From 3bcd3a26a88ebeafa17dcf7e17d589f78e17500b Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Tue, 24 Jul 2018 09:23:26 +0200

Subject: [PATCH 39/89] file-posix: Make .bdrv_co_truncate asynchronous

RH-Author: Kevin Wolf <kwolf@redhat.com>

Message-id: <20180712144258.17303-7-kwolf@redhat.com>

Patchwork-id: 81324

O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 6/6] file-posix: Make .bdrv_co_truncate asynchronous

Bugzilla: 1595173

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: John Snow <jsnow@redhat.com>

This moves the code to resize an image file to the thread pool to avoid

blocking.

Creating large images with preallocation with blockdev-create is now

actually a background job instead of blocking the monitor (and most

other things) until the preallocation has completed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

(cherry picked from commit 93f4e2ff4b31205d8bab0856631a52ed442b8b1c)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

---

 block/file-posix.c      | 266 +++++++++++++++++++++++++++---------------------

 include/block/raw-aio.h |   4 +-

 2 files changed, 154 insertions(+), 116 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c

index f8488ec..24c2367 100644

--- a/block/file-posix.c

+++ b/block/file-posix.c

@@ -186,8 +186,16 @@ typedef struct RawPosixAIOData {

 #define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */

     off_t aio_offset;

     int aio_type;

-    int aio_fd2;

-    off_t aio_offset2;

+    union {

+        struct {

+            int aio_fd2;

+            off_t aio_offset2;

+        };

+        struct {

+            PreallocMode prealloc;

+            Error **errp;

+        };

+    };

 } RawPosixAIOData;

 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)

@@ -1509,6 +1517,122 @@ static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)

     return ret;

 }

+static int handle_aiocb_truncate(RawPosixAIOData *aiocb)

+{

+    int result = 0;

+    int64_t current_length = 0;

+    char *buf = NULL;

+    struct stat st;

+    int fd = aiocb->aio_fildes;

+    int64_t offset = aiocb->aio_offset;

+    Error **errp = aiocb->errp;

+

+    if (fstat(fd, &st) < 0) {

+        result = -errno;

+        error_setg_errno(errp, -result, "Could not stat file");

+        return result;

+    }

+

+    current_length = st.st_size;

+    if (current_length > offset && aiocb->prealloc != PREALLOC_MODE_OFF) {

+        error_setg(errp, "Cannot use preallocation for shrinking files");

+        return -ENOTSUP;

+    }

+

+    switch (aiocb->prealloc) {

+#ifdef CONFIG_POSIX_FALLOCATE

+    case PREALLOC_MODE_FALLOC:

+        /*

+         * Truncating before posix_fallocate() makes it about twice slower on

+         * file systems that do not support fallocate(), trying to check if a

+         * block is allocated before allocating it, so don't do that here.

+         */

+        if (offset != current_length) {

+            result = -posix_fallocate(fd, current_length,

+                                      offset - current_length);

+            if (result != 0) {

+                /* posix_fallocate() doesn't set errno. */

+                error_setg_errno(errp, -result,

+                                 "Could not preallocate new data");

+            }

+        } else {

+            result = 0;

+        }

+        goto out;

+#endif

+    case PREALLOC_MODE_FULL:

+    {

+        int64_t num = 0, left = offset - current_length;

+        off_t seek_result;

+

+        /*

+         * Knowing the final size from the beginning could allow the file

+         * system driver to do less allocations and possibly avoid

+         * fragmentation of the file.

+         */

+        if (ftruncate(fd, offset) != 0) {

+            result = -errno;

+            error_setg_errno(errp, -result, "Could not resize file");

+            goto out;

+        }

+

+        buf = g_malloc0(65536);

+

+        seek_result = lseek(fd, current_length, SEEK_SET);

+        if (seek_result < 0) {

+            result = -errno;

+            error_setg_errno(errp, -result,

+                             "Failed to seek to the old end of file");

+            goto out;

+        }

+

+        while (left > 0) {

+            num = MIN(left, 65536);

+            result = write(fd, buf, num);

+            if (result < 0) {

+                result = -errno;

