linux/fs/notify/inode_mark.c
Linus Torvalds 96680d2b91 Merge branch 'for-next' of git://git.infradead.org/users/eparis/notify
Pull filesystem notification updates from Eric Paris:
 "This pull mostly is about locking changes in the fsnotify system.  By
  switching the group lock from a spin_lock() to a mutex() we can now
  hold the lock across things like iput().  This fixes a problem
  involving unmounting a fs and having inodes be busy, first pointed out
  by FAT, but reproducible with tmpfs.

  This also restores signal driven I/O for inotify, which has been
  broken since about 2.6.32."

Ugh.  I *hate* the timing of this.  It was rebased after the merge
window opened, and then left to sit with the pull request coming the day
before the merge window closes.  That's just crap.  But apparently the
patches themselves have been around for over a year, just gathering
dust, so now it's suddenly critical.

Fixed up semantic conflict in fs/notify/fdinfo.c as per Stephen
Rothwell's fixes from -next.

* 'for-next' of git://git.infradead.org/users/eparis/notify:
  inotify: automatically restart syscalls
  inotify: dont skip removal of watch descriptor if creation of ignored event failed
  fanotify: dont merge permission events
  fsnotify: make fasync generic for both inotify and fanotify
  fsnotify: change locking order
  fsnotify: dont put marks on temporary list when clearing marks by group
  fsnotify: introduce locked versions of fsnotify_add_mark() and fsnotify_remove_mark()
  fsnotify: pass group to fsnotify_destroy_mark()
  fsnotify: use a mutex instead of a spinlock to protect a groups mark list
  fanotify: add an extra flag to mark_remove_from_mask that indicates wheather a mark should be destroyed
  fsnotify: take groups mark_lock before mark lock
  fsnotify: use reference counting for groups
  fsnotify: introduce fsnotify_get_group()
  inotify, fanotify: replace fsnotify_put_group() with fsnotify_destroy_group()
2012-12-20 20:11:52 -08:00

