Am 15.04.2016 um 01:30 hat Max Reitz geschrieben: > On 13.04.2016 13:06, Kevin Wolf wrote: > > Commit 57d6a428 broke blk_aio_write_zeroes() because in some write > > functions in the call path don't have an explicit length argument but > > reuse qiov->size instead. Which is great, except that write_zeroes > > doesn't have a qiov, which this commit interprets as 0 bytes. > > Consequently, blk_aio_write_zeroes() didn't effectively do anything. > > You mean it has written null data? :-) > > Alternative version: So it has written zero bytes? Works as intended, then.
I consciously avoided the latter wording. ;-) > > This patch introduces an explicit acb->bytes in BlkAioEmAIOCB and uses > > that instead of acb->rwco.size. > > > > The synchronous version of the function is okay because it does pass a > > qiov (with the right size and a NULL pointer as its base). > > > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > > @@ -937,7 +940,8 @@ BlockAIOCB *blk_aio_write_zeroes(BlockBackend *blk, > > int64_t sector_num, > > return blk_abort_aio_request(blk, cb, opaque, -EINVAL); > > } > > > > - return blk_aio_prwv(blk, sector_num << BDRV_SECTOR_BITS, NULL, > > + return blk_aio_prwv(blk, sector_num << BDRV_SECTOR_BITS, > > + nb_sectors << BDRV_SECTOR_BITS, NULL, > > blk_aio_write_entry, BDRV_REQ_ZERO_WRITE, cb, > > opaque); > > } > > Another thing about blk_aio_write_zeroes() that might need fixing is > that it completely ignores its flags parameter. > > That can be done in a seperate patch, however (and is probably not > critical, as this currently just means that a potential REQ_MAY_UNMAP > from scsi-disk is ignored), so: Oh dear... Commit 57d6a428 was not my best patch ever, and apparently Stefan wasn't suspicious enough to catch the bugs. Maybe someone should re-review the whole thing... "just" ignoring REQ_MAY_UNMAP is a regression in discard support, so no, that's not what I would call harmless. Definitely needs fixing for 2.6. And we probably need more qtests checking such things. Kevin
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