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block: Move enable_write_cache to BB level

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Whether a write cache is used or not is a decision that concerns the
user (e.g. the guest device) rather than the backend. It was already
logically part of the BB level as bdrv_move_feature_fields() always kept
it on top of the BDS tree; with this patch, the core of it (the actual
flag and the additional flushes) is also implemented there.

Direct callers of bdrv_open() must pass BDRV_O_CACHE_WB now if bs
doesn't have a BlockBackend attached.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2016-03-04 14:28:01 +01:00
parent 855a6a93a1
commit bfd18d1e0b
8 changed files with 53 additions and 35 deletions
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42
block/block-backend.c
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@ -47,6 +47,8 @@ struct BlockBackend {
* can be used to restore those options in the new BDS on insert) */
BlockBackendRootState root_state;
bool enable_write_cache;
/* I/O stats (display with "info blockstats"). */
BlockAcctStats stats;
@ -699,11 +701,17 @@ static int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
unsigned int bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
int ret = blk_check_byte_request(blk, offset, bytes);
int ret;
ret = blk_check_byte_request(blk, offset, bytes);
if (ret < 0) {
return ret;
}
if (!blk->enable_write_cache) {
flags |= BDRV_REQ_FUA;
}
return bdrv_co_do_pwritev(blk_bs(blk), offset, bytes, qiov, flags);
}
@ -1210,26 +1218,19 @@ int blk_is_sg(BlockBackend *blk)
int blk_enable_write_cache(BlockBackend *blk)
{
BlockDriverState *bs = blk_bs(blk);
if (bs) {
return bdrv_enable_write_cache(bs);
} else {
return !!(blk->root_state.open_flags & BDRV_O_CACHE_WB);
}
return blk->enable_write_cache;
}
void blk_set_enable_write_cache(BlockBackend *blk, bool wce)
{
BlockDriverState *bs = blk_bs(blk);
blk->enable_write_cache = wce;
if (bs) {
bdrv_set_enable_write_cache(bs, wce);
} else {
/* TODO Remove this when BDRV_O_CACHE_WB isn't used any more */
if (blk->root) {
if (wce) {
blk->root_state.open_flags |= BDRV_O_CACHE_WB;
blk->root->bs->open_flags |= BDRV_O_CACHE_WB;
} else {
blk->root_state.open_flags &= ~BDRV_O_CACHE_WB;
blk->root->bs->open_flags &= ~BDRV_O_CACHE_WB;
}
}
}
@ -1492,11 +1493,22 @@ int blk_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
int64_t pos, int size)
{
int ret;
if (!blk_is_available(blk)) {
return -ENOMEDIUM;
}
return bdrv_save_vmstate(blk_bs(blk), buf, pos, size);
ret = bdrv_save_vmstate(blk_bs(blk), buf, pos, size);
if (ret < 0) {
return ret;
}
if (ret == size && !blk->enable_write_cache) {
ret = bdrv_flush(blk_bs(blk));
}
return ret < 0 ? ret : size;
}
int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)