On Tue, 2011-08-02 at 14:09 +0200, Jan Kara wrote:
> Hello,
>
> Toshiyuki reported an ext3 error message which implies that we can have
> unlinked but open files on read-only filesystem. Apparently open+unlink
> races with remount in some way. Looking at code in do_remount_sb() I don't
> see what prevents open("file", O_WRONLY) to happen after the check
> fs_may_remount_ro() and before the filesystem is marked as read-only.
> So are we expected to prevent these races? If yes, do I just miss something
> or the above race is really there? Thanks for reply in advance.
Yes, that race is there. I have a patchset to fix most of the races:
https://lkml.org/lkml/2011/1/18/94
I'll update it to the current kernel.
There's still one race that it doesn't fix, if the inode still has a
stray reference not obtained from open() after nlink has gone to zero.
This can be fixed by adding a counter similar to mnt_writers to the
superblock and incrementing it in drop_nlink().
Thanks,
Miklos
>
> Honza
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