325 lines
8.5 KiB
C

/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@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, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
#include "../internal.h"
/*
* Recalculate the mask of events relevant to a given inode locked.
*/
static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
{
struct fsnotify_mark *mark;
struct hlist_node *pos;
__u32 new_mask = 0;
assert_spin_locked(&inode->i_lock);
hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list)
new_mask |= mark->mask;
inode->i_fsnotify_mask = new_mask;
}
/*
* Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
* any notifier is interested in hearing for this inode.
*/
void fsnotify_recalc_inode_mask(struct inode *inode)
{
spin_lock(&inode->i_lock);
fsnotify_recalc_inode_mask_locked(inode);
spin_unlock(&inode->i_lock);
__fsnotify_update_child_dentry_flags(inode);
}
void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
{
struct inode *inode = mark->i.inode;
BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
assert_spin_locked(&mark->lock);
spin_lock(&inode->i_lock);
hlist_del_init_rcu(&mark->i.i_list);
mark->i.inode = NULL;
/*
* this mark is now off the inode->i_fsnotify_marks list and we
* hold the inode->i_lock, so this is the perfect time to update the
* inode->i_fsnotify_mask
*/
fsnotify_recalc_inode_mask_locked(inode);
spin_unlock(&inode->i_lock);
}
/*
* Given an inode, destroy all of the marks associated with that inode.
*/
void fsnotify_clear_marks_by_inode(struct inode *inode)
{
struct fsnotify_mark *mark, *lmark;
struct hlist_node *pos, *n;
LIST_HEAD(free_list);
spin_lock(&inode->i_lock);
hlist_for_each_entry_safe(mark, pos, n, &inode->i_fsnotify_marks, i.i_list) {
list_add(&mark->i.free_i_list, &free_list);
hlist_del_init_rcu(&mark->i.i_list);
fsnotify_get_mark(mark);
}
spin_unlock(&inode->i_lock);
list_for_each_entry_safe(mark, lmark, &free_list, i.free_i_list) {
struct fsnotify_group *group;
spin_lock(&mark->lock);
fsnotify_get_group(mark->group);
group = mark->group;
spin_unlock(&mark->lock);
fsnotify_destroy_mark(mark, group);
fsnotify_put_mark(mark);
fsnotify_put_group(group);
}
}
/*
* Given a group clear all of the inode marks associated with that group.
*/
void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
{
fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
}
/*
* given a group and inode, find the mark associated with that combination.
* if found take a reference to that mark and return it, else return NULL
*/
static struct fsnotify_mark *fsnotify_find_inode_mark_locked(
struct fsnotify_group *group,
struct inode *inode)
{
struct fsnotify_mark *mark;
struct hlist_node *pos;
assert_spin_locked(&inode->i_lock);
hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list) {
if (mark->group == group) {
fsnotify_get_mark(mark);
return mark;
}
}
return NULL;
}
/*
* given a group and inode, find the mark associated with that combination.
* if found take a reference to that mark and return it, else return NULL
*/
struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
struct inode *inode)
{
struct fsnotify_mark *mark;
spin_lock(&inode->i_lock);
mark = fsnotify_find_inode_mark_locked(group, inode);
spin_unlock(&inode->i_lock);
return mark;
}
/*
* If we are setting a mark mask on an inode mark we should pin the inode
* in memory.
*/
void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
__u32 mask)
{
struct inode *inode;
assert_spin_locked(&mark->lock);
if (mask &&
mark->i.inode &&
!(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
inode = igrab(mark->i.inode);
/*
* we shouldn't be able to get here if the inode wasn't
* already safely held in memory. But bug in case it
* ever is wrong.
*/
BUG_ON(!inode);
}
}
/*
* Attach an initialized mark to a given inode.
* These marks may be used for the fsnotify backend to determine which
* event types should be delivered to which group and for which inodes. These
* marks are ordered according to priority, highest number first, and then by
* the group's location in memory.
*/
int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group, struct inode *inode,
int allow_dups)
{
struct fsnotify_mark *lmark;
struct hlist_node *node, *last = NULL;
int ret = 0;
mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
BUG_ON(!mutex_is_locked(&group->mark_mutex));
assert_spin_locked(&mark->lock);
spin_lock(&inode->i_lock);
mark->i.inode = inode;
/* is mark the first mark? */
if (hlist_empty(&inode->i_fsnotify_marks)) {
hlist_add_head_rcu(&mark->i.i_list, &inode->i_fsnotify_marks);
goto out;
}
/* should mark be in the middle of the current list? */
hlist_for_each_entry(lmark, node, &inode->i_fsnotify_marks, i.i_list) {
last = node;
if ((lmark->group == group) && !allow_dups) {
ret = -EEXIST;
goto out;
}
if (mark->group->priority < lmark->group->priority)
continue;
if ((mark->group->priority == lmark->group->priority) &&
(mark->group < lmark->group))
continue;
hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);
goto out;
}
BUG_ON(last == NULL);
/* mark should be the last entry. last is the current last entry */
hlist_add_after_rcu(last, &mark->i.i_list);
out:
fsnotify_recalc_inode_mask_locked(inode);
spin_unlock(&inode->i_lock);
return ret;
}
/**
* fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
* @list: list of inodes being unmounted (sb->s_inodes)
*
* Called during unmount with no locks held, so needs to be safe against
* concurrent modifiers. We temporarily drop inode_sb_list_lock and CAN block.
*/
void fsnotify_unmount_inodes(struct list_head *list)
{
struct inode *inode, *next_i, *need_iput = NULL;
spin_lock(&inode_sb_list_lock);
list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
struct inode *need_iput_tmp;
/*
* We cannot __iget() an inode in state I_FREEING,
* I_WILL_FREE, or I_NEW which is fine because by that point
* the inode cannot have any associated watches.
*/
spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
spin_unlock(&inode->i_lock);
continue;
}
/*
* If i_count is zero, the inode cannot have any watches and
* doing an __iget/iput with MS_ACTIVE clear would actually
* evict all inodes with zero i_count from icache which is
* unnecessarily violent and may in fact be illegal to do.
*/
if (!atomic_read(&inode->i_count)) {
spin_unlock(&inode->i_lock);
continue;
}
need_iput_tmp = need_iput;
need_iput = NULL;
/* In case fsnotify_inode_delete() drops a reference. */
if (inode != need_iput_tmp)
__iget(inode);
else
need_iput_tmp = NULL;
spin_unlock(&inode->i_lock);
/* In case the dropping of a reference would nuke next_i. */
if ((&next_i->i_sb_list != list) &&
atomic_read(&next_i->i_count)) {
spin_lock(&next_i->i_lock);
if (!(next_i->i_state & (I_FREEING | I_WILL_FREE))) {
__iget(next_i);
need_iput = next_i;
}
spin_unlock(&next_i->i_lock);
}
/*
* We can safely drop inode_sb_list_lock here because we hold
* references on both inode and next_i. Also no new inodes
* will be added since the umount has begun.
*/
spin_unlock(&inode_sb_list_lock);
if (need_iput_tmp)
iput(need_iput_tmp);
/* for each watch, send FS_UNMOUNT and then remove it */
fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
fsnotify_inode_delete(inode);
iput(inode);
spin_lock(&inode_sb_list_lock);
}
spin_unlock(&inode_sb_list_lock);
}