Patchwork [v4] qemu-img: let 'qemu-img convert' flush data

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Submitter namei.unix@gmail.com
Date April 20, 2012, 9:10 a.m.
Message ID <1334913056-7183-1-git-send-email-namei.unix@gmail.com>
Download mbox | patch
Permalink /patch/153973/
State New
Headers show

Comments

namei.unix@gmail.com - April 20, 2012, 9:10 a.m.
From: Liu Yuan <tailai.ly@taobao.com>

The 'qemu-img convert -h' advertise that the default cache mode is
'writeback', while in fact it is 'unsafe'.

This patch 1) fix the help manual and 2) let bdrv_close() call bdrv_flush()

2) is needed because some backend storage doesn't have a self-flush
mechanism(for e.g., sheepdog), so we need to call bdrv_flush() to make
sure the image is really writen to the storage instead of hanging around
writeback cache forever.

Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
---
 block.c    |    1 +
 qemu-img.c |    4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)
Kevin Wolf - April 20, 2012, 9:43 a.m.
Am 20.04.2012 11:10, schrieb Liu Yuan:
> From: Liu Yuan <tailai.ly@taobao.com>
> 
> The 'qemu-img convert -h' advertise that the default cache mode is
> 'writeback', while in fact it is 'unsafe'.
> 
> This patch 1) fix the help manual and 2) let bdrv_close() call bdrv_flush()
> 
> 2) is needed because some backend storage doesn't have a self-flush
> mechanism(for e.g., sheepdog), so we need to call bdrv_flush() to make
> sure the image is really writen to the storage instead of hanging around
> writeback cache forever.
> 
> Signed-off-by: Liu Yuan <tailai.ly@taobao.com>

Thanks, applied to the block branch.

Kevin

Patch

diff --git a/block.c b/block.c
index c0c90f0..1ee2bf0 100644
--- a/block.c
+++ b/block.c
@@ -812,6 +812,7 @@  unlink_and_fail:
 
 void bdrv_close(BlockDriverState *bs)
 {
+    bdrv_flush(bs);
     if (bs->drv) {
         if (bs->job) {
             block_job_cancel_sync(bs->job);
diff --git a/qemu-img.c b/qemu-img.c
index 6a61ca8..0ae543c 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -66,8 +66,8 @@  static void help(void)
            "  'filename' is a disk image filename\n"
            "  'fmt' is the disk image format. It is guessed automatically in most cases\n"
            "  'cache' is the cache mode used to write the output disk image, the valid\n"
-           "    options are: 'none', 'writeback' (default), 'writethrough', 'directsync'\n"
-           "    and 'unsafe'\n"
+           "    options are: 'none', 'writeback' (default, except for convert), 'writethrough',\n"
+           "    'directsync' and 'unsafe' (default for convert)\n"
            "  'size' is the disk image size in bytes. Optional suffixes\n"
            "    'k' or 'K' (kilobyte, 1024), 'M' (megabyte, 1024k), 'G' (gigabyte, 1024M)\n"
            "    and T (terabyte, 1024G) are supported. 'b' is ignored.\n"