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Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLim
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit |
Date: |
Tue, 7 Jun 2016 15:19:28 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 03.06.2016 um 19:03 hat Eric Blake geschrieben:
> It makes more sense to have ALL block size limit constraints
> in the same struct. Improve the documentation while at it.
>
> Note that bdrv_refresh_limits() has to keep things alive across
> a memset() of BlockLimits.
>
> Signed-off-by: Eric Blake <address@hidden>
> ---
> include/block/block_int.h | 12 ++++++++----
> block.c | 4 ++--
> block/blkdebug.c | 4 ++--
> block/bochs.c | 2 +-
> block/cloop.c | 2 +-
> block/dmg.c | 2 +-
> block/io.c | 12 +++++++-----
> block/iscsi.c | 2 +-
> block/raw-posix.c | 16 ++++++++--------
> block/raw-win32.c | 6 +++---
> block/vvfat.c | 2 +-
> 11 files changed, 35 insertions(+), 29 deletions(-)
>
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 9dc7af4..0bc7ff4 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -322,6 +322,12 @@ struct BlockDriver {
> };
>
> typedef struct BlockLimits {
> + /* Alignment requirement, in bytes, for offset/length of I/O
> + * requests. Must be a power of 2, and should not exceed
> + * INT_MAX. For now, a value of 0 defaults to 512, but may change
> + * to default to 1. */
> + uint32_t request_alignment;
> +
> /* maximum number of bytes that can be discarded at once (since it
> * is signed, it must be < 2G, if set), should be multiple of
> * pdiscard_alignment, but need not be power of 2. May be 0 if no
> @@ -353,10 +359,10 @@ typedef struct BlockLimits {
> * should be multiple of opt_transfer), or 0 for no 32-bit limit */
> uint32_t max_transfer;
>
> - /* memory alignment so that no bounce buffer is needed */
> + /* memory alignment, in bytes so that no bounce buffer is needed */
> size_t min_mem_alignment;
>
> - /* memory alignment for bounce buffer */
> + /* memory alignment, in bytes, for bounce buffer */
> size_t opt_mem_alignment;
>
> /* maximum number of iovec elements */
> @@ -463,8 +469,6 @@ struct BlockDriverState {
> /* Whether produces zeros when read beyond eof */
> bool zero_beyond_eof;
>
> - /* Alignment requirement for offset/length of I/O requests */
> - unsigned int request_alignment;
> /* Flags honored during pwrite (so far: BDRV_REQ_FUA) */
> unsigned int supported_write_flags;
> /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
> diff --git a/block.c b/block.c
> index f54bc25..1b56161 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->bl.request_alignment = 512;
> bs->zero_beyond_eof = true;
> bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
We don't explicitly initialise any other BlockLimits here, the function
calls bdrv_refresh_limits() to do that.
> diff --git a/block/io.c b/block/io.c
> index e845ef9..aaeedaa 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -71,8 +71,10 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error
> **errp)
> {
> BlockDriver *drv = bs->drv;
> Error *local_err = NULL;
> + uint32_t request_alignment = bs->bl.request_alignment;
>
> memset(&bs->bl, 0, sizeof(bs->bl));
> + bs->bl.request_alignment = request_alignment;
This looks fishy, and it's because you didn't fully convert
request_alignment to work like all the other limits.
You should set the default of 512 here in bdrv_refresh_limits() before
calling into drv->bdrv_refresh_limits() where it can be overridden. No
other fields are set earlier and then preserved here, we start over with
everything.
Of course, this means that drivers that set request_alignment must be
changed so that they don't set it in .bdrv_open(), but only in their
.bdrv_refresh_limits() callback.
Kevin
- [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, (continued)
- [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, Eric Blake, 2016/06/03
- Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, Eric Blake, 2016/06/03
- Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, Eric Blake, 2016/06/14
- Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, Kevin Wolf, 2016/06/14
- Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, Eric Blake, 2016/06/14
- Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit, Kevin Wolf, 2016/06/14
Re: [Qemu-devel] [PATCH 5/5] block: Move request_alignment into BlockLimit,
Kevin Wolf <=
[Qemu-devel] [PATCH 3/5] block: Switch transfer length bounds to byte-based, Eric Blake, 2016/06/03
[Qemu-devel] [PATCH 1/5] block: Tighter assertions on bdrv_aligned_preadv(), Eric Blake, 2016/06/03
[Qemu-devel] [PATCH 2/5] block: Honor flags during bdrv_aligned_preadv(), Eric Blake, 2016/06/03
[Qemu-devel] [PATCH 6/5] block: Fix harmless off-by-one in bdrv_aligned_preadv(), Eric Blake, 2016/06/03