancel(BlockDriverAIOCB *blockacb)
         return;
     }
 
-    acb->canceled = 1;
-
     /* send a task mgmt call to the target to cancel the task on the target */
     iscsi_task_mgmt_abort_task_async(iscsilun->iscsi, acb->task,
                                      iscsi_abort_task_cb, acb);
 
-    while (acb->status == -EINPROGRESS) {
-        aio_poll(iscsilun->aio_context, true);
-    }
 }
 
 static const AIOCBInfo iscsi_aiocb_info = {
     .aiocb_size         = sizeof(IscsiAIOCB),
-    .cancel             = iscsi_aio_cancel,
+    .cancel_async       = iscsi_aio_cancel,
 };
 
 
@@ -638,10 +630,6 @@ iscsi_aio_ioctl_cb(struct iscsi_context *iscsi, int status,
     g_free(acb->buf);
     acb->buf = NULL;
 
-    if (acb->canceled != 0) {
-        return;
-    }
-
     acb->status = 0;
     if (status < 0) {
         error_report("Failed to ioctl(SG_IO) to iSCSI lun. %s",
@@ -683,7 +671,6 @@ static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
     acb = qemu_aio_get(&iscsi_aiocb_info, bs, cb, opaque);
 
     acb->iscsilun = iscsilun;
-    acb->canceled    = 0;
     acb->bh          = NULL;
     acb->status      = -EINPROGRESS;
     acb->buf         = NULL;
@@ -693,7 +680,7 @@ static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
     if (acb->task == NULL) {
         error_report("iSCSI: Failed to allocate task for scsi command. %s",
                      iscsi_get_error(iscsi));
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return NULL;
     }
     memset(acb->task, 0, sizeof(struct scsi_task));
@@ -731,7 +718,7 @@ static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
                                  (data.size > 0) ? &data : NULL,
                                  acb) != 0) {
         scsi_free_scsi_task(acb->task);
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return NULL;
     }
 
diff --git a/block/linux-aio.c b/block/linux-aio.c
index 9aca758..f4baba2 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -85,11 +85,10 @@ static void qemu_laio_process_completion(struct qemu_laio_state *s,
                 ret = -EINVAL;
             }
         }
-
-        laiocb->common.cb(laiocb->common.opaque, ret);
     }
+    laiocb->common.cb(laiocb->common.opaque, ret);
 
-    qemu_aio_release(laiocb);
+    qemu_aio_unref(laiocb);
 }
 
 /* The completion BH fetches completed I/O requests and invokes their
@@ -153,35 +152,22 @@ static void laio_cancel(BlockDriverAIOCB *blockacb)
     struct io_event event;
     int ret;
 
-    if (laiocb->ret != -EINPROGRESS)
+    if (laiocb->ret != -EINPROGRESS) {
         return;
-
-    /*
-     * Note that as of Linux 2.6.31 neither the block device code nor any
-     * filesystem implements cancellation of AIO request.
-     * Thus the polling loop below is the normal code path.
-     */
+    }
     ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
-    if (ret == 0) {
-        laiocb->ret = -ECANCELED;
+    laiocb->ret = -ECANCELED;
+    if (ret != 0) {
+        /* iocb is not cancelled, cb will be called by the event loop later */
         return;
     }
 
-    /*
-     * We have to wait for the iocb to finish.
-     *
-     * The only way to get the iocb status update is by polling the io context.
-     * We might be able to do this slightly more optimal by removing the
-     * O_NONBLOCK flag.
-     */
-    while (laiocb->ret == -EINPROGRESS) {
-        qemu_laio_completion_cb(&laiocb->ctx->e);
-    }
+    laiocb->common.cb(laiocb->common.opaque, laiocb->ret);
 }
 
 static const AIOCBInfo laio_aiocb_info = {
     .aiocb_size         = sizeof(struct qemu_laiocb),
-    .cancel             = laio_cancel,
+    .cancel_async       = laio_cancel,
 };
 
 static void ioq_init(LaioQueue *io_q)
@@ -300,7 +286,7 @@ BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
     return &laiocb->common;
 
 out_free_aiocb:
-    qemu_aio_release(laiocb);
+    qemu_aio_unref(laiocb);
     return NULL;
 }
 