+                error_setg_errno(errp, -result,

+                                 "Could not write zeros for preallocation");

+                goto out;

+            }

+            left -= result;

+        }

+        if (result >= 0) {

+            result = fsync(fd);

+            if (result < 0) {

+                result = -errno;

+                error_setg_errno(errp, -result,

+                                 "Could not flush file to disk");

+                goto out;

+            }

+        }

+        goto out;

+    }

+    case PREALLOC_MODE_OFF:

+        if (ftruncate(fd, offset) != 0) {

+            result = -errno;

+            error_setg_errno(errp, -result, "Could not resize file");

+        }

+        return result;

+    default:

+        result = -ENOTSUP;

+        error_setg(errp, "Unsupported preallocation mode: %s",

+                   PreallocMode_str(aiocb->prealloc));

+        return result;

+    }

+

+out:

+    if (result < 0) {

+        if (ftruncate(fd, current_length) < 0) {

+            error_report("Failed to restore old file length: %s",

+                         strerror(errno));

+        }

+    }

+

+    g_free(buf);

+    return result;

+}

+

 static int aio_worker(void *arg)

 {

     RawPosixAIOData *aiocb = arg;

@@ -1552,6 +1676,9 @@ static int aio_worker(void *arg)

     case QEMU_AIO_COPY_RANGE:

         ret = handle_aiocb_copy_range(aiocb);

         break;

+    case QEMU_AIO_TRUNCATE:

+        ret = handle_aiocb_truncate(aiocb);

+        break;

     default:

         fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);

         ret = -EINVAL;

@@ -1719,117 +1846,25 @@ static void raw_close(BlockDriverState *bs)

  *

  * Returns: 0 on success, -errno on failure.

  */

-static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc,

-                                Error **errp)

+static int coroutine_fn

+raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,

+                     PreallocMode prealloc, Error **errp)

 {

-    int result = 0;

-    int64_t current_length = 0;

-    char *buf = NULL;

-    struct stat st;

-

-    if (fstat(fd, &st) < 0) {

-        result = -errno;

-        error_setg_errno(errp, -result, "Could not stat file");

-        return result;

-    }

-

-    current_length = st.st_size;

-    if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {

-        error_setg(errp, "Cannot use preallocation for shrinking files");

-        return -ENOTSUP;

-    }

-

-    switch (prealloc) {

-#ifdef CONFIG_POSIX_FALLOCATE

-    case PREALLOC_MODE_FALLOC:

-        /*

-         * Truncating before posix_fallocate() makes it about twice slower on

-         * file systems that do not support fallocate(), trying to check if a

-         * block is allocated before allocating it, so don't do that here.

-         */

-        if (offset != current_length) {

-            result = -posix_fallocate(fd, current_length, offset - current_length);

-            if (result != 0) {

-                /* posix_fallocate() doesn't set errno. */

-                error_setg_errno(errp, -result,

-                                 "Could not preallocate new data");

-            }

-        } else {

-            result = 0;

-        }

-        goto out;

-#endif

-    case PREALLOC_MODE_FULL:

-    {

-        int64_t num = 0, left = offset - current_length;

-        off_t seek_result;

-

-        /*

-         * Knowing the final size from the beginning could allow the file

-         * system driver to do less allocations and possibly avoid

-         * fragmentation of the file.

-         */

-        if (ftruncate(fd, offset) != 0) {

-            result = -errno;

-            error_setg_errno(errp, -result, "Could not resize file");

-            goto out;

-        }

-

-        buf = g_malloc0(65536);

-

-        seek_result = lseek(fd, current_length, SEEK_SET);

-        if (seek_result < 0) {

-            result = -errno;

-            error_setg_errno(errp, -result,

-                             "Failed to seek to the old end of file");

-            goto out;

-        }

-

-        while (left > 0) {

-            num = MIN(left, 65536);

-            result = write(fd, buf, num);

-            if (result < 0) {

-                result = -errno;

-                error_setg_errno(errp, -result,

-                                 "Could not write zeros for preallocation");

-                goto out;

-            }

-            left -= result;

-        }

-        if (result >= 0) {

-            result = fsync(fd);

