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[PATCH] hugetlb: overcommit accounting check

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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>
This commit is contained in:
Adam Litke 2005-10-29 18:16:47 -07:00 committed by Linus Torvalds
parent 4c88726597
commit 2e9b367c22
1 changed files with 53 additions and 10 deletions
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63
fs/hugetlbfs/inode.c
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@ -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);