On Mon, Aug 19, 2013 at 7:28 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> On Fri, Aug 16, 2013 at 04:22:09PM -0700, Andy Lutomirski wrote:
>> This is like file_update_time, except that it acts on a struct inode *
>> instead of a struct file *.
>>
>> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
>> ---
>> fs/inode.c | 72 ++++++++++++++++++++++++++++++++++++++++++------------
>> include/linux/fs.h | 1 +
>> 2 files changed, 58 insertions(+), 15 deletions(-)
>>
[...]
>> +
>> +int inode_update_time_writable(struct inode *inode)
>> +{
>> + struct timespec now;
>> + int sync_it = prepare_update_cmtime(inode, &now);
>> + int ret;
>> +
>> + if (!sync_it)
>> + return 0;
>> +
>> + /* sb_start_pagefault and update_time can both sleep. */
>> + sb_start_pagefault(inode->i_sb);
>> + ret = update_time(inode, &now, sync_it);
>> + sb_end_pagefault(inode->i_sb);
>
> This gets called from the writeback path - you can't use
> sb_start_pagefault/sb_end_pagefault in that path.
The race I'm worried about is:
- mmap
- write to the mapping
- remount ro
- flush_cmtime -> inode_update_time_writable
This may be impossible, in which case I'm okay, but it's nice to have
a sanity check. I'll see if I can figure out how to do that.
--Andy
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