From 1aa16aaa360e6d5aa0bc32f0c9942ba2e90a5f28 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 23 Jun 2010 14:52:20 -0300
Subject: [PATCH 08/11] block: Add bdrv_(p)write_sync
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1277304741-19012-2-git-send-email-kwolf@redhat.com>
Patchwork-id: 10132
O-Subject: [RHEL-6 qemu-kvm PATCH 1/2] block: Add bdrv_(p)write_sync
Bugzilla: 607200
RH-Acked-by: Amit Shah <amit.shah@redhat.com>
RH-Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
RH-Acked-by: Christoph Hellwig <chellwig@redhat.com>
Bugzilla: 607200
Add new functions that write and flush the written data to disk immediately.
This is what needs to be used for image format metadata to maintain integrity
for cache=... modes that don't use O_DSYNC. (Actually, we only need barriers,
and therefore the functions are defined as such, but flushes is what is
implemented in this patch - we can try to change that later)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit f08145fe16470aca09304099888f68cfbc5d1de7)
---
block.c | 37 +++++++++++++++++++++++++++++++++++++
block.h | 4 ++++
2 files changed, 41 insertions(+), 0 deletions(-)
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
block.c | 37 +++++++++++++++++++++++++++++++++++++
block.h | 4 ++++
2 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/block.c b/block.c
index 0aa3ce7..976145b 100644
--- a/block.c
+++ b/block.c
@@ -951,6 +951,43 @@ int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
return count1;
}
+/*
+ * Writes to the file and ensures that no writes are reordered across this
+ * request (acts as a barrier)
+ *
+ * Returns 0 on success, -errno in error cases.
+ */
+int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset,
+ const void *buf, int count)
+{
+ int ret;
+
+ ret = bdrv_pwrite(bs, offset, buf, count);
+ if (ret < 0) {
+ return ret;
+ }
+
+ /* No flush needed for cache=writethrough, it uses O_DSYNC */
+ if ((bs->open_flags & BDRV_O_CACHE_MASK) != 0) {
+ bdrv_flush(bs);
+ }
+
+ return 0;
+}
+
+/*
+ * Writes to the file and ensures that no writes are reordered across this
+ * request (acts as a barrier)
+ *
+ * Returns 0 on success, -errno in error cases.
+ */
+int bdrv_write_sync(BlockDriverState *bs, int64_t sector_num,
+ const uint8_t *buf, int nb_sectors)
+{
+ return bdrv_pwrite_sync(bs, BDRV_SECTOR_SIZE * sector_num,
+ buf, BDRV_SECTOR_SIZE * nb_sectors);
+}
+
/**
* Truncate file to 'offset' bytes (needed only for file protocols)
*/
diff --git a/block.h b/block.h
index f8bd98a..a394e2a 100644
--- a/block.h
+++ b/block.h
@@ -78,6 +78,10 @@ int bdrv_pread(BlockDriverState *bs, int64_t offset,
void *buf, int count);
int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
const void *buf, int count);
+int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset,
+ const void *buf, int count);
+int bdrv_write_sync(BlockDriverState *bs, int64_t sector_num,
+ const uint8_t *buf, int nb_sectors);
int bdrv_truncate(BlockDriverState *bs, int64_t offset);
int64_t bdrv_getlength(BlockDriverState *bs);
void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
--
1.7.0.3