From 23b0d9fb1dd39d85fc2e0cabba5cbe005126e7b5 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 3 Jun 2016 16:45:44 +0200
Subject: [PATCH] block: Don't enforce 512 byte minimum alignment
If block drivers say that they can do an alignment < 512 bytes, let's
just suppose they mean it. raw-posix used to be an offender with respect
to this, but it can actually deal with byte-aligned requests now.
The default is still 512 bytes for any drivers that only implement
sector-based interfaces, but it is 1 now for drivers that implement
.bdrv_co_preadv.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block.c | 2 +-
block/io.c | 8 +++-----
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/block.c b/block.c
index f54bc25e8a..3d850a2999 100644
--- a/block.c
+++ b/block.c
@@ -937,7 +937,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
goto fail_opts;
}
- bs->request_alignment = 512;
+ bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;
bs->zero_beyond_eof = true;
bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
diff --git a/block/io.c b/block/io.c
index b261cc6327..b3ff9bec38 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1052,8 +1052,7 @@ int coroutine_fn bdrv_co_preadv(BlockDriverState *bs,
BlockDriver *drv = bs->drv;
BdrvTrackedRequest req;
- /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
- uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+ uint64_t align = bs->request_alignment;
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;
@@ -1305,7 +1304,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BlockDriverState *bs,
uint8_t *buf = NULL;
QEMUIOVector local_qiov;
struct iovec iov;
- uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+ uint64_t align = bs->request_alignment;
unsigned int head_padding_bytes, tail_padding_bytes;
int ret = 0;
@@ -1392,8 +1391,7 @@ int coroutine_fn bdrv_co_pwritev(BlockDriverState *bs,
BdrvRequestFlags flags)
{
BdrvTrackedRequest req;
- /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
- uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+ uint64_t align = bs->request_alignment;
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;