On Tue, 3 Feb 2009 16:19:31 -0700 Jonathan Corbet <corbet@xxxxxxx> wrote: > On Tue, 3 Feb 2009 14:53:46 -0800 > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > Well. We _could_ whack part of this nut with my usual hammer: protect > > f_flags with file->f_dentry->d_inode->i_lock. IIRC there was some > > objection to that - performance? > > Andi has objected to the addition of locks, but i_lock is maybe > sufficiently dispersed to pass muster there. Hope so. I'd wrap it in a lock_file_flags(file*) thing so we can change it later on (add a lock to struct file, take a global, lock, etc). > I had an instinctive > reaction to using a lock which is three pointers away, but I can get > over that. I'll admit a bit of ignorance, though: if a given struct > file exists, do we know for sure that file->f_dentry->d_inode exists? It should. A NULL ->d_inode especially signifies a negative dentry. > > One problem here seems to be that we're trying to change multiple > > things at the same time. We can blame the BKL for that. > > > > Can we break the problem into manageable chunks? Your patchset did > > that, I guess. What were those chunks again? ;) > > I'm not really sure how to break it down any further. If we take the > i_lock approach, the chunks would be something like: > > 1) Use i_lock to protect accesses to f_flags. This would enable some > BKL usage to be removed, but would not fix fasync. > > 2) Move responsibility for the FASYNC bit into ->fasync(), with > fasync_helper() doing it in almost all situations. The remaining > BKL usage would then go away. > > 3) The same optional fasync() return values cleanup. > > Make sense? yup. If the ->i_lock think is no good then we can trivially switch over to a global lock. Heck, we could even go back to lock_kernel() ;) -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
