Re: [PATCH] btrfs: fix the folio leak on S390 hardware acceleration

[Heiko Carstens <hca@linux.ibm.com>]

On Wed, Jan 21, 2026 at 09:22:47AM +1030, Qu Wenruo wrote:
> Adding S390 to the mailing list, I got the incorrect address in the initial
> patch.
> 
> Much appreciated if S390 people can give it a test.
> 
> Thanks,
> Qu
> 
> 在 2026/1/19 16:24, Qu Wenruo 写道:
> > [BUG]
> > After commit aa60fe12b4f4 ("btrfs: zlib: refactor S390x HW acceleration
> > buffer preparation"), we no longer release the folio of the page cache
> > of folio returned by btrfs_compress_filemap_get_folio() for S390
> > hardware accerlation path.
> > 
> > [CAUSE]
> > Before that commit, we call kumap_local() and folio_put() after handling
> > each folio.
> > 
> > Although the timing is not ideal (it release previous folio at the
> > beginning of the loop, and rely on some extra cleanup out of the loop),
> > it at least handles the folio release correctly.
> > 
> > Meanwhile the refactored code is easier to read, it lacks the call to
> > release the filemap folio.
> > 
> > [FIX]
> > Add the missing folio_put() for copy_data_into_buffer().
> > 
> > Cc: linux-s390@vger.kernel.orgaa60fe12b4f49f49fc73e5023f8675e2df1f7805
> > Fixes: aa60fe12b4f4 ("btrfs: zlib: refactor S390x HW acceleration buffer preparation")
> > Signed-off-by: Qu Wenruo <wqu@suse.com>
> > ---
> >   fs/btrfs/zlib.c | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
> > index 6caba8be7c84..10ed48d4a846 100644
> > --- a/fs/btrfs/zlib.c
> > +++ b/fs/btrfs/zlib.c
> > @@ -139,6 +139,7 @@ static int copy_data_into_buffer(struct address_space *mapping,
> >   		data_in = kmap_local_folio(folio, offset);
> >   		memcpy(workspace->buf + cur - filepos, data_in, copy_length);
> >   		kunmap_local(data_in);
> > +		folio_put(folio);
> >   		cur += copy_length;
> >   	}
> >   	return 0;

Mikhail, can you have a look at this, please?