hugetlbfs-2.5.40-1

hugetlbfs-2.5.40-1

[William Lee Irwin III]

hugetlbfs is a trivial filesystem exporting memory-backed files into
the fs namespace and providing the ability to mmap() such files using
hugetlb routines.

Outstanding issues:
------------------
(1) shm is still broken.
	(1A) shmctl still manages to find the wrong thing to do.
	(1B) shm permission checks are probably incorrect
(2) trivial dentry support needs to move to libfs.c
(3) compilation for when its option is turned off is still broken.
(4) hugetlb_prefault() duplicates some code it could be sharing.


New stuff:
---------
(1) hugetlbfs_file_mmap() now returns -EINVAL instead of passing
	unaligned args that would cause hugetlb_prefault() to BUG().
(2) shmdt() now has a chance of working since it now checks to see if
	it's detaching from a hugetlb segment.

Compiled, but not booted or run. I'm partially cut off from my testing
setup at the moment (and was under the weather for a day or so), but
need to push things out for others to test.

shmdt() may end up slightly more efficient if I didn't completely botch
it. The open-coded linear search ended up looking like a mess from all
the indentation and so on going on, so it seemed to be better this way.
If it causes trouble for the normal case, I'll back it out and do the
dispatch on ->vm_ops inside the loop or otherwise fix it.

There's a little bit of excess noise here since a hugetlb fix ended up
in here along with the rest of it. That hunk should be picked up with
or without hugetlbfs. If the list handling touchups are unsettling they
can be omitted. Basically, allocating the hugetlb pages from highmem
cannot work without the fix at all.


Bill


diff --minimal -Nru a/arch/i386/mm/hugetlbpage.c b/arch/i386/mm/hugetlbpage.c
--- a/arch/i386/mm/hugetlbpage.c	Wed Oct  2 00:44:18 2002
+++ b/arch/i386/mm/hugetlbpage.c	Wed Oct  2 00:44:18 2002
@@ -17,7 +17,7 @@
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 
-static struct vm_operations_struct hugetlb_vm_ops;
+struct vm_operations_struct hugetlb_vm_ops;
 struct list_head htlbpage_freelist;
 spinlock_t htlbpage_lock = SPIN_LOCK_UNLOCKED;
 extern long htlbpagemem;
@@ -44,24 +44,22 @@
 static struct page *
 alloc_hugetlb_page(void)
 {
-	struct list_head *curr, *head;
+	int i;
 	struct page *page;
 
 	spin_lock(&htlbpage_lock);
-
-	head = &htlbpage_freelist;
-	curr = head->next;
-
-	if (curr == head) {
+	if (list_empty(&htlbpage_freelist)) {
 		spin_unlock(&htlbpage_lock);
 		return NULL;
 	}
-	page = list_entry(curr, struct page, list);
-	list_del(curr);
+
+	page = list_entry(htlbpage_freelist.next, struct page, list);
+	list_del(&page->list);
 	htlbpagemem--;
 	spin_unlock(&htlbpage_lock);
 	set_page_count(page, 1);
-	memset(page_address(page), 0, HPAGE_SIZE);
+	for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
+		clear_highpage(&page[i]);
 	return page;
 }
 
@@ -459,6 +457,46 @@
 	 return retval;
 }
 
+int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long addr;
+	int ret = 0;
+
+	BUG_ON(vma->vm_start & ~HPAGE_MASK);
+	BUG_ON(vma->vm_end & ~HPAGE_MASK);
+
+	spin_lock(&mm->page_table_lock);
+	for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
+		unsigned long idx;
+		pte_t *pte = huge_pte_alloc(mm, addr);
+		struct page *page;
+
+		if (!pte) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		if (!pte_none(*pte))
+			continue;
+
+		idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
+			+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+		page = find_get_page(mapping, idx);
+		if (!page) {
+			page = alloc_hugetlb_page();
+			if (!page) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			add_to_page_cache(page, mapping, idx);
+		}
+		set_huge_pte(mm, vma, page, pte, vma->vm_flags & VM_WRITE);
+	}
+out:
+	spin_unlock(&mm->page_table_lock);
+	return ret;
+}
+
 static int
 alloc_private_hugetlb_pages(int key, unsigned long addr, unsigned long len,
 			    int prot, int flag)
@@ -540,6 +578,13 @@
 	return (int) htlbzone_pages;
 }
 
