From 457c1b27ed56ec472d202731b12417bff023594a Mon Sep 17 00:00:00 2001 From: Nishanth Aravamudan Date: Tue, 6 May 2014 12:50:00 -0700 Subject: hugetlb: ensure hugepage access is denied if hugepages are not supported Currently, I am seeing the following when I `mount -t hugetlbfs /none /dev/hugetlbfs`, and then simply do a `ls /dev/hugetlbfs`. I think it's related to the fact that hugetlbfs is properly not correctly setting itself up in this state?: Unable to handle kernel paging request for data at address 0x00000031 Faulting instruction address: 0xc000000000245710 Oops: Kernel access of bad area, sig: 11 [#1] SMP NR_CPUS=2048 NUMA pSeries .... In KVM guests on Power, in a guest not backed by hugepages, we see the following: AnonHugePages: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 64 kB HPAGE_SHIFT == 0 in this configuration, which indicates that hugepages are not supported at boot-time, but this is only checked in hugetlb_init(). Extract the check to a helper function, and use it in a few relevant places. This does make hugetlbfs not supported (not registered at all) in this environment. I believe this is fine, as there are no valid hugepages and that won't change at runtime. [akpm@linux-foundation.org: use pr_info(), per Mel] [akpm@linux-foundation.org: fix build when HPAGE_SHIFT is undefined] Signed-off-by: Nishanth Aravamudan Reviewed-by: Aneesh Kumar K.V Acked-by: Mel Gorman Cc: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/hugetlbfs/inode.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'fs/hugetlbfs') diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 204027520937..e19d4c0cacae 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1030,6 +1030,11 @@ static int __init init_hugetlbfs_fs(void) int error; int i; + if (!hugepages_supported()) { + pr_info("hugetlbfs: disabling because there are no supported hugepage sizes\n"); + return -ENOTSUPP; + } + error = bdi_init(&hugetlbfs_backing_dev_info); if (error) return error; -- cgit v1.2.3-70-g09d2