Re: [f2fs-dev] [RFC PATCH] f2fs: compress: reduce one page array alloc and free when write compressed page

[Chao Yu <chao@kernel.org>]

On 2021/7/22 11:47, Fengnan Chang wrote:
> Don't alloc new page array to replace old, just use old page array, try
> to reduce one page array alloc and free when write compress page.

Nope, see whole story in below link:

https://lore.kernel.org/patchwork/patch/1305096/

Thanks,

> 
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
> ---
>   fs/f2fs/compress.c | 14 ++------------
>   fs/f2fs/f2fs.h     |  1 +
>   2 files changed, 3 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index 455561826c7d..43daafe382e7 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -618,7 +618,6 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>   	const struct f2fs_compress_ops *cops =
>   				f2fs_cops[fi->i_compress_algorithm];
>   	unsigned int max_len, new_nr_cpages;
> -	struct page **new_cpages;
>   	u32 chksum = 0;
>   	int i, ret;
>   
> @@ -633,6 +632,7 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>   
>   	max_len = COMPRESS_HEADER_SIZE + cc->clen;
>   	cc->nr_cpages = DIV_ROUND_UP(max_len, PAGE_SIZE);
> +	cc->raw_nr_cpages = cc->nr_cpages;
>   
>   	cc->cpages = page_array_alloc(cc->inode, cc->nr_cpages);
>   	if (!cc->cpages) {
> @@ -683,13 +683,6 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>   
>   	new_nr_cpages = DIV_ROUND_UP(cc->clen + COMPRESS_HEADER_SIZE, PAGE_SIZE);
>   
> -	/* Now we're going to cut unnecessary tail pages */
> -	new_cpages = page_array_alloc(cc->inode, new_nr_cpages);
> -	if (!new_cpages) {
> -		ret = -ENOMEM;
> -		goto out_vunmap_cbuf;
> -	}
> -
>   	/* zero out any unused part of the last page */
>   	memset(&cc->cbuf->cdata[cc->clen], 0,
>   			(new_nr_cpages * PAGE_SIZE) -
> @@ -700,7 +693,6 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>   
>   	for (i = 0; i < cc->nr_cpages; i++) {
>   		if (i < new_nr_cpages) {
> -			new_cpages[i] = cc->cpages[i];
>   			continue;
>   		}
>   		f2fs_compress_free_page(cc->cpages[i]);
> @@ -710,8 +702,6 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
>   	if (cops->destroy_compress_ctx)
>   		cops->destroy_compress_ctx(cc);
>   
> -	page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
> -	cc->cpages = new_cpages;
>   	cc->nr_cpages = new_nr_cpages;
>   
>   	trace_f2fs_compress_pages_end(cc->inode, cc->cluster_idx,
> @@ -1330,7 +1320,7 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
>   	spin_unlock(&fi->i_size_lock);
>   
>   	f2fs_put_rpages(cc);
> -	page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
> +	page_array_free(cc->inode, cc->cpages, cc->raw_nr_cpages);
>   	cc->cpages = NULL;
>   	f2fs_destroy_compress_ctx(cc, false);
>   	return 0;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 867f2c5d9559..8b1f84d88a65 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1454,6 +1454,7 @@ struct compress_ctx {
>   	unsigned int nr_rpages;		/* total page number in rpages */
>   	struct page **cpages;		/* pages store compressed data in cluster */
>   	unsigned int nr_cpages;		/* total page number in cpages */
> +	unsigned int raw_nr_cpages;	/* max total page number in cpages */
>   	void *rbuf;			/* virtual mapped address on rpages */
>   	struct compress_data *cbuf;	/* virtual mapped address on cpages */
>   	size_t rlen;			/* valid data length in rbuf */
> 


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