Commit 457c1b27 authored by Nishanth Aravamudan's avatar Nishanth Aravamudan Committed by Linus Torvalds
Browse files

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: default avatarNishanth Aravamudan <nacc@linux.vnet.ibm.com>
Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 93030d83
......@@ -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;
......
......@@ -412,6 +412,16 @@ static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
return &mm->page_table_lock;
}
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 /* CONFIG_HUGETLB_PAGE */
struct hstate {};
#define alloc_huge_page_node(h, nid) NULL
......
......@@ -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(bool obey_mempolicy,
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 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)
......@@ -2190,6 +2192,8 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
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_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"
......@@ -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",
......
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