[Qemu-devel] [PATCH] block: emulate .bdrv_flush() using .bdrv_aio_flush()

[Stefan Hajnoczi]

Block drivers typically have two copies of the flush operation: a
synchronous .bdrv_flush() and an asynchronous .bdrv_aio_flush().  This
patch applies the same emulation that we already do for
.bdrv_read()/.bdrv_write() to .bdrv_flush().  Now block drivers only
need to provide either .bdrv_aio_flush() or, in the case of legacy
drivers, .bdrv_flush().

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 block.c           |   31 +++++++++++++++++++++++++++----
 block/blkdebug.c  |    6 ------
 block/blkverify.c |    9 ---------
 block/qcow.c      |    6 ------
 block/qcow2.c     |   19 -------------------
 block/qed.c       |    6 ------
 block/raw-posix.c |   11 -----------
 7 files changed, 27 insertions(+), 61 deletions(-)

diff --git a/block.c b/block.c
index a8c789a..4992d98 100644
--- a/block.c
+++ b/block.c
@@ -59,6 +59,7 @@ static int bdrv_read_em(BlockDriverState *bs, int64_t 
sector_num,
                         uint8_t *buf, int nb_sectors);
 static int bdrv_write_em(BlockDriverState *bs, int64_t sector_num,
                          const uint8_t *buf, int nb_sectors);
+static int bdrv_flush_em(BlockDriverState *bs);
 static BlockDriverAIOCB *bdrv_co_aio_readv_em(BlockDriverState *bs,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockDriverCompletionFunc *cb, void *opaque);
@@ -205,8 +206,11 @@ void bdrv_register(BlockDriver *bdrv)
         }
     }
 
-    if (!bdrv->bdrv_aio_flush)
+    if (!bdrv->bdrv_aio_flush) {
         bdrv->bdrv_aio_flush = bdrv_aio_flush_em;
+    } else if (!bdrv->bdrv_flush) {
+        bdrv->bdrv_flush = bdrv_flush_em;
+    }
 
     QLIST_INSERT_HEAD(&bdrv_drivers, bdrv, list);
 }
@@ -2848,7 +2852,7 @@ static BlockDriverAIOCB 
*bdrv_aio_noop_em(BlockDriverState *bs,
 /**************************************************************/
 /* sync block device emulation */
 
-static void bdrv_rw_em_cb(void *opaque, int ret)
+static void bdrv_em_cb(void *opaque, int ret)
 {
     *(int *)opaque = ret;
 }
@@ -2868,7 +2872,7 @@ static int bdrv_read_em(BlockDriverState *bs, int64_t 
sector_num,
     iov.iov_len = nb_sectors * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&qiov, &iov, 1);
     acb = bdrv_aio_readv(bs, sector_num, &qiov, nb_sectors,
-        bdrv_rw_em_cb, &async_ret);
+        bdrv_em_cb, &async_ret);
     if (acb == NULL) {
         async_ret = -1;
         goto fail;
@@ -2896,7 +2900,26 @@ static int bdrv_write_em(BlockDriverState *bs, int64_t 
sector_num,
     iov.iov_len = nb_sectors * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&qiov, &iov, 1);
     acb = bdrv_aio_writev(bs, sector_num, &qiov, nb_sectors,
-        bdrv_rw_em_cb, &async_ret);
+        bdrv_em_cb, &async_ret);
+    if (acb == NULL) {
+        async_ret = -1;
+        goto fail;
+    }
+    while (async_ret == NOT_DONE) {
+        qemu_aio_wait();
+    }
+
+fail:
+    return async_ret;
+}
+
+static int bdrv_flush_em(BlockDriverState *bs)
+{
+    int async_ret;
+    BlockDriverAIOCB *acb;
+
+    async_ret = NOT_DONE;
+    acb = bdrv_aio_flush(bs, bdrv_em_cb, &async_ret);
     if (acb == NULL) {
         async_ret = -1;
         goto fail;
diff --git a/block/blkdebug.c b/block/blkdebug.c
index b3c5d42..9b88535 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -397,11 +397,6 @@ static void blkdebug_close(BlockDriverState *bs)
     }
 }
 
-static int blkdebug_flush(BlockDriverState *bs)
-{
-    return bdrv_flush(bs->file);
-}
-
 static BlockDriverAIOCB *blkdebug_aio_flush(BlockDriverState *bs,
     BlockDriverCompletionFunc *cb, void *opaque)
 {
@@ -454,7 +449,6 @@ static BlockDriver bdrv_blkdebug = {
 
     .bdrv_file_open     = blkdebug_open,
     .bdrv_close         = blkdebug_close,
-    .bdrv_flush         = blkdebug_flush,
 
     .bdrv_aio_readv     = blkdebug_aio_readv,
     .bdrv_aio_writev    = blkdebug_aio_writev,
diff --git a/block/blkverify.c b/block/blkverify.c
index c7522b4..483f3b3 100644
--- a/block/blkverify.c
+++ b/block/blkverify.c
@@ -116,14 +116,6 @@ static void blkverify_close(BlockDriverState *bs)
     s->test_file = NULL;
 }
 
-static int blkverify_flush(BlockDriverState *bs)
-{
-    BDRVBlkverifyState *s = bs->opaque;
-
-    /* Only flush test file, the raw file is not important */
-    return bdrv_flush(s->test_file);
-}
-
 static int64_t blkverify_getlength(BlockDriverState *bs)
 {
     BDRVBlkverifyState *s = bs->opaque;
@@ -368,7 +360,6 @@ static BlockDriver bdrv_blkverify = {
 
