hugetlb: add MAP_HUGETLB for mmaping pseudo-anonymous huge page regions
Eric B Munson [Tue, 22 Sep 2009 00:03:47 +0000 (17:03 -0700)]
Add a flag for mmap that will be used to request a huge page region that
will look like anonymous memory to userspace.  This is accomplished by
using a file on the internal vfsmount.  MAP_HUGETLB is a modifier of
MAP_ANONYMOUS and so must be specified with it.  The region will behave
the same as a MAP_ANONYMOUS region using small pages.

[akpm@linux-foundation.org: fix arch definitions of MAP_HUGETLB]
Signed-off-by: Eric B Munson <ebmunson@us.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Adam Litke <agl@us.ibm.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/hugetlb.h
mm/mmap.c

index f6505ad..176e7ee 100644 (file)
@@ -112,12 +112,19 @@ static inline void hugetlb_report_meminfo(struct seq_file *m)
 
 #endif /* !CONFIG_HUGETLB_PAGE */
 
+#define HUGETLB_ANON_FILE "anon_hugepage"
+
 enum {
        /*
         * The file will be used as an shm file so shmfs accounting rules
         * apply
         */
        HUGETLB_SHMFS_INODE     = 1,
+       /*
+        * The file is being created on the internal vfs mount and shmfs
+        * accounting rules do not apply
+        */
+       HUGETLB_ANONHUGE_INODE  = 2,
 };
 
 #ifdef CONFIG_HUGETLBFS
index 1aeef66..21d4029 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -949,6 +949,24 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
        if (mm->map_count > sysctl_max_map_count)
                return -ENOMEM;
 
+       if (flags & MAP_HUGETLB) {
+               struct user_struct *user = NULL;
+               if (file)
+                       return -EINVAL;
+
+               /*
+                * VM_NORESERVE is used because the reservations will be
+                * taken when vm_ops->mmap() is called
+                * A dummy user value is used because we are not locking
+                * memory so no accounting is necessary
+                */
+               len = ALIGN(len, huge_page_size(&default_hstate));
+               file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE,
+                                               &user, HUGETLB_ANONHUGE_INODE);
+               if (IS_ERR(file))
+                       return PTR_ERR(file);
+       }
+
        /* Obtain the address to map to. we verify (or select) it and ensure
         * that it represents a valid section of the address space.
         */