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[Qemu-block] [PATCH v2 5/8] qcow2: qcow2_co_preadv: improve locking
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[Qemu-block] [PATCH v2 5/8] qcow2: qcow2_co_preadv: improve locking |
Date: |
Tue, 11 Dec 2018 19:43:14 +0300 |
Background: decryption will be done in threads, to take benefit of it,
we should move it out of the lock first.
But let's go further: it turns out, that for locking around switch
cases we have only two variants: when we just do memset(0) not
releasing the lock (it is useless) and when we actually can handle the
whole case out of the lock. So, refactor the whole thing to reduce
locked code region and make it clean.
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
block/qcow2.c | 48 ++++++++++++++++++++++++------------------------
1 file changed, 24 insertions(+), 24 deletions(-)
diff --git a/block/qcow2.c b/block/qcow2.c
index c4b716d4f6..2a49314e42 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1884,6 +1884,7 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState
*bs, uint64_t offset,
ret = qcow2_get_cluster_offset(bs, offset, &cur_bytes,
&cluster_offset);
if (ret < 0) {
+ qemu_co_mutex_unlock(&s->lock);
goto fail;
}
@@ -1892,39 +1893,38 @@ static coroutine_fn int
qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
qemu_iovec_reset(&hd_qiov);
qemu_iovec_concat(&hd_qiov, qiov, bytes_done, cur_bytes);
+ if (ret == QCOW2_CLUSTER_ZERO_PLAIN ||
+ ret == QCOW2_CLUSTER_ZERO_ALLOC ||
+ (ret == QCOW2_CLUSTER_UNALLOCATED && !bs->backing))
+ {
+ /* No sense in releasing the lock */
+
+ qemu_iovec_memset(&hd_qiov, 0, 0, cur_bytes);
+
+ bytes -= cur_bytes;
+ offset += cur_bytes;
+ bytes_done += cur_bytes;
+ continue;
+ }
+
+ qemu_co_mutex_unlock(&s->lock);
+
switch (ret) {
case QCOW2_CLUSTER_UNALLOCATED:
-
- if (bs->backing) {
- BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
- qemu_co_mutex_unlock(&s->lock);
- ret = bdrv_co_preadv(bs->backing, offset, cur_bytes,
- &hd_qiov, 0);
- qemu_co_mutex_lock(&s->lock);
- if (ret < 0) {
- goto fail;
- }
- } else {
- /* Note: in this case, no need to wait */
- qemu_iovec_memset(&hd_qiov, 0, 0, cur_bytes);
+ BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
+ ret = bdrv_co_preadv(bs->backing, offset, cur_bytes, &hd_qiov, 0);
+ if (ret < 0) {
+ goto fail;
}
break;
- case QCOW2_CLUSTER_ZERO_PLAIN:
- case QCOW2_CLUSTER_ZERO_ALLOC:
- qemu_iovec_memset(&hd_qiov, 0, 0, cur_bytes);
- break;
-
case QCOW2_CLUSTER_COMPRESSED:
- qemu_co_mutex_unlock(&s->lock);
ret = qcow2_co_preadv_compressed(bs, cluster_offset,
offset, cur_bytes,
&hd_qiov);
- qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
goto fail;
}
-
break;
case QCOW2_CLUSTER_NORMAL:
@@ -1957,11 +1957,9 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState
*bs, uint64_t offset,
}
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
- qemu_co_mutex_unlock(&s->lock);
ret = bdrv_co_preadv(bs->file,
cluster_offset + offset_in_cluster,
cur_bytes, &hd_qiov, 0);
- qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
goto fail;
}
@@ -1992,12 +1990,14 @@ static coroutine_fn int
qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
bytes -= cur_bytes;
offset += cur_bytes;
bytes_done += cur_bytes;
+
+ qemu_co_mutex_lock(&s->lock);
}
ret = 0;
-fail:
qemu_co_mutex_unlock(&s->lock);
+fail:
qemu_iovec_destroy(&hd_qiov);
qemu_vfree(cluster_data);
--
2.18.0
- [Qemu-block] [PATCH v2 0/8] qcow2: encryption threads, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 7/8] qcow2: bdrv_co_pwritev: move encryption code out of the lock, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 6/8] qcow2: qcow2_co_preadv: skip using hd_qiov when possible, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 4/8] qcow2-threads: split out generic path, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 3/8] qcow2-threads: use thread_pool_submit_co, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 8/8] qcow2: do encryption in threads, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 2/8] qcow2: add separate file for threaded data processing functions, Vladimir Sementsov-Ogievskiy, 2018/12/11
- [Qemu-block] [PATCH v2 5/8] qcow2: qcow2_co_preadv: improve locking,
Vladimir Sementsov-Ogievskiy <=
- [Qemu-block] [PATCH v2 1/8] qcow2.h: add missing include, Vladimir Sementsov-Ogievskiy, 2018/12/11
- Re: [Qemu-block] [PATCH v2 0/8] qcow2: encryption threads, Daniel P . Berrangé, 2018/12/11
- Re: [Qemu-block] [PATCH v2 0/8] qcow2: encryption threads, Vladimir Sementsov-Ogievskiy, 2018/12/17