Commit 2e9b367c authored by Adam Litke's avatar Adam Litke Committed by Linus Torvalds
Browse files

[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: default avatarAdam Litke <agl@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4c887265

fs/hugetlbfs/inode.c

+53 −10
Original line number Diff line number Diff line
@@ -45,9 +45,58 @@ static struct backing_dev_info hugetlbfs_backing_dev_info = { 


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 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) 
	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 @@ static int hugetlbfs_commit_write(struct file *file, 
	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);

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