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[PATCH] block/vvfat: Fix ro shared folder
From: |
Guillaume Roche |
Subject: |
[PATCH] block/vvfat: Fix ro shared folder |
Date: |
Tue, 31 Aug 2021 16:17:27 +0200 |
QEMU exits in error when passing a vfat shared folder in read-only mode.
To fix this issue, this patch removes any potential write permission
from cumulative_perms, when a read-only block device is in use.
Buglink: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=918950
Signed-off-by: Guillaume Roche <groche@genymobile.com>
---
This is an attempt to fix this behavior, but it feels a bit hacky to me
since this patch checks for the vvfat format in a generic function.
However, I'd be glad to have some advice to make it better. Anyway, I
ran the block tests to ensure this does not introduce any regression.
To add some context: I know that this can be worked around by setting
the shared folder in rw mode. But our use-case requires using both
shared and VM snapshots, and QEMU prevents using snapshot with a rw
shared folder.
block.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/block.c b/block.c
index e97ce0b1c8..3f59e3843f 100644
--- a/block.c
+++ b/block.c
@@ -2383,6 +2383,12 @@ void bdrv_get_cumulative_perm(BlockDriverState *bs,
uint64_t *perm,
cumulative_shared_perms &= c->shared_perm;
}
+ /* Discard write permission if vvfat block device is read-only */
+ const char *format = bdrv_get_format_name(bs);
+ if (format != NULL && strncmp(format, "vvfat", 5) == 0 &&
bdrv_is_read_only(bs)) {
+ cumulative_perms &= ~BLK_PERM_WRITE;
+ }
+
*perm = cumulative_perms;
*shared_perm = cumulative_shared_perms;
}
--
2.31.1
- [PATCH] block/vvfat: Fix ro shared folder,
Guillaume Roche <=