f2fs: compress: reduce one page array alloc and free when write compressed page

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>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/compress.c

@@ -154,6 +154,7 @@ 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;
 }
@@ -620,7 +621,6 @@ 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;
 
@@ -635,6 +635,7 @@ 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) {
@@ -685,13 +686,6 @@ 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) -
@@ -701,10 +695,8 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
 	vm_unmap_ram(cc->rbuf, cc->cluster_size);
 
 	for (i = 0; i < cc->nr_cpages; i++) {
-		if (i < new_nr_cpages) {
-			new_cpages[i] = cc->cpages[i];
+		if (i < new_nr_cpages)
 			continue;
-		}
 		f2fs_compress_free_page(cc->cpages[i]);
 		cc->cpages[i] = NULL;
 	}
@@ -712,9 +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);
@@ -1308,14 +1298,14 @@ 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];
@@ -1360,7 +1350,7 @@ 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);
@@ -1385,8 +1375,8 @@ 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)
@@ -1424,9 +1414,7 @@ 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++) {
-		if (!cc->cpages[i])
-			continue;
+	for (i = 0; i < cc->valid_nr_cpages; i++) {
 		f2fs_compress_free_page(cc->cpages[i]);
 		cc->cpages[i] = NULL;
 	}

fs/f2fs/data.c

@@ -2987,6 +2987,7 @@ 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,

fs/f2fs/f2fs.h

@@ -1486,6 +1486,7 @@ 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 */