diff --git a/block/null.c b/block/null.c
new file mode 100644
index 0000000..8284419
--- /dev/null
+++ b/block/null.c
@@ -0,0 +1,168 @@
+/*
+ * Null block driver
+ *
+ * Authors:
+ *  Fam Zheng <famz@redhat.com>
+ *
+ * Copyright (C) 2014 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "block/block_int.h"
+
+typedef struct {
+    int64_t length;
+} BDRVNullState;
+
+static QemuOptsList runtime_opts = {
+    .name = "null",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = "filename",
+            .type = QEMU_OPT_STRING,
+            .help = "",
+        },
+        {
+            .name = BLOCK_OPT_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "size of the null block",
+        },
+        { /* end of list */ }
+    },
+};
+
+static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
+                          Error **errp)
+{
+    QemuOpts *opts;
+    BDRVNullState *s = bs->opaque;
+
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &error_abort);
+    s->length =
+        qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
+    qemu_opts_del(opts);
+    return 0;
+}
+
+static void null_close(BlockDriverState *bs)
+{
+}
+
+static int64_t null_getlength(BlockDriverState *bs)
+{
+    BDRVNullState *s = bs->opaque;
+    return s->length;
+}
+
+static coroutine_fn int null_co_readv(BlockDriverState *bs,
+                                      int64_t sector_num, int nb_sectors,
+                                      QEMUIOVector *qiov)
+{
+    return 0;
+}
+
+static coroutine_fn int null_co_writev(BlockDriverState *bs,
+                                       int64_t sector_num, int nb_sectors,
+                                       QEMUIOVector *qiov)
+{
+    return 0;
+}
+
+static coroutine_fn int null_co_flush(BlockDriverState *bs)
+{
+    return 0;
+}
+
+typedef struct {
+    BlockDriverAIOCB common;
+    QEMUBH *bh;
+} NullAIOCB;
+
+static const AIOCBInfo null_aiocb_info = {
+    .aiocb_size = sizeof(NullAIOCB),
+};
+
+static void null_bh_cb(void *opaque)
+{
+    NullAIOCB *acb = opaque;
+    acb->common.cb(acb->common.opaque, 0);
+    qemu_bh_delete(acb->bh);
+    qemu_aio_unref(acb);
+}
+
+static inline BlockDriverAIOCB *null_aio_common(BlockDriverState *bs,
+                                                BlockDriverCompletionFunc *cb,
+                                                void *opaque)
+{
+    NullAIOCB *acb;
+
+    acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
+    acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
+    qemu_bh_schedule(acb->bh);
+    return &acb->common;
+}
+
+static BlockDriverAIOCB *null_aio_readv(BlockDriverState *bs,
+                                        int64_t sector_num, QEMUIOVector *qiov,
+                                        int nb_sectors,
+                                        BlockDriverCompletionFunc *cb,
+                                        void *opaque)
+{
+    return null_aio_common(bs, cb, opaque);
+}
+
+static BlockDriverAIOCB *null_aio_writev(BlockDriverState *bs,
+                                         int64_t sector_num, QEMUIOVector *qiov,
+                                         int nb_sectors,
+                                         BlockDriverCompletionFunc *cb,
+                                         void *opaque)
+{
+    return null_aio_common(bs, cb, opaque);
+}
+
+static BlockDriverAIOCB *null_aio_flush(BlockDriverState *bs,
+                                        BlockDriverCompletionFunc *cb,
+                                        void *opaque)
+{
+    return null_aio_common(bs, cb, opaque);
+}
+
+static BlockDriver bdrv_null_co = {
+    .format_name            = "null-co",
+    .protocol_name          = "null-co",
+    .instance_size          = sizeof(BDRVNullState),
+
+    .bdrv_file_open         = null_file_open,
+    .bdrv_close             = null_close,
+    .bdrv_getlength         = null_getlength,
+
+    .bdrv_co_readv          = null_co_readv,
+    .bdrv_co_writev         = null_co_writev,
+    .bdrv_co_flush_to_disk  = null_co_flush,
+};
+
+static BlockDriver bdrv_null_aio = {
+    .format_name            = "null-aio",
+    .protocol_name          = "null-aio",
+    .instance_size          = sizeof(BDRVNullState),
+
+    .bdrv_file_open         = null_file_open,
+    .bdrv_close             = null_close,
+    .bdrv_getlength         = null_getlength,
+
+    .bdrv_aio_readv         = null_aio_readv,
+    .bdrv_aio_writev        = null_aio_writev,
+    .bdrv_aio_flush         = null_aio_flush,
+};
+
+static void bdrv_null_init(void)
+{
+    bdrv_register(&bdrv_null_co);
+    bdrv_register(&bdrv_null_aio);
+}
+
+block_init(bdrv_null_init);
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 735f687..f7dd8c0 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -486,6 +486,13 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
         goto out;
     }
 
