Re: [PATCH -next v2] ext4: fix bug_on in ext4_writepages

[yebin <yebin10@huawei.com>]

On 2022/5/14 17:28, yebin wrote:
>
>
> On 2022/5/11 21:47, Jan Kara wrote:
>> On Tue 10-05-22 18:02:28, Ye Bin wrote:
>>> we got issue as follows:
>>> EXT4-fs error (device loop0): ext4_mb_generate_buddy:1141: group 0, 
>>> block bitmap and bg descriptor inconsistent: 25 vs 31513 free cls
>>> ------------[ cut here ]------------
>>> kernel BUG at fs/ext4/inode.c:2708!
>>> invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
>>> CPU: 2 PID: 2147 Comm: rep Not tainted 5.18.0-rc2-next-20220413+ #155
>>> RIP: 0010:ext4_writepages+0x1977/0x1c10
>>> RSP: 0018:ffff88811d3e7880 EFLAGS: 00010246
>>> RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88811c098000
>>> RDX: 0000000000000000 RSI: ffff88811c098000 RDI: 0000000000000002
>>> RBP: ffff888128140f50 R08: ffffffffb1ff6387 R09: 0000000000000000
>>> R10: 0000000000000007 R11: ffffed10250281ea R12: 0000000000000001
>>> R13: 00000000000000a4 R14: ffff88811d3e7bb8 R15: ffff888128141028
>>> FS:  00007f443aed9740(0000) GS:ffff8883aef00000(0000) 
>>> knlGS:0000000000000000
>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 0000000020007200 CR3: 000000011c2a4000 CR4: 00000000000006e0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>> Call Trace:
>>>   <TASK>
>>>   do_writepages+0x130/0x3a0
>>>   filemap_fdatawrite_wbc+0x83/0xa0
>>>   filemap_flush+0xab/0xe0
>>>   ext4_alloc_da_blocks+0x51/0x120
>>>   __ext4_ioctl+0x1534/0x3210
>>>   __x64_sys_ioctl+0x12c/0x170
>>>   do_syscall_64+0x3b/0x90
>>>
>>> It may happen as follows:
>>> 1. write inline_data inode
>>> vfs_write
>>>    new_sync_write
>>>      ext4_file_write_iter
>>>        ext4_buffered_write_iter
>>>          generic_perform_write
>>>            ext4_da_write_begin
>>>              ext4_da_write_inline_data_begin -> If inline data size too
>>>              small will allocate block to write, then mapping will has
>>>              dirty page
>>>                  ext4_da_convert_inline_data_to_extent ->clear 
>>> EXT4_STATE_MAY_INLINE_DATA
>>> 2. fallocate
>>> do_vfs_ioctl
>>>    ioctl_preallocate
>>>      vfs_fallocate
>>>        ext4_fallocate
>>>          ext4_convert_inline_data
>>>            ext4_convert_inline_data_nolock
>>>              ext4_map_blocks -> fail will goto restore data
>>>              ext4_restore_inline_data
>>>                ext4_create_inline_data
>>>                ext4_write_inline_data
>>>                ext4_set_inode_state -> set inode 
>>> EXT4_STATE_MAY_INLINE_DATA
>>> 3. writepages
>>> __ext4_ioctl
>>>    ext4_alloc_da_blocks
>>>      filemap_flush
>>>        filemap_fdatawrite_wbc
>>>          do_writepages
>>>            ext4_writepages
>>>              if (ext4_has_inline_data(inode))
>>>                BUG_ON(ext4_test_inode_state(inode, 
>>> EXT4_STATE_MAY_INLINE_DATA))
>>>
>>> The root cause of this issue is we destory inline data until call 
>>> ext4_writepages
>>> under delay allocation mode. But there maybe already covert from 
>>> inline to extent.
>>> To solved this issue, we call filemap_flush firstly.
>>>
>>> Signed-off-by: Ye Bin <yebin10@huawei.com>
>>> ---
>>>   fs/ext4/inline.c | 8 ++++++++
>>>   1 file changed, 8 insertions(+)
>>>
>>> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
>>> index 6d253edebf9f..130ed5d83734 100644
>>> --- a/fs/ext4/inline.c
>>> +++ b/fs/ext4/inline.c
>>> @@ -2002,6 +2002,14 @@ int ext4_convert_inline_data(struct inode 
>>> *inode)
>>>       if (!ext4_has_inline_data(inode)) {
>>>           ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
>>>           return 0;
>>> +    } else if (test_opt(inode->i_sb, DELALLOC) && 
>>> !S_ISDIR(inode->i_mode)) {
>>> +        error = filemap_flush(inode->i_mapping);
>> This is actually an interesting option and I kind of like it but 
>> shouldn't
>> we restrict this to the situation when EXT4_STATE_MAY_INLINE_DATA is 
>> clear?
>> Otherwise we would be writing out inline data to the inode unnecessarily
>> for each ext4_convert_inline_data() call.
>>
>>                                 Honza
> Acctually,  this issue only exist in delay allocate mode. Do we need 
> to restrict this to
> “test_opt(inode->i_sb, DELALLOC)” as follows ?
I've looked again. There's no need to add this constraint.  I'll send v2 
patch.
> @@ -2002,6 +2002,13 @@ int ext4_convert_inline_data(struct inode *inode)
>         if (!ext4_has_inline_data(inode)) {
>                 ext4_clear_inode_state(inode, 
> EXT4_STATE_MAY_INLINE_DATA);
>                 return 0;
> +       } else if (test_opt(inode->i_sb, DELALLOC) &&
> +                  !ext4_test_inode_state(inode, 
> EXT4_STATE_MAY_INLINE_DATA)) {
> +               error = filemap_flush(inode->i_mapping);
> +               if (error)
> +                       return error;
> +               if (!ext4_has_inline_data(inode))
> +                       return 0;
>         }
>
>
> .
>