kernel_optimize_test/fs/internal.h
Al Viro f03c65993b sanitize vfsmount refcounting changes
Instead of splitting refcount between (per-cpu) mnt_count
and (SMP-only) mnt_longrefs, make all references contribute
to mnt_count again and keep track of how many are longterm
ones.

Accounting rules for longterm count:
	* 1 for each fs_struct.root.mnt
	* 1 for each fs_struct.pwd.mnt
	* 1 for having non-NULL ->mnt_ns
	* decrement to 0 happens only under vfsmount lock exclusive

That allows nice common case for mntput() - since we can't drop the
final reference until after mnt_longterm has reached 0 due to the rules
above, mntput() can grab vfsmount lock shared and check mnt_longterm.
If it turns out to be non-zero (which is the common case), we know
that this is not the final mntput() and can just blindly decrement
percpu mnt_count.  Otherwise we grab vfsmount lock exclusive and
do usual decrement-and-check of percpu mnt_count.

For fs_struct.c we have mnt_make_longterm() and mnt_make_shortterm();
namespace.c uses the latter in places where we don't already hold
vfsmount lock exclusive and opencodes a few remaining spots where
we need to manipulate mnt_longterm.

Note that we mostly revert the code outside of fs/namespace.c back
to what we used to have; in particular, normal code doesn't need
to care about two kinds of references, etc.  And we get to keep
the optimization Nick's variant had bought us...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-16 13:47:07 -05:00

117 lines
2.8 KiB
C

/* fs/ internal definitions
*
* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/lglock.h>
struct super_block;
struct linux_binprm;
struct path;
/*
* block_dev.c
*/
#ifdef CONFIG_BLOCK
extern struct super_block *blockdev_superblock;
extern void __init bdev_cache_init(void);
static inline int sb_is_blkdev_sb(struct super_block *sb)
{
return sb == blockdev_superblock;
}
extern int __sync_blockdev(struct block_device *bdev, int wait);
#else
static inline void bdev_cache_init(void)
{
}
static inline int sb_is_blkdev_sb(struct super_block *sb)
{
return 0;
}
static inline int __sync_blockdev(struct block_device *bdev, int wait)
{
return 0;
}
#endif
/*
* char_dev.c
*/
extern void __init chrdev_init(void);
/*
* exec.c
*/
extern int check_unsafe_exec(struct linux_binprm *);
/*
* namespace.c
*/
extern int copy_mount_options(const void __user *, unsigned long *);
extern int copy_mount_string(const void __user *, char **);
extern void free_vfsmnt(struct vfsmount *);
extern struct vfsmount *alloc_vfsmnt(const char *);
extern unsigned int mnt_get_count(struct vfsmount *mnt);
extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
extern void mnt_set_mountpoint(struct vfsmount *, struct dentry *,
struct vfsmount *);
extern void release_mounts(struct list_head *);
extern void umount_tree(struct vfsmount *, int, struct list_head *);
extern struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int);
extern int do_add_mount(struct vfsmount *, struct path *, int);
extern void mnt_clear_expiry(struct vfsmount *);
extern void mnt_make_longterm(struct vfsmount *);
extern void mnt_make_shortterm(struct vfsmount *);
extern void __init mnt_init(void);
DECLARE_BRLOCK(vfsmount_lock);
/*
* fs_struct.c
*/
extern void chroot_fs_refs(struct path *, struct path *);
/*
* file_table.c
*/
extern void file_sb_list_add(struct file *f, struct super_block *sb);
extern void file_sb_list_del(struct file *f);
extern void mark_files_ro(struct super_block *);
extern struct file *get_empty_filp(void);
/*
* super.c
*/
extern int do_remount_sb(struct super_block *, int, void *, int);
extern void __put_super(struct super_block *sb);
extern void put_super(struct super_block *sb);
/*
* open.c
*/
struct nameidata;
extern struct file *nameidata_to_filp(struct nameidata *);
extern void release_open_intent(struct nameidata *);
/*
* inode.c
*/
extern int get_nr_dirty_inodes(void);
extern void evict_inodes(struct super_block *);
extern int invalidate_inodes(struct super_block *);