The next patch needs access to a device's minimum permitted
alignment, since NBD wants to advertise this to clients. Add
an accessor function, borrowing from blk_get_max_transfer()
for accessing a backend's block limits.
Signed-off-by: Eric Blake <ebl...@redhat.com>
Message-Id: <20180802144834.520904-2-ebl...@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
include/sysemu/block-backend.h | 1 +
block/block-backend.c | 7 +++++++
2 files changed, 8 insertions(+)
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index e2066eb06b2..3be05c2d689 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -177,6 +177,7 @@ bool blk_is_available(BlockBackend *blk);
void blk_lock_medium(BlockBackend *blk, bool locked);
void blk_eject(BlockBackend *blk, bool eject_flag);
int blk_get_flags(BlockBackend *blk);
+uint32_t blk_get_request_alignment(BlockBackend *blk);
uint32_t blk_get_max_transfer(BlockBackend *blk);
int blk_get_max_iov(BlockBackend *blk);
void blk_set_guest_block_size(BlockBackend *blk, int align);
diff --git a/block/block-backend.c b/block/block-backend.c
index edad02a0f2a..f78e82a707f 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1764,6 +1764,13 @@ int blk_get_flags(BlockBackend *blk)
}
}
+/* Returns the minimum request alignment, in bytes; guaranteed nonzero */
+uint32_t blk_get_request_alignment(BlockBackend *blk)
+{
+ BlockDriverState *bs = blk_bs(blk);
+ return bs ? bs->bl.request_alignment : BDRV_SECTOR_SIZE;
+}
+
/* Returns the maximum transfer length, in bytes; guaranteed nonzero */
uint32_t blk_get_max_transfer(BlockBackend *blk)
{
--
2.20.1
