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Blame SOURCES/kvm-file-posix-Make-.bdrv_co_truncate-asynchronous.patch

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From f585ea7b67febdd86a2a1c9d53724a5bce625cad Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Tue, 24 Jul 2018 09:23:26 +0200
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Subject: [PATCH 213/268] file-posix: Make .bdrv_co_truncate asynchronous
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180712144258.17303-7-kwolf@redhat.com>
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Patchwork-id: 81324
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 6/6] file-posix: Make .bdrv_co_truncate asynchronous
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Bugzilla: 1595173
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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This moves the code to resize an image file to the thread pool to avoid
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blocking.
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Creating large images with preallocation with blockdev-create is now
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actually a background job instead of blocking the monitor (and most
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other things) until the preallocation has completed.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 93f4e2ff4b31205d8bab0856631a52ed442b8b1c)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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 block/file-posix.c      | 266 +++++++++++++++++++++++++++---------------------
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 include/block/raw-aio.h |   4 +-
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 2 files changed, 154 insertions(+), 116 deletions(-)
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diff --git a/block/file-posix.c b/block/file-posix.c
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index f8488ec..24c2367 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -186,8 +186,16 @@ typedef struct RawPosixAIOData {
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 #define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */
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     off_t aio_offset;
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     int aio_type;
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-    int aio_fd2;
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-    off_t aio_offset2;
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+    union {
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+        struct {
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+            int aio_fd2;
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+            off_t aio_offset2;
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+        };
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+        struct {
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+            PreallocMode prealloc;
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+            Error **errp;
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+        };
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+    };
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 } RawPosixAIOData;
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 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
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@@ -1509,6 +1517,122 @@ static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)
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     return ret;
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 }
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+static int handle_aiocb_truncate(RawPosixAIOData *aiocb)
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+{
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+    int result = 0;
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+    int64_t current_length = 0;
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+    char *buf = NULL;
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+    struct stat st;
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+    int fd = aiocb->aio_fildes;
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+    int64_t offset = aiocb->aio_offset;
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+    Error **errp = aiocb->errp;
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+
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+    if (fstat(fd, &st) < 0) {
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+        result = -errno;
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+        error_setg_errno(errp, -result, "Could not stat file");
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+        return result;
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+    }
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+
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+    current_length = st.st_size;
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+    if (current_length > offset && aiocb->prealloc != PREALLOC_MODE_OFF) {
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+        error_setg(errp, "Cannot use preallocation for shrinking files");
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+        return -ENOTSUP;
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+    }
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+
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+    switch (aiocb->prealloc) {
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+#ifdef CONFIG_POSIX_FALLOCATE
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+    case PREALLOC_MODE_FALLOC:
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+        /*
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+         * Truncating before posix_fallocate() makes it about twice slower on
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+         * file systems that do not support fallocate(), trying to check if a
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+         * block is allocated before allocating it, so don't do that here.
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+         */
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+        if (offset != current_length) {
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+            result = -posix_fallocate(fd, current_length,
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+                                      offset - current_length);
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+            if (result != 0) {
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+                /* posix_fallocate() doesn't set errno. */
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+                error_setg_errno(errp, -result,
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+                                 "Could not preallocate new data");
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+            }
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+        } else {
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+            result = 0;
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+        }
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+        goto out;
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+#endif
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+    case PREALLOC_MODE_FULL:
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+    {
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+        int64_t num = 0, left = offset - current_length;
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+        off_t seek_result;
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+
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+        /*
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+         * Knowing the final size from the beginning could allow the file
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+         * system driver to do less allocations and possibly avoid
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+         * fragmentation of the file.
