f2fs: fix to avoid potential panic during recovery

During recovery, if FAULT_BLOCK is on, it is possible that
f2fs_reserve_new_block() will return -ENOSPC during recovery,
then it may trigger panic.

Also, if fault injection rate is 1 and only FAULT_BLOCK fault
type is on, it may encounter deadloop in loop of block reservation.

Let's change as below to fix these issues:
- remove bug_on() to avoid panic.
- limit the loop count of block reservation to avoid potential
deadloop.

Fixes: 956fa1dd ("f2fs: fix to check return value of f2fs_reserve_new_block()")
Reported-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -76,6 +76,11 @@ struct f2fs_fault_info {
 
 extern const char *f2fs_fault_name[FAULT_MAX];
 #define IS_FAULT_SET(fi, type) ((fi)->inject_type & BIT(type))
+
+/* maximum retry count for injected failure */
+#define DEFAULT_FAILURE_RETRY_COUNT		8
+#else
+#define DEFAULT_FAILURE_RETRY_COUNT		1
 #endif
 
 /*

fs/f2fs/recovery.c

@@ -611,6 +611,19 @@ static int check_index_in_prev_nodes(struct f2fs_sb_info *sbi,
 	return 0;
 }
 
+static int f2fs_reserve_new_block_retry(struct dnode_of_data *dn)
+{
+	int i, err = 0;
+
+	for (i = DEFAULT_FAILURE_RETRY_COUNT; i > 0; i--) {
+		err = f2fs_reserve_new_block(dn);
+		if (!err)
+			break;
+	}
+
+	return err;
+}
+
 static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
 					struct page *page)
 {
@@ -712,14 +725,8 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
 		 */
 		if (dest == NEW_ADDR) {
 			f2fs_truncate_data_blocks_range(&dn, 1);
-			do {
-				err = f2fs_reserve_new_block(&dn);
-				if (err == -ENOSPC) {
-					f2fs_bug_on(sbi, 1);
-					break;
-				}
-			} while (err &&
-				IS_ENABLED(CONFIG_F2FS_FAULT_INJECTION));
+
+			err = f2fs_reserve_new_block_retry(&dn);
 			if (err)
 				goto err;
 			continue;
@@ -727,16 +734,8 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
 
 		/* dest is valid block, try to recover from src to dest */
 		if (f2fs_is_valid_blkaddr(sbi, dest, META_POR)) {
-
 			if (src == NULL_ADDR) {
-				do {
-					err = f2fs_reserve_new_block(&dn);
-					if (err == -ENOSPC) {
-						f2fs_bug_on(sbi, 1);
-						break;
-					}
-				} while (err &&
-					IS_ENABLED(CONFIG_F2FS_FAULT_INJECTION));
+				err = f2fs_reserve_new_block_retry(&dn);
 				if (err)
 					goto err;
 			}