forked from Minki/linux
4d885f90e3
->fs_lock protects AUTOFS_INF_EXPIRING. We need to be sure that once the flag is set, no new references beneath the dentry are taken. So rcu-walk currently needs to take fs_lock before checking the flag. This hurts performance. Change the expiry to a two-stage process. First set AUTOFS_INF_NO_RCU which forces any path walk into ref-walk mode, then drop the lock and call synchronize_rcu(). Once that returns we can be sure no rcu-walk is active beneath the dentry and we can check reference counts again. Now during an RCU-walk we can test AUTOFS_INF_EXPIRING without taking the lock as along as we test AUTOFS_INF_NO_RCU too. If either are set, we must abort the RCU-walk If neither are set, we know that refcounts will be tested again after we finish the RCU-walk so we are safe to continue. ->fs_lock is still taken in d_manage() to check for a non-trap directory. That will be resolved in the next patch. Signed-off-by: NeilBrown <neilb@suse.de> Reviewed-by: Ian Kent <raven@themaw.net> Tested-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
284 lines
7.9 KiB
C
284 lines
7.9 KiB
C
/* -*- c -*- ------------------------------------------------------------- *
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*
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* linux/fs/autofs/autofs_i.h
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*
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* Copyright 1997-1998 Transmeta Corporation - All Rights Reserved
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* Copyright 2005-2006 Ian Kent <raven@themaw.net>
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*
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* This file is part of the Linux kernel and is made available under
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* the terms of the GNU General Public License, version 2, or at your
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* option, any later version, incorporated herein by reference.
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*
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* ----------------------------------------------------------------------- */
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/* Internal header file for autofs */
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#include <linux/auto_fs4.h>
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#include <linux/auto_dev-ioctl.h>
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#include <linux/mutex.h>
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#include <linux/spinlock.h>
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#include <linux/list.h>
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/* This is the range of ioctl() numbers we claim as ours */
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#define AUTOFS_IOC_FIRST AUTOFS_IOC_READY
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#define AUTOFS_IOC_COUNT 32
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#define AUTOFS_DEV_IOCTL_IOC_FIRST (AUTOFS_DEV_IOCTL_VERSION)
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#define AUTOFS_DEV_IOCTL_IOC_COUNT (AUTOFS_IOC_COUNT - 11)
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/time.h>
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#include <linux/string.h>
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#include <linux/wait.h>
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#include <linux/sched.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <asm/current.h>
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#include <asm/uaccess.h>
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/* #define DEBUG */
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#define DPRINTK(fmt, ...) \
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pr_debug("pid %d: %s: " fmt "\n", \
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current->pid, __func__, ##__VA_ARGS__)
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#define AUTOFS_WARN(fmt, ...) \
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printk(KERN_WARNING "pid %d: %s: " fmt "\n", \
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current->pid, __func__, ##__VA_ARGS__)
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#define AUTOFS_ERROR(fmt, ...) \
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printk(KERN_ERR "pid %d: %s: " fmt "\n", \
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current->pid, __func__, ##__VA_ARGS__)
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/* Unified info structure. This is pointed to by both the dentry and
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inode structures. Each file in the filesystem has an instance of this
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structure. It holds a reference to the dentry, so dentries are never
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flushed while the file exists. All name lookups are dealt with at the
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dentry level, although the filesystem can interfere in the validation
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process. Readdir is implemented by traversing the dentry lists. */
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struct autofs_info {
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struct dentry *dentry;
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struct inode *inode;
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int flags;
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struct completion expire_complete;
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struct list_head active;
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int active_count;
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struct list_head expiring;
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struct autofs_sb_info *sbi;
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unsigned long last_used;
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atomic_t count;
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kuid_t uid;
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kgid_t gid;
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};
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#define AUTOFS_INF_EXPIRING (1<<0) /* dentry is in the process of expiring */
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#define AUTOFS_INF_NO_RCU (1<<1) /* the dentry is being considered
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* for expiry, so RCU_walk is
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* not permitted
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*/
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#define AUTOFS_INF_PENDING (1<<2) /* dentry pending mount */
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struct autofs_wait_queue {
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wait_queue_head_t queue;
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struct autofs_wait_queue *next;
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autofs_wqt_t wait_queue_token;
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/* We use the following to see what we are waiting for */
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struct qstr name;
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u32 dev;
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u64 ino;
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kuid_t uid;
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kgid_t gid;
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pid_t pid;
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pid_t tgid;
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/* This is for status reporting upon return */
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int status;
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unsigned int wait_ctr;
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};
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#define AUTOFS_SBI_MAGIC 0x6d4a556d
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struct autofs_sb_info {
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u32 magic;
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int pipefd;
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struct file *pipe;
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struct pid *oz_pgrp;
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int catatonic;
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int version;
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int sub_version;
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int min_proto;
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int max_proto;
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unsigned long exp_timeout;
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unsigned int type;
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int reghost_enabled;
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int needs_reghost;
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struct super_block *sb;
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struct mutex wq_mutex;
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struct mutex pipe_mutex;
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spinlock_t fs_lock;
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struct autofs_wait_queue *queues; /* Wait queue pointer */
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spinlock_t lookup_lock;
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struct list_head active_list;
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struct list_head expiring_list;
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struct rcu_head rcu;
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};
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static inline struct autofs_sb_info *autofs4_sbi(struct super_block *sb)
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{
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return (struct autofs_sb_info *)(sb->s_fs_info);
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}
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static inline struct autofs_info *autofs4_dentry_ino(struct dentry *dentry)
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{
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return (struct autofs_info *)(dentry->d_fsdata);