+    if (offset_into_cluster(s, l2_offset)) {
+        qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64
+                                " unaligned (L1 index: %#" PRIx64 ")",
+                                l2_offset, l1_index);
+        return -EIO;
+    }
+
     /* load the l2 table in memory */
 
     ret = l2_load(bs, l2_offset, &l2_table);
@@ -508,8 +515,11 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
         break;
     case QCOW2_CLUSTER_ZERO:
         if (s->qcow_version < 3) {
-            qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
-            return -EIO;
+            qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found"
+                                    " in pre-v3 image (L2 offset: %#" PRIx64
+                                    ", L2 index: %#x)", l2_offset, l2_index);
+            ret = -EIO;
+            goto fail;
         }
         c = count_contiguous_clusters(nb_clusters, s->cluster_size,
                 &l2_table[l2_index], QCOW_OFLAG_ZERO);
@@ -525,6 +535,14 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
         c = count_contiguous_clusters(nb_clusters, s->cluster_size,
                 &l2_table[l2_index], QCOW_OFLAG_ZERO);
         *cluster_offset &= L2E_OFFSET_MASK;
+        if (offset_into_cluster(s, *cluster_offset)) {
+            qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset %#"
+                                    PRIx64 " unaligned (L2 offset: %#" PRIx64
+                                    ", L2 index: %#x)", *cluster_offset,
+                                    l2_offset, l2_index);
+            ret = -EIO;
+            goto fail;
+        }
         break;
     default:
         abort();
@@ -541,6 +559,10 @@ out:
     *num = nb_available - index_in_cluster;
 
     return ret;
+
+fail:
+    qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
+    return ret;
 }
 
 /*
@@ -576,6 +598,12 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
 
     assert(l1_index < s->l1_size);
     l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
+    if (offset_into_cluster(s, l2_offset)) {
+        qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64
+                                " unaligned (L1 index: %#" PRIx64 ")",
+                                l2_offset, l1_index);
+        return -EIO;
+    }
 
     /* seek the l2 table of the given l2 offset */
 
@@ -948,6 +976,15 @@ static int handle_copied(BlockDriverState *bs, uint64_t guest_offset,
         bool offset_matches =
             (cluster_offset & L2E_OFFSET_MASK) == *host_offset;
 
+        if (offset_into_cluster(s, cluster_offset & L2E_OFFSET_MASK)) {
+            qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset "
+                                    "%#llx unaligned (guest offset: %#" PRIx64
+                                    ")", cluster_offset & L2E_OFFSET_MASK,
+                                    guest_offset);
+            ret = -EIO;
+            goto out;
+        }
+
         if (*host_offset != 0 && !offset_matches) {
             *bytes = 0;
             ret = 0;
@@ -979,7 +1016,7 @@ out:
 
     /* Only return a host offset if we actually made progress. Otherwise we
      * would make requirements for handle_alloc() that it can't fulfill */
-    if (ret) {
+    if (ret > 0) {
         *host_offset = (cluster_offset & L2E_OFFSET_MASK)
                      + offset_into_cluster(s, guest_offset);
     }
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 43665b8..2bcaaf9 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -26,8 +26,6 @@
 #include "block/block_int.h"
 #include "block/qcow2.h"
 #include "qemu/range.h"
-#include "qapi/qmp/types.h"
-#include "qapi-event.h"
 
 static int64_t alloc_clusters_noref(BlockDriverState *bs, uint64_t size);
 static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
@@ -110,6 +108,13 @@ static int get_refcount(BlockDriverState *bs, int64_t cluster_index)
     if (!refcount_block_offset)
         return 0;
 
+    if (offset_into_cluster(s, refcount_block_offset)) {
+        qcow2_signal_corruption(bs, true, -1, -1, "Refblock offset %#" PRIx64
+                                " unaligned (reftable index: %#" PRIx64 ")",
+                                refcount_block_offset, refcount_table_index);
+        return -EIO;
+    }
+
     ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset,
         (void**) &refcount_block);
     if (ret < 0) {
@@ -183,6 +188,14 @@ static int alloc_refcount_block(BlockDriverState *bs,
 
         /* If it's already there, we're done */
         if (refcount_block_offset) {
+            if (offset_into_cluster(s, refcount_block_offset)) {
+                qcow2_signal_corruption(bs, true, -1, -1, "Refblock offset %#"
+                                        PRIx64 " unaligned (reftable index: "
+                                        "%#x)", refcount_block_offset,
+                                        refcount_table_index);
+                return -EIO;
+            }
+
              return load_refcount_block(bs, refcount_block_offset,
                  (void**) refcount_block);
         }
@@ -838,8 +851,14 @@ void qcow2_free_any_clusters(BlockDriverState *bs, uint64_t l2_entry,
     case QCOW2_CLUSTER_NORMAL:
     case QCOW2_CLUSTER_ZERO:
         if (l2_entry & L2E_OFFSET_MASK) {
-            qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK,
-                                nb_clusters << s->cluster_bits, type);
+            if (offset_into_cluster(s, l2_entry & L2E_OFFSET_MASK)) {
+                qcow2_signal_corruption(bs, false, -1, -1,
+                                        "Cannot free unaligned cluster %#llx",
+                                        l2_entry & L2E_OFFSET_MASK);
+            } else {
+                qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK,
+                                    nb_clusters << s->cluster_bits, type);
+            }
         }
         break;
     case QCOW2_CLUSTER_UNALLOCATED:
@@ -903,6 +922,14 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
             old_l2_offset = l2_offset;
             l2_offset &= L1E_OFFSET_MASK;
 
