Subject: + hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported.patch added to -mm tree
To: nacc@xxxxxxxxxxxxxxxxxx,aneesh.kumar@xxxxxxxxxxxxxxxxxx,mgorman@xxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 18 Apr 2014 13:38:42 -0700
The patch titled
Subject: hugetlb: ensure hugepage access is denied if hugepages are not supported
has been added to the -mm tree. Its filename is
hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported.patch
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From: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
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.
Signed-off-by: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/hugetlbfs/inode.c | 5 +++++
include/linux/hugetlb.h | 10 ++++++++++
mm/hugetlb.c | 19 ++++++++++++++-----
3 files changed, 29 insertions(+), 5 deletions(-)
diff -puN fs/hugetlbfs/inode.c~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported fs/hugetlbfs/inode.c
--- a/fs/hugetlbfs/inode.c~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported
+++ a/fs/hugetlbfs/inode.c
@@ -1030,6 +1030,11 @@ static int __init init_hugetlbfs_fs(void
int error;
int i;
+ if (!hugepages_supported()) {
+ printk(KERN_ERR "hugetlbfs: Disabling because there are no supported hugepage sizes\n");
+ return -ENOTSUPP;
+ }
+
error = bdi_init(&hugetlbfs_backing_dev_info);
if (error)
return error;
diff -puN include/linux/hugetlb.h~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported include/linux/hugetlb.h
--- a/include/linux/hugetlb.h~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported
+++ a/include/linux/hugetlb.h
@@ -460,4 +460,14 @@ static inline spinlock_t *huge_pte_lock(
return ptl;
}
+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;
+}
+
#endif /* _LINUX_HUGETLB_H */
diff -puN mm/hugetlb.c~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported mm/hugetlb.c
--- a/mm/hugetlb.c~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported
+++ a/mm/hugetlb.c
@@ -1981,11 +1981,7 @@ static int __init hugetlb_init(void)
{
int i;
- /* 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)) {
@@ -2112,6 +2108,9 @@ static int hugetlb_sysctl_handler_common
unsigned long tmp;
int ret;
+ if (!hugepages_supported())
+ return -ENOTSUPP;
+
tmp = h->max_huge_pages;
if (write && h->order >= MAX_ORDER)
@@ -2165,6 +2164,9 @@ int hugetlb_overcommit_handler(struct ct
unsigned long tmp;
int ret;
+ if (!hugepages_supported())
+ return -ENOTSUPP;
+
tmp = h->nr_overcommit_huge_pages;
if (write && h->order >= MAX_ORDER)
@@ -2190,6 +2192,8 @@ 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"
@@ -2206,6 +2210,8 @@ void hugetlb_report_meminfo(struct seq_f
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"
@@ -2220,6 +2226,9 @@ void hugetlb_show_meminfo(void)
struct hstate *h;
int nid;
+ if (!hugepages_supported())
+ return;
+
for_each_node_state(nid, N_MEMORY)
for_each_hstate(h)
pr_info("Node %d hugepages_total=%u hugepages_free=%u hugepages_surp=%u hugepages_size=%lukB\n",
_
Patches currently in -mm which might be from nacc@xxxxxxxxxxxxxxxxxx are
hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported.patch
hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported-fix.patch
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