linux/mm/hugetlb.c
Larry Woodman c5c99429fa fix hugepages leak due to pagetable page sharing
The shared page table code for hugetlb memory on x86 and x86_64
is causing a leak.  When a user of hugepages exits using this code
the system leaks some of the hugepages.

-------------------------------------------------------
Part of /proc/meminfo just before database startup:
HugePages_Total:  5500
HugePages_Free:   5500
HugePages_Rsvd:      0
Hugepagesize:     2048 kB

Just before shutdown:
HugePages_Total:  5500
HugePages_Free:   4475
HugePages_Rsvd:      0
Hugepagesize:     2048 kB

After shutdown:
HugePages_Total:  5500
HugePages_Free:   4988
HugePages_Rsvd:
0 Hugepagesize:     2048 kB
----------------------------------------------------------

The problem occurs durring a fork, in copy_hugetlb_page_range().  It
locates the dst_pte using huge_pte_alloc().  Since huge_pte_alloc() calls
huge_pmd_share() it will share the pmd page if can, yet the main loop in
copy_hugetlb_page_range() does a get_page() on every hugepage.  This is a
violation of the shared hugepmd pagetable protocol and creates additional
referenced to the hugepages causing a leak when the unmap of the VMA
occurs.  We can skip the entire replication of the ptes when the hugepage
pagetables are shared.  The attached patch skips copying the ptes and the
get_page() calls if the hugetlbpage pagetable is shared.

[akpm@linux-foundation.org: coding-style cleanups]
Signed-off-by: Larry Woodman <lwoodman@redhat.com>
Signed-off-by: Adam Litke <agl@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ken Chen <kenchen@google.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-01-24 08:07:27 -08:00

1237 lines
31 KiB
C

/*
* Generic hugetlb support.
* (C) William Irwin, April 2004
*/
#include <linux/gfp.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/sysctl.h>
#include <linux/highmem.h>
#include <linux/nodemask.h>
#include <linux/pagemap.h>
#include <linux/mempolicy.h>
#include <linux/cpuset.h>
#include <linux/mutex.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <linux/hugetlb.h>
#include "internal.h"
const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
static unsigned long nr_huge_pages, free_huge_pages, resv_huge_pages;
static unsigned long surplus_huge_pages;
unsigned long max_huge_pages;
static struct list_head hugepage_freelists[MAX_NUMNODES];
static unsigned int nr_huge_pages_node[MAX_NUMNODES];
static unsigned int free_huge_pages_node[MAX_NUMNODES];
static unsigned int surplus_huge_pages_node[MAX_NUMNODES];
static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
unsigned long hugepages_treat_as_movable;
unsigned long nr_overcommit_huge_pages;
static int hugetlb_next_nid;
/*
* Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
*/
static DEFINE_SPINLOCK(hugetlb_lock);
static void clear_huge_page(struct page *page, unsigned long addr)
{
int i;
might_sleep();
for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
cond_resched();
clear_user_highpage(page + i, addr + i * PAGE_SIZE);
}
}
static void copy_huge_page(struct page *dst, struct page *src,
unsigned long addr, struct vm_area_struct *vma)
{
int i;
might_sleep();
for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
cond_resched();
copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
}
}
static void enqueue_huge_page(struct page *page)
{
int nid = page_to_nid(page);
list_add(&page->lru, &hugepage_freelists[nid]);
free_huge_pages++;
free_huge_pages_node[nid]++;
}
static struct page *dequeue_huge_page(struct vm_area_struct *vma,
unsigned long address)
{
int nid;
struct page *page = NULL;
struct mempolicy *mpol;
struct zonelist *zonelist = huge_zonelist(vma, address,
htlb_alloc_mask, &mpol);
struct zone **z;
for (z = zonelist->zones; *z; z++) {
nid = zone_to_nid(*z);
if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
!list_empty(&hugepage_freelists[nid])) {
page = list_entry(hugepage_freelists[nid].next,
struct page, lru);
list_del(&page->lru);
free_huge_pages--;
free_huge_pages_node[nid]--;
if (vma && vma->vm_flags & VM_MAYSHARE)
resv_huge_pages--;
break;
}
}
mpol_free(mpol); /* unref if mpol !NULL */
return page;
}
static void update_and_free_page(struct page *page)
{
int i;
nr_huge_pages--;
nr_huge_pages_node[page_to_nid(page)]--;
for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
1 << PG_private | 1<< PG_writeback);
}
set_compound_page_dtor(page, NULL);
set_page_refcounted(page);
__free_pages(page, HUGETLB_PAGE_ORDER);
}
static void free_huge_page(struct page *page)
{
int nid = page_to_nid(page);
struct address_space *mapping;
mapping = (struct address_space *) page_private(page);
BUG_ON(page_count(page));
INIT_LIST_HEAD(&page->lru);
spin_lock(&hugetlb_lock);
if (surplus_huge_pages_node[nid]) {
update_and_free_page(page);
surplus_huge_pages--;
surplus_huge_pages_node[nid]--;
} else {
enqueue_huge_page(page);
}
spin_unlock(&hugetlb_lock);
if (mapping)
hugetlb_put_quota(mapping, 1);
set_page_private(page, 0);
}
/*
* Increment or decrement surplus_huge_pages. Keep node-specific counters
* balanced by operating on them in a round-robin fashion.