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+         */
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+        if (ftruncate(fd, offset) != 0) {
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+            result = -errno;
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+            error_setg_errno(errp, -result, "Could not resize file");
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+            goto out;
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+        }
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+
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+        buf = g_malloc0(65536);
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+
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+        seek_result = lseek(fd, current_length, SEEK_SET);
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+        if (seek_result < 0) {
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+            result = -errno;
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+            error_setg_errno(errp, -result,
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+                             "Failed to seek to the old end of file");
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+            goto out;
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+        }
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+
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+        while (left > 0) {
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+            num = MIN(left, 65536);
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+            result = write(fd, buf, num);
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+            if (result < 0) {
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+                result = -errno;
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+                error_setg_errno(errp, -result,
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+                                 "Could not write zeros for preallocation");
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+                goto out;
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+            }
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+            left -= result;
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+        }
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+        if (result >= 0) {
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+            result = fsync(fd);
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+            if (result < 0) {
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+                result = -errno;
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+                error_setg_errno(errp, -result,
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+                                 "Could not flush file to disk");
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+                goto out;
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+            }
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+        }
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+        goto out;
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+    }
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+    case PREALLOC_MODE_OFF:
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+        if (ftruncate(fd, offset) != 0) {
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+            result = -errno;
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+            error_setg_errno(errp, -result, "Could not resize file");
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+        }
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+        return result;
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+    default:
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+        result = -ENOTSUP;
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+        error_setg(errp, "Unsupported preallocation mode: %s",
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+                   PreallocMode_str(aiocb->prealloc));
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+        return result;
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+    }
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+
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+out:
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+    if (result < 0) {
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+        if (ftruncate(fd, current_length) < 0) {
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+            error_report("Failed to restore old file length: %s",
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+                         strerror(errno));
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+        }
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+    }
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+
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+    g_free(buf);
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+    return result;
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+}
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+
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 static int aio_worker(void *arg)
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 {
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     RawPosixAIOData *aiocb = arg;
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@@ -1552,6 +1676,9 @@ static int aio_worker(void *arg)
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     case QEMU_AIO_COPY_RANGE:
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         ret = handle_aiocb_copy_range(aiocb);
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         break;
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+    case QEMU_AIO_TRUNCATE:
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+        ret = handle_aiocb_truncate(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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@@ -1719,117 +1846,25 @@ static void raw_close(BlockDriverState *bs)
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  *
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  * Returns: 0 on success, -errno on failure.
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  */
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-static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc,
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-                                Error **errp)
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+static int coroutine_fn
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+raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
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+                     PreallocMode prealloc, Error **errp)
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 {
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-    int result = 0;
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-    int64_t current_length = 0;
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-    char *buf = NULL;
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-    struct stat st;
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-
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-    if (fstat(fd, &st) < 0) {
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-        result = -errno;
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-        error_setg_errno(errp, -result, "Could not stat file");
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-        return result;
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-    }
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-
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-    current_length = st.st_size;
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-    if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
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-        error_setg(errp, "Cannot use preallocation for shrinking files");
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-        return -ENOTSUP;
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-    }
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-
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-    switch (prealloc) {
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-#ifdef CONFIG_POSIX_FALLOCATE
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-    case PREALLOC_MODE_FALLOC:
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-        /*
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-         * Truncating before posix_fallocate() makes it about twice slower on
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-         * file systems that do not support fallocate(), trying to check if a
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-         * block is allocated before allocating it, so don't do that here.
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-         */
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-        if (offset != current_length) {
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-            result = -posix_fallocate(fd, current_length, offset - current_length);
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-            if (result != 0) {
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-                /* posix_fallocate() doesn't set errno. */
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-                error_setg_errno(errp, -result,
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-                                 "Could not preallocate new data");
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-            }
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-        } else {
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-            result = 0;
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-        }
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-        goto out;
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-#endif
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-    case PREALLOC_MODE_FULL:
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-    {
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-        int64_t num = 0, left = offset - current_length;
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-        off_t seek_result;
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-
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-        /*
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-         * Knowing the final size from the beginning could allow the file
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-         * system driver to do less allocations and possibly avoid
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-         * fragmentation of the file.