+            if (offset_into_cluster(s, l2_offset)) {
+                qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#"
+                                        PRIx64 " unaligned (L1 index: %#x)",
+                                        l2_offset, i);
+                ret = -EIO;
+                goto fail;
+            }
+
             ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
                 (void**) &l2_table);
             if (ret < 0) {
@@ -935,6 +962,17 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
 
                     case QCOW2_CLUSTER_NORMAL:
                     case QCOW2_CLUSTER_ZERO:
+                        if (offset_into_cluster(s, offset & L2E_OFFSET_MASK)) {
+                            qcow2_signal_corruption(bs, true, -1, -1, "Data "
+                                                    "cluster offset %#llx "
+                                                    "unaligned (L2 offset: %#"
+                                                    PRIx64 ", L2 index: %#x)",
+                                                    offset & L2E_OFFSET_MASK,
+                                                    l2_offset, j);
+                            ret = -EIO;
+                            goto fail;
+                        }
+
                         cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits;
                         if (!cluster_index) {
                             /* unallocated */
@@ -1838,26 +1876,11 @@ int qcow2_pre_write_overlap_check(BlockDriverState *bs, int ign, int64_t offset,
         return ret;
     } else if (ret > 0) {
         int metadata_ol_bitnr = ffs(ret) - 1;
-        char *message;
-
         assert(metadata_ol_bitnr < QCOW2_OL_MAX_BITNR);
 
-        fprintf(stderr, "qcow2: Preventing invalid write on metadata (overlaps "
-                "with %s); image marked as corrupt.\n",
-                metadata_ol_names[metadata_ol_bitnr]);
-        message = g_strdup_printf("Prevented %s overwrite",
-                metadata_ol_names[metadata_ol_bitnr]);
-        qapi_event_send_block_image_corrupted(bdrv_get_device_name(bs),
-                                              message,
-                                              true,
-                                              offset,
-                                              true,
-                                              size,
-                                              &error_abort);
-        g_free(message);
-
-        qcow2_mark_corrupt(bs);
-        bs->drv = NULL; /* make BDS unusable */
+        qcow2_signal_corruption(bs, true, offset, size, "Preventing invalid "
+                                "write on metadata (overlaps with %s)",
+                                metadata_ol_names[metadata_ol_bitnr]);
         return -EIO;
     }
 
diff --git a/block/qcow2.c b/block/qcow2.c
index 0daf25c..778fc1e 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -31,6 +31,8 @@
 #include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qbool.h"
 #include "qapi/util.h"
+#include "qapi/qmp/types.h"
+#include "qapi-event.h"
 #include "trace.h"
 #include "qemu/option_int.h"
 
@@ -404,6 +406,12 @@ static QemuOptsList qcow2_runtime_opts = {
                     "templates (none, constant, cached, all)",
         },
         {
+            .name = QCOW2_OPT_OVERLAP_TEMPLATE,
+            .type = QEMU_OPT_STRING,
+            .help = "Selects which overlap checks to perform from a range of "
+                    "templates (none, constant, cached, all)",
+        },
+        {
             .name = QCOW2_OPT_OVERLAP_MAIN_HEADER,
             .type = QEMU_OPT_BOOL,
             .help = "Check for unintended writes into the main qcow2 header",
@@ -536,11 +544,11 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     unsigned int len, i;
     int ret = 0;
     QCowHeader header;
-    QemuOpts *opts;
+    QemuOpts *opts = NULL;
     Error *local_err = NULL;
     uint64_t ext_end;
     uint64_t l1_vm_state_index;
-    const char *opt_overlap_check;
+    const char *opt_overlap_check, *opt_overlap_check_template;
     int overlap_check_template = 0;
     uint64_t l2_cache_size, refcount_cache_size;
 
@@ -920,7 +928,21 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     s->discard_passthrough[QCOW2_DISCARD_OTHER] =
         qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_OTHER, false);
 
