f2fs: check in-memory sit version bitmap

This patch adds a mirror for sit version bitmap, and use it to detect
in-memory bitmap corruption which may be caused by bit-transition of
cache or memory overflow.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -2346,7 +2346,7 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
 	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
 	struct sit_info *sit_i;
 	unsigned int sit_segs, start;
-	char *src_bitmap, *dst_bitmap;
+	char *src_bitmap;
 	unsigned int bitmap_size;
 
 	/* allocate memory for SIT information */
@@ -2408,17 +2408,22 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
 	bitmap_size = __bitmap_size(sbi, SIT_BITMAP);
 	src_bitmap = __bitmap_ptr(sbi, SIT_BITMAP);
 
-	dst_bitmap = kmemdup(src_bitmap, bitmap_size, GFP_KERNEL);
-	if (!dst_bitmap)
+	sit_i->sit_bitmap = kmemdup(src_bitmap, bitmap_size, GFP_KERNEL);
+	if (!sit_i->sit_bitmap)
 		return -ENOMEM;
 
+#ifdef CONFIG_F2FS_CHECK_FS
+	sit_i->sit_bitmap_mir = kmemdup(src_bitmap, bitmap_size, GFP_KERNEL);
+	if (!sit_i->sit_bitmap_mir)
+		return -ENOMEM;
+#endif
+
 	/* init SIT information */
 	sit_i->s_ops = &default_salloc_ops;
 
 	sit_i->sit_base_addr = le32_to_cpu(raw_super->sit_blkaddr);
 	sit_i->sit_blocks = sit_segs << sbi->log_blocks_per_seg;
 	sit_i->written_valid_blocks = 0;
-	sit_i->sit_bitmap = dst_bitmap;
 	sit_i->bitmap_size = bitmap_size;
 	sit_i->dirty_sentries = 0;
 	sit_i->sents_per_block = SIT_ENTRY_PER_BLOCK;
@@ -2826,6 +2831,9 @@ static void destroy_sit_info(struct f2fs_sb_info *sbi)
 
 	SM_I(sbi)->sit_info = NULL;
 	kfree(sit_i->sit_bitmap);
+#ifdef CONFIG_F2FS_CHECK_FS
+	kfree(sit_i->sit_bitmap_mir);
+#endif
 	kfree(sit_i);
 }
 

fs/f2fs/segment.h

@@ -209,6 +209,9 @@ struct sit_info {
 	block_t sit_blocks;		/* # of blocks used by SIT area */
 	block_t written_valid_blocks;	/* # of valid blocks in main area */
 	char *sit_bitmap;		/* SIT bitmap pointer */
+#ifdef CONFIG_F2FS_CHECK_FS
+	char *sit_bitmap_mir;		/* SIT bitmap mirror */
+#endif
 	unsigned int bitmap_size;	/* SIT bitmap size */
 
 	unsigned long *tmp_map;			/* bitmap for temporal use */
@@ -423,6 +426,12 @@ static inline void get_sit_bitmap(struct f2fs_sb_info *sbi,
 		void *dst_addr)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
+
+#ifdef CONFIG_F2FS_CHECK_FS
+	if (memcmp(sit_i->sit_bitmap, sit_i->sit_bitmap_mir,
+						sit_i->bitmap_size))
+		f2fs_bug_on(sbi, 1);
+#endif
 	memcpy(dst_addr, sit_i->sit_bitmap, sit_i->bitmap_size);
 }
 
@@ -643,6 +652,12 @@ static inline pgoff_t current_sit_addr(struct f2fs_sb_info *sbi,
 
 	check_seg_range(sbi, start);
 
+#ifdef CONFIG_F2FS_CHECK_FS
+	if (f2fs_test_bit(offset, sit_i->sit_bitmap) !=
+			f2fs_test_bit(offset, sit_i->sit_bitmap_mir))
+		f2fs_bug_on(sbi, 1);
+#endif
+
 	/* calculate sit block address */
 	if (f2fs_test_bit(offset, sit_i->sit_bitmap))
 		blk_addr += sit_i->sit_blocks;
@@ -668,6 +683,9 @@ static inline void set_to_next_sit(struct sit_info *sit_i, unsigned int start)
 	unsigned int block_off = SIT_BLOCK_OFFSET(start);
 
 	f2fs_change_bit(block_off, sit_i->sit_bitmap);
+#ifdef CONFIG_F2FS_CHECK_FS
+	f2fs_change_bit(block_off, sit_i->sit_bitmap_mir);
+#endif
 }
 
 static inline unsigned long long get_mtime(struct f2fs_sb_info *sbi)