2022-07-16 20:51:23

by Fabio M. De Francesco

Subject: [PATCH] f2fs: Use memcpy_page() in f2fs_copy_page()

The use of kmap() is being deprecated in favor of kmap_local_page().

Two main problems with kmap(): (1) It comes with an overhead as mapping
space is restricted and protected by a global lock for synchronization and
(2) it also requires global TLB invalidation when the kmap’s pool wraps
and it might block when the mapping space is fully utilized until a slot
becomes available.

Therefore, replace kmap() with kmap_local_page() in f2fs_copy_page() and
use memcpy_page() instead of open coding kmap_local_page() + memcpy().

Suggested-by: Ira Weiny <[email protected]>
Signed-off-by: Fabio M. De Francesco <[email protected]>
---
fs/f2fs/f2fs.h | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d9bbecd008d2..f04e760bb1c1 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2698,12 +2698,8 @@ static inline struct page *f2fs_pagecache_get_page(

static inline void f2fs_copy_page(struct page *src, struct page *dst)
{
- char *src_kaddr = kmap(src);
- char *dst_kaddr = kmap(dst);

- memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
- kunmap(dst);
- kunmap(src);
+ memcpy_page(dst, 0, src, 0, PAGE_SIZE);
}

static inline void f2fs_put_page(struct page *page, int unlock)
--
2.37.1

2022-07-17 07:03:24

by Christoph Hellwig

Subject: Re: [PATCH] f2fs: Use memcpy_page() in f2fs_copy_page()

On Sat, Jul 16, 2022 at 10:43:53PM +0200, Fabio M. De Francesco wrote:
> static inline void f2fs_copy_page(struct page *src, struct page *dst)
> {
> - char *src_kaddr = kmap(src);
> - char *dst_kaddr = kmap(dst);
>
> - memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> - kunmap(dst);
> - kunmap(src);
> + memcpy_page(dst, 0, src, 0, PAGE_SIZE);

Please remove f2fs_copy_page entirely and open code this in the only
caller.

2022-07-17 08:47:56

by Fabio M. De Francesco

Subject: Re: [PATCH] f2fs: Use memcpy_page() in f2fs_copy_page()

On domenica 17 luglio 2022 08:55:20 CEST Christoph Hellwig wrote:
> On Sat, Jul 16, 2022 at 10:43:53PM +0200, Fabio M. De Francesco wrote:
> > static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > {
> > - char *src_kaddr = kmap(src);
> > - char *dst_kaddr = kmap(dst);
> >
> > - memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > - kunmap(dst);
> > - kunmap(src);
> > + memcpy_page(dst, 0, src, 0, PAGE_SIZE);
>
> Please remove f2fs_copy_page entirely and open code this in the only
> caller.
>
I've changed the subject of the new patch, therefore we won't have a second
version of this:

"f2fs: Delete f2fs_copy_page() and replace with memcpy_page()" is at
https://lore.kernel.org/lkml/[email protected]/

Thanks for your suggestion,

Fabio