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}
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/* autofs4_oz_mode(): do we see the man behind the curtain? (The
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processes which do manipulations for us in user space sees the raw
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filesystem without "magic".) */
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static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
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return sbi->catatonic || task_pgrp(current) == sbi->oz_pgrp;
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}
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struct inode *autofs4_get_inode(struct super_block *, umode_t);
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void autofs4_free_ino(struct autofs_info *);
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/* Expiration */
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int is_autofs4_dentry(struct dentry *);
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int autofs4_expire_wait(struct dentry *dentry, int rcu_walk);
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int autofs4_expire_run(struct super_block *, struct vfsmount *,
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struct autofs_sb_info *,
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struct autofs_packet_expire __user *);
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int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
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struct autofs_sb_info *sbi, int when);
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int autofs4_expire_multi(struct super_block *, struct vfsmount *,
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struct autofs_sb_info *, int __user *);
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struct dentry *autofs4_expire_direct(struct super_block *sb,
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struct vfsmount *mnt,
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struct autofs_sb_info *sbi, int how);
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struct dentry *autofs4_expire_indirect(struct super_block *sb,
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struct vfsmount *mnt,
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struct autofs_sb_info *sbi, int how);
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/* Device node initialization */
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int autofs_dev_ioctl_init(void);
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void autofs_dev_ioctl_exit(void);
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/* Operations structures */
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extern const struct inode_operations autofs4_symlink_inode_operations;
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extern const struct inode_operations autofs4_dir_inode_operations;
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extern const struct file_operations autofs4_dir_operations;
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extern const struct file_operations autofs4_root_operations;
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extern const struct dentry_operations autofs4_dentry_operations;
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/* VFS automount flags management functions */
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static inline void __managed_dentry_set_managed(struct dentry *dentry)
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{
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dentry->d_flags |= (DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
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}
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static inline void managed_dentry_set_managed(struct dentry *dentry)
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{
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spin_lock(&dentry->d_lock);
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__managed_dentry_set_managed(dentry);
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spin_unlock(&dentry->d_lock);
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}
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static inline void __managed_dentry_clear_managed(struct dentry *dentry)
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{
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dentry->d_flags &= ~(DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
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}
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static inline void managed_dentry_clear_managed(struct dentry *dentry)
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{
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spin_lock(&dentry->d_lock);
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__managed_dentry_clear_managed(dentry);
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spin_unlock(&dentry->d_lock);
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}
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/* Initializing function */
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int autofs4_fill_super(struct super_block *, void *, int);
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struct autofs_info *autofs4_new_ino(struct autofs_sb_info *);
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void autofs4_clean_ino(struct autofs_info *);
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static inline int autofs_prepare_pipe(struct file *pipe)
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{
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if (!pipe->f_op->write)
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return -EINVAL;
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if (!S_ISFIFO(file_inode(pipe)->i_mode))
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return -EINVAL;
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/* We want a packet pipe */
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pipe->f_flags |= O_DIRECT;
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return 0;
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}
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/* Queue management functions */
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int autofs4_wait(struct autofs_sb_info *,struct dentry *, enum autofs_notify);
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int autofs4_wait_release(struct autofs_sb_info *,autofs_wqt_t,int);
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void autofs4_catatonic_mode(struct autofs_sb_info *);
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static inline u32 autofs4_get_dev(struct autofs_sb_info *sbi)
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{
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return new_encode_dev(sbi->sb->s_dev);
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}
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static inline u64 autofs4_get_ino(struct autofs_sb_info *sbi)
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{
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return sbi->sb->s_root->d_inode->i_ino;
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}
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static inline int simple_positive(struct dentry *dentry)
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{
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return dentry->d_inode && !d_unhashed(dentry);
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}
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static inline void __autofs4_add_expiring(struct dentry *dentry)
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{
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struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
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struct autofs_info *ino = autofs4_dentry_ino(dentry);
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if (ino) {
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if (list_empty(&ino->expiring))
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list_add(&ino->expiring, &sbi->expiring_list);
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}
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return;
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}
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static inline void autofs4_add_expiring(struct dentry *dentry)
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{
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struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
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struct autofs_info *ino = autofs4_dentry_ino(dentry);
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if (ino) {
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spin_lock(&sbi->lookup_lock);
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if (list_empty(&ino->expiring))
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list_add(&ino->expiring, &sbi->expiring_list);
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spin_unlock(&sbi->lookup_lock);
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}
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return;
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}
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static inline void autofs4_del_expiring(struct dentry *dentry)
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{
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struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
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struct autofs_info *ino = autofs4_dentry_ino(dentry);
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if (ino) {
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spin_lock(&sbi->lookup_lock);
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if (!list_empty(&ino->expiring))
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list_del_init(&ino->expiring);
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spin_unlock(&sbi->lookup_lock);
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}
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return;
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}
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extern void autofs4_kill_sb(struct super_block *);
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