On Thu, Dec 12, 2024 at 09:55:04AM -0800, Darrick J. Wong wrote:
> > +#define IOMAP_IOEND_NOMERGE_FLAGS \
> > + (IOMAP_IOEND_SHARED | IOMAP_IOEND_UNWRITTEN)
>
> Hmm. At first I wondered "Why wouldn't BOUNDARY be in here too? It
> also prevents merging of ioends." Then I remembered that BOUNDARY is an
> explicit nomerge flag, whereas what NOMERGE_FLAGS provides is that we
> always split ioends whenever the ioend work changes.
>
> How about a comment?
>
> /* split ioends when the type of completion work changes */
> #define IOMAP_IOEND_NOMERGE_FLAGS \
> (IOMAP_IOEND_SHARED | IOMAP_IOEND_UNWRITTEN)
>
> Otherwise this looks fine to me.
The interesting thing about BOUNDARY is not just that it's explicit, but
also that it's one-way. We can merge a non-BOUNDARY flag into the end
of a BOUNDARY one, just not a BOUNDARY one into the end of a non-BOUNDARY
one.
>
> --D
>
> > +
> > /*
> > * Structure for writeback I/O completions.
> > */
> > struct iomap_ioend {
> > struct list_head io_list; /* next ioend in chain */
> > - u16 io_type;
> > - u16 io_flags; /* IOMAP_F_* */
> > + u16 io_flags; /* IOMAP_IOEND_* */
> > struct inode *io_inode; /* file being written to */
> > size_t io_size; /* size of the extent */
> > loff_t io_offset; /* offset in the file */
> > --
> > 2.45.2
> >
> >
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