-    opt_overlap_check = qemu_opt_get(opts, "overlap-check") ?: "cached";
+    opt_overlap_check = qemu_opt_get(opts, QCOW2_OPT_OVERLAP);
+    opt_overlap_check_template = qemu_opt_get(opts, QCOW2_OPT_OVERLAP_TEMPLATE);
+    if (opt_overlap_check_template && opt_overlap_check &&
+        strcmp(opt_overlap_check_template, opt_overlap_check))
+    {
+        error_setg(errp, "Conflicting values for qcow2 options '"
+                   QCOW2_OPT_OVERLAP "' ('%s') and '" QCOW2_OPT_OVERLAP_TEMPLATE
+                   "' ('%s')", opt_overlap_check, opt_overlap_check_template);
+        ret = -EINVAL;
+        goto fail;
+    }
+    if (!opt_overlap_check) {
+        opt_overlap_check = opt_overlap_check_template ?: "cached";
+    }
+
     if (!strcmp(opt_overlap_check, "none")) {
         overlap_check_template = 0;
     } else if (!strcmp(opt_overlap_check, "constant")) {
@@ -933,7 +955,6 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
         error_setg(errp, "Unsupported value '%s' for qcow2 option "
                    "'overlap-check'. Allowed are either of the following: "
                    "none, constant, cached, all", opt_overlap_check);
-        qemu_opts_del(opts);
         ret = -EINVAL;
         goto fail;
     }
@@ -948,6 +969,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     qemu_opts_del(opts);
+    opts = NULL;
 
     if (s->use_lazy_refcounts && s->qcow_version < 3) {
         error_setg(errp, "Lazy refcounts require a qcow2 image with at least "
@@ -965,6 +987,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     return ret;
 
  fail:
+    qemu_opts_del(opts);
     g_free(s->unknown_header_fields);
     cleanup_unknown_header_ext(bs);
     qcow2_free_snapshots(bs);
@@ -2529,6 +2552,52 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts)
     return 0;
 }
 
+/*
+ * If offset or size are negative, respectively, they will not be included in
+ * the BLOCK_IMAGE_CORRUPTED event emitted.
+ * fatal will be ignored for read-only BDS; corruptions found there will always
+ * be considered non-fatal.
+ */
+void qcow2_signal_corruption(BlockDriverState *bs, bool fatal, int64_t offset,
+                             int64_t size, const char *message_format, ...)
+{
+    BDRVQcowState *s = bs->opaque;
+    char *message;
+    va_list ap;
+
+    fatal = fatal && !bs->read_only;
+
+    if (s->signaled_corruption &&
+        (!fatal || (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT)))
+    {
+        return;
+    }
+
+    va_start(ap, message_format);
+    message = g_strdup_vprintf(message_format, ap);
+    va_end(ap);
+
+    if (fatal) {
+        fprintf(stderr, "qcow2: Marking image as corrupt: %s; further "
+                "corruption events will be suppressed\n", message);
+    } else {
+        fprintf(stderr, "qcow2: Image is corrupt: %s; further non-fatal "
+                "corruption events will be suppressed\n", message);
+    }
+
+    qapi_event_send_block_image_corrupted(bdrv_get_device_name(bs), message,
+                                          offset >= 0, offset, size >= 0, size,
+                                          fatal, &error_abort);
+    g_free(message);
+
+    if (fatal) {
+        qcow2_mark_corrupt(bs);
+        bs->drv = NULL; /* make BDS unusable */
+    }
+
+    s->signaled_corruption = true;
+}
+
 static QemuOptsList qcow2_create_opts = {
     .name = "qcow2-create-opts",
     .head = QTAILQ_HEAD_INITIALIZER(qcow2_create_opts.head),
diff --git a/block/qcow2.h b/block/qcow2.h
index 6aeb7ea..7d61e61 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -83,6 +83,7 @@
 #define QCOW2_OPT_DISCARD_SNAPSHOT "pass-discard-snapshot"
 #define QCOW2_OPT_DISCARD_OTHER "pass-discard-other"
 #define QCOW2_OPT_OVERLAP "overlap-check"
+#define QCOW2_OPT_OVERLAP_TEMPLATE "overlap-check.template"
 #define QCOW2_OPT_OVERLAP_MAIN_HEADER "overlap-check.main-header"
 #define QCOW2_OPT_OVERLAP_ACTIVE_L1 "overlap-check.active-l1"
 #define QCOW2_OPT_OVERLAP_ACTIVE_L2 "overlap-check.active-l2"
@@ -261,6 +262,7 @@ typedef struct BDRVQcowState {
     bool discard_passthrough[QCOW2_DISCARD_MAX];
 
     int overlap_check; /* bitmask of Qcow2MetadataOverlap values */
+    bool signaled_corruption;
 
     uint64_t incompatible_features;
     uint64_t compatible_features;
@@ -477,6 +479,10 @@ int qcow2_mark_corrupt(BlockDriverState *bs);
 int qcow2_mark_consistent(BlockDriverState *bs);
 int qcow2_update_header(BlockDriverState *bs);
 
