path: root/fs
diff options
authorEric B Munson <ebmunson@us.ibm.com>2009-09-21 17:03:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:41 -0700
commit6bfde05bf5c9682e255c6a2c669dc80f91af6296 (patch)
tree3ff62bb87fc12c1ce808a54f789c42c35be7c049 /fs
parentf8dbf0a7a4c5d98e8b70da9f7f4f6a89f3b7a7bb (diff)
hugetlbfs: allow the creation of files suitable for MAP_PRIVATE on the vfs internal mount
This patchset adds a flag to mmap that allows the user to request that an anonymous mapping be backed with huge pages. This mapping will borrow functionality from the huge page shm code to create a file on the kernel internal mount and use it to approximate an anonymous mapping. The MAP_HUGETLB flag is a modifier to MAP_ANONYMOUS and will not work without both flags being preset. A new flag is necessary because there is no other way to hook into huge pages without creating a file on a hugetlbfs mount which wouldn't be MAP_ANONYMOUS. To userspace, this mapping will behave just like an anonymous mapping because the file is not accessible outside of the kernel. This patchset is meant to simplify the programming model. Presently there is a large chunk of boiler platecode, contained in libhugetlbfs, required to create private, hugepage backed mappings. This patch set would allow use of hugepages without linking to libhugetlbfs or having hugetblfs mounted. Unification of the VM code would provide these same benefits, but it has been resisted each time that it has been suggested for several reasons: it would break PAGE_SIZE assumptions across the kernel, it makes page-table abstractions really expensive, and it does not provide any benefit on architectures that do not support huge pages, incurring fast path penalties without providing any benefit on these architectures. This patch: There are two means of creating mappings backed by huge pages: 1. mmap() a file created on hugetlbfs 2. Use shm which creates a file on an internal mount which essentially maps it MAP_SHARED The internal mount is only used for shared mappings but there is very little that stops it being used for private mappings. This patch extends hugetlbfs_file_setup() to deal with the creation of files that will be mapped MAP_PRIVATE on the internal hugetlbfs mount. This extended API is used in a subsequent patch to implement the MAP_HUGETLB mmap() flag. Signed-off-by: Eric 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
1 files changed, 17 insertions, 4 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a93b885311d..06b7c2623f9 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -507,6 +507,13 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb, uid_t uid,
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
info = HUGETLBFS_I(inode);
+ /*
+ * The policy is initialized here even if we are creating a
+ * private inode because initialization simply creates an
+ * an empty rb tree and calls spin_lock_init(), later when we
+ * call mpol_free_shared_policy() it will just return because
+ * the rb tree will still be empty.
+ */
mpol_shared_policy_init(&info->policy, NULL);
switch (mode & S_IFMT) {
@@ -931,13 +938,19 @@ static struct file_system_type hugetlbfs_fs_type = {
static struct vfsmount *hugetlbfs_vfsmount;
-static int can_do_hugetlb_shm(void)
+static int can_do_hugetlb_shm(int creat_flags)
- return capable(CAP_IPC_LOCK) || in_group_p(sysctl_hugetlb_shm_group);
+ if (creat_flags != HUGETLB_SHMFS_INODE)
+ return 0;
+ if (capable(CAP_IPC_LOCK))
+ return 1;
+ if (in_group_p(sysctl_hugetlb_shm_group))
+ return 1;
+ return 0;
struct file *hugetlb_file_setup(const char *name, size_t size, int acctflag,
- struct user_struct **user)
+ struct user_struct **user, int creat_flags)
int error = -ENOMEM;
struct file *file;
@@ -949,7 +962,7 @@ struct file *hugetlb_file_setup(const char *name, size_t size, int acctflag,
if (!hugetlbfs_vfsmount)
return ERR_PTR(-ENOENT);
- if (!can_do_hugetlb_shm()) {
+ if (!can_do_hugetlb_shm(creat_flags)) {
*user = current_user();
if (user_shm_lock(size, *user)) {