[PATCH 2/2] mm: Account for MAP_SHARED mappings using VM_MAYSHARE and not VM_SHARED in hugetlbfs
From: Mel Gorman
Date: Wed May 27 2009 - 07:15:53 EST
hugetlbfs reserves huge pages but does not fault them at mmap() time to ensure
that future faults succeed. The reservation behaviour differs depending on
whether the mapping was mapped MAP_SHARED or MAP_PRIVATE. For MAP_SHARED
mappings, hugepages are reserved when mmap() is first called and are tracked
based on information associated with the inode. Other processes mapping
MAP_SHARED use the same reservation. MAP_PRIVATE track the reservations
based on the VMA created as part of the mmap() operation. Each process
mapping MAP_PRIVATE must make its own reservation.
hugetlbfs currently checks if a VMA is MAP_SHARED with the VM_SHARED flag and
not VM_MAYSHARE. For file-backed mappings, such as hugetlbfs, VM_SHARED is
set only if the mapping is MAP_SHARED and the file was opened read-write. If a
shared memory mapping was mapped shared-read-write for populating of data and
mapped shared-read-only by other processes, then hugetlbfs would account for
the mapping as if it was MAP_PRIVATE. This causes processes to fail to map
the file MAP_SHARED even though it should succeed as the reservation is there.
This patch alters mm/hugetlb.c and replaces VM_SHARED with VM_MAYSHARE when
the intent of the code was to check whether the VMA was mapped MAP_SHARED
or MAP_PRIVATE.
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
---
mm/hugetlb.c | 26 +++++++++++++-------------
1 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 28c655b..e83ad2c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -316,7 +316,7 @@ static void resv_map_release(struct kref *ref)
static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
{
VM_BUG_ON(!is_vm_hugetlb_page(vma));
- if (!(vma->vm_flags & VM_SHARED))
+ if (!(vma->vm_flags & VM_MAYSHARE))
return (struct resv_map *)(get_vma_private_data(vma) &
~HPAGE_RESV_MASK);
return NULL;
@@ -325,7 +325,7 @@ static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
{
VM_BUG_ON(!is_vm_hugetlb_page(vma));
- VM_BUG_ON(vma->vm_flags & VM_SHARED);
+ VM_BUG_ON(vma->vm_flags & VM_MAYSHARE);
set_vma_private_data(vma, (get_vma_private_data(vma) &
HPAGE_RESV_MASK) | (unsigned long)map);
@@ -334,7 +334,7 @@ static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
{
VM_BUG_ON(!is_vm_hugetlb_page(vma));
- VM_BUG_ON(vma->vm_flags & VM_SHARED);
+ VM_BUG_ON(vma->vm_flags & VM_MAYSHARE);
set_vma_private_data(vma, get_vma_private_data(vma) | flags);
}
@@ -353,7 +353,7 @@ static void decrement_hugepage_resv_vma(struct hstate *h,
if (vma->vm_flags & VM_NORESERVE)
return;
- if (vma->vm_flags & VM_SHARED) {
+ if (vma->vm_flags & VM_MAYSHARE) {
/* Shared mappings always use reserves */
h->resv_huge_pages--;
} else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
@@ -369,14 +369,14 @@ static void decrement_hugepage_resv_vma(struct hstate *h,
void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
{
VM_BUG_ON(!is_vm_hugetlb_page(vma));
- if (!(vma->vm_flags & VM_SHARED))
+ if (!(vma->vm_flags & VM_MAYSHARE))
vma->vm_private_data = (void *)0;
}
/* Returns true if the VMA has associated reserve pages */
static int vma_has_reserves(struct vm_area_struct *vma)
{
- if (vma->vm_flags & VM_SHARED)
+ if (vma->vm_flags & VM_MAYSHARE)
return 1;
if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
return 1;
@@ -924,7 +924,7 @@ static long vma_needs_reservation(struct hstate *h,
struct address_space *mapping = vma->vm_file->f_mapping;
struct inode *inode = mapping->host;
- if (vma->vm_flags & VM_SHARED) {
+ if (vma->vm_flags & VM_MAYSHARE) {
pgoff_t idx = vma_hugecache_offset(h, vma, addr);
return region_chg(&inode->i_mapping->private_list,
idx, idx + 1);
@@ -949,7 +949,7 @@ static void vma_commit_reservation(struct hstate *h,
struct address_space *mapping = vma->vm_file->f_mapping;
struct inode *inode = mapping->host;
- if (vma->vm_flags & VM_SHARED) {
+ if (vma->vm_flags & VM_MAYSHARE) {
pgoff_t idx = vma_hugecache_offset(h, vma, addr);
region_add(&inode->i_mapping->private_list, idx, idx + 1);
@@ -1893,7 +1893,7 @@ retry_avoidcopy:
* at the time of fork() could consume its reserves on COW instead
* of the full address range.
*/
- if (!(vma->vm_flags & VM_SHARED) &&
+ if (!(vma->vm_flags & VM_MAYSHARE) &&
is_vma_resv_set(vma, HPAGE_RESV_OWNER) &&
old_page != pagecache_page)
outside_reserve = 1;
@@ -2000,7 +2000,7 @@ retry:
clear_huge_page(page, address, huge_page_size(h));
__SetPageUptodate(page);
- if (vma->vm_flags & VM_SHARED) {
+ if (vma->vm_flags & VM_MAYSHARE) {
int err;
struct inode *inode = mapping->host;
@@ -2104,7 +2104,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
goto out_mutex;
}
- if (!(vma->vm_flags & VM_SHARED))
+ if (!(vma->vm_flags & VM_MAYSHARE))
pagecache_page = hugetlbfs_pagecache_page(h,
vma, address);
}
@@ -2289,7 +2289,7 @@ int hugetlb_reserve_pages(struct inode *inode,
* to reserve the full area even if read-only as mprotect() may be
* called to make the mapping read-write. Assume !vma is a shm mapping
*/
- if (!vma || vma->vm_flags & VM_SHARED)
+ if (!vma || vma->vm_flags & VM_MAYSHARE)
chg = region_chg(&inode->i_mapping->private_list, from, to);
else {
struct resv_map *resv_map = resv_map_alloc();
@@ -2330,7 +2330,7 @@ int hugetlb_reserve_pages(struct inode *inode,
* consumed reservations are stored in the map. Hence, nothing
* else has to be done for private mappings here
*/
- if (!vma || vma->vm_flags & VM_SHARED)
+ if (!vma || vma->vm_flags & VM_MAYSHARE)
region_add(&inode->i_mapping->private_list, from, to);
return 0;
}
--
1.5.6.5
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