+void qcow2_signal_corruption(BlockDriverState *bs, bool fatal, int64_t offset,
+                             int64_t size, const char *message_format, ...)
+                             GCC_FMT_ATTR(5, 6);
+
 /* qcow2-refcount.c functions */
 int qcow2_refcount_init(BlockDriverState *bs);
 void qcow2_refcount_close(BlockDriverState *bs);
diff --git a/block/qed.c b/block/qed.c
index f8d9e12..e2316d7 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -18,22 +18,8 @@
 #include "qapi/qmp/qerror.h"
 #include "migration/migration.h"
 
-static void qed_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    QEDAIOCB *acb = (QEDAIOCB *)blockacb;
-    AioContext *aio_context = bdrv_get_aio_context(blockacb->bs);
-    bool finished = false;
-
-    /* Wait for the request to finish */
-    acb->finished = &finished;
-    while (!finished) {
-        aio_poll(aio_context, true);
-    }
-}
-
 static const AIOCBInfo qed_aiocb_info = {
     .aiocb_size         = sizeof(QEDAIOCB),
-    .cancel             = qed_aio_cancel,
 };
 
 static int bdrv_qed_probe(const uint8_t *buf, int buf_size,
@@ -919,18 +905,12 @@ static void qed_aio_complete_bh(void *opaque)
     BlockDriverCompletionFunc *cb = acb->common.cb;
     void *user_opaque = acb->common.opaque;
     int ret = acb->bh_ret;
-    bool *finished = acb->finished;
 
     qemu_bh_delete(acb->bh);
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
 
     /* Invoke callback */
     cb(user_opaque, ret);
-
-    /* Signal cancel completion */
-    if (finished) {
-        *finished = true;
-    }
 }
 
 static void qed_aio_complete(QEDAIOCB *acb, int ret)
@@ -1397,7 +1377,6 @@ static BlockDriverAIOCB *qed_aio_setup(BlockDriverState *bs,
                         opaque, flags);
 
     acb->flags = flags;
-    acb->finished = NULL;
     acb->qiov = qiov;
     acb->qiov_offset = 0;
     acb->cur_pos = (uint64_t)sector_num * BDRV_SECTOR_SIZE;
diff --git a/block/quorum.c b/block/quorum.c
index 093382e..7687466 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -138,16 +138,15 @@ static void quorum_aio_cancel(BlockDriverAIOCB *blockacb)
 
     /* cancel all callbacks */
     for (i = 0; i < s->num_children; i++) {
-        bdrv_aio_cancel(acb->qcrs[i].aiocb);
+        if (acb->qcrs[i].aiocb) {
+            bdrv_aio_cancel_async(acb->qcrs[i].aiocb);
+        }
     }
-
-    g_free(acb->qcrs);
-    qemu_aio_release(acb);
 }
 
 static AIOCBInfo quorum_aiocb_info = {
     .aiocb_size         = sizeof(QuorumAIOCB),
-    .cancel             = quorum_aio_cancel,
+    .cancel_async       = quorum_aio_cancel,
 };
 
 static void quorum_aio_finalize(QuorumAIOCB *acb)
@@ -169,7 +168,7 @@ static void quorum_aio_finalize(QuorumAIOCB *acb)
     }
 
     g_free(acb->qcrs);
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
 }
 
 static bool quorum_sha256_compare(QuorumVoteValue *a, QuorumVoteValue *b)
diff --git a/block/rbd.c b/block/rbd.c
index b7f7d5f..96947e3 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -77,7 +77,6 @@ typedef struct RBDAIOCB {
     int64_t sector_num;
     int error;
     struct BDRVRBDState *s;
-    int cancelled;
     int status;
 } RBDAIOCB;
 
@@ -408,9 +407,7 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
     acb->common.cb(acb->common.opaque, (acb->ret > 0 ? 0 : acb->ret));
     acb->status = 0;
 
-    if (!acb->cancelled) {
-        qemu_aio_release(acb);
-    }
+    qemu_aio_unref(acb);
 }
 
 /* TODO Convert to fine grained options */
@@ -539,25 +536,8 @@ static void qemu_rbd_close(BlockDriverState *bs)
     rados_shutdown(s->cluster);
 }
 
-/*
- * Cancel aio. Since we don't reference acb in a non qemu threads,
- * it is safe to access it here.
- */
-static void qemu_rbd_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    RBDAIOCB *acb = (RBDAIOCB *) blockacb;
-    acb->cancelled = 1;
-
-    while (acb->status == -EINPROGRESS) {
-        aio_poll(bdrv_get_aio_context(acb->common.bs), true);
-    }
-
-    qemu_aio_release(acb);
-}
-
 static const AIOCBInfo rbd_aiocb_info = {
     .aiocb_size = sizeof(RBDAIOCB),
-    .cancel = qemu_rbd_aio_cancel,
 };
 
 static void rbd_finish_bh(void *opaque)
@@ -640,7 +620,6 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
     acb->ret = 0;
     acb->error = 0;
     acb->s = s;
-    acb->cancelled = 0;
     acb->bh = NULL;
     acb->status = -EINPROGRESS;
 
