Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 17 Apr 2012 15:08:26 -0700 | Subject | Re: [git pull] vfs and fs fixes |
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On Tue, Apr 17, 2012 at 2:14 PM, J. Bruce Fields <bfields@fieldses.org> wrote: > On Tue, Apr 17, 2012 at 07:28:26PM +0100, Al Viro wrote:> > Maybe instead I could continue using the i_mutex but handle rename some > other way; e.g. in delegation code: > > if (!mutex_trylock(inode->i_mutex)) > return -EAGAIN; > if (atomic_read(inode->i_renames_in_progress)) > return -EAGAIN; > > and add an > > atomic_inc(inode->i_renames_in_progress); > atomic_dec(inode->i_renames_in_progress); > > pair around rename.
Please don't make up your own locking. Plus it's broken anyway, since a rename could come in directly after your atomic_read (and this is *why* people shouldn't make up their own locks - they are invariably broken).
> Or I could increment that counter for all the conflicting operations and > rely on it instead of the i_mutex. I was trying to avoid adding > something like that (an inc, a dec, another error path) to every > operation. And hoping to avoid adding another field to struct inode. > Oh well.
We could just say that we can do a double inode lock, but then standardize on the order. And the only sane order is comparing inode pointers, not inode numbers like ext4 apparently does.
With a standard order, I don't think it would be at all wrong to just take the inode lock on rename.
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