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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        Nick Terrell <terrelln@fb.com>,
        Chris Down <chris@chrisdown.name>,
        Filipe Manana <fdmanana@suse.com>, Qu Wenruo <wqu@suse.com>,
        Nikolay Borisov <nborisov@suse.com>,
        Gabriel Niebler <gniebler@suse.com>,
        Ira Weiny <ira.weiny@intel.com>, linux-btrfs@vger.kernel.org,
        linux-kernel@vger.kernel.org, Qu Wenruo <quwenruo.btrfs@gmx.com>
Subject: Re: [RFC PATCH v2 1/3] btrfs: Convert zlib_decompress_bio() to use kmap_local_page()
Date:   Fri, 17 Jun 2022 19:35:42 +0200
Message-ID: <13038994.uLZWGnKmhe@opensuse>
In-Reply-To: <f1e0383b-b68e-2044-8e1c-22ea4950c3c6@gmx.com>
References: <20220617120538.18091-1-fmdefrancesco@gmail.com> <20220617120538.18091-2-fmdefrancesco@gmail.com> <f1e0383b-b68e-2044-8e1c-22ea4950c3c6@gmx.com>
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On venerd=C3=AC 17 giugno 2022 14:51:03 CEST Qu Wenruo wrote:
>=20
> On 2022/6/17 20:05, Fabio M. De Francesco wrote:
> > The use of kmap() is being deprecated in favor of kmap_local_page().=20
With
> > kmap_local_page(), the mapping is per thread, CPU local and not=20
globally
> > visible.
> >
> > Therefore, use kmap_local_page() / kunmap_local() in=20
zlib_decompress_bio()
> > because in this function the mappings are per thread and are not=20
visible
> > in other contexts.
> >
> > Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and
> > HIGHMEM64G enabled. This patch passes 26/26 tests of group "compress".
> >
> > Suggested-by: Ira Weiny <ira.weiny@intel.com>
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
>=20
> Reviewed-by: Qu Wenruo <wqu@suse.com>
>=20

Thanks for your review.
I'll forward your tag on to the "real" patch.

=46abio

> Thanks,
> Qu
> > ---
> >   fs/btrfs/zlib.c | 10 +++++-----
> >   1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
> > index 767a0c6c9694..770c4c6bbaef 100644
> > --- a/fs/btrfs/zlib.c
> > +++ b/fs/btrfs/zlib.c
> > @@ -287,7 +287,7 @@ int zlib_decompress_bio(struct list_head *ws,=20
struct compressed_bio *cb)
> >   	unsigned long buf_start;
> >   	struct page **pages_in =3D cb->compressed_pages;
> >
> > -	data_in =3D kmap(pages_in[page_in_index]);
> > +	data_in =3D kmap_local_page(pages_in[page_in_index]);
> >   	workspace->strm.next_in =3D data_in;
> >   	workspace->strm.avail_in =3D min_t(size_t, srclen, PAGE_SIZE);
> >   	workspace->strm.total_in =3D 0;
> > @@ -309,7 +309,7 @@ int zlib_decompress_bio(struct list_head *ws,=20
struct compressed_bio *cb)
> >
> >   	if (Z_OK !=3D zlib_inflateInit2(&workspace->strm, wbits)) {
> >   		pr_warn("BTRFS: inflateInit failed\n");
> > -		kunmap(pages_in[page_in_index]);
> > +		kunmap_local(data_in);
> >   		return -EIO;
> >   	}
> >   	while (workspace->strm.total_in < srclen) {
> > @@ -336,13 +336,13 @@ int zlib_decompress_bio(struct list_head *ws,=20
struct compressed_bio *cb)
> >
> >   		if (workspace->strm.avail_in =3D=3D 0) {
> >   			unsigned long tmp;
> > -			kunmap(pages_in[page_in_index]);
> > +			kunmap_local(data_in);
> >   			page_in_index++;
> >   			if (page_in_index >=3D total_pages_in) {
> >   				data_in =3D NULL;
> >   				break;
> >   			}
> > -			data_in =3D kmap(pages_in[page_in_index]);
> > +			data_in =3D=20
kmap_local_page(pages_in[page_in_index]);
> >   			workspace->strm.next_in =3D data_in;
> >   			tmp =3D srclen - workspace->strm.total_in;
> >   			workspace->strm.avail_in =3D min(tmp,=20
PAGE_SIZE);
> > @@ -355,7 +355,7 @@ int zlib_decompress_bio(struct list_head *ws,=20
struct compressed_bio *cb)
> >   done:
> >   	zlib_inflateEnd(&workspace->strm);
> >   	if (data_in)
> > -		kunmap(pages_in[page_in_index]);
> > +		kunmap_local(data_in);
> >   	if (!ret)
> >   		zero_fill_bio(cb->orig_bio);
> >   	return ret;
>=20