@@ -692,7 +671,7 @@ failed_completion:
 failed:
     g_free(rcb);
     qemu_vfree(acb->bounce);
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
     return NULL;
 }
 
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 7da36e1..2d78ef9 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -315,7 +315,6 @@ struct SheepdogAIOCB {
     void (*aio_done_func)(SheepdogAIOCB *);
 
     bool cancelable;
-    bool *finished;
     int nr_pending;
 };
 
@@ -446,10 +445,7 @@ static inline void free_aio_req(BDRVSheepdogState *s, AIOReq *aio_req)
 static void coroutine_fn sd_finish_aiocb(SheepdogAIOCB *acb)
 {
     qemu_coroutine_enter(acb->coroutine, NULL);
-    if (acb->finished) {
-        *acb->finished = true;
-    }
-    qemu_aio_release(acb);
+    qemu_aio_unref(acb);
 }
 
 /*
@@ -482,36 +478,33 @@ static void sd_aio_cancel(BlockDriverAIOCB *blockacb)
     SheepdogAIOCB *acb = (SheepdogAIOCB *)blockacb;
     BDRVSheepdogState *s = acb->common.bs->opaque;
     AIOReq *aioreq, *next;
-    bool finished = false;
-
-    acb->finished = &finished;
-    while (!finished) {
-        if (sd_acb_cancelable(acb)) {
-            /* Remove outstanding requests from pending and failed queues.  */
-            QLIST_FOREACH_SAFE(aioreq, &s->pending_aio_head, aio_siblings,
-                               next) {
-                if (aioreq->aiocb == acb) {
-                    free_aio_req(s, aioreq);
-                }
+
+    if (sd_acb_cancelable(acb)) {
+        /* Remove outstanding requests from pending and failed queues.  */
+        QLIST_FOREACH_SAFE(aioreq, &s->pending_aio_head, aio_siblings,
+                           next) {
+            if (aioreq->aiocb == acb) {
+                free_aio_req(s, aioreq);
             }
-            QLIST_FOREACH_SAFE(aioreq, &s->failed_aio_head, aio_siblings,
-                               next) {
-                if (aioreq->aiocb == acb) {
-                    free_aio_req(s, aioreq);
-                }
+        }
+        QLIST_FOREACH_SAFE(aioreq, &s->failed_aio_head, aio_siblings,
+                           next) {
+            if (aioreq->aiocb == acb) {
+                free_aio_req(s, aioreq);
             }
+        }
 
-            assert(acb->nr_pending == 0);
-            sd_finish_aiocb(acb);
-            return;
+        assert(acb->nr_pending == 0);
+        if (acb->common.cb) {
+            acb->common.cb(acb->common.opaque, -ECANCELED);
         }
-        aio_poll(s->aio_context, true);
+        sd_finish_aiocb(acb);
     }
 }
 
 static const AIOCBInfo sd_aiocb_info = {
-    .aiocb_size = sizeof(SheepdogAIOCB),
-    .cancel = sd_aio_cancel,
+    .aiocb_size     = sizeof(SheepdogAIOCB),
+    .cancel_async   = sd_aio_cancel,
 };
 
 static SheepdogAIOCB *sd_aio_setup(BlockDriverState *bs, QEMUIOVector *qiov,
@@ -528,7 +521,6 @@ static SheepdogAIOCB *sd_aio_setup(BlockDriverState *bs, QEMUIOVector *qiov,
 
     acb->aio_done_func = NULL;
     acb->cancelable = true;
-    acb->finished = NULL;
     acb->coroutine = qemu_coroutine_self();
     acb->ret = 0;
     acb->nr_pending = 0;
@@ -2138,7 +2130,7 @@ static coroutine_fn int sd_co_writev(BlockDriverState *bs, int64_t sector_num,
 
     ret = sd_co_rw_vector(acb);
     if (ret <= 0) {
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return ret;
     }
 
@@ -2159,7 +2151,7 @@ static coroutine_fn int sd_co_readv(BlockDriverState *bs, int64_t sector_num,
 
     ret = sd_co_rw_vector(acb);
     if (ret <= 0) {
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return ret;
     }
 