* Returns 1 if an adjustment was made.
*/
static int adjust_pool_surplus(int delta)
{
static int prev_nid;
int nid = prev_nid;
int ret = 0;
VM_BUG_ON(delta != -1 && delta != 1);
do {
nid = next_node(nid, node_online_map);
if (nid == MAX_NUMNODES)
nid = first_node(node_online_map);
/* To shrink on this node, there must be a surplus page */
if (delta < 0 && !surplus_huge_pages_node[nid])
continue;
/* Surplus cannot exceed the total number of pages */
if (delta > 0 && surplus_huge_pages_node[nid] >=
nr_huge_pages_node[nid])
continue;
surplus_huge_pages += delta;
surplus_huge_pages_node[nid] += delta;
ret = 1;
break;
} while (nid != prev_nid);
prev_nid = nid;
return ret;
}
static struct page *alloc_fresh_huge_page_node(int nid)
{
struct page *page;
page = alloc_pages_node(nid,
htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|__GFP_NOWARN,
HUGETLB_PAGE_ORDER);
if (page) {
set_compound_page_dtor(page, free_huge_page);
spin_lock(&hugetlb_lock);
nr_huge_pages++;
nr_huge_pages_node[nid]++;
spin_unlock(&hugetlb_lock);
put_page(page); /* free it into the hugepage allocator */
}
return page;
}
static int alloc_fresh_huge_page(void)
{
struct page *page;
int start_nid;
int next_nid;
int ret = 0;
start_nid = hugetlb_next_nid;
do {
page = alloc_fresh_huge_page_node(hugetlb_next_nid);
if (page)
ret = 1;
/*
* Use a helper variable to find the next node and then
* copy it back to hugetlb_next_nid afterwards:
* otherwise there's a window in which a racer might
* pass invalid nid MAX_NUMNODES to alloc_pages_node.
* But we don't need to use a spin_lock here: it really
* doesn't matter if occasionally a racer chooses the
* same nid as we do. Move nid forward in the mask even
* if we just successfully allocated a hugepage so that
* the next caller gets hugepages on the next node.
*/
next_nid = next_node(hugetlb_next_nid, node_online_map);
if (next_nid == MAX_NUMNODES)
next_nid = first_node(node_online_map);
hugetlb_next_nid = next_nid;
} while (!page && hugetlb_next_nid != start_nid);
return ret;
}
static struct page *alloc_buddy_huge_page(struct vm_area_struct *vma,
unsigned long address)
{
struct page *page;
unsigned int nid;
/*
* Assume we will successfully allocate the surplus page to
* prevent racing processes from causing the surplus to exceed
* overcommit
*
* This however introduces a different race, where a process B
* tries to grow the static hugepage pool while alloc_pages() is
* called by process A. B will only examine the per-node
* counters in determining if surplus huge pages can be
* converted to normal huge pages in adjust_pool_surplus(). A
* won't be able to increment the per-node counter, until the
* lock is dropped by B, but B doesn't drop hugetlb_lock until
* no more huge pages can be converted from surplus to normal
* state (and doesn't try to convert again). Thus, we have a
* case where a surplus huge page exists, the pool is grown, and
* the surplus huge page still exists after, even though it
* should just have been converted to a normal huge page. This
* does not leak memory, though, as the hugepage will be freed
* once it is out of use. It also does not allow the counters to
* go out of whack in adjust_pool_surplus() as we don't modify
* the node values until we've gotten the hugepage and only the
* per-node value is checked there.
