3 files changed, 154 insertions, 64 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index b35195289945..1a1c2fcb7823 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -56,48 +56,10 @@ static void huge_pagevec_release(struct pagevec *pvec)
         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()
- */
-static 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 >> (HPAGE_SHIFT - PAGE_SHIFT);
-        pgoff_t endpg = next + hugepages;
-
-        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;
+        struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
         loff_t len, vma_len;
         int ret;
 
@@ -113,10 +75,6 @@ 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);
 
         mutex_lock(&inode->i_mutex);
@@ -129,6 +87,10 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
         if (!(vma->vm_flags & VM_WRITE) && len > inode->i_size)
                 goto out;
 
+        if (vma->vm_flags & VM_MAYSHARE)
+                if (hugetlb_extend_reservation(info, len >> HPAGE_SHIFT) != 0)
+                        goto out;
+
         ret = 0;
         hugetlb_prefault_arch_hook(vma->vm_mm);
         if (inode->i_size < len)
@@ -227,13 +189,18 @@ static void truncate_huge_page(struct page *page)
         put_page(page);
 }
 
-static void truncate_hugepages(struct address_space *mapping, loff_t lstart)
+static void truncate_hugepages(struct inode *inode, loff_t lstart)
 {
+        struct address_space *mapping = &inode->i_data;
         const pgoff_t start = lstart >> HPAGE_SHIFT;
         struct pagevec pvec;
         pgoff_t next;
         int i;
 
+        hugetlb_truncate_reservation(HUGETLBFS_I(inode),
+                                     lstart >> HPAGE_SHIFT);
+        if (!mapping->nrpages)
+                return;
         pagevec_init(&pvec, 0);
         next = start;
         while (1) {
@@ -262,8 +229,7 @@ static void truncate_hugepages(struct address_space *mapping, loff_t lstart)
 
 static void hugetlbfs_delete_inode(struct inode *inode)
 {
-        if (inode->i_data.nrpages)
-                truncate_hugepages(&inode->i_data, 0);
+        truncate_hugepages(inode, 0);
         clear_inode(inode);
 }
 
@@ -296,8 +262,7 @@ static void hugetlbfs_forget_inode(struct inode *inode)
         inode->i_state |= I_FREEING;
         inodes_stat.nr_inodes--;
         spin_unlock(&inode_lock);
-        if (inode->i_data.nrpages)
-                truncate_hugepages(&inode->i_data, 0);
+        truncate_hugepages(inode, 0);
         clear_inode(inode);
         destroy_inode(inode);
 }
@@ -356,7 +321,7 @@ static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
         if (!prio_tree_empty(&mapping->i_mmap))
                 hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
         spin_unlock(&mapping->i_mmap_lock);
-        truncate_hugepages(mapping, offset);
+        truncate_hugepages(inode, offset);
         return 0;
 }
 
@@ -573,6 +538,7 @@ static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
                 hugetlbfs_inc_free_inodes(sbinfo);
                 return NULL;
         }
+        p->prereserved_hpages = 0;
         return &p->vfs_inode;
 }
 
@@ -805,9 +771,6 @@ struct file *hugetlb_zero_setup(size_t size)
         if (!can_do_hugetlb_shm())
                 return ERR_PTR(-EPERM);
 
-        if (!is_hugepage_mem_enough(size))
-                return ERR_PTR(-ENOMEM);
-
         if (!user_shm_lock(size, current->user))
                 return ERR_PTR(-ENOMEM);
 
@@ -831,6 +794,11 @@ struct file *hugetlb_zero_setup(size_t size)
         if (!inode)
                 goto out_file;
 
+        error = -ENOMEM;
+        if (hugetlb_extend_reservation(HUGETLBFS_I(inode),
+                                       size >> HPAGE_SHIFT) != 0)
+                goto out_inode;
+
         d_instantiate(dentry, inode);
         inode->i_size = size;
         inode->i_nlink = 0;
@@ -841,6 +809,8 @@ struct file *hugetlb_zero_setup(size_t size)
         file->f_mode = FMODE_WRITE | FMODE_READ;
         return file;
 
+out_inode:
+        iput(inode);
 out_file:
         put_filp(file);
 out_dentry:
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index fa83836b63d2..cafe73eecb05 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -20,7 +20,6 @@ void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long)
 int hugetlb_prefault(struct address_space *, struct vm_area_struct *);
 int hugetlb_report_meminfo(char *);
 int hugetlb_report_node_meminfo(int, char *);
-int is_hugepage_mem_enough(size_t);
 unsigned long hugetlb_total_pages(void);
 struct page *alloc_huge_page(struct vm_area_struct *, unsigned long);
 void free_huge_page(struct page *);
@@ -89,7 +88,6 @@ static inline unsigned long hugetlb_total_pages(void)
 #define copy_hugetlb_page_range(src, dst, vma)  ({ BUG(); 0; })
 #define hugetlb_prefault(mapping, vma)          ({ BUG(); 0; })
 #define unmap_hugepage_range(vma, start, end)   BUG()
-#define is_hugepage_mem_enough(size)            0
 #define hugetlb_report_meminfo(buf)             0
 #define hugetlb_report_node_meminfo(n, buf)     0
 #define follow_huge_pmd(mm, addr, pmd, write)   NULL
@@ -132,6 +130,8 @@ struct hugetlbfs_sb_info {
 
 struct hugetlbfs_inode_info {
         struct shared_policy policy;
+        /* Protected by the (global) hugetlb_lock */
+        unsigned long prereserved_hpages;
         struct inode vfs_inode;
 };
 
@@ -148,6 +148,10 @@ static inline struct hugetlbfs_sb_info *HUGETLBFS_SB(struct super_block *sb)
 extern struct file_operations hugetlbfs_file_operations;
 extern struct vm_operations_struct hugetlb_vm_ops;
 struct file *hugetlb_zero_setup(size_t);
+int hugetlb_extend_reservation(struct hugetlbfs_inode_info *info,
+                               unsigned long atleast_hpages);
+void hugetlb_truncate_reservation(struct hugetlbfs_inode_info *info,
+                                  unsigned long atmost_hpages);
 int hugetlb_get_quota(struct address_space *mapping);
 void hugetlb_put_quota(struct address_space *mapping);
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d5987a87bbe5..27fad5d9bcf6 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -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)
 {