     .bdrv_file_open     = blkverify_open,
     .bdrv_close         = blkverify_close,
-    .bdrv_flush         = blkverify_flush,
 
     .bdrv_aio_readv     = blkverify_aio_readv,
     .bdrv_aio_writev    = blkverify_aio_writev,
diff --git a/block/qcow.c b/block/qcow.c
index c8bfecc..9b71116 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -781,11 +781,6 @@ static int qcow_write_compressed(BlockDriverState *bs, 
int64_t sector_num,
     return 0;
 }
 
-static int qcow_flush(BlockDriverState *bs)
-{
-    return bdrv_flush(bs->file);
-}
-
 static BlockDriverAIOCB *qcow_aio_flush(BlockDriverState *bs,
         BlockDriverCompletionFunc *cb, void *opaque)
 {
@@ -826,7 +821,6 @@ static BlockDriver bdrv_qcow = {
     .bdrv_open         = qcow_open,
     .bdrv_close                = qcow_close,
     .bdrv_create       = qcow_create,
-    .bdrv_flush                = qcow_flush,
     .bdrv_is_allocated = qcow_is_allocated,
     .bdrv_set_key      = qcow_set_key,
     .bdrv_make_empty   = qcow_make_empty,
diff --git a/block/qcow2.c b/block/qcow2.c
index 8aed310..2b4ea0d 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1092,24 +1092,6 @@ static int qcow2_write_compressed(BlockDriverState *bs, 
int64_t sector_num,
     return 0;
 }
 
-static int qcow2_flush(BlockDriverState *bs)
-{
-    BDRVQcowState *s = bs->opaque;
-    int ret;
-
-    ret = qcow2_cache_flush(bs, s->l2_table_cache);
-    if (ret < 0) {
-        return ret;
-    }
-
-    ret = qcow2_cache_flush(bs, s->refcount_block_cache);
-    if (ret < 0) {
-        return ret;
-    }
-
-    return bdrv_flush(bs->file);
-}
-
 static BlockDriverAIOCB *qcow2_aio_flush(BlockDriverState *bs,
                                          BlockDriverCompletionFunc *cb,
                                          void *opaque)
@@ -1242,7 +1224,6 @@ static BlockDriver bdrv_qcow2 = {
     .bdrv_open          = qcow2_open,
     .bdrv_close         = qcow2_close,
     .bdrv_create        = qcow2_create,
-    .bdrv_flush         = qcow2_flush,
     .bdrv_is_allocated  = qcow2_is_allocated,
     .bdrv_set_key       = qcow2_set_key,
     .bdrv_make_empty    = qcow2_make_empty,
diff --git a/block/qed.c b/block/qed.c
index 624e261..5cf4e08 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -533,11 +533,6 @@ static void bdrv_qed_close(BlockDriverState *bs)
     qemu_vfree(s->l1_table);
 }
 
-static int bdrv_qed_flush(BlockDriverState *bs)
-{
-    return bdrv_flush(bs->file);
-}
-
 static int qed_create(const char *filename, uint32_t cluster_size,
                       uint64_t image_size, uint32_t table_size,
                       const char *backing_file, const char *backing_fmt)
@@ -1479,7 +1474,6 @@ static BlockDriver bdrv_qed = {
     .bdrv_open                = bdrv_qed_open,
     .bdrv_close               = bdrv_qed_close,
     .bdrv_create              = bdrv_qed_create,
-    .bdrv_flush               = bdrv_qed_flush,
     .bdrv_is_allocated        = bdrv_qed_is_allocated,
     .bdrv_make_empty          = bdrv_qed_make_empty,
     .bdrv_aio_readv           = bdrv_qed_aio_readv,
diff --git a/block/raw-posix.c b/block/raw-posix.c
index bcf50b2..f5a011a 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -836,12 +836,6 @@ static int raw_create(const char *filename, 
QEMUOptionParameter *options)
     return result;
 }
 
-static int raw_flush(BlockDriverState *bs)
-{
-    BDRVRawState *s = bs->opaque;
-    return qemu_fdatasync(s->fd);
-}
-
 #ifdef CONFIG_XFS
 static int xfs_discard(BDRVRawState *s, int64_t sector_num, int nb_sectors)
 {
@@ -893,7 +887,6 @@ static BlockDriver bdrv_file = {
     .bdrv_write = raw_write,
     .bdrv_close = raw_close,
     .bdrv_create = raw_create,
-    .bdrv_flush = raw_flush,
     .bdrv_discard = raw_discard,
 
     .bdrv_aio_readv = raw_aio_readv,
@@ -1163,7 +1156,6 @@ static BlockDriver bdrv_host_device = {
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
     .bdrv_has_zero_init = hdev_has_zero_init,
-    .bdrv_flush         = raw_flush,
 
     .bdrv_aio_readv    = raw_aio_readv,
     .bdrv_aio_writev   = raw_aio_writev,
@@ -1284,7 +1276,6 @@ static BlockDriver bdrv_host_floppy = {
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
     .bdrv_has_zero_init = hdev_has_zero_init,
-    .bdrv_flush         = raw_flush,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
@@ -1385,7 +1376,6 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
     .bdrv_has_zero_init = hdev_has_zero_init,
-    .bdrv_flush         = raw_flush,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
@@ -1506,7 +1496,6 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
     .bdrv_has_zero_init = hdev_has_zero_init,
-    .bdrv_flush         = raw_flush,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
-- 
1.7.5.4