-static struct vm_operations_struct hugetlb_vm_ops = {
+static struct page * hugetlb_nopage(struct vm_area_struct * area, unsigned long address, int unused)
+{
+	BUG();
+	return NULL;
+}
+
+struct vm_operations_struct hugetlb_vm_ops = {
 	.close	= zap_hugetlb_resources,
+	.nopage = hugetlb_nopage,
 };
diff --minimal -Nru a/fs/Config.in b/fs/Config.in
--- a/fs/Config.in	Wed Oct  2 00:44:18 2002
+++ b/fs/Config.in	Wed Oct  2 00:44:18 2002
@@ -56,6 +56,11 @@
 bool 'Virtual memory file system support (former shm fs)' CONFIG_TMPFS
 define_bool CONFIG_RAMFS y
 
+if [ "$CONFIG_HUGETLB_PAGE" = "y" ] ; then
+   bool 'HugeTLB file system support' CONFIG_HUGETLBFS
+   define_bool CONFIG_HUGETLBFS y
+fi
+
 tristate 'ISO 9660 CDROM file system support' CONFIG_ISO9660_FS
 dep_mbool '  Microsoft Joliet CDROM extensions' CONFIG_JOLIET $CONFIG_ISO9660_FS
 dep_mbool '  Transparent decompression extension' CONFIG_ZISOFS $CONFIG_ISO9660_FS
diff --minimal -Nru a/fs/Makefile b/fs/Makefile
--- a/fs/Makefile	Wed Oct  2 00:44:18 2002
+++ b/fs/Makefile	Wed Oct  2 00:44:18 2002
@@ -46,6 +46,7 @@
 obj-$(CONFIG_EXT2_FS)		+= ext2/
 obj-$(CONFIG_CRAMFS)		+= cramfs/
 obj-$(CONFIG_RAMFS)		+= ramfs/
+obj-$(CONFIG_HUGETLBFS)		+= hugetlbfs/
 obj-$(CONFIG_CODA_FS)		+= coda/
 obj-$(CONFIG_INTERMEZZO_FS)	+= intermezzo/
 obj-$(CONFIG_MINIX_FS)		+= minix/
diff --minimal -Nru a/fs/hugetlbfs/Makefile b/fs/hugetlbfs/Makefile
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/fs/hugetlbfs/Makefile	Wed Oct  2 00:44:18 2002
@@ -0,0 +1,9 @@
+#
+# Makefile for the linux ramfs routines.
+#
+
+obj-$(CONFIG_HUGETLBFS) += hugetlbfs.o
+
+hugetlbfs-objs := inode.o
+
+include $(TOPDIR)/Rules.make
diff --minimal -Nru a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/fs/hugetlbfs/inode.c	Wed Oct  2 00:44:18 2002
@@ -0,0 +1,425 @@
+/*
+ * Resizable simple ram filesystem for Linux.
+ *
+ * Copyright (C) 2000 Linus Torvalds.
+ *               2000 Transmeta Corp.
+ *
+ * Usage limits added by David Gibson, Linuxcare Australia.
+ * This file is released under the GPL.
+ */
+
+/*
+ * NOTE! This filesystem is probably most useful
+ * not as a real filesystem, but as an example of
+ * how virtual filesystems can be written.
+ *
+ * It doesn't get much simpler than this. Consider
+ * that this file implements the full semantics of
+ * a POSIX-compliant read-write filesystem.
+ *
+ * Note in particular how the filesystem does not
+ * need to implement any data structures of its own
+ * to keep track of the virtual data: using the VFS
+ * caches is sufficient.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/smp_lock.h>
+#include <linux/backing-dev.h>
+
+#include <asm/uaccess.h>
+
+/* some random number */
+#define HUGETLBFS_MAGIC	0x958458f6
+
+static struct super_operations hugetlbfs_ops;
+static struct address_space_operations hugetlbfs_aops;
+struct file_operations hugetlbfs_file_operations;
+static struct inode_operations hugetlbfs_dir_inode_operations;
+
+static struct backing_dev_info hugetlbfs_backing_dev_info = {
+	.ra_pages	= 0,	/* No readahead */
+	.memory_backed	= 1,	/* Does not contribute to dirty memory */
+};
+
+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;
