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Re: [Qemu-devel] [PATCH] block: Avoid bogus flags during mirroring
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH] block: Avoid bogus flags during mirroring |
Date: |
Sun, 12 Jun 2016 10:15:13 +0800 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Sat, 06/11 19:18, Eric Blake wrote:
> Commit e253f4b8 converted mirroring from sector-based bdrv_aio_*
> to byte-based blk_aio_*, but failed to account for the subtle
> difference in signatures (the former takes a semi-redundant length,
> the latter takes a flags parameter). Since all of our flags are
> currently smaller in size than BDRV_SECTOR_SIZE, it has no ill
> effects until we either perform sub-sector mirroring, or we start
> asserting that no unexpected flags are set. I found it while
> testing new asserts when qemu-iotests 132 started warning about an
> unknown flag 0x200000.
>
> Add an assert to help us catch any other improper flags.
>
> Signed-off-by: Eric Blake <address@hidden>
> ---
> block/block-backend.c | 2 ++
> block/mirror.c | 6 ++----
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 34500e6..a5dc6e3 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -945,6 +945,8 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk,
> int64_t offset, int bytes,
> acb->bh = NULL;
> acb->has_returned = false;
>
> + assert(flags <= 0x1f);
> +
Maybe define BDRV_REQ_FLAGS_MAX in include/block/block.h so it's easier to keep
this assertion valid when we introduce more flags in the future?
Otherwise the patch looks good.
Fam
> co = qemu_coroutine_create(co_entry);
> qemu_coroutine_enter(co, acb);
>
> diff --git a/block/mirror.c b/block/mirror.c
> index fbbc496..41848b2 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -157,8 +157,7 @@ static void mirror_read_complete(void *opaque, int ret)
> return;
> }
> blk_aio_pwritev(s->target, op->sector_num * BDRV_SECTOR_SIZE, &op->qiov,
> - op->nb_sectors * BDRV_SECTOR_SIZE,
> - mirror_write_complete, op);
> + 0, mirror_write_complete, op);
> }
>
> static inline void mirror_clip_sectors(MirrorBlockJob *s,
> @@ -275,8 +274,7 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t
> sector_num,
> s->sectors_in_flight += nb_sectors;
> trace_mirror_one_iteration(s, sector_num, nb_sectors);
>
> - blk_aio_preadv(source, sector_num * BDRV_SECTOR_SIZE, &op->qiov,
> - nb_sectors * BDRV_SECTOR_SIZE,
> + blk_aio_preadv(source, sector_num * BDRV_SECTOR_SIZE, &op->qiov, 0,
> mirror_read_complete, op);
> return ret;
> }
> --
> 2.5.5
>
>