[PATCH 4/9] kvm tools, qcow: Introduce qcow_disk_flush()

Pekka Enberg
2011-07-09T13:03:01Z

This patch introduces a QCOW specific qcow_disk_flush() in preparation for
delaying QCOW metadata writeout until VIRTIO_BLK_T_FLUSH time.

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>
---
tools/kvm/disk/qcow.c | 22 ++++++++++------------
1 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/tools/kvm/disk/qcow.c b/tools/kvm/disk/qcow.c
index 939bc61..1a6a969 100644
--- a/tools/kvm/disk/qcow.c
+++ b/tools/kvm/disk/qcow.c
@@ -244,7 +244,7 @@ static ssize_t qcow_read_cluster(struct qcow *q, u64 offset, void *dst, u32 dst_
length = dst_len;

mutex_lock(&q->mutex);
- l2_table_offset = table->l1_table[l1_idx] & ~header->oflag_mask;
+ l2_table_offset = be64_to_cpu(table->l1_table[l1_idx]) & ~header->oflag_mask;
if (!l2_table_offset)
goto zero_cluster;

@@ -400,7 +400,7 @@ static ssize_t qcow_write_cluster(struct qcow *q, u64 offset, void *buf, u32 src

mutex_lock(&q->mutex);

- l2t_off = table->l1_table[l1t_idx] & ~header->oflag_mask;
+ l2t_off = be64_to_cpu(table->l1_table[l1t_idx]) & ~header->oflag_mask;
if (l2t_off) {
/* read and cache l2 table */
l2t = qcow_read_l2_table(q, l2t_off);
@@ -440,7 +440,7 @@ static ssize_t qcow_write_cluster(struct qcow *q, u64 offset, void *buf, u32 src
}

/* Update the in-core entry */
- table->l1_table[l1t_idx] = l2t_off;
+ table->l1_table[l1t_idx] = cpu_to_be64(l2t_off);
}

/* Capture the state of the consistent QCOW image */
@@ -520,6 +520,11 @@ static ssize_t qcow_nowrite_sector(struct disk_image *disk, u64 sector, void *sr
return -1;
}

+static int qcow_disk_flush(struct disk_image *disk)
+{
+ return fsync(disk->fd);
+}
+
static int qcow_disk_close(struct disk_image *disk)
{
struct qcow *q;
@@ -546,6 +551,7 @@ static struct disk_image_operations qcow_disk_readonly_ops = {
static struct disk_image_operations qcow_disk_ops = {
.read_sector = qcow_read_sector,
.write_sector = qcow_write_sector,
+ .flush = qcow_disk_flush,
.close = qcow_disk_close,
};

@@ -553,7 +559,6 @@ static int qcow_read_l1_table(struct qcow *q)
{
struct qcow_header *header = q->header;
struct qcow_table *table = &q->table;
- u64 i;

table->table_size = header->l1_size;

@@ -561,14 +566,7 @@ static int qcow_read_l1_table(struct qcow *q)
if (!table->l1_table)
return -1;

- if (pread_in_full(q->fd, table->l1_table, sizeof(u64) *
- table->table_size, header->l1_table_offset) < 0)
- return -1;
-
- for (i = 0; i < table->table_size; i++)
- be64_to_cpus(&table->l1_table[i]);
-
- return 0;
+ return pread_in_full(q->fd, table->l1_table, sizeof(u64) * table->table_size, header->l1_table_offset);
}

static void *qcow2_read_header(int fd)
--
1.7.0.4