Messages in this thread | | | Date | Wed, 22 Aug 2012 16:55:57 -0400 | From | Aristeu Rozanski <> | Subject | Re: [PATCH v6 1/4] xattr: extract simple_xattr code from tmpfs |
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On Wed, Aug 22, 2012 at 01:25:06PM -0700, Hugh Dickins wrote: > > > Probably more important would be to remove spin_lock() and spin_unlock() > > > (and INIT_LIST_HEAD) from simple_xattrs_free() - those are unnecessary > > > in shmem_evict_inode(), and wouldn't they be unnecessary whenever > > > simple_xattrs_free() gets called? > > > > Removing INIT_LIST_HEAD() it's possible by actually unlinking each xattr > > inside the loop before freeing them. still, it'll have to check if the list is > > empty or not, which might end up being the same? > > > > About the locking, I'm not sure, I'm investigating it. > > I think we have a misunderstanding. > > INIT_LIST_HEAD() is not expensive, I just meant to remove it because > I thought it unnecessary by that point.
ah, I see.
> Do you envisage anywhere that would call simple_xattrs_free() except > a filesystem's evict_inode()?
cgroup does it differently and it's called in d_iput() path (see cgroup_diput), because it needs to selectively remove files upon remount.
> By that point, the inode is on its way out of the system: nothing > much (yes, I am being a bit vague there ;) can get to it any more, > there's no need to reinitialize the list head and there's no need for > locking, because nothing else can be playing with those xattrs now.
I agree with you. That's why I'm looking into it because I'm pretty sure I removed it at some point in the past and decided to put it back after investigating the easily reproducible oops. Sadly I managed to forget the analisys I did at the time.
-- Aristeu
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