[PATCH 2/2] jffs2: Use a folio in jffs2_garbage_collect_dnode()

[Zhihao Cheng]

在 2024/8/15 3:59, Matthew Wilcox (Oracle) 写道:
> Call read_cache_folio() instead of read_cache_page() to get the folio
> containing the page.  No attempt is made here to support large folios
> as I assume that will never be interesting for jffs2.  Includes a switch
> from kmap to kmap_local which looks safe.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org>
> ---
>   fs/jffs2/gc.c | 25 ++++++++++++-------------
>   1 file changed, 12 insertions(+), 13 deletions(-)

Reviewed-by: Zhihao Cheng <chengzhihao1 at huawei.com>
> 
> diff --git a/fs/jffs2/gc.c b/fs/jffs2/gc.c
> index 5c6602f3c189..822949d0eb00 100644
> --- a/fs/jffs2/gc.c
> +++ b/fs/jffs2/gc.c
> @@ -1171,7 +1171,7 @@ static int jffs2_garbage_collect_dnode(struct jffs2_sb_info *c, struct jffs2_era
>   	uint32_t alloclen, offset, orig_end, orig_start;
>   	int ret = 0;
>   	unsigned char *comprbuf = NULL, *writebuf;
> -	struct page *page;
> +	struct folio *folio;
>   	unsigned char *pg_ptr;
>   
>   	memset(&ri, 0, sizeof(ri));
> @@ -1317,25 +1317,25 @@ static int jffs2_garbage_collect_dnode(struct jffs2_sb_info *c, struct jffs2_era
>   		BUG_ON(start > orig_start);
>   	}
>   
> -	/* The rules state that we must obtain the page lock *before* f->sem, so
> +	/* The rules state that we must obtain the folio lock *before* f->sem, so
>   	 * drop f->sem temporarily. Since we also hold c->alloc_sem, nothing's
>   	 * actually going to *change* so we're safe; we only allow reading.
>   	 *
>   	 * It is important to note that jffs2_write_begin() will ensure that its
> -	 * page is marked Uptodate before allocating space. That means that if we
> -	 * end up here trying to GC the *same* page that jffs2_write_begin() is
> -	 * trying to write out, read_cache_page() will not deadlock. */
> +	 * folio is marked uptodate before allocating space. That means that if we
> +	 * end up here trying to GC the *same* folio that jffs2_write_begin() is
> +	 * trying to write out, read_cache_folio() will not deadlock. */
>   	mutex_unlock(&f->sem);
> -	page = read_cache_page(inode->i_mapping, start >> PAGE_SHIFT,
> +	folio = read_cache_folio(inode->i_mapping, start >> PAGE_SHIFT,
>   			       __jffs2_read_folio, NULL);
> -	if (IS_ERR(page)) {
> -		pr_warn("read_cache_page() returned error: %ld\n",
> -			PTR_ERR(page));
> +	if (IS_ERR(folio)) {
> +		pr_warn("read_cache_folio() returned error: %ld\n",
> +			PTR_ERR(folio));
>   		mutex_lock(&f->sem);
> -		return PTR_ERR(page);
> +		return PTR_ERR(folio);
>   	}
>   
> -	pg_ptr = kmap(page);
> +	pg_ptr = kmap_local_folio(folio, 0);
>   	mutex_lock(&f->sem);
>   
>   	offset = start;
> @@ -1400,7 +1400,6 @@ static int jffs2_garbage_collect_dnode(struct jffs2_sb_info *c, struct jffs2_era
>   		}
>   	}
>   
> -	kunmap(page);
> -	put_page(page);
> +	folio_release_kmap(folio, pg_ptr);
>   	return ret;
>   }
>