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[Qemu-devel] [PULL 1/7] block: Don't use BLK_PERM_CONSISTENT_READ for fo
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 1/7] block: Don't use BLK_PERM_CONSISTENT_READ for format probing |
Date: |
Tue, 21 Nov 2017 16:10:11 +0100 |
For format probing, we don't really care whether all of the image
content is consistent. The only thing we're looking at is the image
header, and specifically the magic numbers that are expected to never
change, no matter how inconsistent the guest visible disk content is.
Therefore, don't request BLK_PERM_CONSISTENT_READ. This allows to use
format probing, e.g. in the context of 'qemu-img info', even while the
guest visible data in the image is inconsistent during a running block
job.
Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
---
block.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index 6c8ef98dfa..68b724206d 100644
--- a/block.c
+++ b/block.c
@@ -2579,7 +2579,10 @@ static BlockDriverState *bdrv_open_inherit(const char
*filename,
goto fail;
}
if (file_bs != NULL) {
- file = blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL);
+ /* Not requesting BLK_PERM_CONSISTENT_READ because we're only
+ * looking at the header to guess the image format. This works even
+ * in cases where a guest would not see a consistent state. */
+ file = blk_new(0, BLK_PERM_ALL);
blk_insert_bs(file, file_bs, &local_err);
bdrv_unref(file_bs);
if (local_err) {
--
2.13.6
- [Qemu-devel] [PULL 0/7] Block layer patches for 2.11.0-rc2, Kevin Wolf, 2017/11/21
- [Qemu-devel] [PULL 1/7] block: Don't use BLK_PERM_CONSISTENT_READ for format probing,
Kevin Wolf <=
- [Qemu-devel] [PULL 2/7] block: Don't request I/O permission with BDRV_O_NO_IO, Kevin Wolf, 2017/11/21
- [Qemu-devel] [PULL 4/7] block: Add errp to bdrv_all_goto_snapshot(), Kevin Wolf, 2017/11/21
- [Qemu-devel] [PULL 3/7] block: Add errp to bdrv_snapshot_goto(), Kevin Wolf, 2017/11/21
- [Qemu-devel] [PULL 6/7] block: Close a BlockDriverState completely even when bs->drv is NULL, Kevin Wolf, 2017/11/21
- [Qemu-devel] [PULL 5/7] block: Error out on load_vm with active dirty bitmaps, Kevin Wolf, 2017/11/21
- [Qemu-devel] [PULL 7/7] iotests: Fix 176 on 32-bit host, Kevin Wolf, 2017/11/21
- Re: [Qemu-devel] [PULL 0/7] Block layer patches for 2.11.0-rc2, Peter Maydell, 2017/11/21