Hi Yunlei,

On 12/08, Yunlei He wrote:
> Came across a dead loop in recovery like this:
> 
> ......
> [   24.680480s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597696
> [   24.698394s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597697
> [   24.724334s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724334s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724365s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724365s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724365s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724395s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724395s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724395s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724395s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> [   24.724426s][pid:320,cpu0,init]find_fsync_dnodes: blkaddr =13597698
> ......
> 
> Mount process will block in dead loop and fsck can do nothing with this
> error, This patch abandon recovery if node chain is cyclical.
> 
> Signed-off-by: Yunlei He <[email protected]>
> ---
>  fs/f2fs/node.h          |  8 +++++---
>  fs/f2fs/recovery.c      | 22 ++++++++++++++--------
>  include/linux/f2fs_fs.h |  3 ++-
>  3 files changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index 0ee3e5f..049ff5e 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -399,9 +399,10 @@ static inline int is_node(struct page *page, int type)
>       return le32_to_cpu(rn->footer.flag) & (1 << type);
>  }
>  
> -#define is_cold_node(page)   is_node(page, COLD_BIT_SHIFT)
> -#define is_fsync_dnode(page) is_node(page, FSYNC_BIT_SHIFT)
> -#define is_dent_dnode(page)  is_node(page, DENT_BIT_SHIFT)
> +#define is_cold_node(page)           is_node(page, COLD_BIT_SHIFT)
> +#define is_fsync_dnode(page)         is_node(page, FSYNC_BIT_SHIFT)
> +#define is_dent_dnode(page)          is_node(page, DENT_BIT_SHIFT)
> +#define is_recovered_dnode(page)     is_node(page, RECOVERED_BIT_SHIFT)
>  
>  static inline int is_inline_node(struct page *page)
>  {
> @@ -442,3 +443,4 @@ static inline void set_mark(struct page *page, int mark, 
> int type)
>  }
>  #define set_dentry_mark(page, mark)  set_mark(page, mark, DENT_BIT_SHIFT)
>  #define set_fsync_mark(page, mark)   set_mark(page, mark, FSYNC_BIT_SHIFT)
> +#define set_recovered_mark(page, mark)       set_mark(page, mark, 
> RECOVERED_BIT_SHIFT)
> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> index 7d63faf..bfbb3e4 100644
> --- a/fs/f2fs/recovery.c
> +++ b/fs/f2fs/recovery.c
> @@ -220,6 +220,14 @@ static void recover_inode(struct inode *inode, struct 
> page *page)
>                       ino_of_node(page), name);
>  }
>  
> +static void destroy_fsync_dnodes(struct list_head *head)
> +{
> +     struct fsync_inode_entry *entry, *tmp;
> +
> +     list_for_each_entry_safe(entry, tmp, head, list)
> +             del_fsync_inode(entry);
> +}
> +
>  static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head 
> *head,
>                               bool check_only)
>  {
> @@ -239,7 +247,13 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, 
> struct list_head *head,
>                       return 0;
>  
>               page = get_tmp_page(sbi, blkaddr);
> +             if (unlikely(is_recovered_dnode(page))) {
> +                     f2fs_msg(sbi->sb, KERN_ERR, "Abandon dead loop node 
> block list");
> +                     destroy_fsync_dnodes(head);
> +                     break;
> +             }
>  
> +             set_recovered_mark(page, RECOVERED_BIT_SHIFT);
>               if (!is_recoverable_dnode(page))
>                       break;
>  
> @@ -288,14 +302,6 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, 
> struct list_head *head,
>       return err;
>  }
>  
> -static void destroy_fsync_dnodes(struct list_head *head)
> -{
> -     struct fsync_inode_entry *entry, *tmp;
> -
> -     list_for_each_entry_safe(entry, tmp, head, list)
> -             del_fsync_inode(entry);
> -}
> -
>  static int check_index_in_prev_nodes(struct f2fs_sb_info *sbi,
>                       block_t blkaddr, struct dnode_of_data *dn)
>  {
> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> index 43e98d3..9aa85b1 100644
> --- a/include/linux/f2fs_fs.h
> +++ b/include/linux/f2fs_fs.h
> @@ -265,7 +265,8 @@ enum {
>       COLD_BIT_SHIFT = 0,
>       FSYNC_BIT_SHIFT,
>       DENT_BIT_SHIFT,
> -     OFFSET_BIT_SHIFT
> +     OFFSET_BIT_SHIFT,
> +     RECOVERED_BIT_SHIFT

This will make adding new bits be difficult in future. Can we get another
in-memory one to check block loop?

Thanks,

>  };
>  
>  #define OFFSET_BIT_MASK              (0x07)  /* (0x01 << OFFSET_BIT_SHIFT) - 
> 1 */
> -- 
> 1.9.1

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