dnotify.c

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    1 /*
    2  * Directory notifications for Linux.
    3  *
    4  * Copyright (C) 2000,2001,2002 Stephen Rothwell
    5  *
    6  * This program is free software; you can redistribute it and/or modify it
    7  * under the terms of the GNU General Public License as published by the
    8  * Free Software Foundation; either version 2, or (at your option) any
    9  * later version.
   10  *
   11  * This program is distributed in the hope that it will be useful, but
   12  * WITHOUT ANY WARRANTY; without even the implied warranty of
   13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   14  * General Public License for more details.
   15  */
   16 #include <linux/fs.h>
   17 #include <linux/module.h>
   18 #include <linux/sched.h>
   19 #include <linux/dnotify.h>
   20 #include <linux/init.h>
   21 #include <linux/spinlock.h>
   22 #include <linux/slab.h>
   23 #include <linux/fdtable.h>
   24 
   25 int dir_notify_enable __read_mostly = 1;
   26 
   27 static struct kmem_cache *dn_cache __read_mostly;
   28 
   29 static void redo_inode_mask(struct inode *inode)
   30 {
   31         unsigned long new_mask;
   32         struct dnotify_struct *dn;
   33 
   34         new_mask = 0;
   35         for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
   36                 new_mask |= dn->dn_mask & ~DN_MULTISHOT;
   37         inode->i_dnotify_mask = new_mask;
   38 }
   39 
   40 void dnotify_flush(struct file *filp, fl_owner_t id)
   41 {
   42         struct dnotify_struct *dn;
   43         struct dnotify_struct **prev;
   44         struct inode *inode;
   45 
   46         inode = filp->f_path.dentry->d_inode;
   47         if (!S_ISDIR(inode->i_mode))
   48                 return;
   49         spin_lock(&inode->i_lock);
   50         prev = &inode->i_dnotify;
   51         while ((dn = *prev) != NULL) {
   52                 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
   53                         *prev = dn->dn_next;
   54                         redo_inode_mask(inode);
   55                         kmem_cache_free(dn_cache, dn);
   56                         break;
   57                 }
   58                 prev = &dn->dn_next;
   59         }
   60         spin_unlock(&inode->i_lock);
   61 }
   62 
   63 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
   64 {
   65         struct dnotify_struct *dn;
   66         struct dnotify_struct *odn;
   67         struct dnotify_struct **prev;
   68         struct inode *inode;
   69         fl_owner_t id = current->files;
   70         struct file *f;
   71         int error = 0;
   72 
   73         if ((arg & ~DN_MULTISHOT) == 0) {
   74                 dnotify_flush(filp, id);
   75                 return 0;
   76         }
   77         if (!dir_notify_enable)
   78                 return -EINVAL;
   79         inode = filp->f_path.dentry->d_inode;
   80         if (!S_ISDIR(inode->i_mode))
   81                 return -ENOTDIR;
   82         dn = kmem_cache_alloc(dn_cache, GFP_KERNEL);
   83         if (dn == NULL)
   84                 return -ENOMEM;
   85         spin_lock(&inode->i_lock);
   86         prev = &inode->i_dnotify;
   87         while ((odn = *prev) != NULL) {
   88                 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
   89                         odn->dn_fd = fd;
   90                         odn->dn_mask |= arg;
   91                         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
   92                         goto out_free;
   93                 }
   94                 prev = &odn->dn_next;
   95         }
   96 
   97         rcu_read_lock();
   98         f = fcheck(fd);
   99         rcu_read_unlock();
  100         /* we'd lost the race with close(), sod off silently */
  101         /* note that inode->i_lock prevents reordering problems
  102          * between accesses to descriptor table and ->i_dnotify */
  103         if (f != filp)
  104                 goto out_free;
  105 
  106         error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
  107         if (error)
  108                 goto out_free;
  109 
  110         dn->dn_mask = arg;
  111         dn->dn_fd = fd;
  112         dn->dn_filp = filp;
  113         dn->dn_owner = id;
  114         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
  115         dn->dn_next = inode->i_dnotify;
  116         inode->i_dnotify = dn;
  117         spin_unlock(&inode->i_lock);
  118 
  119         if (filp->f_op && filp->f_op->dir_notify)
  120                 return filp->f_op->dir_notify(filp, arg);
  121         return 0;
  122 
  123 out_free:
  124         spin_unlock(&inode->i_lock);
  125         kmem_cache_free(dn_cache, dn);
  126         return error;
  127 }
  128 
  129 void __inode_dir_notify(struct inode *inode, unsigned long event)
  130 {
  131         struct dnotify_struct * dn;
  132         struct dnotify_struct **prev;
  133         struct fown_struct *    fown;
  134         int                     changed = 0;
  135 
  136         spin_lock(&inode->i_lock);
  137         prev = &inode->i_dnotify;
  138         while ((dn = *prev) != NULL) {
  139                 if ((dn->dn_mask & event) == 0) {
  140                         prev = &dn->dn_next;
  141                         continue;
  142                 }
  143                 fown = &dn->dn_filp->f_owner;
  144                 send_sigio(fown, dn->dn_fd, POLL_MSG);
  145                 if (dn->dn_mask & DN_MULTISHOT)
  146                         prev = &dn->dn_next;
  147                 else {
  148                         *prev = dn->dn_next;
  149                         changed = 1;
  150                         kmem_cache_free(dn_cache, dn);
  151                 }
  152         }
  153         if (changed)
  154                 redo_inode_mask(inode);
  155         spin_unlock(&inode->i_lock);
  156 }
  157 
  158 EXPORT_SYMBOL(__inode_dir_notify);
  159 
  160 /*
  161  * This is hopelessly wrong, but unfixable without API changes.  At
  162  * least it doesn't oops the kernel...
  163  *
  164  * To safely access ->d_parent we need to keep d_move away from it.  Use the
  165  * dentry's d_lock for this.
  166  */
  167 void dnotify_parent(struct dentry *dentry, unsigned long event)
  168 {
  169         struct dentry *parent;
  170 
  171         if (!dir_notify_enable)
  172                 return;
  173 
  174         spin_lock(&dentry->d_lock);
  175         parent = dentry->d_parent;
  176         if (parent->d_inode->i_dnotify_mask & event) {
  177                 dget(parent);
  178                 spin_unlock(&dentry->d_lock);
  179                 __inode_dir_notify(parent->d_inode, event);
  180                 dput(parent);
  181         } else {
  182                 spin_unlock(&dentry->d_lock);
  183         }
  184 }
  185 EXPORT_SYMBOL_GPL(dnotify_parent);
  186 
  187 static int __init dnotify_init(void)
  188 {
  189         dn_cache = kmem_cache_create("dnotify_cache",
  190                 sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL);
  191         return 0;
  192 }
  193 
  194 module_init(dnotify_init)

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FreeBSD/Linux Kernel Cross Reference sys/fs/dnotify.c

FreeBSD/Linux Kernel Cross Reference
sys/fs/dnotify.c