*/
spin_lock(&hugetlb_lock);
if (surplus_huge_pages >= nr_overcommit_huge_pages) {
spin_unlock(&hugetlb_lock);
return NULL;
} else {
nr_huge_pages++;
surplus_huge_pages++;
}
spin_unlock(&hugetlb_lock);
page = alloc_pages(htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
HUGETLB_PAGE_ORDER);
spin_lock(&hugetlb_lock);
if (page) {
nid = page_to_nid(page);
set_compound_page_dtor(page, free_huge_page);
/*
* We incremented the global counters already
*/
nr_huge_pages_node[nid]++;
surplus_huge_pages_node[nid]++;
} else {
nr_huge_pages--;
surplus_huge_pages--;
}
spin_unlock(&hugetlb_lock);
return page;
}
/*
* Increase the hugetlb pool such that it can accomodate a reservation
* of size 'delta'.
*/
static int gather_surplus_pages(int delta)
{
struct list_head surplus_list;
struct page *page, *tmp;
int ret, i;
int needed, allocated;
needed = (resv_huge_pages + delta) - free_huge_pages;
if (needed <= 0)
return 0;
allocated = 0;
INIT_LIST_HEAD(&surplus_list);
ret = -ENOMEM;
retry:
spin_unlock(&hugetlb_lock);
for (i = 0; i < needed; i++) {
page = alloc_buddy_huge_page(NULL, 0);
if (!page) {
/*
* We were not able to allocate enough pages to
* satisfy the entire reservation so we free what
* we've allocated so far.
*/
spin_lock(&hugetlb_lock);
needed = 0;
goto free;
}
list_add(&page->lru, &surplus_list);
}
allocated += needed;
/*
* After retaking hugetlb_lock, we need to recalculate 'needed'
* because either resv_huge_pages or free_huge_pages may have changed.
*/
spin_lock(&hugetlb_lock);
needed = (resv_huge_pages + delta) - (free_huge_pages + allocated);
if (needed > 0)
goto retry;
/*
* The surplus_list now contains _at_least_ the number of extra pages
* needed to accomodate the reservation. Add the appropriate number
* of pages to the hugetlb pool and free the extras back to the buddy
* allocator.
*/
needed += allocated;
ret = 0;
free:
list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
list_del(&page->lru);
if ((--needed) >= 0)
enqueue_huge_page(page);
else {
/*
* Decrement the refcount and free the page using its
* destructor. This must be done with hugetlb_lock
* unlocked which is safe because free_huge_page takes
* hugetlb_lock before deciding how to free the page.
*/
spin_unlock(&hugetlb_lock);
put_page(page);
spin_lock(&hugetlb_lock);
}
}
return ret;
}
/*
* When releasing a hugetlb pool reservation, any surplus pages that were
* allocated to satisfy the reservation must be explicitly freed if they were
* never used.
