f2fs: avoid an infinite loop in f2fs_sync_dirty_inodes

If one read IO is always failing, we can fall into an infinite loop in
f2fs_sync_dirty_inodes. This happens during xfstests/generic/475.

[  142.803335] Buffer I/O error on dev dm-1, logical block 8388592, async page read
...
[  382.887210]  submit_bio_noacct+0xdd/0x2a0
[  382.887213]  submit_bio+0x80/0x110
[  382.887223]  __submit_bio+0x4d/0x300 [f2fs]
[  382.887282]  f2fs_submit_page_bio+0x125/0x200 [f2fs]
[  382.887299]  __get_meta_page+0xc9/0x280 [f2fs]
[  382.887315]  f2fs_get_meta_page+0x13/0x20 [f2fs]
[  382.887331]  f2fs_get_node_info+0x317/0x3c0 [f2fs]
[  382.887350]  f2fs_do_write_data_page+0x327/0x6f0 [f2fs]
[  382.887367]  f2fs_write_single_data_page+0x5b7/0x960 [f2fs]
[  382.887386]  f2fs_write_cache_pages+0x302/0x890 [f2fs]
[  382.887405]  ? preempt_count_add+0x7a/0xc0
[  382.887408]  f2fs_write_data_pages+0xfd/0x320 [f2fs]
[  382.887425]  ? _raw_spin_unlock+0x1a/0x30
[  382.887428]  do_writepages+0xd3/0x1d0
[  382.887432]  filemap_fdatawrite_wbc+0x69/0x90
[  382.887434]  filemap_fdatawrite+0x50/0x70
[  382.887437]  f2fs_sync_dirty_inodes+0xa4/0x270 [f2fs]
[  382.887453]  f2fs_write_checkpoint+0x189/0x1640 [f2fs]
[  382.887469]  ? schedule_timeout+0x114/0x150
[  382.887471]  ? ttwu_do_activate+0x6d/0xb0
[  382.887473]  ? preempt_count_add+0x7a/0xc0
[  382.887476]  kill_f2fs_super+0xca/0x100 [f2fs]
[  382.887491]  deactivate_locked_super+0x35/0xa0
[  382.887494]  deactivate_super+0x40/0x50
[  382.887497]  cleanup_mnt+0x139/0x190
[  382.887499]  __cleanup_mnt+0x12/0x20
[  382.887501]  task_work_run+0x64/0xa0
[  382.887505]  exit_to_user_mode_prepare+0x1b7/0x1c0
[  382.887508]  syscall_exit_to_user_mode+0x27/0x50
[  382.887510]  do_syscall_64+0x48/0xc0
[  382.887513]  entry_SYSCALL_64_after_hwframe+0x44/0xae
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -98,6 +98,13 @@ static struct page *__get_meta_page(struct f2fs_sb_info *sbi, pgoff_t index,
 	}
 
 	if (unlikely(!PageUptodate(page))) {
+		if (page->index == sbi->metapage_eio_ofs &&
+			sbi->metapage_eio_cnt++ == MAX_RETRY_META_PAGE_EIO) {
+			set_ckpt_flags(sbi, CP_ERROR_FLAG);
+		} else {
+			sbi->metapage_eio_ofs = page->index;
+			sbi->metapage_eio_cnt = 0;
+		}
 		f2fs_put_page(page, 1);
 		return ERR_PTR(-EIO);
 	}

fs/f2fs/f2fs.h

@@ -577,6 +577,9 @@ enum {
 /* maximum retry quota flush count */
 #define DEFAULT_RETRY_QUOTA_FLUSH_COUNT		8
 
+/* maximum retry of EIO'ed meta page */
+#define MAX_RETRY_META_PAGE_EIO			100
+
 #define F2FS_LINK_MAX	0xffffffff	/* maximum link count per file */
 
 #define MAX_DIR_RA_PAGES	4	/* maximum ra pages of dir */
@@ -1614,6 +1617,8 @@ struct f2fs_sb_info {
 	/* keep migration IO order for LFS mode */
 	struct f2fs_rwsem io_order_lock;
 	mempool_t *write_io_dummy;		/* Dummy pages */
+	pgoff_t metapage_eio_ofs;		/* EIO page offset */
+	int metapage_eio_cnt;			/* EIO count */
 
 	/* for checkpoint */
 	struct f2fs_checkpoint *ckpt;		/* raw checkpoint pointer */