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/f2fs.h     |  6 +++++
 fs/f2fs/recovery.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 67 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 82f1dc3..4649663 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -289,6 +289,12 @@ struct fsync_inode_entry {
        block_t last_dentry;    /* block address locating the last dentry */
 };
 
+/* for the block of node chain, used only during recovery */
+struct fsync_node_entry {
+       struct list_head list;  /* list head */
+       block_t blkaddr;        /* locating the node block in recovery chain */
+};
+
 #define nats_in_cursum(jnl)            (le16_to_cpu((jnl)->n_nats))
 #define sits_in_cursum(jnl)            (le16_to_cpu((jnl)->n_sits))
 
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 7d63faf..9958abb 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -46,6 +46,7 @@
  */
 
 static struct kmem_cache *fsync_entry_slab;
+static struct kmem_cache *fsync_node_chain_slab;
 
 bool space_for_roll_forward(struct f2fs_sb_info *sbi)
 {
@@ -220,14 +221,55 @@ static void recover_inode(struct inode *inode, struct 
page *page)
                        ino_of_node(page), name);
 }
 
+static void destroy_node_blocks(struct list_head *head)
+{
+       struct fsync_node_entry *entry, *tmp;
+
+       list_for_each_entry_safe(entry, tmp, head, list) {
+               list_del(&entry->list);
+               kmem_cache_free(fsync_node_chain_slab, entry);
+       }
+}
+
+static bool blkaddr_already_in_list(struct list_head *head, block_t blkaddr)
+{
+       struct fsync_node_entry *entry;
+
+       list_for_each_entry(entry, head, list)
+               if (entry->blkaddr == blkaddr)
+                       return true;
+
+       return false;
+}
+
+static void add_fsync_node(struct list_head *head, block_t blkaddr)
+{
+       struct fsync_node_entry *entry;
+
+       entry = f2fs_kmem_cache_alloc(fsync_node_chain_slab, GFP_F2FS_ZERO);
+       entry->blkaddr = blkaddr;
+       list_add_tail(&entry->list, head);
+}
+
+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)
 {
        struct curseg_info *curseg;
        struct page *page = NULL;
+       struct list_head node_block_list;
        block_t blkaddr;
        int err = 0;
 
+       INIT_LIST_HEAD(&node_block_list);
+
        /* get node pages in the current segment */
        curseg = CURSEG_I(sbi, CURSEG_WARM_NODE);
        blkaddr = NEXT_FREE_BLKADDR(sbi, curseg);
@@ -239,7 +281,13 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, 
struct list_head *head,
                        return 0;
 
                page = get_tmp_page(sbi, blkaddr);
+               if (unlikely(blkaddr_already_in_list(&node_block_list, 
blkaddr))) {
+                       f2fs_msg(sbi->sb, KERN_ERR, "Abandon dead loop node 
block list");
+                       destroy_fsync_dnodes(head);
+                       break;
+               }
 
+               add_fsync_node(&node_block_list, blkaddr);
                if (!is_recoverable_dnode(page))
                        break;
 
@@ -284,18 +332,12 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, 
struct list_head *head,
 
                ra_meta_pages_cond(sbi, blkaddr);
        }
+
+       destroy_node_blocks(&node_block_list);
        f2fs_put_page(page, 1);
        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)
 {
@@ -614,7 +656,14 @@ int recover_fsync_data(struct f2fs_sb_info *sbi, bool 
check_only)
                        sizeof(struct fsync_inode_entry));
        if (!fsync_entry_slab) {
                err = -ENOMEM;
-               goto out;
+               goto free_inode_entry;
+       }
+
+       fsync_node_chain_slab = f2fs_kmem_cache_create("f2fs_fsync_node_entry",
+                       sizeof(struct fsync_node_entry));
+       if (!fsync_node_chain_slab) {
+               err = -ENOMEM;
+               goto free_node_entry;
        }
 
        INIT_LIST_HEAD(&inode_list);
@@ -664,8 +713,10 @@ int recover_fsync_data(struct f2fs_sb_info *sbi, bool 
check_only)
                err = write_checkpoint(sbi, &cpc);
        }
 
+       kmem_cache_destroy(fsync_node_chain_slab);
+free_node_entry:
        kmem_cache_destroy(fsync_entry_slab);
-out:
+free_inode_entry:
 #ifdef CONFIG_QUOTA
        /* Turn quotas off */
        if (quota_enabled)
-- 
1.9.1


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