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Commit 2fc39cec authored by Adam Litke's avatar Adam Litke Committed by Linus Torvalds
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hugetlb: debit quota in alloc_huge_page 



Now that quota is credited by free_huge_page(), calls to hugetlb_get_quota()
seem out of place.  The alloc/free API is unbalanced because we handle the
hugetlb_put_quota() but expect the caller to open-code hugetlb_get_quota().
Move the get inside alloc_huge_page to clean up this disparity.

This patch has been kept apart from the previous patch because of the somewhat
dodgy ERR_PTR() use herein.  Moving the quota logic means that
alloc_huge_page() has two failure modes.  Quota failure must result in a
SIGBUS while a standard allocation failure is OOM.  Unfortunately, ERR_PTR()
doesn't like the small positive errnos we have in VM_FAULT_* so they must be
negated before they are used.

Does anyone take issue with the way I am using PTR_ERR.  If so, what are your
thoughts on how to clean this up (without needing an if,else if,else block at
each alloc_huge_page() callsite)?

Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
Cc: Ken Chen <kenchen@google.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: David Gibson <hermes@gibson.dropbear.id.au>
Cc: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c79fb75e

mm/hugetlb.c

+12 −12
Original line number Diff line number Diff line
@@ -388,6 +388,10 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma, 
				    unsigned long addr)

{

	struct page *page;

	struct address_space *mapping = vma->vm_file->f_mapping;



	if (hugetlb_get_quota(mapping))

		return ERR_PTR(-VM_FAULT_SIGBUS);



	if (vma->vm_flags & VM_MAYSHARE)

		page = alloc_huge_page_shared(vma, addr);
@@ -395,9 +399,10 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma, 
		page = alloc_huge_page_private(vma, addr);

	if (page) {

		set_page_refcounted(page);

		set_page_private(page, (unsigned long) vma->vm_file->f_mapping);

	}

		set_page_private(page, (unsigned long) mapping);

		return page;

	} else

		return ERR_PTR(-VM_FAULT_OOM);

}



static int __init hugetlb_init(void)
@@ -737,15 +742,13 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma, 
		set_huge_ptep_writable(vma, address, ptep);

		return 0;

	}

	if (hugetlb_get_quota(vma->vm_file->f_mapping))

		return VM_FAULT_SIGBUS;



	page_cache_get(old_page);

	new_page = alloc_huge_page(vma, address);



	if (!new_page) {

	if (IS_ERR(new_page)) {

		page_cache_release(old_page);

		return VM_FAULT_OOM;

		return -PTR_ERR(new_page);

	}



	spin_unlock(&mm->page_table_lock);
@@ -789,12 +792,9 @@ retry: 
		size = i_size_read(mapping->host) >> HPAGE_SHIFT;

		if (idx >= size)

			goto out;

		if (hugetlb_get_quota(mapping))

			goto out;

		page = alloc_huge_page(vma, address);

		if (!page) {

			hugetlb_put_quota(mapping);

			ret = VM_FAULT_OOM;

		if (IS_ERR(page)) {

			ret = -PTR_ERR(page);

			goto out;

		}

		clear_huge_page(page, address);