@@ -2518,7 +2510,7 @@ static coroutine_fn int sd_co_discard(BlockDriverState *bs, int64_t sector_num,
 
     ret = sd_co_rw_vector(acb);
     if (ret <= 0) {
-        qemu_aio_release(acb);
+        qemu_aio_unref(acb);
         return ret;
     }
 
diff --git a/block/vhdx.c b/block/vhdx.c
index 5bf292e..b046448 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -99,7 +99,8 @@ static const MSGUID logical_sector_guid = { .data1 = 0x8141bf1d,
 /* Each parent type must have a valid GUID; this is for parent images
  * of type 'VHDX'.  If we were to allow e.g. a QCOW2 parent, we would
  * need to make up our own QCOW2 GUID type */
-static const MSGUID parent_vhdx_guid = { .data1 = 0xb04aefb7,
+static const MSGUID parent_vhdx_guid __attribute__((unused))
+                                     = { .data1 = 0xb04aefb7,
                                          .data2 = 0xd19e,
                                          .data3 = 0x4a81,
                                          .data4 = { 0xb7, 0x89, 0x25, 0xb8,
@@ -1407,6 +1408,12 @@ exit:
     return ret;
 }
 
+#define VHDX_METADATA_ENTRY_BUFFER_SIZE \
+                                    (sizeof(VHDXFileParameters)               +\
+                                     sizeof(VHDXVirtualDiskSize)              +\
+                                     sizeof(VHDXPage83Data)                   +\
+                                     sizeof(VHDXVirtualDiskLogicalSectorSize) +\
+                                     sizeof(VHDXVirtualDiskPhysicalSectorSize))
 
 /*
  * Create the Metadata entries.
@@ -1445,11 +1452,7 @@ static int vhdx_create_new_metadata(BlockDriverState *bs,
     VHDXVirtualDiskLogicalSectorSize  *mt_log_sector_size;
     VHDXVirtualDiskPhysicalSectorSize *mt_phys_sector_size;
 
-    entry_buffer = g_malloc0(sizeof(VHDXFileParameters)               +
-                             sizeof(VHDXVirtualDiskSize)              +
-                             sizeof(VHDXPage83Data)                   +
-                             sizeof(VHDXVirtualDiskLogicalSectorSize) +
-                             sizeof(VHDXVirtualDiskPhysicalSectorSize));
+    entry_buffer = g_malloc0(VHDX_METADATA_ENTRY_BUFFER_SIZE);
 
     mt_file_params = entry_buffer;
     offset += sizeof(VHDXFileParameters);
@@ -1530,7 +1533,7 @@ static int vhdx_create_new_metadata(BlockDriverState *bs,
     }
 
     ret = bdrv_pwrite(bs, metadata_offset + (64 * KiB), entry_buffer,
-                      VHDX_HEADER_BLOCK_SIZE);
+                      VHDX_METADATA_ENTRY_BUFFER_SIZE);
     if (ret < 0) {
         goto exit;
     }
@@ -1725,7 +1728,6 @@ static int vhdx_create_new_region_table(BlockDriverState *bs,
         goto exit;
     }
 
-
 exit:
     g_free(s);
     g_free(buffer);
@@ -1876,7 +1878,6 @@ static int vhdx_create(const char *filename, QemuOpts *opts, Error **errp)
     }
 
 
-
 delete_and_exit:
     bdrv_unref(bs);
 exit:
diff --git a/block/win32-aio.c b/block/win32-aio.c
index 5030e32..9323c1a 100644
--- a/block/win32-aio.c
+++ b/block/win32-aio.c
@@ -88,7 +88,7 @@ static void win32_aio_process_completion(QEMUWin32AIOState *s,
 
 
     waiocb->common.cb(waiocb->common.opaque, ret);
-    qemu_aio_release(waiocb);
+    qemu_aio_unref(waiocb);
 }
 
 static void win32_aio_completion_cb(EventNotifier *e)
@@ -106,22 +106,8 @@ static void win32_aio_completion_cb(EventNotifier *e)
     }
 }
 
-static void win32_aio_cancel(BlockDriverAIOCB *blockacb)
-{
-    QEMUWin32AIOCB *waiocb = (QEMUWin32AIOCB *)blockacb;
-
-    /*
-     * CancelIoEx is only supported in Vista and newer.  For now, just
-     * wait for completion.
-     */
-    while (!HasOverlappedIoCompleted(&waiocb->ov)) {
-        aio_poll(bdrv_get_aio_context(blockacb->bs), true);
-    }
-}
-
 static const AIOCBInfo win32_aiocb_info = {
     .aiocb_size         = sizeof(QEMUWin32AIOCB),
-    .cancel             = win32_aio_cancel,
 };
 
 BlockDriverAIOCB *win32_aio_submit(BlockDriverState *bs,
@@ -172,7 +158,7 @@ BlockDriverAIOCB *win32_aio_submit(BlockDriverState *bs,
 out_dec_count:
     aio->count--;
 out:
-    qemu_aio_release(waiocb);
+    qemu_aio_unref(waiocb);
     return NULL;
 }