f2fs: invalidate temporary meta page

To avoid meeting garbage data in next free node block at the end of warm
node chain when doing recovery, we will try to zero out that invalid block.

If the device is not support discard, our way for zeroing out block is:
grabbing a temporary zeroed page in meta inode, then, issue write request
with this page.

But, we forget to release that temporary page, so our memory usage will
increase without gaining any hit ratio benefit, so it's better to free it
for saving memory.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -896,12 +896,15 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	__u32 crc32 = 0;
 	int i;
 	int cp_payload_blks = __cp_payload(sbi);
+	block_t discard_blk = NEXT_FREE_BLKADDR(sbi, curseg);
+	bool invalidate = false;
 
 	/*
 	 * This avoids to conduct wrong roll-forward operations and uses
 	 * metapages, so should be called prior to sync_meta_pages below.
 	 */
-	discard_next_dnode(sbi, NEXT_FREE_BLKADDR(sbi, curseg));
+	if (discard_next_dnode(sbi, discard_blk))
+		invalidate = true;
 
 	/* Flush all the NAT/SIT pages */
 	while (get_pages(sbi, F2FS_DIRTY_META)) {
@@ -1030,6 +1033,14 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	/* wait for previous submitted meta pages writeback */
 	wait_on_all_pages_writeback(sbi);
 
+	/*
+	 * invalidate meta page which is used temporarily for zeroing out
+	 * block at the end of warm node chain.
+	 */
+	if (invalidate)
+		invalidate_mapping_pages(META_MAPPING(sbi), discard_blk,
+								discard_blk);
+
 	release_dirty_inode(sbi);
 
 	if (unlikely(f2fs_cp_error(sbi)))

fs/f2fs/f2fs.h

@@ -1707,7 +1707,7 @@ void invalidate_blocks(struct f2fs_sb_info *, block_t);
 void refresh_sit_entry(struct f2fs_sb_info *, block_t, block_t);
 void clear_prefree_segments(struct f2fs_sb_info *, struct cp_control *);
 void release_discard_addrs(struct f2fs_sb_info *);
-void discard_next_dnode(struct f2fs_sb_info *, block_t);
+bool discard_next_dnode(struct f2fs_sb_info *, block_t);
 int npages_for_summary_flush(struct f2fs_sb_info *, bool);
 void allocate_new_segments(struct f2fs_sb_info *);
 int f2fs_trim_fs(struct f2fs_sb_info *, struct fstrim_range *);

fs/f2fs/recovery.c

@@ -561,11 +561,20 @@ out:
 
 	clear_sbi_flag(sbi, SBI_POR_DOING);
 	if (err) {
-		discard_next_dnode(sbi, blkaddr);
+		bool invalidate = false;
+
+		if (discard_next_dnode(sbi, blkaddr))
+			invalidate = true;
 
 		/* Flush all the NAT/SIT pages */
 		while (get_pages(sbi, F2FS_DIRTY_META))
 			sync_meta_pages(sbi, META, LONG_MAX);
+
+		/* invalidate temporary meta page */
+		if (invalidate)
+			invalidate_mapping_pages(META_MAPPING(sbi),
+							blkaddr, blkaddr);
+
 		set_ckpt_flags(sbi->ckpt, CP_ERROR_FLAG);
 		mutex_unlock(&sbi->cp_mutex);
 	} else if (need_writecp) {

fs/f2fs/segment.c

@@ -514,7 +514,7 @@ static int f2fs_issue_discard(struct f2fs_sb_info *sbi,
 	return blkdev_issue_discard(sbi->sb->s_bdev, start, len, GFP_NOFS, 0);
 }
 
-void discard_next_dnode(struct f2fs_sb_info *sbi, block_t blkaddr)
+bool discard_next_dnode(struct f2fs_sb_info *sbi, block_t blkaddr)
 {
 	int err = -ENOTSUPP;
 
@@ -524,13 +524,16 @@ void discard_next_dnode(struct f2fs_sb_info *sbi, block_t blkaddr)
 		unsigned int offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
 
 		if (f2fs_test_bit(offset, se->discard_map))
-			return;
+			return false;
 
 		err = f2fs_issue_discard(sbi, blkaddr, 1);
 	}
 
-	if (err)
+	if (err) {
 		update_meta_page(sbi, NULL, blkaddr);
+		return true;
+	}
+	return false;
 }
 
 static void __add_discard_entry(struct f2fs_sb_info *sbi,