f2fs: return error during fill_super

BugLink: https://bugs.launchpad.net/bugs/1818797

commit c39a1b34 upstream.

Let's avoid BUG_ON during fill_super, when on-disk was totall corrupted.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

fs/f2fs/segment.c

@@ -2101,7 +2101,7 @@ static int build_curseg(struct f2fs_sb_info *sbi)
 	return restore_curseg_summaries(sbi);
 }
 
-static void build_sit_entries(struct f2fs_sb_info *sbi)
+static int build_sit_entries(struct f2fs_sb_info *sbi)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
 	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_COLD_DATA);
@@ -2110,6 +2110,7 @@ static void build_sit_entries(struct f2fs_sb_info *sbi)
 	unsigned int i, start, end;
 	unsigned int readed, start_blk = 0;
 	int nrpages = MAX_BIO_BLOCKS(sbi);
+	int err = 0;
 
 	do {
 		readed = ra_meta_pages(sbi, start_blk, nrpages, META_SIT, true);
@@ -2128,7 +2129,9 @@ static void build_sit_entries(struct f2fs_sb_info *sbi)
 			sit = sit_blk->entries[SIT_ENTRY_OFFSET(sit_i, start)];
 			f2fs_put_page(page, 1);
 
-			check_block_count(sbi, start, &sit);
+			err = check_block_count(sbi, start, &sit);
+			if (err)
+				return err;
 			seg_info_from_raw_sit(se, &sit);
 
 			/* build discard map only one time */
@@ -2154,7 +2157,9 @@ static void build_sit_entries(struct f2fs_sb_info *sbi)
 
 		old_valid_blocks = se->valid_blocks;
 
-		check_block_count(sbi, start, &sit);
+		err = check_block_count(sbi, start, &sit);
+		if (err)
+			break;
 		seg_info_from_raw_sit(se, &sit);
 
 		memcpy(se->discard_map, se->cur_valid_map, SIT_VBLOCK_MAP_SIZE);
@@ -2165,6 +2170,7 @@ static void build_sit_entries(struct f2fs_sb_info *sbi)
 				se->valid_blocks - old_valid_blocks;
 	}
 	mutex_unlock(&curseg->curseg_mutex);
+	return err;
 }
 
 static void init_free_segmap(struct f2fs_sb_info *sbi)
@@ -2326,7 +2332,9 @@ int build_segment_manager(struct f2fs_sb_info *sbi)
 		return err;
 
 	/* reinit free segmap based on SIT */
-	build_sit_entries(sbi);
+	err = build_sit_entries(sbi);
+	if (err)
+		return err;
 
 	init_free_segmap(sbi);
 	err = build_dirty_segmap(sbi);

fs/f2fs/segment.h

@@ -585,7 +585,7 @@ static inline void verify_block_addr(struct f2fs_sb_info *sbi, block_t blk_addr)
 /*
  * Summary block is always treated as an invalid block
  */
-static inline void check_block_count(struct f2fs_sb_info *sbi,
+static inline int check_block_count(struct f2fs_sb_info *sbi,
 		int segno, struct f2fs_sit_entry *raw_sit)
 {
 #ifdef CONFIG_F2FS_CHECK_FS
@@ -607,11 +607,25 @@ static inline void check_block_count(struct f2fs_sb_info *sbi,
 		cur_pos = next_pos;
 		is_valid = !is_valid;
 	} while (cur_pos < sbi->blocks_per_seg);
-	BUG_ON(GET_SIT_VBLOCKS(raw_sit) != valid_blocks);
+
+	if (unlikely(GET_SIT_VBLOCKS(raw_sit) != valid_blocks)) {
+		f2fs_msg(sbi->sb, KERN_ERR,
+				"Mismatch valid blocks %d vs. %d",
+					GET_SIT_VBLOCKS(raw_sit), valid_blocks);
+		set_sbi_flag(sbi, SBI_NEED_FSCK);
+		return -EINVAL;
+	}
 #endif
 	/* check segment usage, and check boundary of a given segment number */
-	f2fs_bug_on(sbi, GET_SIT_VBLOCKS(raw_sit) > sbi->blocks_per_seg
-					|| segno > TOTAL_SEGS(sbi) - 1);
+	if (unlikely(GET_SIT_VBLOCKS(raw_sit) > sbi->blocks_per_seg
+					|| segno > TOTAL_SEGS(sbi) - 1)) {
+		f2fs_msg(sbi->sb, KERN_ERR,
+				"Wrong valid blocks %d or segno %u",
+					GET_SIT_VBLOCKS(raw_sit), segno);
+		set_sbi_flag(sbi, SBI_NEED_FSCK);
+		return -EINVAL;
+	}
+	return 0;
 }
 
 static inline pgoff_t current_sit_addr(struct f2fs_sb_info *sbi,