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: Adam 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 12 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3992bd5120e7..bc12b0adfa87 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -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);
-        }
-        return page;
+                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);