-            if (result < 0) {

-                result = -errno;

-                error_setg_errno(errp, -result,

-                                 "Could not flush file to disk");

-                goto out;

-            }

-        }

-        goto out;

-    }

-    case PREALLOC_MODE_OFF:

-        if (ftruncate(fd, offset) != 0) {

-            result = -errno;

-            error_setg_errno(errp, -result, "Could not resize file");

-        }

-        return result;

-    default:

-        result = -ENOTSUP;

-        error_setg(errp, "Unsupported preallocation mode: %s",

-                   PreallocMode_str(prealloc));

-        return result;

-    }

+    RawPosixAIOData *acb = g_new(RawPosixAIOData, 1);

+    ThreadPool *pool;

-out:

-    if (result < 0) {

-        if (ftruncate(fd, current_length) < 0) {

-            error_report("Failed to restore old file length: %s",

-                         strerror(errno));

-        }

-    }

+    *acb = (RawPosixAIOData) {

+        .bs             = bs,

+        .aio_fildes     = fd,

+        .aio_type       = QEMU_AIO_TRUNCATE,

+        .aio_offset     = offset,

+        .prealloc       = prealloc,

+        .errp           = errp,

+    };

-    g_free(buf);

-    return result;

+    /* @bs can be NULL, bdrv_get_aio_context() returns the main context then */

+    pool = aio_get_thread_pool(bdrv_get_aio_context(bs));

+    return thread_pool_submit_co(pool, aio_worker, acb);

 }

 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,

@@ -1846,7 +1881,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,

     }

     if (S_ISREG(st.st_mode)) {

-        return raw_regular_truncate(s->fd, offset, prealloc, errp);

+        return raw_regular_truncate(bs, s->fd, offset, prealloc, errp);

     }

     if (prealloc != PREALLOC_MODE_OFF) {

@@ -2048,7 +2083,8 @@ static int64_t raw_get_allocated_file_size(BlockDriverState *bs)

     return (int64_t)st.st_blocks * 512;

 }

-static int raw_co_create(BlockdevCreateOptions *options, Error **errp)

+static int coroutine_fn

+raw_co_create(BlockdevCreateOptions *options, Error **errp)

 {

     BlockdevCreateOptionsFile *file_opts;

     Error *local_err = NULL;

@@ -2101,7 +2137,7 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp)

     }

     /* Clear the file by truncating it to 0 */

-    result = raw_regular_truncate(fd, 0, PREALLOC_MODE_OFF, errp);

+    result = raw_regular_truncate(NULL, fd, 0, PREALLOC_MODE_OFF, errp);

     if (result < 0) {

         goto out_unlock;

     }

@@ -2123,8 +2159,8 @@ static int raw_co_create(BlockdevCreateOptions *options, Error **errp)

     /* Resize and potentially preallocate the file to the desired

      * final size */

-    result = raw_regular_truncate(fd, file_opts->size, file_opts->preallocation,

-                                  errp);

+    result = raw_regular_truncate(NULL, fd, file_opts->size,

+                                  file_opts->preallocation, errp);

     if (result < 0) {

         goto out_unlock;

     }

diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h

index 3240530..2ffcd9d 100644

--- a/include/block/raw-aio.h

+++ b/include/block/raw-aio.h

@@ -26,6 +26,7 @@

 #define QEMU_AIO_DISCARD      0x0010

 #define QEMU_AIO_WRITE_ZEROES 0x0020

 #define QEMU_AIO_COPY_RANGE   0x0040

+#define QEMU_AIO_TRUNCATE     0x0080

 #define QEMU_AIO_TYPE_MASK \

         (QEMU_AIO_READ | \

          QEMU_AIO_WRITE | \

@@ -33,7 +34,8 @@

          QEMU_AIO_FLUSH | \

          QEMU_AIO_DISCARD | \

          QEMU_AIO_WRITE_ZEROES | \

-         QEMU_AIO_COPY_RANGE)

+         QEMU_AIO_COPY_RANGE | \

+         QEMU_AIO_TRUNCATE)

 /* AIO flags */

 #define QEMU_AIO_MISALIGNED   0x1000

-- 

1.8.3.1