On Tue 30-07-24 15:32:48, Jan Kara wrote:
> On Tue 30-07-24 19:33:32, Kemeng Shi wrote:
> > Remove kmap for page of b_frozen_data from jbd2_alloc() which always
> > provides an address from the direct kernel mapping.
> >
> > Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
>
> I don't think this is really a win. On majority of installations kmap is a
> noop anyway and for the remainder kmap_local() is cheap. And the
> readability of the code is just worse with this.
Ah, the following patch actually improves the code flow so the end result
looks fine. OK, feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Maybe mention in the changelog that following patch will further improve
the function.
Honza
> > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> > index 312c7575b54f..9c1ffb0dc740 100644
> > --- a/fs/jbd2/journal.c
> > +++ b/fs/jbd2/journal.c
> > @@ -352,12 +352,13 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
> > done_copy_out = 1;
> > new_folio = virt_to_folio(jh_in->b_frozen_data);
> > new_offset = offset_in_folio(new_folio, jh_in->b_frozen_data);
> > + mapped_data = jh_in->b_frozen_data;
> > } else {
> > new_folio = bh_in->b_folio;
> > new_offset = offset_in_folio(new_folio, bh_in->b_data);
> > + mapped_data = kmap_local_folio(new_folio, new_offset);
> > }
> >
> > - mapped_data = kmap_local_folio(new_folio, new_offset);
> > /*
> > * Fire data frozen trigger if data already wasn't frozen. Do this
> > * before checking for escaping, as the trigger may modify the magic
> > @@ -373,7 +374,8 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
> > */
> > if (*((__be32 *)mapped_data) == cpu_to_be32(JBD2_MAGIC_NUMBER))
> > do_escape = 1;
> > - kunmap_local(mapped_data);
> > + if (!jh_in->b_frozen_data)
> > + kunmap_local(mapped_data);
> >
> > /*
> > * Do we need to do a data copy?
> > --
> > 2.30.0
> >
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
