f2fs: do not skip dentry block writes

Previously, we skip dentry block writes when wbc is SYNC_NONE with no memory
pressure and the number of dirty pages is pretty small.

But, we didn't skip for normal data writes, which gives us not much big impact
on overall performance.
Moreover, by skipping some data writes, kworker falls into infinite loop to try
to write blocks, when many dir inodes have only one dentry block.

So, this patch removes skipping data writes.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1340,11 +1340,6 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 	if (!get_dirty_pages(inode) && wbc->sync_mode == WB_SYNC_NONE)
 		return 0;
 
-	if (S_ISDIR(inode->i_mode) && wbc->sync_mode == WB_SYNC_NONE &&
-			get_dirty_pages(inode) < nr_pages_to_skip(sbi, DATA) &&
-			available_free_memory(sbi, DIRTY_DENTS))
-		goto skip_write;
-
 	/* during POR, we don't need to trigger writepage at all. */
 	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
 		goto skip_write;

fs/f2fs/node.c

@@ -52,11 +52,6 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int type)
 		mem_size = (nm_i->nat_cnt * sizeof(struct nat_entry)) >>
 							PAGE_CACHE_SHIFT;
 		res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 2);
-	} else if (type == DIRTY_DENTS) {
-		if (sbi->sb->s_bdi->wb.dirty_exceeded)
-			return false;
-		mem_size = get_pages(sbi, F2FS_DIRTY_DENTS);
-		res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 1);
 	} else if (type == INO_ENTRIES) {
 		int i;
 

fs/f2fs/node.h

@@ -118,7 +118,6 @@ static inline void raw_nat_from_node_info(struct f2fs_nat_entry *raw_ne,
 enum mem_type {
 	FREE_NIDS,	/* indicates the free nid list */
 	NAT_ENTRIES,	/* indicates the cached nat entry */
-	DIRTY_DENTS,	/* indicates dirty dentry pages */
 	INO_ENTRIES,	/* indicates inode entries */
 	EXTENT_CACHE,	/* indicates extent cache */
 	BASE_CHECK,	/* check kernel status */

fs/f2fs/segment.h

@@ -697,9 +697,7 @@ static inline int nr_pages_to_skip(struct f2fs_sb_info *sbi, int type)
 	if (sbi->sb->s_bdi->wb.dirty_exceeded)
 		return 0;
 
-	if (type == DATA)
-		return sbi->blocks_per_seg;
-	else if (type == NODE)
+	if (type == NODE)
 		return 3 * sbi->blocks_per_seg;
 	else if (type == META)
 		return MAX_BIO_BLOCKS(sbi);