*/
static void return_unused_surplus_pages(unsigned long unused_resv_pages)
{
static int nid = -1;
struct page *page;
unsigned long nr_pages;
nr_pages = min(unused_resv_pages, surplus_huge_pages);
while (nr_pages) {
nid = next_node(nid, node_online_map);
if (nid == MAX_NUMNODES)
nid = first_node(node_online_map);
if (!surplus_huge_pages_node[nid])
continue;
if (!list_empty(&hugepage_freelists[nid])) {
page = list_entry(hugepage_freelists[nid].next,
struct page, lru);
list_del(&page->lru);
update_and_free_page(page);
free_huge_pages--;
free_huge_pages_node[nid]--;
surplus_huge_pages--;
surplus_huge_pages_node[nid]--;
nr_pages--;
}
}
}
static struct page *alloc_huge_page_shared(struct vm_area_struct *vma,
unsigned long addr)
{
struct page *page;
spin_lock(&hugetlb_lock);
page = dequeue_huge_page(vma, addr);
spin_unlock(&hugetlb_lock);
return page ? page : ERR_PTR(-VM_FAULT_OOM);
}
static struct page *alloc_huge_page_private(struct vm_area_struct *vma,
unsigned long addr)
{
struct page *page = NULL;
if (hugetlb_get_quota(vma->vm_file->f_mapping, 1))
return ERR_PTR(-VM_FAULT_SIGBUS);
spin_lock(&hugetlb_lock);
if (free_huge_pages > resv_huge_pages)
page = dequeue_huge_page(vma, addr);
spin_unlock(&hugetlb_lock);
if (!page) {
page = alloc_buddy_huge_page(vma, addr);
if (!page) {
hugetlb_put_quota(vma->vm_file->f_mapping, 1);
return ERR_PTR(-VM_FAULT_OOM);
}
}
return page;
}
static struct page *alloc_huge_page(struct vm_area_struct *vma,
unsigned long addr)
{
struct page *page;
struct address_space *mapping = vma->vm_file->f_mapping;
if (vma->vm_flags & VM_MAYSHARE)
page = alloc_huge_page_shared(vma, addr);
else
page = alloc_huge_page_private(vma, addr);
if (!IS_ERR(page)) {
set_page_refcounted(page);
set_page_private(page, (unsigned long) mapping);
}
return page;
}
static int __init hugetlb_init(void)
{
unsigned long i;
if (HPAGE_SHIFT == 0)
return 0;
for (i = 0; i < MAX_NUMNODES; ++i)
INIT_LIST_HEAD(&hugepage_freelists[i]);
hugetlb_next_nid = first_node(node_online_map);
for (i = 0; i < max_huge_pages; ++i) {
if (!alloc_fresh_huge_page())
break;
}
max_huge_pages = free_huge_pages = nr_huge_pages = i;
printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
return 0;
}
module_init(hugetlb_init);
static int __init hugetlb_setup(char *s)
{
if (sscanf(s, "%lu", &max_huge_pages) <= 0)
max_huge_pages = 0;
return 1;
}
__setup("hugepages=", hugetlb_setup);
static unsigned int cpuset_mems_nr(unsigned int *array)
{
int node;
unsigned int nr = 0;
for_each_node_mask(node, cpuset_current_mems_allowed)
nr += array[node];
return nr;
}
#ifdef CONFIG_SYSCTL
#ifdef CONFIG_HIGHMEM
static void try_to_free_low(unsigned long count)
{
int i;
for (i = 0; i < MAX_NUMNODES; ++i) {
struct page *page, *next;
list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
if (count >= nr_huge_pages)
return;
if (PageHighMem(page))
continue;
list_del(&page->lru);
update_and_free_page(page);
free_huge_pages--;
free_huge_pages_node[page_to_nid(page)]--;
}
}
}
#else
static inline void try_to_free_low(unsigned long count)
{
}
#endif
#define persistent_huge_pages (nr_huge_pages - surplus_huge_pages)
static unsigned long set_max_huge_pages(unsigned long count)
{
unsigned long min_count, ret;
/*
* Increase the pool size
* First take pages out of surplus state. Then make up the
* remaining difference by allocating fresh huge pages.
*
* We might race with alloc_buddy_huge_page() here and be unable
* to convert a surplus huge page to a normal huge page. That is
* not critical, though, it just means the overall size of the
* pool might be one hugepage larger than it needs to be, but
* within all the constraints specified by the sysctls.
*/
spin_lock(&hugetlb_lock);
while (surplus_huge_pages && count > persistent_huge_pages) {
if (!adjust_pool_surplus(-1))
break;
}
while (count > persistent_huge_pages) {
int ret;
/*
* If this allocation races such that we no longer need the
* page, free_huge_page will handle it by freeing the page
* and reducing the surplus.
*/
spin_unlock(&hugetlb_lock);
ret = alloc_fresh_huge_page();
spin_lock(&hugetlb_lock);
if (!ret)
goto out;
}
/*
* Decrease the pool size
* First return free pages to the buddy allocator (being careful
* to keep enough around to satisfy reservations). Then place
* pages into surplus state as needed so the pool will shrink
* to the desired size as pages become free.
