Re: [f2fs-dev] [PATCH v2] f2fs: compress: reduce one page array alloc and free when write compressed page

[Chao Yu <chao@kernel.org>]

On 2021/11/9 11:54, Fengnan Chang wrote:
> Don't alloc new page pointers array to replace old, just use old, introduce
> valid_nr_cpages to indicate valid number of page pointers in array, try to
> reduce one page array alloc and free when write compress page.
> 
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
> ---
>   fs/f2fs/compress.c | 27 +++++++++------------------
>   fs/f2fs/data.c     |  1 +
>   fs/f2fs/f2fs.h     |  1 +
>   3 files changed, 11 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index 9b663eaf4805..28785dd78c6f 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -153,6 +153,7 @@ void f2fs_destroy_compress_ctx(struct compress_ctx *cc, bool reuse)
>   	cc->rpages = NULL;
>   	cc->nr_rpages = 0;
>   	cc->nr_cpages = 0;
> +	cc->valid_nr_cpages = 0;
>   	if (!reuse)
>   		cc->cluster_idx = NULL_CLUSTER;
>   }
> @@ -619,7 +620,6 @@ 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;
>   
> @@ -634,6 +634,7 @@ 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->valid_nr_cpages = cc->nr_cpages;
>   
>   	cc->cpages = page_array_alloc(cc->inode, cc->nr_cpages);
>   	if (!cc->cpages) {
> @@ -684,13 +685,6 @@ 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;

It removes last user of out_vunmap_cbuf label, so we can remove below
dead codes in error path as well.

out_vunmap_cbuf:
	vm_unmap_ram(cc->cbuf, cc->nr_cpages);

> -	}
> -
>   	/* zero out any unused part of the last page */
>   	memset(&cc->cbuf->cdata[cc->clen], 0,
>   			(new_nr_cpages * PAGE_SIZE) -
> @@ -701,7 +695,6 @@ 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;
>   		}

if (i < new_nr_cpages)
	continue;

>   		f2fs_compress_free_page(cc->cpages[i]);
> @@ -711,9 +704,7 @@ 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;
> +	cc->valid_nr_cpages = new_nr_cpages;
>   
>   	trace_f2fs_compress_pages_end(cc->inode, cc->cluster_idx,
>   							cc->clen, ret);
> @@ -1288,14 +1279,14 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
>   
>   	cic->magic = F2FS_COMPRESSED_PAGE_MAGIC;
>   	cic->inode = inode;
> -	atomic_set(&cic->pending_pages, cc->nr_cpages);
> +	atomic_set(&cic->pending_pages, cc->valid_nr_cpages);
>   	cic->rpages = page_array_alloc(cc->inode, cc->cluster_size);
>   	if (!cic->rpages)
>   		goto out_put_cic;
>   
>   	cic->nr_rpages = cc->cluster_size;
>   
> -	for (i = 0; i < cc->nr_cpages; i++) {
> +	for (i = 0; i < cc->valid_nr_cpages; i++) {
>   		f2fs_set_compressed_page(cc->cpages[i], inode,
>   					cc->rpages[i + 1]->index, cic);
>   		fio.compressed_page = cc->cpages[i];
> @@ -1340,7 +1331,7 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
>   		if (fio.compr_blocks && __is_valid_data_blkaddr(blkaddr))
>   			fio.compr_blocks++;
>   
> -		if (i > cc->nr_cpages) {
> +		if (i > cc->valid_nr_cpages) {
>   			if (__is_valid_data_blkaddr(blkaddr)) {
>   				f2fs_invalidate_blocks(sbi, blkaddr);
>   				f2fs_update_data_blkaddr(&dn, NEW_ADDR);
> @@ -1365,8 +1356,8 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
>   
>   	if (fio.compr_blocks)
>   		f2fs_i_compr_blocks_update(inode, fio.compr_blocks - 1, false);
> -	f2fs_i_compr_blocks_update(inode, cc->nr_cpages, true);
> -	add_compr_block_stat(inode, cc->nr_cpages);
> +	f2fs_i_compr_blocks_update(inode, cc->valid_nr_cpages, true);
> +	add_compr_block_stat(inode, cc->valid_nr_cpages);
>   
>   	set_inode_flag(cc->inode, FI_APPEND_WRITE);
>   	if (cc->cluster_idx == 0)
> @@ -1404,7 +1395,7 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
>   	else
>   		f2fs_unlock_op(sbi);
>   out_free:
> -	for (i = 0; i < cc->nr_cpages; i++) {
> +	for (i = 0; i < cc->valid_nr_cpages; i++) {
>   		if (!cc->cpages[i])
>   			continue;

We can remove above cpages check?

Thanks,

>   		f2fs_compress_free_page(cc->cpages[i]);
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index f4fd6c246c9a..4ddc0ba0f2c0 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2934,6 +2934,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>   		.rpages = NULL,
>   		.nr_rpages = 0,
>   		.cpages = NULL,
> +		.valid_nr_cpages = 0,
>   		.rbuf = NULL,
>   		.cbuf = NULL,
>   		.rlen = PAGE_SIZE * F2FS_I(inode)->i_cluster_size,
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 039a229e11c9..acb587f054db 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1481,6 +1481,7 @@ 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 valid_nr_cpages;	/* valid 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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