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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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26
block.c
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@ -2038,6 +2038,11 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
goto error;
}
}
if (!reopen_state->bs->blk && !(reopen_state->flags & BDRV_O_CACHE_WB)) {
error_setg(errp, "Cannot disable cache.writeback: No BlockBackend");
ret = -EINVAL;
goto error;
}
/* node-name and driver must be unchanged. Put them back into the QDict, so
* that they are checked at the end of this function. */
@ -2138,10 +2143,10 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
reopen_state->bs->explicit_options = reopen_state->explicit_options;
reopen_state->bs->open_flags = reopen_state->flags;
reopen_state->bs->enable_write_cache = !!(reopen_state->flags &
BDRV_O_CACHE_WB);
reopen_state->bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
bdrv_set_enable_write_cache(reopen_state->bs,
!!(reopen_state->flags & BDRV_O_CACHE_WB));
bdrv_refresh_limits(reopen_state->bs, NULL);
}
@ -2271,9 +2276,6 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
BlockDriverState *bs_src)
{
/* move some fields that need to stay attached to the device */
/* dev info */
bs_dest->enable_write_cache = bs_src->enable_write_cache;
}
static void change_parent_backing_link(BlockDriverState *from,
@ -2753,12 +2755,18 @@ int bdrv_is_sg(BlockDriverState *bs)
int bdrv_enable_write_cache(BlockDriverState *bs)
{
return bs->enable_write_cache;
if (bs->blk) {
return blk_enable_write_cache(bs->blk);
} else {
return true;
}
}
void bdrv_set_enable_write_cache(BlockDriverState *bs, bool wce)
{
bs->enable_write_cache = wce;
if (bs->blk) {
blk_set_enable_write_cache(bs->blk, wce);
}
/* so a reopen() will preserve wce */
if (wce) {
@ -3618,8 +3626,8 @@ void bdrv_img_create(const char *filename, const char *fmt,
}
/* backing files always opened read-only */
back_flags =
flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
back_flags = flags | BDRV_O_CACHE_WB;
back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
if (backing_fmt) {
backing_options = qdict_new();