+	int ret;
+
+	if (vma->vm_start & ~HPAGE_MASK)
+		return -EINVAL;
+
+	if (vma->vm_end & ~HPAGE_MASK)
+		return -EINVAL;
+
+	down(&inode->i_sem);
+
+	UPDATE_ATIME(inode);
+	vma->vm_flags |= VM_HUGETLB | VM_RESERVED;
+	vma->vm_ops = &hugetlb_vm_ops;
+	ret = hugetlb_prefault(mapping, vma);
+
+	up(&inode->i_sem);
+
+	return ret;
+}
+
+/*
+ * Read a page. Again trivial. If it didn't already exist
+ * in the page cache, it is zero-filled.
+ */
+static int hugetlbfs_readpage(struct file *file, struct page * page)
+{
+	return -EINVAL;
+}
+
+static int hugetlbfs_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
+{
+	return -EINVAL;
+}
+
+static int hugetlbfs_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to)
+{
+	return -EINVAL;
+}
+
+struct inode *hugetlbfs_get_inode(struct super_block *sb, int mode, int dev)
+{
+	struct inode * inode = new_inode(sb);
+
+	if (inode) {
+		inode->i_mode = mode;
+		inode->i_uid = current->fsuid;
+		inode->i_gid = current->fsgid;
+		inode->i_blksize = PAGE_CACHE_SIZE;
+		inode->i_blocks = 0;
+		inode->i_rdev = NODEV;
+		inode->i_mapping->a_ops = &hugetlbfs_aops;
+		inode->i_mapping->backing_dev_info = &hugetlbfs_backing_dev_info;
+		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+		switch (mode & S_IFMT) {
+		default:
+			init_special_inode(inode, mode, dev);
+			break;
+		case S_IFREG:
+			inode->i_fop = &hugetlbfs_file_operations;
+			break;
+		case S_IFDIR:
+			inode->i_op = &hugetlbfs_dir_inode_operations;
+			inode->i_fop = &simple_dir_operations;
+
+			/* directory inodes start off with i_nlink == 2 (for "." entry) */
+			inode->i_nlink++;
+			break;
+		case S_IFLNK:
+			inode->i_op = &page_symlink_inode_operations;
+			break;
+		}
+	}
+	return inode;
+}
+
+/*
+ * File creation. Allocate an inode, and we're done..
+ */
+/* SMP-safe */
+static int hugetlbfs_mknod(struct inode *dir, struct dentry *dentry, int mode, int dev)
+{
+	struct inode * inode = hugetlbfs_get_inode(dir->i_sb, mode, dev);
+	int error = -ENOSPC;
+
+	if (inode) {
+		d_instantiate(dentry, inode);
+		dget(dentry);		/* Extra count - pin the dentry in core */
+		error = 0;
+	}
+	return error;
+}
+
+static int hugetlbfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
+{
+	int retval = hugetlbfs_mknod(dir, dentry, mode | S_IFDIR, 0);
+	if (!retval)
+		dir->i_nlink++;
+	return retval;
+}
+
+static int hugetlbfs_create(struct inode *dir, struct dentry *dentry, int mode)
+{
+	return hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0);
+}
+
+/*
+ * Link a file..
+ */
+static int hugetlbfs_link(struct dentry *old_dentry, struct inode * dir, struct dentry * dentry)
+{
+	struct inode *inode = old_dentry->d_inode;
+
+	inode->i_nlink++;
+	atomic_inc(&inode->i_count);	/* New dentry reference */
+	dget(dentry);		/* Extra pinning count for the created dentry */
+	d_instantiate(dentry, inode);
+	return 0;
+}
+
+static inline int hugetlbfs_positive(struct dentry *dentry)
+{
+	return dentry->d_inode && !d_unhashed(dentry);
+}
+
+/*
+ * Check that a directory is empty (this works
+ * for regular files too, they'll just always be
+ * considered empty..).
+ *
+ * Note that an empty directory can still have
