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authorVladimir Sementsov-Ogievskiy <vsementsov@openvz.org>2022-04-07 16:27:25 +0300
committerVladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>2022-06-29 10:56:12 +0300
commit6db7fd1ca980f8dd2fd082f13613166e170afd05 (patch)
tree0ba7ed482f029250b27470ac63e5c52b35bda546 /block/copy-before-write.c
parent15df6e698719505570f8532772c2b08cb278a45a (diff)
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block/copy-before-write: implement cbw-timeout option
In some scenarios, when copy-before-write operations lasts too long time, it's better to cancel it. Most useful would be to use the new option together with on-cbw-error=break-snapshot: this way if cbw operation takes too long time we'll just cancel backup process but do not disturb the guest too much. Note the tricky point of realization: we keep additional point in bs->in_flight during block_copy operation even if it's timed-out. Background "cancelled" block_copy operations will finish at some point and will want to access state. We should care to not free the state in .bdrv_close() earlier. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org> Reviewed-by: Hanna Reitz <hreitz@redhat.com> [vsementsov: use bdrv_inc_in_flight()/bdrv_dec_in_flight() instead of direct manipulation on bs->in_flight] Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Diffstat (limited to 'block/copy-before-write.c')
-rw-r--r--block/copy-before-write.c22
1 files changed, 21 insertions, 1 deletions
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index fc13c7c..c24b8dd 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -42,6 +42,7 @@ typedef struct BDRVCopyBeforeWriteState {
BlockCopyState *bcs;
BdrvChild *target;
OnCbwError on_cbw_error;
+ uint32_t cbw_timeout_ns;
/*
* @lock: protects access to @access_bitmap, @done_bitmap and
@@ -83,6 +84,13 @@ static coroutine_fn int cbw_co_preadv(
return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
}
+static void block_copy_cb(void *opaque)
+{
+ BlockDriverState *bs = opaque;
+
+ bdrv_dec_in_flight(bs);
+}
+
/*
* Do copy-before-write operation.
*
@@ -111,7 +119,16 @@ static coroutine_fn int cbw_do_copy_before_write(BlockDriverState *bs,
off = QEMU_ALIGN_DOWN(offset, cluster_size);
end = QEMU_ALIGN_UP(offset + bytes, cluster_size);
- ret = block_copy(s->bcs, off, end - off, true, 0, NULL, NULL);
+ /*
+ * Increase in_flight, so that in case of timed-out block-copy, the
+ * remaining background block_copy() request (which can't be immediately
+ * cancelled by timeout) is presented in bs->in_flight. This way we are
+ * sure that on bs close() we'll previously wait for all timed-out but yet
+ * running block_copy calls.
+ */
+ bdrv_inc_in_flight(bs);
+ ret = block_copy(s->bcs, off, end - off, true, s->cbw_timeout_ns,
+ block_copy_cb, bs);
if (ret < 0 && s->on_cbw_error == ON_CBW_ERROR_BREAK_GUEST_WRITE) {
return ret;
}
@@ -377,6 +394,7 @@ static BlockdevOptions *cbw_parse_options(QDict *options, Error **errp)
*/
qdict_extract_subqdict(options, NULL, "bitmap");
qdict_del(options, "on-cbw-error");
+ qdict_del(options, "cbw-timeout");
out:
visit_free(v);
@@ -423,6 +441,8 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
}
s->on_cbw_error = opts->has_on_cbw_error ? opts->on_cbw_error :
ON_CBW_ERROR_BREAK_GUEST_WRITE;
+ s->cbw_timeout_ns = opts->has_cbw_timeout ?
+ opts->cbw_timeout * NANOSECONDS_PER_SECOND : 0;
bs->total_sectors = bs->file->bs->total_sectors;
bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |