On Mon, Jul 27, 2020 at 12:04 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Sun, Jul 26, 2020 at 10:57:26AM -0400, Yafang Shao wrote:
> > Bellow comment is quoted from Dave,
>
> FYI, you mean "Below", not "Bellow". Dave doesn't often bellow.
Ah, thanks for pointing that out. I often make that kind of misstake.
>
> > As a result, we should reintroduce PF_FSTRANS. Because PF_FSTRANS is only
> > set by current, we can move it out of task->flags to avoid being out of PF_
> > flags. So a new flag in_fstrans is introduced.
>
> I don't think we need a new flag for this. I think you can just set
> current->journal_info to a non-NULL value.
Seems like a good suggestion.
I will think about it.
>
> > +++ b/fs/xfs/xfs_linux.h
> > @@ -111,6 +111,20 @@ typedef __u32 xfs_nlink_t;
> > #define current_restore_flags_nested(sp, f) \
> > (current->flags = ((current->flags & ~(f)) | (*(sp) & (f))))
> >
> > +static inline unsigned int xfs_trans_context_start(void)
> > +{
> > + unsigned int flags = current->in_fstrans;
> > +
> > + current->in_fstrans = 1;
> > +
> > + return flags;
> > +}
> > +
> > +static inline void xfs_trans_context_end(unsigned int flags)
> > +{
> > + current->in_fstrans = flags ? 1 : 0;
> > +}
>
> Does XFS support nested transactions? If we're just using
> current->journal_info, we can pretend its an unsigned long and use it
> as a counter rather than handle the nesting the same way as the GFP flags.
>
--
Thanks
Yafang
