@subject: It's a bit long, and it's missing a prefix telling what this
patch is about. I would have probably used "block/vdi: Use bdrv_flush
after metadata updates" or something like that.
On 01.05.2015 17:03, phoeagon wrote:
Looks like VDI is the only writable image format that does not use
write-with-barrier(sync) when updating the metadata. A sequence of
commits b0ad5a455d~078a458e077d6b0db2 fixes this for
QCOW/COW/QCOW2/VPC/VMDK, but the VDI does not issue a barrier by sync
after updating the metadata.
This commit adds a `bdrv_flush` after updating block map.
Signed-off-by: Zhe Qiu <address@hidden>
Hm, this doesn't look quite right. :-)
---------------
These should be only "---", I guess, so the block below is omitted from
the commit message.
From 2ea36d9a0e676b534483dc54c191f421f9889dc6 Mon Sep 17 00:00:00 2001
From: phoeagon <address@hidden>
Date: Fri, 1 May 2015 19:00:22 +0800
Subject: [PATCH] use bdrv_flush to provide barrier semantic in block/vdi.c
In reference to
b0ad5a455d7e5352d4c86ba945112011dbeadfb8~078a458e077d6b0db262c4b05fee51d01de2d1d2,
metadata writes to qcow2/cow/qcow/vpc/vmdk are all synced prior to
succeeding writes.
---
block/vdi.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/block/vdi.c b/block/vdi.c
index 7642ef3..5d09b36 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -713,6 +713,7 @@ static int vdi_co_write(BlockDriverState *bs,
logout("will write %u block map sectors starting from entry
%u\n",
n_sectors, bmap_first);
ret = bdrv_write(bs->file, offset, base, n_sectors);
+ ret = bdrv_flush(bs->file);
This overwrites the return value from bdrv_write(), which I don't think
is right. We could either ignore bdrv_flush()'s return value, or make it
something like "if (ret < 0) { bdrv_flush(bs->file); } else { ret =
bdrv_flush(bs->file); }" or "ret_flush = bdrv_flush(bs->file); if (!(ret
< 0)) { ret = ret_flush; }". Or skip the flush in case bdrv_write()
failed ("if (ret < 0) { return ret; } ret = bdrv_flush(bs->file);"),
like bdrv_pwrite_sync() does.
The idea of the change (adding the flush) looks good, though.
Max
}
return ret;
--
2.3.7
