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Re: [PATCH for-5.0 v4 1/5] block: Add bdrv_qapi_perm_to_blk_perm()
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [PATCH for-5.0 v4 1/5] block: Add bdrv_qapi_perm_to_blk_perm() |
Date: |
Fri, 8 Nov 2019 14:05:54 +0000 |
08.11.2019 15:34, Max Reitz wrote:
> We need some way to correlate QAPI BlockPermission values with
> BLK_PERM_* flags. We could:
>
> (1) have the same order in the QAPI definition as the the BLK_PERM_*
> flags are in LSb-first order. However, then there is no guarantee
> that they actually match (e.g. when someone modifies the QAPI schema
> without thinking of the BLK_PERM_* definitions).
> We could add static assertions, but these would break what’s good
> about this solution, namely its simplicity.
>
> (2) define the BLK_PERM_* flags based on the BlockPermission values.
> But this way whenever someone were to modify the QAPI order
> (perfectly sensible in theory), the BLK_PERM_* values would change.
> Because these values are used for file locking, this might break
> file locking between different qemu versions.
>
> Therefore, go the slightly more cumbersome way: Add a function to
> translate from the QAPI constants to the BLK_PERM_* flags.
>
> Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> block.c | 18 ++++++++++++++++++
> include/block/block.h | 1 +
> 2 files changed, 19 insertions(+)
>
> diff --git a/block.c b/block.c
> index 4cffc2bc35..066433f3e2 100644
> --- a/block.c
> +++ b/block.c
> @@ -2227,6 +2227,24 @@ void bdrv_format_default_perms(BlockDriverState *bs,
> BdrvChild *c,
> *nshared = shared;
> }
>
> +uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission qapi_perm)
> +{
> + static const uint64_t permissions[] = {
> + [BLOCK_PERMISSION_CONSISTENT_READ] = BLK_PERM_CONSISTENT_READ,
> + [BLOCK_PERMISSION_WRITE] = BLK_PERM_WRITE,
> + [BLOCK_PERMISSION_WRITE_UNCHANGED] = BLK_PERM_WRITE_UNCHANGED,
> + [BLOCK_PERMISSION_RESIZE] = BLK_PERM_RESIZE,
> + [BLOCK_PERMISSION_GRAPH_MOD] = BLK_PERM_GRAPH_MOD,
> + };
> +
> + QEMU_BUILD_BUG_ON(ARRAY_SIZE(permissions) != BLOCK_PERMISSION__MAX);
> + QEMU_BUILD_BUG_ON(1UL << ARRAY_SIZE(permissions) != BLK_PERM_ALL + 1);
safe enough)
> +
> + assert(qapi_perm < BLOCK_PERMISSION__MAX);
> +
> + return permissions[qapi_perm];
> +}
> +
> static void bdrv_replace_child_noperm(BdrvChild *child,
> BlockDriverState *new_bs)
> {
> diff --git a/include/block/block.h b/include/block/block.h
> index 1df9848e74..e9dcfef7fa 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -280,6 +280,7 @@ enum {
> };
>
> char *bdrv_perm_names(uint64_t perm);
> +uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission qapi_perm);
>
> /* disk I/O throttling */
> void bdrv_init(void);
>
--
Best regards,
Vladimir
- [PATCH for-5.0 v4 0/5] iotests: Test failing mirror complete, Max Reitz, 2019/11/08
- [PATCH for-5.0 v4 2/5] block: Use bdrv_qapi_perm_to_blk_perm(), Max Reitz, 2019/11/08
- [PATCH for-5.0 v4 1/5] block: Add bdrv_qapi_perm_to_blk_perm(), Max Reitz, 2019/11/08
- Re: [PATCH for-5.0 v4 1/5] block: Add bdrv_qapi_perm_to_blk_perm(),
Vladimir Sementsov-Ogievskiy <=
- [PATCH for-5.0 v4 3/5] blkdebug: Allow taking/unsharing permissions, Max Reitz, 2019/11/08
- [PATCH for-5.0 v4 5/5] iotests: Add test for failing mirror complete, Max Reitz, 2019/11/08
- [PATCH for-5.0 v4 4/5] iotests: Add @error to wait_until_completed, Max Reitz, 2019/11/08
- Re: [PATCH for-5.0 v4 0/5] iotests: Test failing mirror complete, Max Reitz, 2019/11/26