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From adf32529b8b95ed360356f13bd9a7f2a4b707412 Mon Sep 17 00:00:00 2001
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Message-Id: <adf32529b8b95ed360356f13bd9a7f2a4b707412.1389014116.git.minovotn@redhat.com>
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In-Reply-To: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>
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References: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Mon, 9 Dec 2013 14:09:29 +0100
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Subject: [PATCH 41/50] raw-posix: add support for write_zeroes on XFS and
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 block devices
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <1386598178-11845-44-git-send-email-pbonzini@redhat.com>
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Patchwork-id: 56080
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O-Subject: [RHEL 7.0 qemu-kvm PATCH 43/52] raw-posix: add support for write_zeroes on XFS and block devices
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Bugzilla: 1007815
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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The code is similar to the implementation of discard and write_zeroes
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with UNMAP.  However, failure must be propagated up to block.c.
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The stale page cache problem can be reproduced as follows:
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    # modprobe scsi-debug lbpws=1 lbprz=1
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    # ./qemu-io /dev/sdXX
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    qemu-io> write -P 0xcc 0 2M
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    qemu-io> write -z 0 1M
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    qemu-io> read -P 0x00 0 512
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    Pattern verification failed at offset 0, 512 bytes
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    qemu-io> read -v 0 512
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    00000000:  cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc  ................
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    ...
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    # ./qemu-io --cache=none /dev/sdXX
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    qemu-io> write -P 0xcc 0 2M
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    qemu-io> write -z 0 1M
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    qemu-io> read -P 0x00 0 512
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    qemu-io> read -v 0 512
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    00000000:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
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    ...
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And similarly with discard instead of "write -z".
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 97a2ae34537882df34810d538ab1f51085499d2c)
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---
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 block/raw-aio.h   |  3 +-
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 block/raw-posix.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++--------
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 2 files changed, 74 insertions(+), 13 deletions(-)
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Signed-off-by: Michal Novotny <minovotn@redhat.com>
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---
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 block/raw-aio.h   |  3 +-
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 block/raw-posix.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++--------
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 2 files changed, 74 insertions(+), 13 deletions(-)
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diff --git a/block/raw-aio.h b/block/raw-aio.h
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index c61f159..7ad0a8a 100644
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--- a/block/raw-aio.h
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+++ b/block/raw-aio.h
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@@ -21,9 +21,10 @@
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 #define QEMU_AIO_IOCTL        0x0004
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 #define QEMU_AIO_FLUSH        0x0008
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 #define QEMU_AIO_DISCARD      0x0010
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+#define QEMU_AIO_WRITE_ZEROES 0x0020
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 #define QEMU_AIO_TYPE_MASK \
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         (QEMU_AIO_READ|QEMU_AIO_WRITE|QEMU_AIO_IOCTL|QEMU_AIO_FLUSH| \
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-         QEMU_AIO_DISCARD)
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+         QEMU_AIO_DISCARD|QEMU_AIO_WRITE_ZEROES)
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 /* AIO flags */
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 #define QEMU_AIO_MISALIGNED   0x1000
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diff --git a/block/raw-posix.c b/block/raw-posix.c
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index 815a80b..f410668 100644
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--- a/block/raw-posix.c
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+++ b/block/raw-posix.c
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@@ -142,6 +142,7 @@ typedef struct BDRVRawState {
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     bool is_xfs:1;
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 #endif
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     bool has_discard:1;
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+    bool has_write_zeroes:1;
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     bool discard_zeroes:1;
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 } BDRVRawState;
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@@ -327,6 +328,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
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 #endif
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     s->has_discard = true;
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+    s->has_write_zeroes = true;
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     if (fstat(s->fd, &st) < 0) {
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         error_setg_errno(errp, errno, "Could not stat file");
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@@ -345,9 +347,11 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
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 #ifdef __linux__
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         /* On Linux 3.10, BLKDISCARD leaves stale data in the page cache.  Do
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          * not rely on the contents of discarded blocks unless using O_DIRECT.
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+         * Same for BLKZEROOUT.
