On Thu, Feb 01, 2018 at 05:16:31PM +0300, Anton Nefedov wrote: > The normal bdrv_co_pwritev() use is either > - BDRV_REQ_ZERO_WRITE reset and iovector provided > - BDRV_REQ_ZERO_WRITE set and iovector == NULL > > while > - the flag reset and iovector == NULL is an assertion failure > in bdrv_co_do_zero_pwritev() > - the flag set and iovector provided is in fact allowed > (the flag prevails and zeroes are written) > > However the alignment logic does not support the latter case so the padding > areas get overwritten with zeroes.
Please include a test case. Berto mentioned that bdrv_pwrite_zeroes() hits this issue, that might be one way to test it. > Solution could be to forbid such case or just use bdrv_co_do_zero_pwritev() > alignment for it which also makes the code a bit more obvious anyway. > > Signed-off-by: Anton Nefedov <[email protected]> > --- > block/io.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/io.c b/block/io.c > index 7ea4023..cf63fd0 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1701,7 +1701,7 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child, > */ > tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE); > > - if (!qiov) { > + if (flags & BDRV_REQ_ZERO_WRITE) { > ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req); > goto out; > } Looks good.
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