linux-kernel - Re: [PATCH] staging: lustre: llite: drop acl from cache

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Message-ID: <alpine.LFD.2.20.1605242135500.4622@casper.infradead.org>
Date:	Tue, 24 May 2016 21:38:19 +0100 (BST)
From:	James Simmons <jsimmons@...radead.org>
To:	Andreas Grünbacher 
	<andreas.gruenbacher@...il.com>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devel@...verdev.osuosl.org,
	Andreas Dilger <andreas.dilger@...el.com>,
	Oleg Drokin <oleg.drokin@...el.com>,
	Andreas Gruenbacher <agruenba@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH] staging: lustre: llite: drop acl from cache


> 2016-05-24 2:35 GMT+02:00 James Simmons <jsimmons@...radead.org>:
> > Commit b8a7a3a6 change get_acl() for posix xattr to always cache
> > the ACL which increases the reference count. That reference count
> > can be reduced by have ll_get_acl() call forget_cached_acl() which
> > it wasn't. When an inode gets deleted by Lustre the POSIX ACL
> > reference count is tested to ensure its 1 and if not produces an error.
> 
> Lustre shouldn't assume that the VFS immediately drops the reference
> it is passed. Please remove that check as well.

The piece of code in question from ll_delete_inode() is

#ifdef CONFIG_FS_POSIX_ACL
        else if (lli->lli_posix_acl) {
                LASSERT(atomic_read(&lli->lli_posix_acl->a_refcount) == 
1);
                LASSERT(!lli->lli_remote_perms);
                posix_acl_release(lli->lli_posix_acl);
                lli->lli_posix_acl = NULL;
        }
#endif
 
So we want to prevent a leak should I do a 

while (atomic_read(&lli->lli_posix_acl->a_refcount))
	posix_acl_release(lli->lli_posix_acl);
lli->lli_posix_acl = NULL;

Or does the VFS do this cleanup for us?

> > Since forget_cached_acl() was not called Lustre started to complain.
> > This patch changes ll_get_acl() to call forget_cached_acl().
> >
> > Signed-off-by: James Simmons <jsimmons@...radead.org>
> 
> Reviewed-by: Andreas Gruenbacher <agruenba@...hat.com>
> 
> > ---
> >  drivers/staging/lustre/lustre/llite/file.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/staging/lustre/lustre/llite/file.c b/drivers/staging/lustre/lustre/llite/file.c
> > index f47f2ac..0191945 100644
> > --- a/drivers/staging/lustre/lustre/llite/file.c
> > +++ b/drivers/staging/lustre/lustre/llite/file.c
> > @@ -3124,6 +3124,7 @@ struct posix_acl *ll_get_acl(struct inode *inode, int type)
> >         spin_lock(&lli->lli_lock);
> >         /* VFS' acl_permission_check->check_acl will release the refcount */
> >         acl = posix_acl_dup(lli->lli_posix_acl);
> > +       forget_cached_acl(inode, type);
> >         spin_unlock(&lli->lli_lock);
> >
> >         return acl;
> > --
> > 1.7.1
> >
>