*
* By placing pages into the surplus state independent of the
* overcommit value, we are allowing the surplus pool size to
* exceed overcommit. There are few sane options here. Since
* alloc_buddy_huge_page() is checking the global counter,
* though, we'll note that we're not allowed to exceed surplus
* and won't grow the pool anywhere else. Not until one of the
* sysctls are changed, or the surplus pages go out of use.
*/
min_count = resv_huge_pages + nr_huge_pages - free_huge_pages;
min_count = max(count, min_count);
try_to_free_low(min_count);
while (min_count < persistent_huge_pages) {
struct page *page = dequeue_huge_page(NULL, 0);
if (!page)
break;
update_and_free_page(page);
}
while (count < persistent_huge_pages) {
if (!adjust_pool_surplus(1))
break;
}
out:
ret = persistent_huge_pages;
spin_unlock(&hugetlb_lock);
return ret;
}
int hugetlb_sysctl_handler(struct ctl_table *table, int write,
struct file *file, void __user *buffer,
size_t *length, loff_t *ppos)
{
proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
max_huge_pages = set_max_huge_pages(max_huge_pages);
return 0;
}
int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
struct file *file, void __user *buffer,
size_t *length, loff_t *ppos)
{
proc_dointvec(table, write, file, buffer, length, ppos);
if (hugepages_treat_as_movable)
htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
else
htlb_alloc_mask = GFP_HIGHUSER;
return 0;
}
#endif /* CONFIG_SYSCTL */
int hugetlb_report_meminfo(char *buf)
{
return sprintf(buf,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
"HugePages_Rsvd: %5lu\n"
"HugePages_Surp: %5lu\n"
"Hugepagesize: %5lu kB\n",
nr_huge_pages,
free_huge_pages,
resv_huge_pages,
surplus_huge_pages,
HPAGE_SIZE/1024);
}
int hugetlb_report_node_meminfo(int nid, char *buf)
{
return sprintf(buf,
"Node %d HugePages_Total: %5u\n"
"Node %d HugePages_Free: %5u\n",
nid, nr_huge_pages_node[nid],
nid, free_huge_pages_node[nid]);
}
/* Return the number pages of memory we physically have, in PAGE_SIZE units. */
unsigned long hugetlb_total_pages(void)
{
return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
}
/*
* We cannot handle pagefaults against hugetlb pages at all. They cause
* handle_mm_fault() to try to instantiate regular-sized pages in the
* hugegpage VMA. do_page_fault() is supposed to trap this, so BUG is we get
* this far.
*/
static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
BUG();
return 0;
}
struct vm_operations_struct hugetlb_vm_ops = {
.fault = hugetlb_vm_op_fault,
};
static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
int writable)
{
pte_t entry;
if (writable) {
entry =
pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
} else {
entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
}
entry = pte_mkyoung(entry);
entry = pte_mkhuge(entry);
return entry;
}
static void set_huge_ptep_writable(struct vm_area_struct *vma,
unsigned long address, pte_t *ptep)
{
pte_t entry;
entry = pte_mkwrite(pte_mkdirty(*ptep));
if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
update_mmu_cache(vma, address, entry);
}
}
int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
struct vm_area_struct *vma)
{
pte_t *src_pte, *dst_pte, entry;
struct page *ptepage;
unsigned long addr;
int cow;
cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
src_pte = huge_pte_offset(src, addr);
if (!src_pte)
continue;
dst_pte = huge_pte_alloc(dst, addr);
if (!dst_pte)
goto nomem;
/* If the pagetables are shared don't copy or take references */
if (dst_pte == src_pte)
continue;
spin_lock(&dst->page_table_lock);
spin_lock(&src->page_table_lock);
if (!pte_none(*src_pte)) {
if (cow)
ptep_set_wrprotect(src, addr, src_pte);
entry = *src_pte;
ptepage = pte_page(entry);
get_page(ptepage);
set_huge_pte_at(dst, addr, dst_pte, entry);
}
spin_unlock(&src->page_table_lock);
spin_unlock(&dst->page_table_lock);
}
return 0;
nomem:
return -ENOMEM;
}
void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
pte_t *ptep;
pte_t pte;
struct page *page;
struct page *tmp;
/*
* A page gathering list, protected by per file i_mmap_lock. The
* lock is used to avoid list corruption from multiple unmapping
* of the same page since we are using page->lru.
