[PATCH] hugepage: Strict page reservation for hugepage inodes
[linux-2.6.git] / mm / hugetlb.c
index d5987a8..27fad5d 100644 (file)
@@ -22,7 +22,7 @@
 #include "internal.h"
 
 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
-static unsigned long nr_huge_pages, free_huge_pages;
+static unsigned long nr_huge_pages, free_huge_pages, reserved_huge_pages;
 unsigned long max_huge_pages;
 static struct list_head hugepage_freelists[MAX_NUMNODES];
 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
@@ -120,17 +120,136 @@ void free_huge_page(struct page *page)
 
 struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr)
 {
+       struct inode *inode = vma->vm_file->f_dentry->d_inode;
        struct page *page;
+       int use_reserve = 0;
+       unsigned long idx;
 
        spin_lock(&hugetlb_lock);
-       page = dequeue_huge_page(vma, addr);
-       if (!page) {
-               spin_unlock(&hugetlb_lock);
-               return NULL;
+
+       if (vma->vm_flags & VM_MAYSHARE) {
+
+               /* idx = radix tree index, i.e. offset into file in
+                * HPAGE_SIZE units */
+               idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
+                       + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+
+               /* The hugetlbfs specific inode info stores the number
+                * of "guaranteed available" (huge) pages.  That is,
+                * the first 'prereserved_hpages' pages of the inode
+                * are either already instantiated, or have been
+                * pre-reserved (by hugetlb_reserve_for_inode()). Here
+                * we're in the process of instantiating the page, so
+                * we use this to determine whether to draw from the
+                * pre-reserved pool or the truly free pool. */
+               if (idx < HUGETLBFS_I(inode)->prereserved_hpages)
+                       use_reserve = 1;
+       }
+
+       if (!use_reserve) {
+               if (free_huge_pages <= reserved_huge_pages)
+                       goto fail;
+       } else {
+               BUG_ON(reserved_huge_pages == 0);
+               reserved_huge_pages--;
        }
+
+       page = dequeue_huge_page(vma, addr);
+       if (!page)
+               goto fail;
+
        spin_unlock(&hugetlb_lock);
        set_page_refcounted(page);
        return page;
+
+ fail:
+       WARN_ON(use_reserve); /* reserved allocations shouldn't fail */
+       spin_unlock(&hugetlb_lock);
+       return NULL;
+}
+
+/* hugetlb_extend_reservation()
+ *
+ * Ensure that at least 'atleast' hugepages are, and will remain,
+ * available to instantiate the first 'atleast' pages of the given
+ * inode.  If the inode doesn't already have this many pages reserved
+ * or instantiated, set aside some hugepages in the reserved pool to
+ * satisfy later faults (or fail now if there aren't enough, rather
+ * than getting the SIGBUS later).
+ */
+int hugetlb_extend_reservation(struct hugetlbfs_inode_info *info,
+                              unsigned long atleast)
+{
+       struct inode *inode = &info->vfs_inode;
+       unsigned long change_in_reserve = 0;
+       int ret = 0;
+
+       spin_lock(&hugetlb_lock);
+       read_lock_irq(&inode->i_mapping->tree_lock);
+
+       if (info->prereserved_hpages >= atleast)
+               goto out;
+
+       /* Because we always call this on shared mappings, none of the
+        * pages beyond info->prereserved_hpages can have been
+        * instantiated, so we need to reserve all of them now. */
+       change_in_reserve = atleast - info->prereserved_hpages;
+
+       if ((reserved_huge_pages + change_in_reserve) > free_huge_pages) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       reserved_huge_pages += change_in_reserve;
+       info->prereserved_hpages = atleast;
+
+ out:
+       read_unlock_irq(&inode->i_mapping->tree_lock);
+       spin_unlock(&hugetlb_lock);
+
+       return ret;
+}
+
+/* hugetlb_truncate_reservation()
+ *
+ * This returns pages reserved for the given inode to the general free
+ * hugepage pool.  If the inode has any pages prereserved, but not
+ * instantiated, beyond offset (atmost << HPAGE_SIZE), then release
+ * them.
+ */
+void hugetlb_truncate_reservation(struct hugetlbfs_inode_info *info,
+                                 unsigned long atmost)
+{
+       struct inode *inode = &info->vfs_inode;
+       struct address_space *mapping = inode->i_mapping;
+       unsigned long idx;
+       unsigned long change_in_reserve = 0;
+       struct page *page;
+
+       spin_lock(&hugetlb_lock);
+       read_lock_irq(&inode->i_mapping->tree_lock);
+
+       if (info->prereserved_hpages <= atmost)
+               goto out;
+
+       /* Count pages which were reserved, but not instantiated, and
+        * which we can now release. */
+       for (idx = atmost; idx < info->prereserved_hpages; idx++) {
+               page = radix_tree_lookup(&mapping->page_tree, idx);
+               if (!page)
+                       /* Pages which are already instantiated can't
+                        * be unreserved (and in fact have already
+                        * been removed from the reserved pool) */
+                       change_in_reserve++;
+       }
+
+       BUG_ON(reserved_huge_pages < change_in_reserve);
+       reserved_huge_pages -= change_in_reserve;
+       info->prereserved_hpages = atmost;
+
+ out:
+       read_unlock_irq(&inode->i_mapping->tree_lock);
+       spin_unlock(&hugetlb_lock);
 }
 
 static int __init hugetlb_init(void)
@@ -238,9 +357,11 @@ int hugetlb_report_meminfo(char *buf)
        return sprintf(buf,
                        "HugePages_Total: %5lu\n"
                        "HugePages_Free:  %5lu\n"
+                       "HugePages_Rsvd:  %5lu\n"
                        "Hugepagesize:    %5lu kB\n",
                        nr_huge_pages,
                        free_huge_pages,
+                       reserved_huge_pages,
                        HPAGE_SIZE/1024);
 }
 
@@ -253,11 +374,6 @@ int hugetlb_report_node_meminfo(int nid, char *buf)
                nid, free_huge_pages_node[nid]);
 }
 
-int is_hugepage_mem_enough(size_t size)
-{
-       return (size + ~HPAGE_MASK)/HPAGE_SIZE <= free_huge_pages;
-}
-
 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 unsigned long hugetlb_total_pages(void)
 {