From 27468d24c717327232b7de5bc7762691cd44ae43 Mon Sep 17 00:00:00 2001 From: Nishanth Aravamudan Date: Tue, 6 May 2014 12:50:00 -0700 Subject: [PATCH] hugetlb: ensure hugepage access is denied if hugepages are not supported commit 457c1b27ed56ec472d202731b12417bff023594a upstream. 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 [bwh: Backported to 3.2: - Drop changes to hugetlb_show_meminfo() - Adjust context] Signed-off-by: Ben Hutchings --- fs/hugetlbfs/inode.c | 5 +++++ include/linux/hugetlb.h | 10 ++++++++++ mm/hugetlb.c | 16 +++++++++++----- 3 files changed, 26 insertions(+), 5 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 0aa424a02344..ebab116b0779 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -979,6 +979,11 @@ static int __init init_hugetlbfs_fs(void) int error; struct vfsmount *vfsmount; + 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; diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 4bc9445222f2..c5e40ff916ad 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -344,6 +344,16 @@ static inline pgoff_t basepage_index(struct page *page) return __basepage_index(page); } +static inline bool hugepages_supported(void) +{ + /* + * Some platform decide whether they support huge pages at boot + * time. On these, such as powerpc, HPAGE_SHIFT is set to 0 when + * there is no such support + */ + return HPAGE_SHIFT != 0; +} + #else struct hstate {}; #define alloc_huge_page_node(h, nid) NULL diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 9256590bdd0e..c52095ce40b4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1889,11 +1889,7 @@ module_exit(hugetlb_exit); static int __init hugetlb_init(void) { - /* Some platform decide whether they support huge pages at boot - * time. On these, such as powerpc, HPAGE_SHIFT is set to 0 when - * there is no such support - */ - if (HPAGE_SHIFT == 0) + if (!hugepages_supported()) return 0; if (!size_to_hstate(default_hstate_size)) { @@ -2010,6 +2006,9 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy, unsigned long tmp; int ret; + if (!hugepages_supported()) + return -ENOTSUPP; + tmp = h->max_huge_pages; if (write && h->order >= MAX_ORDER) @@ -2075,6 +2074,9 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write, unsigned long tmp; int ret; + if (!hugepages_supported()) + return -ENOTSUPP; + tmp = h->nr_overcommit_huge_pages; if (write && h->order >= MAX_ORDER) @@ -2100,6 +2102,8 @@ out: void hugetlb_report_meminfo(struct seq_file *m) { struct hstate *h = &default_hstate; + if (!hugepages_supported()) + return; seq_printf(m, "HugePages_Total: %5lu\n" "HugePages_Free: %5lu\n" @@ -2116,6 +2120,8 @@ void hugetlb_report_meminfo(struct seq_file *m) int hugetlb_report_node_meminfo(int nid, char *buf) { struct hstate *h = &default_hstate; + if (!hugepages_supported()) + return 0; return sprintf(buf, "Node %d HugePages_Total: %5u\n" "Node %d HugePages_Free: %5u\n" -- 2.39.2