*/
LIST_HEAD(page_list);
WARN_ON(!is_vm_hugetlb_page(vma));
BUG_ON(start & ~HPAGE_MASK);
BUG_ON(end & ~HPAGE_MASK);
spin_lock(&mm->page_table_lock);
for (address = start; address < end; address += HPAGE_SIZE) {
ptep = huge_pte_offset(mm, address);
if (!ptep)
continue;
if (huge_pmd_unshare(mm, &address, ptep))
continue;
pte = huge_ptep_get_and_clear(mm, address, ptep);
if (pte_none(pte))
continue;
page = pte_page(pte);
if (pte_dirty(pte))
set_page_dirty(page);
list_add(&page->lru, &page_list);
}
spin_unlock(&mm->page_table_lock);
flush_tlb_range(vma, start, end);
list_for_each_entry_safe(page, tmp, &page_list, lru) {
list_del(&page->lru);
put_page(page);
}
}
void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
unsigned long end)
{
/*
* It is undesirable to test vma->vm_file as it should be non-null
* for valid hugetlb area. However, vm_file will be NULL in the error
* cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails,
* do_mmap_pgoff() nullifies vma->vm_file before calling this function
* to clean up. Since no pte has actually been setup, it is safe to
* do nothing in this case.
*/
if (vma->vm_file) {
spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
__unmap_hugepage_range(vma, start, end);
spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
}
}
static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *ptep, pte_t pte)
{
struct page *old_page, *new_page;
int avoidcopy;
old_page = pte_page(pte);
/* If no-one else is actually using this page, avoid the copy
* and just make the page writable */
avoidcopy = (page_count(old_page) == 1);
if (avoidcopy) {
set_huge_ptep_writable(vma, address, ptep);
return 0;
}
page_cache_get(old_page);
new_page = alloc_huge_page(vma, address);
if (IS_ERR(new_page)) {
page_cache_release(old_page);
return -PTR_ERR(new_page);
}
spin_unlock(&mm->page_table_lock);
copy_huge_page(new_page, old_page, address, vma);
spin_lock(&mm->page_table_lock);
ptep = huge_pte_offset(mm, address & HPAGE_MASK);
if (likely(pte_same(*ptep, pte))) {
/* Break COW */
set_huge_pte_at(mm, address, ptep,
make_huge_pte(vma, new_page, 1));
/* Make the old page be freed below */
new_page = old_page;
}
page_cache_release(new_page);
page_cache_release(old_page);
return 0;
}
static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *ptep, int write_access)
{
int ret = VM_FAULT_SIGBUS;
unsigned long idx;
unsigned long size;
struct page *page;
struct address_space *mapping;
pte_t new_pte;
mapping = vma->vm_file->f_mapping;
idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
/*
* Use page lock to guard against racing truncation
* before we get page_table_lock.
*/
retry:
page = find_lock_page(mapping, idx);
if (!page) {
size = i_size_read(mapping->host) >> HPAGE_SHIFT;
if (idx >= size)
goto out;
page = alloc_huge_page(vma, address);
if (IS_ERR(page)) {
ret = -PTR_ERR(page);
goto out;
}
clear_huge_page(page, address);
if (vma->vm_flags & VM_SHARED) {
int err;
struct inode *inode = mapping->host;
err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
if (err) {
put_page(page);
if (err == -EEXIST)
goto retry;
goto out;
}
spin_lock(&inode->i_lock);
inode->i_blocks += BLOCKS_PER_HUGEPAGE;
spin_unlock(&inode->i_lock);
} else
lock_page(page);
}
spin_lock(&mm->page_table_lock);
size = i_size_read(mapping->host) >> HPAGE_SHIFT;
if (idx >= size)
goto backout;
ret = 0;
if (!pte_none(*ptep))
goto backout;
new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
&& (vma->vm_flags & VM_SHARED)));
set_huge_pte_at(mm, address, ptep, new_pte);
if (write_access && !(vma->vm_flags & VM_SHARED)) {
/* Optimization, do the COW without a second fault */
ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
}
spin_unlock(&mm->page_table_lock);
unlock_page(page);
out:
return ret;
backout:
spin_unlock(&mm->page_table_lock);
unlock_page(page);
put_page(page);
goto out;
}
int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, int write_access)
{
pte_t *ptep;
pte_t entry;
int ret;
static DEFINE_MUTEX(hugetlb_instantiation_mutex);
ptep = huge_pte_alloc(mm, address);
if (!ptep)
return VM_FAULT_OOM;
/*
* Serialize hugepage allocation and instantiation, so that we don't
* get spurious allocation failures if two CPUs race to instantiate
* the same page in the page cache.
