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block: Move request_alignment into BlockLimit

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It makes more sense to have ALL block size limit constraints
in the same struct.  Improve the documentation while at it.

Simplify a couple of conditionals, now that we have audited and
documented that request_alignment is always non-zero.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2016-06-23 16:37:24 -06:00 • committed by Kevin Wolf
parent d9e0dfa246
commit a5b8dd2ce8
12 changed files with 39 additions and 35 deletions
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22
include/block/block_int.h
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@ -324,6 +324,12 @@ struct BlockDriver {
};
typedef struct BlockLimits {
/* Alignment requirement, in bytes, for offset/length of I/O
* requests. Must be a power of 2 less than INT_MAX; defaults to
* 1 for drivers with modern byte interfaces, and to 512
* otherwise. */
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
@ -332,8 +338,8 @@ typedef struct BlockLimits {
/* optimal alignment for discard requests in bytes, must be power
* of 2, less than max_pdiscard if that is set, and multiple of
* bs->request_alignment. May be 0 if bs->request_alignment is
* good enough */
* bl.request_alignment. May be 0 if bl.request_alignment is good
* enough */
uint32_t pdiscard_alignment;
/* maximum number of bytes that can zeroized at once (since it is
@ -343,12 +349,12 @@ typedef struct BlockLimits {
/* optimal alignment for write zeroes requests in bytes, must be
* power of 2, less than max_pwrite_zeroes if that is set, and
* multiple of bs->request_alignment. May be 0 if
* bs->request_alignment is good enough */
* multiple of bl.request_alignment. May be 0 if
* bl.request_alignment is good enough */
uint32_t pwrite_zeroes_alignment;
/* optimal transfer length in bytes (must be power of 2, and
* multiple of bs->request_alignment), or 0 if no preferred size */
* multiple of bl.request_alignment), or 0 if no preferred size */
uint32_t opt_transfer;
/* maximal transfer length in bytes (need not be power of 2, but
@ -356,10 +362,10 @@ typedef struct BlockLimits {
* For now, anything larger than INT_MAX is clamped down. */
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 */
@ -465,8 +471,6 @@ struct BlockDriverState {
/* I/O Limits */
BlockLimits bl;
/* 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,