+ * children, they just all have to be negative..
+ */
+static int hugetlbfs_empty(struct dentry *dentry)
+{
+	struct list_head *list;
+
+	spin_lock(&dcache_lock);
+	list = dentry->d_subdirs.next;
+
+	while (list != &dentry->d_subdirs) {
+		struct dentry *de = list_entry(list, struct dentry, d_child);
+
+		if (hugetlbfs_positive(de)) {
+			spin_unlock(&dcache_lock);
+			return 0;
+		}
+		list = list->next;
+	}
+	spin_unlock(&dcache_lock);
+	return 1;
+}
+
+/*
+ * Unlink a hugetlbfs entry
+ */
+static int hugetlbfs_unlink(struct inode * dir, struct dentry *dentry)
+{
+	struct inode *inode = dentry->d_inode;
+
+	inode->i_nlink--;
+	dput(dentry);			/* Undo the count from "create" - this does all the work */
+	return 0;
+}
+
+static int hugetlbfs_rmdir(struct inode * dir, struct dentry *dentry)
+{
+	int retval = -ENOTEMPTY;
+
+	if (hugetlbfs_empty(dentry)) {
+		dentry->d_inode->i_nlink--;
+		hugetlbfs_unlink(dir, dentry);
+		dir->i_nlink--;
+		retval = 0;
+	}
+	return retval;
+}
+
+/*
+ * The VFS layer already does all the dentry stuff for rename,
+ * we just have to decrement the usage count for the target if
+ * it exists so that the VFS layer correctly free's it when it
+ * gets overwritten.
+ */
+static int hugetlbfs_rename(struct inode * old_dir, struct dentry *old_dentry, struct inode * new_dir,struct dentry *new_dentry)
+{
+	int error = -ENOTEMPTY;
+
+	if (hugetlbfs_empty(new_dentry)) {
+		struct inode *inode = new_dentry->d_inode;
+		if (inode) {
+			inode->i_nlink--;
+			dput(new_dentry);
+		}
+		if (S_ISDIR(old_dentry->d_inode->i_mode)) {
+			old_dir->i_nlink--;
+			new_dir->i_nlink++;
+		}
+		error = 0;
+	}
+	return error;
+}
+
+static int hugetlbfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
+{
+	struct inode *inode;
+	int error = -ENOSPC;
+
+	inode = hugetlbfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
+	if (inode) {
+		int l = strlen(symname)+1;
+		error = page_symlink(inode, symname, l);
+		if (!error) {
+			d_instantiate(dentry, inode);
+			dget(dentry);
+		} else
+			iput(inode);
+	}
+	return error;
+}
+
+static int hugetlbfs_sync_file(struct file * file, struct dentry *dentry, int datasync)
+{
+	return 0;
+}
+
+static struct address_space_operations hugetlbfs_aops = {
+	readpage:	hugetlbfs_readpage,
+	writepage:	fail_writepage,
+	prepare_write:	hugetlbfs_prepare_write,
+	commit_write:	hugetlbfs_commit_write
+};
+
+struct file_operations hugetlbfs_file_operations = {
+	read:		generic_file_read,
+	write:		generic_file_write,
+	mmap:		hugetlbfs_file_mmap,
+	fsync:		hugetlbfs_sync_file,
+	sendfile:	generic_file_sendfile,
+};
+
+static struct inode_operations hugetlbfs_dir_inode_operations = {
+	create:		hugetlbfs_create,
+	lookup:		simple_lookup,
+	link:		hugetlbfs_link,
+	unlink:		hugetlbfs_unlink,
+	symlink:	hugetlbfs_symlink,
+	mkdir:		hugetlbfs_mkdir,
+	rmdir:		hugetlbfs_rmdir,
+	mknod:		hugetlbfs_mknod,
+	rename:		hugetlbfs_rename,
+};
+
+static struct super_operations hugetlbfs_ops = {
+	statfs:		simple_statfs,
+	drop_inode:	generic_delete_inode,
+};
+
+static int hugetlbfs_fill_super(struct super_block * sb, void * data, int silent)
+{
+	struct inode * inode;
+	struct dentry * root;
+