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          */
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         if (!(bs->open_flags & BDRV_O_NOCACHE)) {
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             s->discard_zeroes = false;
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+            s->has_write_zeroes = false;
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         }
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 #endif
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     }
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@@ -703,6 +707,23 @@ static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
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 }
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 #ifdef CONFIG_XFS
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+static int xfs_write_zeroes(BDRVRawState *s, int64_t offset, uint64_t bytes)
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+{
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+    struct xfs_flock64 fl;
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+
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+    memset(&fl, 0, sizeof(fl));
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+    fl.l_whence = SEEK_SET;
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+    fl.l_start = offset;
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+    fl.l_len = bytes;
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+
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+    if (xfsctl(NULL, s->fd, XFS_IOC_ZERO_RANGE, &fl) < 0) {
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+        DEBUG_BLOCK_PRINT("cannot write zero range (%s)\n", strerror(errno));
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+        return -errno;
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+    }
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+
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+    return 0;
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+}
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+
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 static int xfs_discard(BDRVRawState *s, int64_t offset, uint64_t bytes)
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 {
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     struct xfs_flock64 fl;
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@@ -721,6 +742,42 @@ static int xfs_discard(BDRVRawState *s, int64_t offset, uint64_t bytes)
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 }
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 #endif
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+static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
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+{
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+    int ret = -EOPNOTSUPP;
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+    BDRVRawState *s = aiocb->bs->opaque;
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+
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+    if (s->has_write_zeroes == 0) {
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+        return -ENOTSUP;
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+    }
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+
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+    if (aiocb->aio_type & QEMU_AIO_BLKDEV) {
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+#ifdef BLKZEROOUT
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+        do {
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+            uint64_t range[2] = { aiocb->aio_offset, aiocb->aio_nbytes };
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+            if (ioctl(aiocb->aio_fildes, BLKZEROOUT, range) == 0) {
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+                return 0;
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+            }
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+        } while (errno == EINTR);
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+
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+        ret = -errno;
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+#endif
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+    } else {
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+#ifdef CONFIG_XFS
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+        if (s->is_xfs) {
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+            return xfs_write_zeroes(s, aiocb->aio_offset, aiocb->aio_nbytes);
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+        }
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+#endif
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+    }
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+
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+    if (ret == -ENODEV || ret == -ENOSYS || ret == -EOPNOTSUPP ||
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+        ret == -ENOTTY) {
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+        s->has_write_zeroes = false;
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+        ret = -ENOTSUP;
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+    }
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+    return ret;
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+}
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+
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 static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)
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 {
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     int ret = -EOPNOTSUPP;
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@@ -805,6 +862,9 @@ static int aio_worker(void *arg)
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     case QEMU_AIO_DISCARD:
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         ret = handle_aiocb_discard(aiocb);
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         break;
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+    case QEMU_AIO_WRITE_ZEROES:
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+        ret = handle_aiocb_write_zeroes(aiocb);
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+        break;
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     default:
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         fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
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         ret = -EINVAL;
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@@ -1257,13 +1317,13 @@ static int coroutine_fn raw_co_write_zeroes(
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     BDRVRawState *s = bs->opaque;
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     if (!(flags & BDRV_REQ_MAY_UNMAP)) {
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-        return -ENOTSUP;
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-    }
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-    if (!s->discard_zeroes) {
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-        return -ENOTSUP;
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+        return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
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+                              QEMU_AIO_WRITE_ZEROES);
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+    } else if (s->discard_zeroes) {
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+        return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
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+                              QEMU_AIO_DISCARD);
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     }
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-    return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
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-                          QEMU_AIO_DISCARD);
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+    return -ENOTSUP;
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 }
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 static int raw_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
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@@ -1613,13 +1673,13 @@ static coroutine_fn int hdev_co_write_zeroes(BlockDriverState *bs,
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         return rc;
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     }
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     if (!(flags & BDRV_REQ_MAY_UNMAP)) {
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-        return -ENOTSUP;
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-    }
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-    if (!s->discard_zeroes) {
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-        return -ENOTSUP;
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+        return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
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+                              QEMU_AIO_WRITE_ZEROES|QEMU_AIO_BLKDEV);
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+    } else if (s->discard_zeroes) {
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+        return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
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+                              QEMU_AIO_DISCARD|QEMU_AIO_BLKDEV);
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     }
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-    return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
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-                          QEMU_AIO_DISCARD|QEMU_AIO_BLKDEV);
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+    return -ENOTSUP;
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 }
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 static int hdev_create(const char *filename, QEMUOptionParameter *options,
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-- 
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1.7.11.7
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