Non-active block commits do not discard blocks only containing zeros,
causing images to lose sparseness after the commit. This commit fixes
that by writing zero blocks using blk_co_pwrite_zeroes rather than
writing them out as any oother arbitrary data.
Signed-off-by: Vincent Vanlaer <libvirt-e6954...@volkihar.be>
---
block/commit.c | 71 +++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 58 insertions(+), 13 deletions(-)
diff --git a/block/commit.c b/block/commit.c
index 7c3fdcb0ca..5bd97b5a74 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -12,9 +12,13 @@
*
*/
+#include "bits/time.h"
#include "qemu/osdep.h"
#include "qemu/cutils.h"
+#include "time.h"
#include "trace.h"
+#include "block/block-common.h"
+#include "block/coroutines.h"
#include "block/block_int.h"
#include "block/blockjob_int.h"
#include "qapi/error.h"
@@ -126,6 +130,12 @@ static void commit_clean(Job *job)
blk_unref(s->top);
}
+typedef enum CommitMethod {
+ COMMIT_METHOD_COPY,
+ COMMIT_METHOD_ZERO,
+ COMMIT_METHOD_IGNORE,
+} CommitMethod;
+
static int coroutine_fn commit_run(Job *job, Error **errp)
{
CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
@@ -156,8 +166,9 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
for (offset = 0; offset < len; offset += n) {
- bool copy;
bool error_in_source = true;
+ CommitMethod commit_method = COMMIT_METHOD_COPY;
+
/* Note that even when no rate limit is applied we need to yield
* with no pending I/O here so that bdrv_drain_all() returns.
@@ -167,21 +178,54 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
break;
}
/* Copy if allocated above the base */
- ret = blk_co_is_allocated_above(s->top, s->base_overlay, true,
- offset, COMMIT_BUFFER_SIZE, &n);
- copy = (ret > 0);
+ WITH_GRAPH_RDLOCK_GUARD() {
+ ret = bdrv_co_common_block_status_above(blk_bs(s->top),
+ s->base_overlay, true, true, offset, COMMIT_BUFFER_SIZE,
+ &n, NULL, NULL, NULL);
+ }
+
trace_commit_one_iteration(s, offset, n, ret);
- if (copy) {
- assert(n < SIZE_MAX);
-
- ret = blk_co_pread(s->top, offset, n, buf, 0);
- if (ret >= 0) {
- ret = blk_co_pwrite(s->base, offset, n, buf, 0);
- if (ret < 0) {
- error_in_source = false;
+
+ if (ret >= 0 && !(ret & BDRV_BLOCK_ALLOCATED)) {
+ commit_method = COMMIT_METHOD_IGNORE;
+ } else if (ret >= 0 && ret & BDRV_BLOCK_ZERO) {
+ int64_t target_offset;
+ int64_t target_bytes;
+ WITH_GRAPH_RDLOCK_GUARD() {
+ bdrv_round_to_subclusters(s->base_bs, offset, n,
+ &target_offset, &target_bytes);
+ }
+
+ if (target_offset == offset &&
+ target_bytes == n) {
+ commit_method = COMMIT_METHOD_ZERO;
+ }
+ }
+
+ if (ret >= 0) {
+ switch (commit_method) {
+ case COMMIT_METHOD_COPY:
+ assert(n < SIZE_MAX);
+ ret = blk_co_pread(s->top, offset, n, buf, 0);
+ if (ret >= 0) {
+ ret = blk_co_pwrite(s->base, offset, n, buf, 0);
+ if (ret < 0) {
+ error_in_source = false;
+ }
}
+ break;
+ case COMMIT_METHOD_ZERO:
+ ret = blk_co_pwrite_zeroes(s->base, offset, n,
+ BDRV_REQ_MAY_UNMAP);
+ error_in_source = false;
+ break;
+ case COMMIT_METHOD_IGNORE:
+ break;
+ default:
+ abort();
}
}
+
if (ret < 0) {
BlockErrorAction action =
block_job_error_action(&s->common, s->on_error,
@@ -193,10 +237,11 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
continue;
}
}
+
/* Publish progress */
job_progress_update(&s->common.job, n);
- if (copy) {
+ if (commit_method == COMMIT_METHOD_COPY) {
block_job_ratelimit_processed_bytes(&s->common, n);
}
}
--
2.42.0
