[Qemu-devel] [PATCH 02/11] 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_pwritev_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                | 78 +++++++++++++++++++++++++++++++++++++++++++----
 include/block/block_int.h |  5 +++
 qemu-img.c                |  2 +-
 3 files changed, 78 insertions(+), 7 deletions(-)

diff --git a/block/io.c b/block/io.c
index c5bb6ae..54cd9a4 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1779,8 +1779,8 @@ int bdrv_is_allocated_above(BlockDriverState *top,
     return 0;
 }
 
-int bdrv_pwrite_compressed(BlockDriverState *bs, int64_t offset,
-                           const void *buf, int count)
+int coroutine_fn bdrv_co_pwritev_compressed(BlockDriverState *bs,
+    int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
 {
     BlockDriver *drv = bs->drv;
     int ret;
@@ -1788,18 +1788,84 @@ int bdrv_pwrite_compressed(BlockDriverState *bs, int64_t offset,
     if (!drv) {
         return -ENOMEDIUM;
     }
-    if (!drv->bdrv_write_compressed) {
+
+    if (!drv->bdrv_co_write_compressed) {
         return -ENOTSUP;
     }
-    ret = bdrv_check_byte_request(bs, offset, count);
+
+    ret = bdrv_check_byte_request(bs, offset, bytes);
     if (ret < 0) {
         return ret;
     }
 
     assert(QLIST_EMPTY(&bs->dirty_bitmaps));
+    assert(qemu_in_coroutine());
+
+    return drv->bdrv_co_write_compressed(bs, offset >> BDRV_SECTOR_BITS,
+                                         bytes >> BDRV_SECTOR_BITS, qiov);
+}
+
+typedef struct BdrvWriteCompressedCo {
+    BlockDriverState *bs;
+    int64_t offset;
+    QEMUIOVector *qiov;
+    int ret;
+} BdrvWriteCompressedCo;
+
+static void bdrv_write_compressed_co_entry(void *opaque)
+{
+    BdrvWriteCompressedCo *co = opaque;
+
+    co->ret = bdrv_co_pwritev_compressed(co->bs, co->offset, co->qiov->size,
+                                         co->qiov);
+}
+
+int bdrv_pwrite_compressed(BlockDriverState *bs, int64_t offset,
+                           const void *buf, int count)
+{
+    BdrvWriteCompressedCo data;
+    QEMUIOVector qiov;
+    BlockDriver *drv = bs->drv;
+    struct iovec iov = {
+        .iov_base = (void *)buf,
+        .iov_len = count,
+    };
+    qemu_iovec_init_external(&qiov, &iov, 1);
 
-    return drv->bdrv_write_compressed(bs, offset >> BDRV_SECTOR_BITS, buf,
-                                      count >> BDRV_SECTOR_BITS);
+    data = (BdrvWriteCompressedCo) {
+        .bs     = bs,
+        .offset = offset,
+        .qiov   = &qiov,
+        .ret    = -EINPROGRESS,
+    };
+
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+
+    if (drv->bdrv_write_compressed) {
+        int ret = bdrv_check_byte_request(bs, offset, count);
+        if (ret < 0) {
+            return ret;
+        }
+        assert(QLIST_EMPTY(&bs->dirty_bitmaps));
+        return drv->bdrv_write_compressed(bs, offset >> BDRV_SECTOR_BITS, buf,
+                                          count >> BDRV_SECTOR_BITS);
+    }
+
+    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_int.h b/include/block/block_int.h
index 30a9717..ccba9c9 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -207,6 +207,9 @@ struct BlockDriver {
     int (*bdrv_write_compressed)(BlockDriverState *bs, int64_t sector_num,
                                  const uint8_t *buf, int nb_sectors);
 
+    int coroutine_fn (*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,
@@ -535,6 +538,8 @@ int coroutine_fn bdrv_co_preadv(BlockDriverState *bs,
 int coroutine_fn bdrv_co_pwritev(BlockDriverState *bs,
     int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
     BdrvRequestFlags flags);
+int coroutine_fn bdrv_co_pwritev_compressed(BlockDriverState *bs,
+    int64_t offset, unsigned int bytes, QEMUIOVector *qiov);
 
 int get_tmp_filename(char *filename, int size);
 BlockDriver *bdrv_probe_all(const uint8_t *buf, int buf_size,
diff --git a/qemu-img.c b/qemu-img.c
index eb744d4..ab54027 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2024,7 +2024,7 @@ 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