On 2/26/25 11:28, Jaegeuk Kim wrote:
> On 02/24, Chao Yu wrote:
>> On 2/14/25 09:44, Chao Yu wrote:
>>> On 2/14/25 01:38, Jaegeuk Kim wrote:
>>>> On 02/13, Chao Yu wrote:
>>>>> On 2/13/25 00:47, Jaegeuk Kim wrote:
>>>>>> On 02/12, Chao Yu wrote:
>>>>>>> From: Leo Stone <leocst...@gmail.com>
>>>>>>>
>>>>>>> The syzbot reproducer mounts a f2fs image, then tries to unlink an
>>>>>>> existing file. However, the unlinked file already has a link count of 0
>>>>>>> when it is read for the first time in do_read_inode().
>>>>>>>
>>>>>>> Add a check to sanity_check_inode() for i_nlink == 0.
>>>>>>>
>>>>>>> [Chao Yu: rebase the code and fix orphan inode recovery issue]
>>>>>>> Reported-by: syzbot+b01a36acd7007e273...@syzkaller.appspotmail.com
>>>>>>> Closes: https://syzkaller.appspot.com/bug?extid=b01a36acd7007e273a83
>>>>>>> Fixes: 39a53e0ce0df ("f2fs: add superblock and major in-memory 
>>>>>>> structure")
>>>>>>> Signed-off-by: Leo Stone <leocst...@gmail.com>
>>>>>>> Signed-off-by: Chao Yu <c...@kernel.org>
>>>>>>> ---
>>>>>>>  fs/f2fs/checkpoint.c | 4 ++++
>>>>>>>  fs/f2fs/f2fs.h       | 1 +
>>>>>>>  fs/f2fs/inode.c      | 6 ++++++
>>>>>>>  3 files changed, 11 insertions(+)
>>>>>>>
>>>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>>>> index bd890738b94d..ada2c548645c 100644
>>>>>>> --- a/fs/f2fs/checkpoint.c
>>>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>>>> @@ -751,6 +751,8 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info 
>>>>>>> *sbi)
>>>>>>>         if (is_sbi_flag_set(sbi, SBI_IS_WRITABLE))
>>>>>>>                 f2fs_info(sbi, "orphan cleanup on readonly fs");
>>>>>>>  
>>>>>>> +       set_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>>>>>>
>>>>>> What about using SBI_POR_DOING?
>>>>>
>>>>> SBI_POR_DOING will cover most flow of f2fs_fill_super(), I think we can 
>>>>> add a
>>>>> separated flag just covering f2fs_recover_orphan_inodes(), so that we can 
>>>>> allow
>>>>> iget() of root_inode and all inodes during roll-forward recovery to do 
>>>>> sanity
>>>>> check nlink w/ zero. What do you think?
>>>>
>>>> Can we do this sanity check after f2fs_iget in the f2fs_unlink() only?
>>>
>>> Sure, we need to cover f2fs_rename() as well, please check this:
>>>
>>> https://lore.kernel.org/all/67450f9a.050a0220.21d33d.0003....@google.com
>>
>> Hi Jaegeuk,
>>
>> I'm testing this, seems there is a problem, once we opened an inode that
>> has zeroed nlink, in f2fs_evict_inode(), the inode and all its data will be
>> deleted, then leaving its stale dir entry in parent directory.
>>
>> What do you think using v4? so that we may has chance to repair it w/ fsck
>> rather than just deleting it?
> 
> Do you mean v4 as the below change?

I mean this v4 patch:

---
 fs/f2fs/checkpoint.c | 4 ++++
 fs/f2fs/f2fs.h       | 1 +
 fs/f2fs/inode.c      | 6 ++++++
 3 files changed, 11 insertions(+)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index bd890738b94d..ada2c548645c 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -751,6 +751,8 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
        if (is_sbi_flag_set(sbi, SBI_IS_WRITABLE))
                f2fs_info(sbi, "orphan cleanup on readonly fs");

+       set_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
+
        start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
        orphan_blocks = __start_sum_addr(sbi) - 1 - __cp_payload(sbi);

@@ -778,9 +780,11 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
                }
                f2fs_put_page(page, 1);
        }
+
        /* clear Orphan Flag */
        clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
 out:
+       clear_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
        set_sbi_flag(sbi, SBI_IS_RECOVERED);

        return err;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 05879c6dc4d6..1c75081c0c14 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1322,6 +1322,7 @@ enum {
        SBI_IS_CLOSE,                           /* specify unmounting */
        SBI_NEED_FSCK,                          /* need fsck.f2fs to fix */
        SBI_POR_DOING,                          /* recovery is doing or not */
+       SBI_ORPHAN_RECOVERY,                    /* orphan inodes recovery is 
doing */
        SBI_NEED_SB_WRITE,                      /* need to recover superblock */
        SBI_NEED_CP,                            /* need to checkpoint */
        SBI_IS_SHUTDOWN,                        /* shutdown by ioctl */
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index d6ad7810df69..02f1b69d03d8 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -386,6 +386,12 @@ static bool sanity_check_inode(struct inode *inode, struct 
page *node_page)
                }
        }

