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.
Honza
> ---
> fs/jbd2/journal.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> 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
