kvm tools, qcow: Flush only dirty L2 tables
This patch improves qcow_l2_cache_write() to only flush dirty L2 tables.
Cc: Asias He <asias.hejun@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Prasad Joshi <prasadjoshi124@gmail.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/disk/qcow.c b/disk/qcow.c
index b71762f..13c8bea 100644
--- a/disk/qcow.c
+++ b/disk/qcow.c
@@ -93,9 +93,17 @@
struct qcow_header *header = q->header;
u64 size;
+ if (!c->dirty)
+ return 0;
+
size = 1 << header->l2_bits;
- return pwrite_in_full(q->fd, c->table, size * sizeof(u64), c->offset);
+ if (pwrite_in_full(q->fd, c->table, size * sizeof(u64), c->offset) < 0)
+ return -1;
+
+ c->dirty = 0;
+
+ return 0;
}
static int cache_table(struct qcow *q, struct qcow_l2_table *c)
@@ -447,6 +455,7 @@
if (!clust_start) {
clust_start = ALIGN(f_sz, clust_sz);
l2t->table[l2t_idx] = cpu_to_be64(clust_start);
+ l2t->dirty = 1;
}
mutex_unlock(&q->mutex);
