[Qemu-devel] [PATCH v2 1/4] qcow2: multiple clusters write compressed

[Anton Nefedov <anton.nefedov@virtuozzo.com>]

From: Pavel Butsykin <pbutsykin@virtuozzo.com>

At the moment, qcow2_co_pwritev_compressed can process the requests size
less than or equal to one cluster. This patch added possibility to write
compressed data in the QCOW2 more than one cluster. The implementation
is simple, we just split large requests into separate clusters and write
using existing functionality.

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
---
 block/qcow2.c | 73 ++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 52 insertions(+), 21 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index c276b24..f1e2759 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3332,11 +3332,9 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
     return 0;
 }
 
-/* XXX: put compressed sectors first, then all the cluster aligned
-   tables to avoid losing bytes in alignment */
 static coroutine_fn int
-qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
-                            uint64_t bytes, QEMUIOVector *qiov)
+qcow2_co_pwritev_cluster_compressed(BlockDriverState *bs, uint64_t offset,
+                                    uint64_t bytes, QEMUIOVector *qiov)
 {
     BDRVQcow2State *s = bs->opaque;
     QEMUIOVector hd_qiov;
@@ -3346,25 +3344,12 @@ qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
     uint8_t *buf, *out_buf;
     int64_t cluster_offset;
 
-    if (bytes == 0) {
-        /* align end of file to a sector boundary to ease reading with
-           sector based I/Os */
-        cluster_offset = bdrv_getlength(bs->file->bs);
-        if (cluster_offset < 0) {
-            return cluster_offset;
-        }
-        return bdrv_truncate(bs->file, cluster_offset, PREALLOC_MODE_OFF, NULL);
-    }
-
-    if (offset_into_cluster(s, offset)) {
-        return -EINVAL;
-    }
+    assert(bytes <= s->cluster_size);
+    assert(!offset_into_cluster(s, offset));
 
     buf = qemu_blockalign(bs, s->cluster_size);
-    if (bytes != s->cluster_size) {
-        if (bytes > s->cluster_size ||
-            offset + bytes != bs->total_sectors << BDRV_SECTOR_BITS)
-        {
+    if (bytes < s->cluster_size) {
+        if (offset + bytes != bs->total_sectors << BDRV_SECTOR_BITS) {
             qemu_vfree(buf);
             return -EINVAL;
         }
@@ -3444,6 +3429,52 @@ fail:
     return ret;
 }
 
+/* XXX: put compressed sectors first, then all the cluster aligned
+   tables to avoid losing bytes in alignment */
+static coroutine_fn int
+qcow2_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
+                            uint64_t bytes, QEMUIOVector *qiov)
+{
+    BDRVQcow2State *s = bs->opaque;
+    QEMUIOVector hd_qiov;
+    uint64_t curr_off = 0;
+    int ret;
+
+    if (bytes == 0) {
+        /* align end of file to a sector boundary to ease reading with
+           sector based I/Os */
+        int64_t cluster_offset = bdrv_getlength(bs->file->bs);
+        if (cluster_offset < 0) {
+            return cluster_offset;
+        }
+        return bdrv_truncate(bs->file, cluster_offset, PREALLOC_MODE_OFF, NULL);
+    }
+
+    if (offset_into_cluster(s, offset)) {
+        return -EINVAL;
+    }
+
+    qemu_iovec_init(&hd_qiov, qiov->niov);
+    do {
+        uint32_t chunk_size;
+
+        qemu_iovec_reset(&hd_qiov);
+        chunk_size = MIN(bytes, s->cluster_size);
+        qemu_iovec_concat(&hd_qiov, qiov, curr_off, chunk_size);
+
+        ret = qcow2_co_pwritev_cluster_compressed(bs, offset + curr_off,
+                                                  chunk_size, &hd_qiov);
+        if (ret < 0) {
+            break;
+        }
+        curr_off += chunk_size;
+        bytes -= chunk_size;
+    } while (bytes);
+    qemu_iovec_destroy(&hd_qiov);
+
+    return ret;
+}
+
 static int make_completely_empty(BlockDriverState *bs)
 {
     BDRVQcow2State *s = bs->opaque;
-- 
2.7.4