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-         */
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-        if (ftruncate(fd, offset) != 0) {
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-            result = -errno;
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-            error_setg_errno(errp, -result, "Could not resize file");
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-            goto out;
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-        }
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-
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-        buf = g_malloc0(65536);
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-
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-        seek_result = lseek(fd, current_length, SEEK_SET);
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-        if (seek_result < 0) {
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-            result = -errno;
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-            error_setg_errno(errp, -result,
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-                             "Failed to seek to the old end of file");
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-            goto out;
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-        }
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-
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-        while (left > 0) {
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-            num = MIN(left, 65536);
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-            result = write(fd, buf, num);
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-            if (result < 0) {
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-                result = -errno;
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-                error_setg_errno(errp, -result,
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-                                 "Could not write zeros for preallocation");
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-                goto out;
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-            }
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-            left -= result;
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-        }
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-        if (result >= 0) {
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-            result = fsync(fd);
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-            if (result < 0) {
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-                result = -errno;
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-                error_setg_errno(errp, -result,
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-                                 "Could not flush file to disk");
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-                goto out;
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-            }
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-        }
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-        goto out;
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-    }
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-    case PREALLOC_MODE_OFF:
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-        if (ftruncate(fd, offset) != 0) {
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-            result = -errno;
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-            error_setg_errno(errp, -result, "Could not resize file");
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-        }
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-        return result;
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-    default:
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-        result = -ENOTSUP;
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-        error_setg(errp, "Unsupported preallocation mode: %s",
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-                   PreallocMode_str(prealloc));
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-        return result;
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-    }
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+    RawPosixAIOData *acb = g_new(RawPosixAIOData, 1);
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+    ThreadPool *pool;
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-out:
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-    if (result < 0) {
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-        if (ftruncate(fd, current_length) < 0) {
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-            error_report("Failed to restore old file length: %s",
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-                         strerror(errno));
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-        }
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-    }
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+    *acb = (RawPosixAIOData) {
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+        .bs             = bs,
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+        .aio_fildes     = fd,
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+        .aio_type       = QEMU_AIO_TRUNCATE,
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+        .aio_offset     = offset,
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+        .prealloc       = prealloc,
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+        .errp           = errp,
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+    };
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-    g_free(buf);
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-    return result;
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+    /* @bs can be NULL, bdrv_get_aio_context() returns the main context then */
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+    pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
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+    return thread_pool_submit_co(pool, aio_worker, acb);
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 }
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 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
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@@ -1846,7 +1881,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
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     }
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     if (S_ISREG(st.st_mode)) {
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-        return raw_regular_truncate(s->fd, offset, prealloc, errp);
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+        return raw_regular_truncate(bs, s->fd, offset, prealloc, errp);
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     }
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     if (prealloc != PREALLOC_MODE_OFF) {
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@@ -2048,7 +2083,8 @@ static int64_t raw_get_allocated_file_size(BlockDriverState *bs)
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     return (int64_t)st.st_blocks * 512;
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 }
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-static int raw_co_create(BlockdevCreateOptions *options, Error **errp)
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+static int coroutine_fn
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+raw_co_create(BlockdevCreateOptions *options, Error **errp)
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 {
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     BlockdevCreateOptionsFile *file_opts;
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     Error *local_err = NULL;
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@@ -2101,7 +2137,7 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp)
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     }
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     /* Clear the file by truncating it to 0 */
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-    result = raw_regular_truncate(fd, 0, PREALLOC_MODE_OFF, errp);
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+    result = raw_regular_truncate(NULL, fd, 0, PREALLOC_MODE_OFF, errp);
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     if (result < 0) {
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         goto out_unlock;
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     }
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@@ -2123,8 +2159,8 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp)
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     /* Resize and potentially preallocate the file to the desired
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      * final size */
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-    result = raw_regular_truncate(fd, file_opts->size, file_opts->preallocation,
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-                                  errp);
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+    result = raw_regular_truncate(NULL, fd, file_opts->size,
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+                                  file_opts->preallocation, errp);
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     if (result < 0) {
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         goto out_unlock;
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     }
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diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h
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index 3240530..2ffcd9d 100644
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--- a/include/block/raw-aio.h
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+++ b/include/block/raw-aio.h
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@@ -26,6 +26,7 @@
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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_COPY_RANGE   0x0040
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+#define QEMU_AIO_TRUNCATE     0x0080
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 #define QEMU_AIO_TYPE_MASK \
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         (QEMU_AIO_READ | \
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          QEMU_AIO_WRITE | \
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@@ -33,7 +34,8 @@
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          QEMU_AIO_FLUSH | \
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          QEMU_AIO_DISCARD | \
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          QEMU_AIO_WRITE_ZEROES | \
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-         QEMU_AIO_COPY_RANGE)
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+         QEMU_AIO_COPY_RANGE | \
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+         QEMU_AIO_TRUNCATE)
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 /* AIO flags */
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 #define QEMU_AIO_MISALIGNED   0x1000
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-- 
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1.8.3.1
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