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/openbmc/qemu/include/block/
H A Dblock.hdiff 7b1d9c4df0603fbc526226a9c5ef91118aa6c957 Fri Nov 08 06:34:51 CST 2019 Max Reitz <mreitz@redhat.com> block: Add bdrv_qapi_perm_to_blk_perm()

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 <mreitz@redhat.com>
Message-id: 20191108123455.39445-2-mreitz@redhat.com
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
/openbmc/qemu/
H A Dblock.cdiff 7b1d9c4df0603fbc526226a9c5ef91118aa6c957 Fri Nov 08 06:34:51 CST 2019 Max Reitz <mreitz@redhat.com> block: Add bdrv_qapi_perm_to_blk_perm()

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 <mreitz@redhat.com>
Message-id: 20191108123455.39445-2-mreitz@redhat.com
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>