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block: Add bdrv_(p)write_sync 

Add new functions that write and flush the written data to disk immediately.
This is what needs to be used for image format metadata to maintain integrity
for cache=... modes that don't use O_DSYNC. (Actually, we only need barriers,
and therefore the functions are defined as such, but flushes is what is
implemented in this patch - we can try to change that later)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2010-06-16 16:38:15 +02:00
parent 3b5276b5ec
commit f08145fe16
2 changed files with 41 additions and 0 deletions
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37
block.c
View File

@ -1010,6 +1010,43 @@ int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
return count1;
}
/*
* Writes to the file and ensures that no writes are reordered across this
* request (acts as a barrier)
*
* Returns 0 on success, -errno in error cases.
*/
int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset,
const void *buf, int count)
{
int ret;
ret = bdrv_pwrite(bs, offset, buf, count);
if (ret < 0) {
return ret;
}
/* No flush needed for cache=writethrough, it uses O_DSYNC */
if ((bs->open_flags & BDRV_O_CACHE_MASK) != 0) {
bdrv_flush(bs);
}
return 0;
}
/*
* Writes to the file and ensures that no writes are reordered across this
* request (acts as a barrier)
*
* Returns 0 on success, -errno in error cases.
*/
int bdrv_write_sync(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
return bdrv_pwrite_sync(bs, BDRV_SECTOR_SIZE * sector_num,
buf, BDRV_SECTOR_SIZE * nb_sectors);
}
/**
* Truncate file to 'offset' bytes (needed only for file protocols)
*/

4
block.h
View File

@ -80,6 +80,10 @@ int bdrv_pread(BlockDriverState *bs, int64_t offset,
void *buf, int count);
int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
const void *buf, int count);
int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset,
const void *buf, int count);
int bdrv_write_sync(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors);
int bdrv_truncate(BlockDriverState *bs, int64_t offset);
int64_t bdrv_getlength(BlockDriverState *bs);
void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);