+	sb->s_blocksize = PAGE_CACHE_SIZE;
+	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	sb->s_magic = HUGETLBFS_MAGIC;
+	sb->s_op = &hugetlbfs_ops;
+	inode = hugetlbfs_get_inode(sb, S_IFDIR | 0755, 0);
+	if (!inode)
+		return -ENOMEM;
+
+	root = d_alloc_root(inode);
+	if (!root) {
+		iput(inode);
+		return -ENOMEM;
+	}
+	sb->s_root = root;
+	return 0;
+}
+
+static struct super_block *hugetlbfs_get_sb(struct file_system_type *fs_type,
+	int flags, char *dev_name, void *data)
+{
+	return get_sb_nodev(fs_type, flags, data, hugetlbfs_fill_super);
+}
+
+static struct file_system_type hugetlbfs_fs_type = {
+	name:		"hugetlbfs",
+	get_sb:		hugetlbfs_get_sb,
+	kill_sb:	kill_litter_super,
+};
+
+static struct vfsmount *hugetlbfs_vfsmount;
+
+static atomic_t hugetlbfs_counter = ATOMIC_INIT(0);
+
+struct file *hugetlb_zero_setup(size_t size)
+{
+	int error, n;
+	struct file *file;
+	struct inode *inode;
+	struct dentry *dentry, *root;
+	struct qstr quick_string;
+	char buf[16];
+
+	n = atomic_read(&hugetlbfs_counter);
+	atomic_inc(&hugetlbfs_counter);
+
+	root = hugetlbfs_vfsmount->mnt_root;
+	snprintf(buf, 16, "%d", n);
+	quick_string.name = buf;
+	quick_string.len = strlen(quick_string.name);
+	quick_string.hash = 0;
+	dentry = d_alloc(root, &quick_string);
+	if (!dentry)
+		return ERR_PTR(-ENOMEM);
+
+	error = -ENFILE;
+	file = get_empty_filp();
+	if (!file)
+		goto out_dentry;
+
+	error = -ENOSPC;
+	inode = hugetlbfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
+	if (!inode)
+		goto out_file;
+
+	d_instantiate(dentry, inode);
+	inode->i_size = size;
+	inode->i_nlink = 0;
+	file->f_vfsmnt = mntget(hugetlbfs_vfsmount);
+	file->f_dentry = dentry;
+	file->f_op = &hugetlbfs_file_operations;
+	file->f_mode = FMODE_WRITE | FMODE_READ;
+	return file;
+
+out_file:
+	put_filp(file);
+out_dentry:
+	dput(dentry);
+	return ERR_PTR(error);
+}
+
+static int __init init_hugetlbfs_fs(void)
+{
+	int error;
+	struct vfsmount *vfsmount;
+
+	error = register_filesystem(&hugetlbfs_fs_type);
+	if (error)
+		return error;
+
+	vfsmount = kern_mount(&hugetlbfs_fs_type);
+
+	if (!IS_ERR(vfsmount)) {
+		hugetlbfs_vfsmount = vfsmount;
+		return 0;
+	}
+
+	error = PTR_ERR(vfsmount);
+	return error;
+}
+
+static void __exit exit_hugetlbfs_fs(void)
+{
+	unregister_filesystem(&hugetlbfs_fs_type);
+}
+
+module_init(init_hugetlbfs_fs)
+module_exit(exit_hugetlbfs_fs)
+
+MODULE_LICENSE("GPL");
diff --minimal -Nru a/include/linux/mm.h b/include/linux/mm.h
--- a/include/linux/mm.h	Wed Oct  2 00:44:18 2002
+++ b/include/linux/mm.h	Wed Oct  2 00:44:18 2002
@@ -386,7 +386,9 @@
 extern int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *);
 extern int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, unsigned long *, int *, int);
 extern	int free_hugepages(struct vm_area_struct *);
-
+extern int hugetlb_prefault(struct address_space *, struct vm_area_struct *);
+extern struct file *hugetlb_zero_setup(size_t);
+extern struct file_operations hugetlbfs_file_operations;
 #else
 #define is_vm_hugetlb_page(vma) (0)
 #define follow_hugetlb_page(mm, vma, pages, vmas, start, len, i) (0)
@@ -394,6 +396,7 @@
 #define free_hugepages(mpnt)  do { } while(0)
 #endif
 
