@@ -2135,6 +2135,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
uint64_t align = bs->bl.request_alignment;
BdrvRequestPadding pad;
int ret;
+ bool padded = false;
trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
@@ -2166,20 +2167,32 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
return 0;
}
+ if (!(flags & BDRV_REQ_ZERO_WRITE)) {
+ /*
+ * Pad request for following read-modify-write cycle.
+ * bdrv_co_do_zero_pwritev() does aligning by itself, so, we do
+ * alignment only if there is no ZERO flag.
+ */
+ padded = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes,
+ &pad);
+ }
+
bdrv_inc_in_flight(bs);
- /*
- * Align write if necessary by performing a read-modify-write cycle.
- * Pad qiov with the read parts and be sure to have a tracked request not
- * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle.
- */
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE);
if (flags & BDRV_REQ_ZERO_WRITE) {
+ assert(!padded);
ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req);
goto out;
}
- if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) {
+ if (padded) {
+ /*
+ * Request was unaligned to request_alignment and therefore
+ * padded. We are going to do read-modify-write, and must
+ * serialize the request to prevent interactions of the
+ * widened region with other transactions.
+ */
bdrv_make_request_serialising(&req, align);
bdrv_padding_rmw_read(child, &req, &pad, false);
}
new file mode 100644
@@ -0,0 +1,40 @@
+diff a/block/io.c b/block/io.c (rejected hunks)
+@@ -2138,20 +2139,32 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
+ return 0;
+ }
+
++ if (!(flags & BDRV_REQ_ZERO_WRITE)) {
++ /*
++ * Pad request for following read-modify-write cycle.
++ * bdrv_co_do_zero_pwritev() does aligning by itself, so, we do
++ * alignment only if there is no ZERO flag.
++ */
++ padded = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes,
++ &pad);
++ }
++
+ bdrv_inc_in_flight(bs);
+- /*
+- * Align write if necessary by performing a read-modify-write cycle.
+- * Pad qiov with the read parts and be sure to have a tracked request not
+- * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle.
+- */
+ tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE);
+
+ if (flags & BDRV_REQ_ZERO_WRITE) {
++ assert(!padded);
+ ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req);
+ goto out;
+ }
+
+- if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) {
++ if (padded) {
++ /*
++ * Request was unaligned to request_alignment and therefore padded.
++ * We are going to do read-modify-write. User is not prepared to widened
++ * request intersections with other requests, so we serialize the
++ * request.
++ */
+ bdrv_mark_request_serialising(&req, align);
+ bdrv_padding_rmw_read(child, &req, &pad, false);
+ }