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block: Add bdrv_get_request_alignment()

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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 <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190329042750.14704-6-eblake@redhat.com>
This commit is contained in:
Eric Blake 2019-03-28 23:27:49 -05:00
parent 9cf638508c
commit 4841211e0d
2 changed files with 8 additions and 0 deletions
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7
block/block-backend.c
View File

@ -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 */ /* Returns the maximum transfer length, in bytes; guaranteed nonzero */
uint32_t blk_get_max_transfer(BlockBackend *blk) uint32_t blk_get_max_transfer(BlockBackend *blk)
{ {

1
include/sysemu/block-backend.h
View File

@ -177,6 +177,7 @@ bool blk_is_available(BlockBackend *blk);
void blk_lock_medium(BlockBackend *blk, bool locked); void blk_lock_medium(BlockBackend *blk, bool locked);
void blk_eject(BlockBackend *blk, bool eject_flag); void blk_eject(BlockBackend *blk, bool eject_flag);
int blk_get_flags(BlockBackend *blk); int blk_get_flags(BlockBackend *blk);
uint32_t blk_get_request_alignment(BlockBackend *blk);
uint32_t blk_get_max_transfer(BlockBackend *blk); uint32_t blk_get_max_transfer(BlockBackend *blk);
int blk_get_max_iov(BlockBackend *blk); int blk_get_max_iov(BlockBackend *blk);
void blk_set_guest_block_size(BlockBackend *blk, int align); void blk_set_guest_block_size(BlockBackend *blk, int align);