On martedì 5 luglio 2022 21:04:04 CEST Ira Weiny wrote:
> On Mon, Jul 04, 2022 at 05:23:22PM +0200, 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 zstd.c because in
this
> > file the mappings are per thread and are not visible in other contexts.
In
> > the meanwhile use plain page_address() on pages allocated with the
GFP_NOFS
> > flag instead of calling kmap*() on them (since they are always
allocated
> > from ZONE_NORMAL).
> >
> > Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and
> > booting a kernel with HIGHMEM64G enabled.
> >
> > Cc: Filipe Manana <fdmanana@xxxxxxxxxx>
> > Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> > ---
> > fs/btrfs/zstd.c | 34 ++++++++++++++--------------------
> > 1 file changed, 14 insertions(+), 20 deletions(-)
> >
> > diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
> > index 0fe31a6f6e68..78e0272e770e 100644
> > --- a/fs/btrfs/zstd.c
> > +++ b/fs/btrfs/zstd.c
> > @@ -403,7 +403,7 @@ int zstd_compress_pages(struct list_head *ws,
struct address_space *mapping,
> >
> > /* map in the first page of input data */
> > in_page = find_get_page(mapping, start >> PAGE_SHIFT);
> > - workspace->in_buf.src = kmap(in_page);
> > + workspace->in_buf.src = kmap_local_page(in_page);
> > workspace->in_buf.pos = 0;
> > workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
> >
> > @@ -415,7 +415,7 @@ int zstd_compress_pages(struct list_head *ws,
struct address_space *mapping,
> > goto out;
> > }
> > pages[nr_pages++] = out_page;
> > - workspace->out_buf.dst = kmap(out_page);
> > + workspace->out_buf.dst = page_address(out_page);
> > workspace->out_buf.pos = 0;
> > workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
> >
> > @@ -450,9 +450,7 @@ int zstd_compress_pages(struct list_head *ws,
struct address_space *mapping,
> > if (workspace->out_buf.pos == workspace->out_buf.size)
{
> > tot_out += PAGE_SIZE;
> > max_out -= PAGE_SIZE;
> > - kunmap(out_page);
> > if (nr_pages == nr_dest_pages) {
> > - out_page = NULL;
> > ret = -E2BIG;
> > goto out;
> > }
> > @@ -462,7 +460,7 @@ int zstd_compress_pages(struct list_head *ws,
struct address_space *mapping,
> > goto out;
> > }
> > pages[nr_pages++] = out_page;
> > - workspace->out_buf.dst = kmap(out_page);
> > + workspace->out_buf.dst =
page_address(out_page);
> > workspace->out_buf.pos = 0;
> > workspace->out_buf.size = min_t(size_t,
max_out,
> >
PAGE_SIZE);
> > @@ -477,15 +475,15 @@ int zstd_compress_pages(struct list_head *ws,
struct address_space *mapping,
> > /* Check if we need more input */
> > if (workspace->in_buf.pos == workspace->in_buf.size) {
> > tot_in += PAGE_SIZE;
> > - kunmap(in_page);
> > + kunmap_local(workspace->in_buf.src);
> > put_page(in_page);
> > -
> > start += PAGE_SIZE;
> > len -= PAGE_SIZE;
> > in_page = find_get_page(mapping, start >>
PAGE_SHIFT);
> > - workspace->in_buf.src = kmap(in_page);
> > + workspace->in_buf.src =
kmap_local_page(in_page);
> > workspace->in_buf.pos = 0;
> > workspace->in_buf.size = min_t(size_t, len,
PAGE_SIZE);
> > + workspace->out_buf.dst =
page_address(out_page);
>
> Why is this needed?
Sorry. This initialization is not needed at all.
Probably made a mistake with copy-pasting snippets of code.
I'm going to send ASAP the fifth version of this series.
> The rest looks good,
Thanks,
Fabio
> Ira
>
> [snip]
>
