Return-Path: linux-nfs-owner@vger.kernel.org Received: from cantor2.suse.de ([195.135.220.15]:33681 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762064Ab2EQOvm (ORCPT ); Thu, 17 May 2012 10:51:42 -0400 From: Mel Gorman To: Andrew Morton Cc: Linux-MM , Linux-Netdev , Linux-NFS , LKML , David Miller , Trond Myklebust , Neil Brown , Christoph Hellwig , Peter Zijlstra , Mike Christie , Eric B Munson , Mel Gorman Subject: [PATCH 12/12] Avoid dereferencing bd_disk during swap_entry_free for network storage Date: Thu, 17 May 2012 15:51:25 +0100 Message-Id: <1337266285-8102-13-git-send-email-mgorman@suse.de> In-Reply-To: <1337266285-8102-1-git-send-email-mgorman@suse.de> References: <1337266285-8102-1-git-send-email-mgorman@suse.de> Sender: linux-nfs-owner@vger.kernel.org List-ID: Commit [b3a27d: swap: Add swap slot free callback to block_device_operations] dereferences p->bdev->bd_disk but this is a NULL dereference if using swap-over-NFS. This patch checks SWP_BLKDEV on the swap_info_struct before dereferencing. With reference to this callback, Christoph Hellwig stated "Please just remove the callback entirely. It has no user outside the staging tree and was added clearly against the rules for that staging tree". This would also be my preference but there was not an obvious way of keeping zram in staging/ happy. Signed-off-by: Xiaotian Feng Signed-off-by: Mel Gorman --- mm/swapfile.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 80b3415..d85d842 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -547,7 +547,6 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, /* free if no reference */ if (!usage) { - struct gendisk *disk = p->bdev->bd_disk; if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) @@ -557,9 +556,11 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, swap_list.next = p->type; nr_swap_pages++; p->inuse_pages--; - if ((p->flags & SWP_BLKDEV) && - disk->fops->swap_slot_free_notify) - disk->fops->swap_slot_free_notify(p->bdev, offset); + if (p->flags & SWP_BLKDEV) { + struct gendisk *disk = p->bdev->bd_disk; + if (disk->fops->swap_slot_free_notify) + disk->fops->swap_slot_free_notify(p->bdev, offset); + } } return usage; -- 1.7.9.2