*/
mutex_lock(&hugetlb_instantiation_mutex);
entry = *ptep;
if (pte_none(entry)) {
ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
mutex_unlock(&hugetlb_instantiation_mutex);
return ret;
}
ret = 0;
spin_lock(&mm->page_table_lock);
/* Check for a racing update before calling hugetlb_cow */
if (likely(pte_same(entry, *ptep)))
if (write_access && !pte_write(entry))
ret = hugetlb_cow(mm, vma, address, ptep, entry);
spin_unlock(&mm->page_table_lock);
mutex_unlock(&hugetlb_instantiation_mutex);
return ret;
}
int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page **pages, struct vm_area_struct **vmas,
unsigned long *position, int *length, int i,
int write)
{
unsigned long pfn_offset;
unsigned long vaddr = *position;
int remainder = *length;
spin_lock(&mm->page_table_lock);
while (vaddr < vma->vm_end && remainder) {
pte_t *pte;
struct page *page;
/*
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make * sure we get the
* first, for the page indexing below to work.
*/
pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);
if (!pte || pte_none(*pte) || (write && !pte_write(*pte))) {
int ret;
spin_unlock(&mm->page_table_lock);
ret = hugetlb_fault(mm, vma, vaddr, write);
spin_lock(&mm->page_table_lock);
if (!(ret & VM_FAULT_ERROR))
continue;
remainder = 0;
if (!i)
i = -EFAULT;
break;
}
pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
page = pte_page(*pte);
same_page:
if (pages) {
get_page(page);
pages[i] = page + pfn_offset;
}
if (vmas)
vmas[i] = vma;
vaddr += PAGE_SIZE;
++pfn_offset;
--remainder;
++i;
if (vaddr < vma->vm_end && remainder &&
pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
/*
* We use pfn_offset to avoid touching the pageframes
* of this compound page.
*/
goto same_page;
}
}
spin_unlock(&mm->page_table_lock);
*length = remainder;
*position = vaddr;
return i;
}
void hugetlb_change_protection(struct vm_area_struct *vma,
unsigned long address, unsigned long end, pgprot_t newprot)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long start = address;
pte_t *ptep;
pte_t pte;
BUG_ON(address >= end);
flush_cache_range(vma, address, end);
spin_lock(&vma->vm_file->f_mapping->i_mmap_lock);
spin_lock(&mm->page_table_lock);
for (; address < end; address += HPAGE_SIZE) {
ptep = huge_pte_offset(mm, address);
if (!ptep)
continue;
if (huge_pmd_unshare(mm, &address, ptep))
continue;
if (!pte_none(*ptep)) {
pte = huge_ptep_get_and_clear(mm, address, ptep);
pte = pte_mkhuge(pte_modify(pte, newprot));
set_huge_pte_at(mm, address, ptep, pte);
}
}
spin_unlock(&mm->page_table_lock);
spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock);
flush_tlb_range(vma, start, end);
}
struct file_region {
struct list_head link;
long from;
long to;
};
static long region_add(struct list_head *head, long f, long t)
{
struct file_region *rg, *nrg, *trg;
/* Locate the region we are either in or before. */
list_for_each_entry(rg, head, link)
if (f <= rg->to)
break;
/* Round our left edge to the current segment if it encloses us. */
if (f > rg->from)
f = rg->from;
/* Check for and consume any regions we now overlap with. */
nrg = rg;
list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
if (&rg->link == head)
break;
if (rg->from > t)
break;
/* If this area reaches higher then extend our area to
* include it completely. If this is not the first area
* which we intend to reuse, free it. */
if (rg->to > t)
t = rg->to;
if (rg != nrg) {
list_del(&rg->link);
kfree(rg);
}
}
nrg->from = f;
nrg->to = t;
return 0;
}
static long region_chg(struct list_head *head, long f, long t)
{
struct file_region *rg, *nrg;
long chg = 0;
/* Locate the region we are before or in. */
list_for_each_entry(rg, head, link)
if (f <= rg->to)
break;
/* If we are below the current region then a new region is required.