+       if (inode->i_nlink == 0 && !is_sbi_flag_set(sbi, SBI_ORPHAN_RECOVERY)) {
+               f2fs_warn(sbi, "%s: inode (ino=%lx) has a link count of 0",
+                         __func__, inode->i_ino);
+               return false;
+       }
+
        return true;
 }

Thanks,

> 
>>
>> ---
>>  fs/f2fs/namei.c | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
>> index a278c7da8177..949621bc0d07 100644
>> --- a/fs/f2fs/namei.c
>> +++ b/fs/f2fs/namei.c
>> @@ -547,6 +547,16 @@ static int f2fs_unlink(struct inode *dir, struct dentry 
>> *dentry)
>>              goto fail;
>>      }
>>
>> +    if (unlikely(S_ISDIR(inode->i_mode) ?
>> +                    inode->i_nlink <= 1 : inode->i_nlink == 0)) {
>> +            f2fs_err_ratelimited(sbi, "%s: inode (ino=%lx) has inconsistent 
>> nlink: %u, isdir: %d",
>> +                            __func__, inode->i_ino, inode->i_nlink,
>> +                            S_ISDIR(inode->i_mode));
>> +            err = -EFSCORRUPTED;
>> +            set_sbi_flag(sbi, SBI_NEED_FSCK);
>> +            goto fail;
>> +    }
>> +
>>      err = f2fs_dquot_initialize(dir);
>>      if (err)
>>              goto fail;
>> @@ -968,6 +978,15 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct 
>> inode *old_dir,
>>      }
>>
>>      if (new_inode) {
>> +            if (unlikely(old_is_dir ?
>> +                    new_inode->i_nlink <= 1 : new_inode->i_nlink == 0)) {
>> +                    f2fs_err_ratelimited(sbi, "%s: inode (ino=%lx) has 
>> inconsistent nlink: %u, isdir: %d",
>> +                            __func__, new_inode->i_ino, new_inode->i_nlink,
>> +                            S_ISDIR(new_inode->i_mode));
>> +                    err = -EFSCORRUPTED;
>> +                    set_sbi_flag(sbi, SBI_NEED_FSCK);
>> +                    goto out_dir;
>> +            }
>>
>>              err = -ENOTEMPTY;
>>              if (old_is_dir && !f2fs_empty_dir(new_inode))
>> -- 
>> 2.48.1.601.g30ceb7b040-goog
>>
>>>
>>> Thanks,
>>>
>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>>> +
>>>>>>>         start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
>>>>>>>         orphan_blocks = __start_sum_addr(sbi) - 1 - __cp_payload(sbi);
>>>>>>>  
>>>>>>> @@ -778,9 +780,11 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info 
>>>>>>> *sbi)
>>>>>>>                 }
>>>>>>>                 f2fs_put_page(page, 1);
>>>>>>>         }
>>>>>>> +
>>>>>>>         /* clear Orphan Flag */
>>>>>>>         clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>>>>>>>  out:
>>>>>>> +       clear_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>>>>>>>         set_sbi_flag(sbi, SBI_IS_RECOVERED);
>>>>>>>  
>>>>>>>         return err;
>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>> index 05879c6dc4d6..1c75081c0c14 100644
>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>> @@ -1322,6 +1322,7 @@ enum {
>>>>>>>         SBI_IS_CLOSE,                           /* specify unmounting */
>>>>>>>         SBI_NEED_FSCK,                          /* need fsck.f2fs to 
>>>>>>> fix */
>>>>>>>         SBI_POR_DOING,                          /* recovery is doing or 
>>>>>>> not */
>>>>>>> +       SBI_ORPHAN_RECOVERY,                    /* orphan inodes 
>>>>>>> recovery is doing */
>>>>>>>         SBI_NEED_SB_WRITE,                      /* need to recover 
>>>>>>> superblock */
>>>>>>>         SBI_NEED_CP,                            /* need to checkpoint */
>>>>>>>         SBI_IS_SHUTDOWN,                        /* shutdown by ioctl */
>>>>>>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>>>>>>> index d6ad7810df69..02f1b69d03d8 100644
>>>>>>> --- a/fs/f2fs/inode.c
>>>>>>> +++ b/fs/f2fs/inode.c
>>>>>>> @@ -386,6 +386,12 @@ static bool sanity_check_inode(struct inode 
>>>>>>> *inode, struct page *node_page)
>>>>>>>                 }
>>>>>>>         }
>>>>>>>  
>>>>>>> +       if (inode->i_nlink == 0 && !is_sbi_flag_set(sbi, 
>>>>>>> SBI_ORPHAN_RECOVERY)) {
>>>>>>> +               f2fs_warn(sbi, "%s: inode (ino=%lx) has a link count of 
>>>>>>> 0",
>>>>>>> +                         __func__, inode->i_ino);
>>>>>>> +               return false;
>>>>>>> +       }
>>>>>>> +
>>>>>>>         return true;
>>>>>>>  }
>>>>>>>  
>>>>>>> -- 
>>>>>>> 2.48.1.502.g6dc24dfdaf-goog
>>>



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