[Ocfs2-devel] BUG_ON(le64_to_cpu(fe->i_size) != i_size_read(inode)) is triggered in ocfs2_truncate_file()

[Gang He]

Hi Zhen,

This should be file system consistency issue between inode in memory and inode in disk, 
You should look at the code that modify the file size in memory, and then whether the code also sync the change to the disk.


Thanks
Gang




>>> 
> Hi all,
> 
> Any one ever see this BUG_ON() assertion 
> (https://github.com/torvalds/linux/blob/master/fs/ocfs2/file.c#L460)
> triggered? (paste log message at the end). I cannot reproduced it so far.
> 
> fallocate with FALLOC_FL_KEEP_SIZE flag (man 2 fallocate) can result in  
> "le64_to_cpu(fe->i_size) != i_size_read(inode)"
> as explained in this commit message:
> 
> ```
> commit d62e74be1270c89fbaf7aada8218bfdf62d00a58
> Author: Younger Liu <younger.liu at huawei.com <mailto:younger.liu at huawei.com>>
> Date:   Mon Feb 10 14:25:51 2014 -0800
> 
>      ocfs2: fix issue that ocfs2_setattr() does not deal with 
> new_i_size==i_size
> 
> The issue scenario is as following:
> 
> - Create a small file and fallocate a large disk space for a file with
>    FALLOC_FL_KEEP_SIZE option.
> 
> - ftruncate the file back to the original size again.  but the disk free
>    space is not changed back.  This is a real bug that be fixed in this
>    patch.
> 
> In order to solve the issue above, we modified ocfs2_setattr(), if
> attr->ia_size != i_size_read(inode), It calls ocfs2_truncate_file(), and
> truncate disk space to attr->ia_size.
> ```
> 
> I was thinking to remove this BUG_ON() assertion. But, the following steps 
> cannot
> trigger it:
> 
> $dd if=/dev/zero of=/mnt/ocfs2/test2 bs=512 count=1
> $fallocate --keep-size --length 1024000000 /mnt/ocfs2/test2
> $truncate --size=512 /mnt/ocfs2/test2
> 
> I'm wondering why the testing result goes against what I expect? Finally, I 
> find that:
> 
> ocfs2_inode_lock(inode, bh, 1) in ocfs2_setattr() will update the 
> inode->i_size filed from LVB value
> or ocfs2_dinode from disk.
> ---
> vfs_truncate
>   do_truncate
>     inode_lock()
>     notify_change
>      ocfs2_setattr
>       ocfs2_rw_lock()
>       ocfs2_inode_lock()
>        ocfs2_truncate_file
>       ocfs2_rw_lock()
>       ocfs2_inode_unlock
>     inode_unlock()
> 
> ---
> ocfs2_inode_lock()
>   ocfs2_inode_lock_full_nested() ocfs2_inode_lock_update() ==> 
> https://github.com/torvalds/linux/blob/master/fs/ocfs2/dlmglue.c#L2204 if 
> (ocfs2_meta_lvb_is_trustable()) ocfs2_refresh_inode_from_lvb() else { 
> ocfs2_read_inode_block() ocfs2_refresh_inode() } Since we update 
> inode->i_size under the protection of thus locks, how was the assertion 
> triggered?
> As always, any comments and suggestion will be appreciated!
> 
> Thanks,
> Eric
> 
> Log message:
> ```
> kernel-default-3.0.101-80
> ocfs2-kmp-default-1.6_3.0.101_68-0.25.6
> 
> [239098.534619] (dsmc,8244,6):ocfs2_truncate_file:466 ERROR: bug expression: 
> le64_to_cpu(fe->i_size) != i_size_read(inode)
> [239098.534633] (dsmc,8244,6):ocfs2_truncate_file:466 ERROR: Inode 10812, 
> inode i_size = 677 != di i_size = 738, i_flags = 0x1
> 
> ...
> 
> [239098.534724] kernel BUG at 
> /usr/src/packages/BUILD/ocfs2-1.6/default/ocfs2/file.c:466!
> 
> PID: 8244   TASK: ffff8801dfb862c0  CPU: 6   COMMAND: "dsmc"
>   #0 [ffff8801f59618d0] machine_kexec at ffffffff8102c54e
>   #1 [ffff8801f5961920] crash_kexec at ffffffff810ae858
>   #2 [ffff8801f59619f0] oops_end at ffffffff8146b558
>   #3 [ffff8801f5961a10] do_invalid_op at ffffffff810036c4
>   #4 [ffff8801f5961ab0] invalid_op at ffffffff81472d5b
>      [exception RIP: ocfs2_truncate_file+165]
>      RIP: ffffffffa0929ba5  RSP: ffff8801f5961b68  RFLAGS: 00010296
>      RAX: 0000000000000085  RBX: ffff8801dfb862c0  RCX: 0000000000007335
>      RDX: 0000000000000000  RSI: 0000000000000007  RDI: 0000000000000246
>      RBP: 1000000000000000   R8: ffffffff81da3ac0   R9: 0000000000000000
>      R10: 0000000000000003  R11: 00000000ffffffff  R12: ffff8801cbb864f8
>      R13: ffff8801dfb86930  R14: ffff8801bf5ad000  R15: 00000000000002a5
>      ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>   #5 [ffff8801f5961bd0] ocfs2_setattr at ffffffffa092c43e [ocfs2]
>   #6 [ffff8801f5961c90] notify_change at ffffffff8117a0cf
>   #7 [ffff8801f5961cf0] do_truncate at ffffffff8115e177
>   #8 [ffff8801f5961d60] do_last at ffffffff8116d0c3
>   #9 [ffff8801f5961dc0] path_openat at ffffffff8116df29
> #10 [ffff8801f5961e50] do_filp_open at ffffffff8116e39c
> #11 [ffff8801f5961f20] do_sys_open at ffffffff8115eabf
> #12 [ffff8801f5961f80] system_call_fastpath at ffffffff81471d72
>      RIP: 00007f7da23f67b0  RSP: 00007fffae4a3470  RFLAGS: 00010246
>      RAX: 0000000000000002  RBX: ffffffff81471d72  RCX: 0000000000000000
>      RDX: 00000000000001b6  RSI: 0000000000000241  RDI: 0000000000cff3df
>      RBP: 00007fffae4a4ab0   R8: 0000000000000004   R9: 0000000000000001
>      R10: 0000000000000241  R11: 0000000000000246  R12: 0000000000000000
>      R13: 0000000000d1d2f0  R14: 0000000000930a68  R15: 0000000000000004
>      ORIG_RAX: 0000000000000002  CS: 0033  SS: 002b