* Subtle, allocate a new region at the position but make it zero
* size such that we can guarantee to record the reservation. */
if (&rg->link == head || t < rg->from) {
nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
if (!nrg)
return -ENOMEM;
nrg->from = f;
nrg->to = f;
INIT_LIST_HEAD(&nrg->link);
list_add(&nrg->link, rg->link.prev);
return t - f;
}
/* Round our left edge to the current segment if it encloses us. */
if (f > rg->from)
f = rg->from;
chg = t - f;
/* Check for and consume any regions we now overlap with. */
list_for_each_entry(rg, rg->link.prev, link) {
if (&rg->link == head)
break;
if (rg->from > t)
return chg;
/* We overlap with this area, if it extends futher than
* us then we must extend ourselves. Account for its
* existing reservation. */
if (rg->to > t) {
chg += rg->to - t;
t = rg->to;
}
chg -= rg->to - rg->from;
}
return chg;
}
static long region_truncate(struct list_head *head, long end)
{
struct file_region *rg, *trg;
long chg = 0;
/* Locate the region we are either in or before. */
list_for_each_entry(rg, head, link)
if (end <= rg->to)
break;
if (&rg->link == head)
return 0;
/* If we are in the middle of a region then adjust it. */
if (end > rg->from) {
chg = rg->to - end;
rg->to = end;
rg = list_entry(rg->link.next, typeof(*rg), link);
}
/* Drop any remaining regions. */
list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
if (&rg->link == head)
break;
chg += rg->to - rg->from;
list_del(&rg->link);
kfree(rg);
}
return chg;
}
static int hugetlb_acct_memory(long delta)
{
int ret = -ENOMEM;
spin_lock(&hugetlb_lock);
/*
* When cpuset is configured, it breaks the strict hugetlb page
* reservation as the accounting is done on a global variable. Such
* reservation is completely rubbish in the presence of cpuset because
* the reservation is not checked against page availability for the
* current cpuset. Application can still potentially OOM'ed by kernel
* with lack of free htlb page in cpuset that the task is in.
* Attempt to enforce strict accounting with cpuset is almost
* impossible (or too ugly) because cpuset is too fluid that
* task or memory node can be dynamically moved between cpusets.
*
* The change of semantics for shared hugetlb mapping with cpuset is
* undesirable. However, in order to preserve some of the semantics,
* we fall back to check against current free page availability as
* a best attempt and hopefully to minimize the impact of changing
* semantics that cpuset has.
*/
if (delta > 0) {
if (gather_surplus_pages(delta) < 0)
goto out;
if (delta > cpuset_mems_nr(free_huge_pages_node))
goto out;
}
ret = 0;
resv_huge_pages += delta;
if (delta < 0)
return_unused_surplus_pages((unsigned long) -delta);
out:
spin_unlock(&hugetlb_lock);
return ret;
}
int hugetlb_reserve_pages(struct inode *inode, long from, long to)
{
long ret, chg;
chg = region_chg(&inode->i_mapping->private_list, from, to);
if (chg < 0)
return chg;
if (hugetlb_get_quota(inode->i_mapping, chg))
return -ENOSPC;
ret = hugetlb_acct_memory(chg);
if (ret < 0) {
hugetlb_put_quota(inode->i_mapping, chg);
return ret;
}
region_add(&inode->i_mapping->private_list, from, to);
return 0;
}
void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
{
long chg = region_truncate(&inode->i_mapping->private_list, offset);
spin_lock(&inode->i_lock);
inode->i_blocks -= BLOCKS_PER_HUGEPAGE * freed;
spin_unlock(&inode->i_lock);
hugetlb_put_quota(inode->i_mapping, (chg - freed));
hugetlb_acct_memory(-(chg - freed));
}