Re: [RFC PATCH v2 1/3] btrfs: Convert zlib_decompress_bio() to use kmap_local_page()

[Fabio M. De Francesco]

On venerdì 17 giugno 2022 14:51:03 CEST Qu Wenruo wrote:
> 
> On 2022/6/17 20:05, Fabio M. De Francesco wrote:
> > The use of kmap() is being deprecated in favor of kmap_local_page(). 
With
> > kmap_local_page(), the mapping is per thread, CPU local and not 
globally
> > visible.
> >
> > Therefore, use kmap_local_page() / kunmap_local() in 
zlib_decompress_bio()
> > because in this function the mappings are per thread and are not 
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@xxxxxxxxx>
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> 
> Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
> 

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

Fabio

> 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, 
struct compressed_bio *cb)
> >   	unsigned long buf_start;
> >   	struct page **pages_in = cb->compressed_pages;
> >
> > -	data_in = kmap(pages_in[page_in_index]);
> > +	data_in = kmap_local_page(pages_in[page_in_index]);
> >   	workspace->strm.next_in = data_in;
> >   	workspace->strm.avail_in = min_t(size_t, srclen, PAGE_SIZE);
> >   	workspace->strm.total_in = 0;
> > @@ -309,7 +309,7 @@ int zlib_decompress_bio(struct list_head *ws, 
struct compressed_bio *cb)
> >
> >   	if (Z_OK != 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, 
struct compressed_bio *cb)
> >
> >   		if (workspace->strm.avail_in == 0) {
> >   			unsigned long tmp;
> > -			kunmap(pages_in[page_in_index]);
> > +			kunmap_local(data_in);
> >   			page_in_index++;
> >   			if (page_in_index >= total_pages_in) {
> >   				data_in = NULL;
> >   				break;
> >   			}
> > -			data_in = kmap(pages_in[page_in_index]);
> > +			data_in = 
kmap_local_page(pages_in[page_in_index]);
> >   			workspace->strm.next_in = data_in;
> >   			tmp = srclen - workspace->strm.total_in;
> >   			workspace->strm.avail_in = min(tmp, 
PAGE_SIZE);
> > @@ -355,7 +355,7 @@ int zlib_decompress_bio(struct list_head *ws, 
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;
>