linux-kernel - Re: [PATCHv5 1/7] mm: drop page->slab

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Message-ID: <20150907121907.GA5531@node.dhcp.inet.fi>
Date:	Mon, 7 Sep 2015 15:19:07 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCHv5 1/7] mm: drop page->slab_page

On Sun, Sep 06, 2015 at 10:00:57PM -0700, Alexander Duyck wrote:
> On 09/03/2015 05:35 AM, Kirill A. Shutemov wrote:
> >Since 8456a648cf44 ("slab: use struct page for slab management") nobody
> >uses slab_page field in struct page.
> >
> >Let's drop it.
> >
> >Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> >Acked-by: Christoph Lameter <cl@...ux.com>
> >Acked-by: David Rientjes <rientjes@...gle.com>
> >Acked-by: Vlastimil Babka <vbabka@...e.cz>
> >Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> >Cc: Andi Kleen <ak@...ux.intel.com>
> >---
> >  include/linux/mm_types.h |  1 -
> >  mm/slab.c                | 17 +++--------------
> >  2 files changed, 3 insertions(+), 15 deletions(-)
> >
> >diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> >index 0038ac7466fd..58620ac7f15c 100644
> >--- a/include/linux/mm_types.h
> >+++ b/include/linux/mm_types.h
> >@@ -140,7 +140,6 @@ struct page {
> >  #endif
> >  		};
> >-		struct slab *slab_page; /* slab fields */
> >  		struct rcu_head rcu_head;	/* Used by SLAB
> >  						 * when destroying via RCU
> >  						 */
> >diff --git a/mm/slab.c b/mm/slab.c
> >index 200e22412a16..649044f26e5d 100644
> >--- a/mm/slab.c
> >+++ b/mm/slab.c
> >@@ -1888,21 +1888,10 @@ static void slab_destroy(struct kmem_cache *cachep, struct page *page)
> >  	freelist = page->freelist;
> >  	slab_destroy_debugcheck(cachep, page);
> >-	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
> >-		struct rcu_head *head;
> >-
> >-		/*
> >-		 * RCU free overloads the RCU head over the LRU.
> >-		 * slab_page has been overloeaded over the LRU,
> >-		 * however it is not used from now on so that
> >-		 * we can use it safely.
> >-		 */
> >-		head = (void *)&page->rcu_head;
> >-		call_rcu(head, kmem_rcu_free);
> >-
> >-	} else {
> >+	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
> >+		call_rcu(&page->rcu_head, kmem_rcu_free);
> >+	else
> >  		kmem_freepages(cachep, page);
> >-	}
> >  	/*
> >  	 * From now on, we don't use freelist
> 
> This second piece looks like it belongs in patch 2, not patch 1 based on the
> descriptions.

You're right.

Although I don't think I would re-spin the patchset just for this change.
If any other change would be required, I'll fix this too.

-- 
 Kirill A. Shutemov
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