From f08145fe16470aca09304099888f68cfbc5d1de7 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 16 Jun 2010 16:38:15 +0200 Subject: 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 --- block.c | 37 +++++++++++++++++++++++++++++++++++++ block.h | 4 ++++ 2 files changed, 41 insertions(+) diff --git a/block.c b/block.c index 3fc2969..e71a771 100644 --- a/block.c +++ b/block.c @@ -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) */ diff --git a/block.h b/block.h index 9df9b38..6a157f4 100644 --- a/block.h +++ b/block.h @@ -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); -- cgit v1.1