Version 2 (Tue, 18 Oct 2005)
Added comment to huge_pages_needed
Removed erroneous shared memory exemption logic
Initial Post (Thu, 18 Aug 2005)
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 <[email protected]>
---
inode.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 54 insertions(+), 10 deletions(-)
diff -upN reference/fs/hugetlbfs/inode.c current/fs/hugetlbfs/inode.c
--- reference/fs/hugetlbfs/inode.c
+++ current/fs/hugetlbfs/inode.c
@@ -45,9 +45,59 @@ static struct backing_dev_info hugetlbfs
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);
+ struct inode *inode = vma->vm_file->f_dentry->d_inode;
+
+ 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 +116,10 @@ static int hugetlbfs_file_mmap(struct fi
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 +222,6 @@ static int hugetlbfs_commit_write(struct
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);
--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center
-
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