[PATCH] hugetlb: overcommit accounting check
Basic overcommit checking for hugetlb_file_map() based on an implementation
used with demand faulting in SLES9.
Since demand faulting can't guarantee the availability of pages at mmap
time, this patch implements a basic sanity check to ensure that the number
of huge pages required to satisfy the mmap are currently available.
Despite the obvious race, I think it is a good start on doing proper
accounting. I'd like to work towards an accounting system that mimics the
semantics of normal pages (especially for the MAP_PRIVATE/COW case). That
work is underway and builds on what this patch starts.
Huge page shared memory segments are simpler and still maintain their
commit on shmget semantics.
Signed-off-by: Adam Litke <agl@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 2627efe..e026c80 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -45,9 +45,58 @@
int sysctl_hugetlb_shm_group;
+static void huge_pagevec_release(struct pagevec *pvec)
+{
+ int i;
+
+ for (i = 0; i < pagevec_count(pvec); ++i)
+ put_page(pvec->pages[i]);
+
+ pagevec_reinit(pvec);
+}
+
+/*
+ * huge_pages_needed tries to determine the number of new huge pages that
+ * will be required to fully populate this VMA. This will be equal to
+ * the size of the VMA in huge pages minus the number of huge pages
+ * (covered by this VMA) that are found in the page cache.
+ *
+ * Result is in bytes to be compatible with is_hugepage_mem_enough()
+ */
+unsigned long
+huge_pages_needed(struct address_space *mapping, struct vm_area_struct *vma)
+{
+ int i;
+ struct pagevec pvec;
+ unsigned long start = vma->vm_start;
+ unsigned long end = vma->vm_end;
+ unsigned long hugepages = (end - start) >> HPAGE_SHIFT;
+ pgoff_t next = vma->vm_pgoff;
+ pgoff_t endpg = next + ((end - start) >> PAGE_SHIFT);
+
+ pagevec_init(&pvec, 0);
+ while (next < endpg) {
+ if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE))
+ break;
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+ if (page->index > next)
+ next = page->index;
+ if (page->index >= endpg)
+ break;
+ next++;
+ hugepages--;
+ }
+ huge_pagevec_release(&pvec);
+ }
+ return hugepages << HPAGE_SHIFT;
+}
+
static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
struct inode *inode = file->f_dentry->d_inode;
+ struct address_space *mapping = inode->i_mapping;
+ unsigned long bytes;
loff_t len, vma_len;
int ret;
@@ -66,6 +115,10 @@
if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
return -EINVAL;
+ bytes = huge_pages_needed(mapping, vma);
+ if (!is_hugepage_mem_enough(bytes))
+ return -ENOMEM;
+
vma_len = (loff_t)(vma->vm_end - vma->vm_start);
down(&inode->i_sem);
@@ -168,16 +221,6 @@
return -EINVAL;
}
-static void huge_pagevec_release(struct pagevec *pvec)
-{
- int i;
-
- for (i = 0; i < pagevec_count(pvec); ++i)
- put_page(pvec->pages[i]);
-
- pagevec_reinit(pvec);
-}
-
static void truncate_huge_page(struct page *page)
{
clear_page_dirty(page);