inode_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/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;

    assert_spin_locked(&mark->lock);
    assert_spin_locked(&mark->group->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) {
        fsnotify_destroy_mark(mark);
        fsnotify_put_mark(mark);
    }
}

/*
 * 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
 */
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;

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

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);
}