[Qemu-devel] [PATCH 01/10] block/io: add bdrv_co_write_compressed

["Denis V. Lunev" <den@openvz.org>]

From: Pavel Butsykin <pbutsykin@virtuozzo.com>

This patch just adds the interface to the bdrv_co_write_compressed, which
is currently not used but will be useful for safe implementation of the
bdrv_co_write_compressed callback in format drivers.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Jeff Cody <jcody@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: John Snow <jsnow@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c                | 71 ++++++++++++++++++++++++++++++++++++++++++++---
 include/block/block.h     |  2 ++
 include/block/block_int.h |  3 ++
 qemu-img.c                |  2 +-
 4 files changed, 73 insertions(+), 5 deletions(-)

diff --git a/block/io.c b/block/io.c
index cd6d71a..88af10c 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1828,8 +1828,8 @@ int bdrv_is_allocated_above(BlockDriverState *top,
     return 0;
 }
 
-int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
-                          const uint8_t *buf, int nb_sectors)
+int bdrv_co_write_compressed(BlockDriverState *bs, int64_t sector_num,
+                             int nb_sectors, QEMUIOVector *qiov)
 {
     BlockDriver *drv = bs->drv;
     int ret;
@@ -1837,7 +1837,7 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
     if (!drv) {
         return -ENOMEDIUM;
     }
-    if (!drv->bdrv_write_compressed) {
+    if (!drv->bdrv_co_write_compressed) {
         return -ENOTSUP;
     }
     ret = bdrv_check_request(bs, sector_num, nb_sectors);
@@ -1846,8 +1846,71 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
     }
 
     assert(QLIST_EMPTY(&bs->dirty_bitmaps));
+    assert(qemu_in_coroutine());
+
+    return drv->bdrv_co_write_compressed(bs, sector_num, nb_sectors, qiov);
+}
+
+typedef struct BdrvWriteCompressedCo {
+    BlockDriverState *bs;
+    int64_t sector_num;
+    const uint8_t *buf;
+    int nb_sectors;
+    int ret;
+} BdrvWriteCompressedCo;
+
+static void bdrv_write_compressed_co_entry(void *opaque)
+{
+    BdrvWriteCompressedCo *co = opaque;
+    QEMUIOVector qiov;
+    struct iovec iov = {
+        .iov_base   = (uint8_t *)co->buf,
+        .iov_len    = co->nb_sectors << BDRV_SECTOR_BITS,
+    };
+    qemu_iovec_init_external(&qiov, &iov, 1);
+
+    co->ret = bdrv_co_write_compressed(co->bs, co->sector_num,
+                                       co->nb_sectors, &qiov);
+}
+
+int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
+                          const uint8_t *buf, int nb_sectors)
+{
+    BlockDriver *drv = bs->drv;
+    BdrvWriteCompressedCo data = {
+        .bs         = bs,
+        .sector_num = sector_num,
+        .buf        = buf,
+        .nb_sectors = nb_sectors,
+        .ret        = -EINPROGRESS,
+    };
+
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
+    if (drv->bdrv_write_compressed) {
+        int ret = bdrv_check_request(bs, sector_num, nb_sectors);
+        if (ret < 0) {
+            return ret;
+        }
+        assert(QLIST_EMPTY(&bs->dirty_bitmaps));
+        return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors);
+    }
 
-    return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors);
+    if (qemu_in_coroutine()) {
+        /* Fast-path if already in coroutine context */
+        bdrv_write_compressed_co_entry(&data);
+    } else {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        Coroutine *co = qemu_coroutine_create(bdrv_write_compressed_co_entry);
+        qemu_coroutine_enter(co, &data);
+        while (data.ret == -EINPROGRESS) {
+            aio_poll(aio_context, true);
+        }
+    }
+    return data.ret;
 }
 
 int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
diff --git a/include/block/block.h b/include/block/block.h
index b210832..ae67fd8 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -423,6 +423,8 @@ const char *bdrv_get_device_or_node_name(const BlockDriverState *bs);
 int bdrv_get_flags(BlockDriverState *bs);
 int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
                           const uint8_t *buf, int nb_sectors);
+int bdrv_co_write_compressed(BlockDriverState *bs, int64_t sector_num,
+                             int nb_sectors, QEMUIOVector *qiov);
 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
 ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs);
 void bdrv_round_to_clusters(BlockDriverState *bs,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index a029c20..3c93ddb 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -208,6 +208,9 @@ struct BlockDriver {
     int (*bdrv_write_compressed)(BlockDriverState *bs, int64_t sector_num,
                                  const uint8_t *buf, int nb_sectors);
 
+    int (*bdrv_co_write_compressed)(BlockDriverState *bs, int64_t sector_num,
+                                    int nb_sectors, QEMUIOVector *qiov);
+
     int (*bdrv_snapshot_create)(BlockDriverState *bs,
                                 QEMUSnapshotInfo *sn_info);
     int (*bdrv_snapshot_goto)(BlockDriverState *bs,
diff --git a/qemu-img.c b/qemu-img.c
index 4792366..0d38eac 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2022,7 +2022,7 @@ static int img_convert(int argc, char **argv)
         const char *preallocation =
             qemu_opt_get(opts, BLOCK_OPT_PREALLOC);
 
-        if (!drv->bdrv_write_compressed) {
+        if (!drv->bdrv_write_compressed && !drv->bdrv_co_write_compressed) {
             error_report("Compression not supported for this file format");
             ret = -1;
             goto out;
-- 
2.1.4