+extern struct vm_operations_struct hugetlb_vm_ops;
 
 /*
  * If the mapping doesn't provide a set_page_dirty a_op, then
diff --minimal -Nru a/include/linux/shm.h b/include/linux/shm.h
--- a/include/linux/shm.h	Wed Oct  2 00:44:18 2002
+++ b/include/linux/shm.h	Wed Oct  2 00:44:18 2002
@@ -88,6 +88,7 @@
 /* shm_mode upper byte flags */
 #define	SHM_DEST	01000	/* segment will be destroyed on last detach */
 #define SHM_LOCKED      02000   /* segment will not be swapped */
+#define SHM_HUGETLB     04000   /* segment will use huge TLB pages */
 
 asmlinkage long sys_shmget (key_t key, size_t size, int flag);
 asmlinkage long sys_shmat (int shmid, char *shmaddr, int shmflg, unsigned long *addr);
diff --minimal -Nru a/ipc/shm.c b/ipc/shm.c
--- a/ipc/shm.c	Wed Oct  2 00:44:18 2002
+++ b/ipc/shm.c	Wed Oct  2 00:44:18 2002
@@ -185,8 +185,12 @@
 	shp->shm_perm.key = key;
 	shp->shm_flags = (shmflg & S_IRWXUGO);
 
-	sprintf (name, "SYSV%08x", key);
-	file = shmem_file_setup(name, size, VM_ACCOUNT);
+	if (shmflg & SHM_HUGETLB)
+		file = hugetlb_zero_setup(size);
+	else {
+		sprintf (name, "SYSV%08x", key);
+		file = shmem_file_setup(name, size, VM_ACCOUNT);
+	}
 	error = PTR_ERR(file);
 	if (IS_ERR(file))
 		goto no_file;
@@ -205,7 +209,10 @@
 	shp->id = shm_buildid(id,shp->shm_perm.seq);
 	shp->shm_file = file;
 	file->f_dentry->d_inode->i_ino = shp->id;
-	file->f_op = &shm_file_operations;
+	if (shmflg & SHM_HUGETLB)
+		file->f_op = &hugetlbfs_file_operations;
+	else
+		file->f_op = &shm_file_operations;
 	shm_tot += numpages;
 	shm_unlock (id);
 	return shp->id;
@@ -663,18 +670,26 @@
 asmlinkage long sys_shmdt (char *shmaddr)
 {
 	struct mm_struct *mm = current->mm;
-	struct vm_area_struct *shmd, *shmdnext;
+	struct vm_area_struct *vma;
+	unsigned long address = (unsigned long)shmaddr;
 	int retval = -EINVAL;
 
 	down_write(&mm->mmap_sem);
-	for (shmd = mm->mmap; shmd; shmd = shmdnext) {
-		shmdnext = shmd->vm_next;
-		if (shmd->vm_ops == &shm_vm_ops
-		    && shmd->vm_start - (shmd->vm_pgoff << PAGE_SHIFT) == (ulong) shmaddr) {
-			do_munmap(mm, shmd->vm_start, shmd->vm_end - shmd->vm_start);
-			retval = 0;
-		}
-	}
+	vma = find_vma(mm, address);
+	if (!vma)
+		goto out;
+	if (vma->vm_start != address)
+		goto out;
+	
+	/* ->vm_pgoff is always 0, see do_mmap() in sys_shmat() */
+	retval = 0;
+	if (vma->vm_ops == &shm_vm_ops)
+		do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
+	else if (vma->vm_ops == &hugetlb_vm_ops)
+		free_hugepages(vma);
+	else
+		retval = -EINVAL;
+out:
 	up_write(&mm->mmap_sem);
 	return retval;
 }
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