raw: Probe required direct I/O alignment
Add a bs->request_alignment field that contains the required
offset/length alignment for I/O requests and fill it in the raw block
drivers. Use ioctls if possible, else see what alignment it takes for
O_DIRECT to succeed.
While at it, also expose the memory alignment requirements, which may be
(and in practice are) different from the disk alignment requirements.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/block.c b/block.c
index 195beff..d4dd7fe 100644
--- a/block.c
+++ b/block.c
@@ -852,6 +852,7 @@
bs->open_flags = flags;
bs->guest_block_size = 512;
+ bs->request_alignment = 512;
bs->zero_beyond_eof = true;
open_flags = bdrv_open_flags(bs, flags);
bs->read_only = !(open_flags & BDRV_O_RDWR);
@@ -920,6 +921,8 @@
}
bdrv_refresh_limits(bs);
+ assert(bdrv_opt_mem_align(bs) != 0);
+ assert(bs->request_alignment != 0);
#ifndef _WIN32
if (bs->is_temporary) {
