| Re: [PATCH] incorrect error handling inside generic_file_direct_write [message #8924 is a reply to message #8917] |
Mon, 11 December 2006 12:27   |
dev
Messages: 1693
Registered: September 2005
Location: Moscow
|
Senior Member |
|
|
I guess you forgot to add Andrew on CC.
Thanks,
Kirill
> OpenVZ team has discovered error inside generic_file_direct_write()
> If generic_file_direct_IO() has fail (ENOSPC condition) it may have instantiated
> a few blocks outside i_size. And fsck will complain about wrong i_size
> (ext2, ext3 and reiserfs interpret i_size and biggest block difference as error),
> after fsck will fix error i_size will be increased to the biggest block,
> but this blocks contain gurbage from previous write attempt, this is not
> information leak, but its silence file data corruption.
> We need truncate any block beyond i_size after write have failed , do in simular
> generic_file_buffered_write() error path.
>
> Exampe:
> open("mnt2/FILE3", O_WRONLY|O_CREAT|O_DIRECT, 0666) = 3
> write(3, "aaaaaa"..., 4096) = -1 ENOSPC (No space left on device)
>
> stat mnt2/FILE3
> File: `mnt2/FILE3'
> Size: 0 Blocks: 4 IO Block: 4096 regular empty file
>
>>>>>>>>>>>>>>>>>>>>>>>^^^^^^^^^^ file size is less than biggest block idx
>
> Device: 700h/1792d Inode: 14 Links: 1
> Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
>
> fsck.ext2 -f -n mnt1/fs_img
> Pass 1: Checking inodes, blocks, and sizes
> Inode 14, i_size is 0, should be 2048. Fix? no
>
> Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
> ----------
>
>
> ------------------------------------------------------------ ------------
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 7b84dc8..bf7cf6c 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2041,6 +2041,14 @@ generic_file_direct_write(struct kiocb *
> mark_inode_dirty(inode);
> }
> *ppos = end;
> + } else if (written < 0) {
> + loff_t isize = i_size_read(inode);
> + /*
> + * generic_file_direct_IO() may have instantiated a few blocks
> + * outside i_size. Trim these off again.
> + */
> + if (pos + count > isize)
> + vmtruncate(inode, isize);
> }
>
> /*
>
>
> ------------------------------------------------------------ ------------
>
|
|
|
|
OpenVZ Forum
Members
Search
Help
Register
Login
Home
