vfsmount_mark.c

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/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <[email protected]>
 *
 *  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/mount.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>

#include <linux/atomic.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
#include "../mount.h"

void fsnotify_clear_marks_by_mount(struct vfsmount *mnt)
{
    struct fsnotify_mark *mark, *lmark;
    struct hlist_node *pos, *n;
    struct mount *m = real_mount(mnt);
    LIST_HEAD(free_list);

    spin_lock(&mnt->mnt_root->d_lock);
    hlist_for_each_entry_safe(mark, pos, n, &m->mnt_fsnotify_marks, m.m_list) {
        list_add(&mark->m.free_m_list, &free_list);
        hlist_del_init_rcu(&mark->m.m_list);
        fsnotify_get_mark(mark);
    }
    spin_unlock(&mnt->mnt_root->d_lock);

    list_for_each_entry_safe(mark, lmark, &free_list, m.free_m_list) {
        fsnotify_destroy_mark(mark);
        fsnotify_put_mark(mark);
    }
}

void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
{
    fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_VFSMOUNT);
}

/*
 * Recalculate the mask of events relevant to a given vfsmount locked.
 */
static void fsnotify_recalc_vfsmount_mask_locked(struct vfsmount *mnt)
{
    struct mount *m = real_mount(mnt);
    struct fsnotify_mark *mark;
    struct hlist_node *pos;
    __u32 new_mask = 0;

    assert_spin_locked(&mnt->mnt_root->d_lock);

    hlist_for_each_entry(mark, pos, &m->mnt_fsnotify_marks, m.m_list)
        new_mask |= mark->mask;
    m->mnt_fsnotify_mask = new_mask;
}

/*
 * Recalculate the mnt->mnt_fsnotify_mask, or the mask of all FS_* event types
 * any notifier is interested in hearing for this mount point
 */
void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt)
{
    spin_lock(&mnt->mnt_root->d_lock);
    fsnotify_recalc_vfsmount_mask_locked(mnt);
    spin_unlock(&mnt->mnt_root->d_lock);
}

void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark)
{
    struct vfsmount *mnt = mark->m.mnt;

    assert_spin_locked(&mark->lock);
    assert_spin_locked(&mark->group->mark_lock);

    spin_lock(&mnt->mnt_root->d_lock);

    hlist_del_init_rcu(&mark->m.m_list);
    mark->m.mnt = NULL;

    fsnotify_recalc_vfsmount_mask_locked(mnt);

    spin_unlock(&mnt->mnt_root->d_lock);
}

static struct fsnotify_mark *fsnotify_find_vfsmount_mark_locked(struct fsnotify_group *group,
                                struct vfsmount *mnt)
{
    struct mount *m = real_mount(mnt);
    struct fsnotify_mark *mark;
    struct hlist_node *pos;

    assert_spin_locked(&mnt->mnt_root->d_lock);

    hlist_for_each_entry(mark, pos, &m->mnt_fsnotify_marks, m.m_list) {
        if (mark->group == group) {
            fsnotify_get_mark(mark);
            return mark;
        }
    }
    return NULL;
}

/*
 * given a group and vfsmount, 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_vfsmount_mark(struct fsnotify_group *group,
                          struct vfsmount *mnt)
{
    struct fsnotify_mark *mark;

    spin_lock(&mnt->mnt_root->d_lock);
    mark = fsnotify_find_vfsmount_mark_locked(group, mnt);
    spin_unlock(&mnt->mnt_root->d_lock);

    return mark;
}

/*
 * Attach an initialized mark to a given group and vfsmount.
 * These marks may be used for the fsnotify backend to determine which
 * event types should be delivered to which groups.
 */
int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
                   struct fsnotify_group *group, struct vfsmount *mnt,
                   int allow_dups)
{
    struct mount *m = real_mount(mnt);
    struct fsnotify_mark *lmark;
    struct hlist_node *node, *last = NULL;
    int ret = 0;

    mark->flags |= FSNOTIFY_MARK_FLAG_VFSMOUNT;

    assert_spin_locked(&mark->lock);
    assert_spin_locked(&group->mark_lock);

    spin_lock(&mnt->mnt_root->d_lock);

    mark->m.mnt = mnt;

    /* is mark the first mark? */
    if (hlist_empty(&m->mnt_fsnotify_marks)) {
        hlist_add_head_rcu(&mark->m.m_list, &m->mnt_fsnotify_marks);
        goto out;
    }

    /* should mark be in the middle of the current list? */
    hlist_for_each_entry(lmark, node, &m->mnt_fsnotify_marks, m.m_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->m.m_list, &lmark->m.m_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->m.m_list);
out:
    fsnotify_recalc_vfsmount_mask_locked(mnt);
    spin_unlock(&mnt->mnt_root->d_lock);

    return ret;
}