f2fs: use blk_plug in all the possible paths

This patch reverts 19a5f5e2 (f2fs: drop any block plugging),
and adds blk_plug in write paths additionally.

The main reason is that blk_start_plug can be used to wake up from low-power
mode before submitting further bios.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -265,6 +265,7 @@ static int f2fs_write_meta_pages(struct address_space *mapping,
 				struct writeback_control *wbc)
 {
 	struct f2fs_sb_info *sbi = F2FS_M_SB(mapping);
+	struct blk_plug plug;
 	long diff, written;
 
 	/* collect a number of dirty meta pages and write together */
@@ -277,7 +278,9 @@ static int f2fs_write_meta_pages(struct address_space *mapping,
 	/* if mounting is failed, skip writing node pages */
 	mutex_lock(&sbi->cp_mutex);
 	diff = nr_pages_to_write(sbi, META, wbc);
+	blk_start_plug(&plug);
 	written = sync_meta_pages(sbi, META, wbc->nr_to_write);
+	blk_finish_plug(&plug);
 	mutex_unlock(&sbi->cp_mutex);
 	wbc->nr_to_write = max((long)0, wbc->nr_to_write - written - diff);
 	return 0;
@@ -899,8 +902,11 @@ static int block_operations(struct f2fs_sb_info *sbi)
 		.nr_to_write = LONG_MAX,
 		.for_reclaim = 0,
 	};
+	struct blk_plug plug;
 	int err = 0;
 
+	blk_start_plug(&plug);
+
 retry_flush_dents:
 	f2fs_lock_all(sbi);
 	/* write all the dirty dentry pages */
@@ -937,6 +943,7 @@ static int block_operations(struct f2fs_sb_info *sbi)
 		goto retry_flush_nodes;
 	}
 out:
+	blk_finish_plug(&plug);
 	return err;
 }
 

fs/f2fs/data.c

@@ -1438,6 +1438,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 {
 	struct inode *inode = mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	struct blk_plug plug;
 	int ret;
 
 	/* deal with chardevs and other special file */
@@ -1463,7 +1464,9 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 
 	trace_f2fs_writepages(mapping->host, wbc, DATA);
 
+	blk_start_plug(&plug);
 	ret = f2fs_write_cache_pages(mapping, wbc);
+	blk_finish_plug(&plug);
 	/*
 	 * if some pages were truncated, we cannot guarantee its mapping->host
 	 * to detect pending bios.

fs/f2fs/file.c

@@ -2102,6 +2102,7 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
+	struct blk_plug plug;
 	ssize_t ret;
 
 	if (f2fs_encrypted_inode(inode) &&
@@ -2113,8 +2114,11 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ret = generic_write_checks(iocb, from);
 	if (ret > 0) {
 		ret = f2fs_preallocate_blocks(iocb, from);
-		if (!ret)
+		if (!ret) {
+			blk_start_plug(&plug);
 			ret = __generic_file_write_iter(iocb, from);
+			blk_finish_plug(&plug);
+		}
 	}
 	inode_unlock(inode);
 

fs/f2fs/gc.c

@@ -808,6 +808,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 {
 	struct page *sum_page;
 	struct f2fs_summary_block *sum;
+	struct blk_plug plug;
 	unsigned int segno = start_segno;
 	unsigned int end_segno = start_segno + sbi->segs_per_sec;
 	int seg_freed = 0;
@@ -825,6 +826,8 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 		unlock_page(sum_page);
 	}
 
+	blk_start_plug(&plug);
+
 	for (segno = start_segno; segno < end_segno; segno++) {
 
 		if (get_valid_blocks(sbi, segno, 1) == 0)
@@ -862,6 +865,8 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 		f2fs_submit_merged_bio(sbi,
 				(type == SUM_TYPE_NODE) ? NODE : DATA, WRITE);
 
+	blk_finish_plug(&plug);
+
 	if (gc_type == FG_GC) {
 		while (start_segno < end_segno)
 			if (get_valid_blocks(sbi, start_segno++, 1) == 0)

fs/f2fs/node.c

@@ -1618,6 +1618,7 @@ static int f2fs_write_node_pages(struct address_space *mapping,
 			    struct writeback_control *wbc)
 {
 	struct f2fs_sb_info *sbi = F2FS_M_SB(mapping);
+	struct blk_plug plug;
 	long diff;
 
 	/* balancing f2fs's metadata in background */
@@ -1631,7 +1632,9 @@ static int f2fs_write_node_pages(struct address_space *mapping,
 
 	diff = nr_pages_to_write(sbi, NODE, wbc);
 	wbc->sync_mode = WB_SYNC_NONE;
+	blk_start_plug(&plug);
 	sync_node_pages(sbi, wbc);
+	blk_finish_plug(&plug);
 	wbc->nr_to_write = max((long)0, wbc->nr_to_write - diff);
 	return 0;
 

fs/f2fs/segment.c

@@ -381,8 +381,13 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
 			excess_prefree_segs(sbi) ||
 			excess_dirty_nats(sbi) ||
 			(is_idle(sbi) && f2fs_time_over(sbi, CP_TIME))) {
-		if (test_opt(sbi, DATA_FLUSH))
+		if (test_opt(sbi, DATA_FLUSH)) {
+			struct blk_plug plug;
+
+			blk_start_plug(&plug);
 			sync_dirty_inodes(sbi, FILE_INODE);
+			blk_finish_plug(&plug);
+		}
 		f2fs_sync_fs(sbi->sb, true);
 		stat_inc_bg_cp_count(sbi->stat_info);
 	}