On Sat, Apr 21, 2018 at 02:54:05PM +0200, Jan Kara wrote:
> > - if (iocb->ki_flags & IOCB_DSYNC)
> > + if (iocb->ki_flags & IOCB_DSYNC) {
> > dio->flags |= IOMAP_DIO_NEED_SYNC;
> > + /*
> > + * We optimistically try using FUA for this IO. Any
> > + * non-FUA write that occurs will clear this flag, hence
> > + * we know before completion whether a cache flush is
> > + * necessary.
> > + */
> > + dio->flags |= IOMAP_DIO_WRITE_FUA;
> > + }
>
> So I don't think this is quite correct. IOCB_DSYNC gets set also for O_SYNC
> writes (in that case we also set IOCB_SYNC). And for those we cannot use
> the FUA optimization AFAICT (definitely IOMAP_F_DIRTY isn't a safe
> indicator of a need of full fsync for O_SYNC). Other than that the patch
> looks good to me.
Oops, good catch. I think the above if should just be
if (iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC) == IOCB_DSYNC)) {
and we are fine.
>
> Honza
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
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