1 files changed, 33 insertions, 20 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 20746420954..107da3d809a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2272,10 +2272,18 @@ int hugetlb_reserve_pages(struct inode *inode,
                                         struct vm_area_struct *vma,
                                         int acctflag)
 {
-        long ret = 0, chg;
+        long ret, chg;
         struct hstate *h = hstate_inode(inode);
 
         /*
+         * Only apply hugepage reservation if asked. At fault time, an
+         * attempt will be made for VM_NORESERVE to allocate a page
+         * and filesystem quota without using reserves
+         */
+        if (acctflag & VM_NORESERVE)
+                return 0;
+
+        /*
          * Shared mappings base their reservation on the number of pages that
          * are already allocated on behalf of the file. Private mappings need
          * to reserve the full area even if read-only as mprotect() may be
@@ -2283,42 +2291,47 @@ int hugetlb_reserve_pages(struct inode *inode,
          */
         if (!vma || vma->vm_flags & VM_SHARED)
                 chg = region_chg(&inode->i_mapping->private_list, from, to);
-        else
+        else {
+                struct resv_map *resv_map = resv_map_alloc();
+                if (!resv_map)
+                        return -ENOMEM;
+
                 chg = to - from;
 
+                set_vma_resv_map(vma, resv_map);
+                set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
+        }
+
         if (chg < 0)
                 return chg;
 
+        /* There must be enough filesystem quota for the mapping */
         if (hugetlb_get_quota(inode->i_mapping, chg))
                 return -ENOSPC;
 
         /*
-         * Only apply hugepage reservation if asked. We still have to
-         * take the filesystem quota because it is an upper limit
-         * defined for the mount and not necessarily memory as a whole
+         * Check enough hugepages are available for the reservation.
+         * Hand back the quota if there are not
          */
-        if (acctflag & VM_NORESERVE) {
-                reset_vma_resv_huge_pages(vma);
-                return 0;
-        }
-
         ret = hugetlb_acct_memory(h, chg);
         if (ret < 0) {
                 hugetlb_put_quota(inode->i_mapping, chg);
                 return ret;
         }
+
+        /*
+         * Account for the reservations made. Shared mappings record regions
+         * that have reservations as they are shared by multiple VMAs.
+         * When the last VMA disappears, the region map says how much
+         * the reservation was and the page cache tells how much of
+         * the reservation was consumed. Private mappings are per-VMA and
+         * only the consumed reservations are tracked. When the VMA
+         * disappears, the original reservation is the VMA size and the
+         * consumed reservations are stored in the map. Hence, nothing
+         * else has to be done for private mappings here
+         */
         if (!vma || vma->vm_flags & VM_SHARED)
                 region_add(&inode->i_mapping->private_list, from, to);
-        else {
-                struct resv_map *resv_map = resv_map_alloc();
-
-                if (!resv_map)
-                        return -ENOMEM;
-
-                set_vma_resv_map(vma, resv_map);
-                set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
-        }
-
         return 0;
 }