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block: define get_block_status return value 

Define the return value of get_block_status.  Bits 0, 1, 2 and 9-62
are valid; bit 63 (the sign bit) is reserved for errors.  Bits 3-8
are left for future extensions.

The return code is compatible with the old is_allocated API: if a driver
only returns 0 or 1 (aka BDRV_BLOCK_DATA) like is_allocated used to,
clients of is_allocated will not have any change in behavior.  Still,
we will return more precise information in the next patches and the
new definition of bdrv_is_allocated is already prepared for this.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-09-04 19:00:29 +02:00 committed by Stefan Hajnoczi
parent b6b8a33354
commit 4333bb7140
2 changed files with 34 additions and 2 deletions
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10
block.c
View File

@ -3093,7 +3093,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
if (!bs->drv->bdrv_co_get_block_status) {
*pnum = nb_sectors;
return 1;
return BDRV_BLOCK_DATA;
}
return bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum);
@ -3143,7 +3143,13 @@ int64_t bdrv_get_block_status(BlockDriverState *bs, int64_t sector_num,
int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
return bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
if (ret < 0) {
return ret;
}
return
(ret & BDRV_BLOCK_DATA) ||
((ret & BDRV_BLOCK_ZERO) && !bdrv_has_zero_init(bs));
}
/*

26
include/block/block.h
View File

@ -81,6 +81,32 @@ typedef struct BlockDevOps {
#define BDRV_SECTOR_SIZE (1ULL << BDRV_SECTOR_BITS)
#define BDRV_SECTOR_MASK ~(BDRV_SECTOR_SIZE - 1)
/* BDRV_BLOCK_DATA: data is read from bs->file or another file
* BDRV_BLOCK_ZERO: sectors read as zero
* BDRV_BLOCK_OFFSET_VALID: sector stored in bs->file as raw data
*
* If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 represent the offset in
* bs->file where sector data can be read from as raw data.
*
* DATA == 0 && ZERO == 0 means that data is read from backing_hd if present.
*
* DATA ZERO OFFSET_VALID
* t t t sectors read as zero, bs->file is zero at offset
* t f t sectors read as valid from bs->file at offset
* f t t sectors preallocated, read as zero, bs->file not
* necessarily zero at offset
* f f t sectors preallocated but read from backing_hd,
* bs->file contains garbage at offset
* t t f sectors preallocated, read as zero, unknown offset
* t f f sectors read from unknown file or offset
* f t f not allocated or unknown offset, read as zero
* f f f not allocated or unknown offset, read from backing_hd
*/
#define BDRV_BLOCK_DATA 1
#define BDRV_BLOCK_ZERO 2
#define BDRV_BLOCK_OFFSET_VALID 4
#define BDRV_BLOCK_OFFSET_MASK BDRV_SECTOR_MASK
typedef enum {
BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
} BlockErrorAction;