The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/fs/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/sched.h>
   18 #include <linux/dnotify.h>
   19 #include <linux/init.h>
   20 #include <linux/spinlock.h>
   21 #include <linux/slab.h>
   22 
   23 extern void send_sigio(struct fown_struct *fown, int fd, int band);
   24 
   25 int dir_notify_enable = 1;
   26 
   27 static rwlock_t dn_lock = RW_LOCK_UNLOCKED;
   28 static kmem_cache_t *dn_cache;
   29 
   30 static void redo_inode_mask(struct inode *inode)
   31 {
   32         unsigned long new_mask;
   33         struct dnotify_struct *dn;
   34 
   35         new_mask = 0;
   36         for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
   37                 new_mask |= dn->dn_mask & ~DN_MULTISHOT;
   38         inode->i_dnotify_mask = new_mask;
   39 }
   40 
   41 void dnotify_flush(struct file *filp, fl_owner_t id)
   42 {
   43         struct dnotify_struct *dn;
   44         struct dnotify_struct **prev;
   45         struct inode *inode;
   46 
   47         inode = filp->f_dentry->d_inode;
   48         if (!S_ISDIR(inode->i_mode))
   49                 return;
   50         write_lock(&dn_lock);
   51         prev = &inode->i_dnotify;
   52         while ((dn = *prev) != NULL) {
   53                 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
   54                         *prev = dn->dn_next;
   55                         redo_inode_mask(inode);
   56                         kmem_cache_free(dn_cache, dn);
   57                         break;
   58                 }
   59                 prev = &dn->dn_next;
   60         }
   61         write_unlock(&dn_lock);
   62 }
   63 
   64 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
   65 {
   66         struct dnotify_struct *dn;
   67         struct dnotify_struct *odn;
   68         struct dnotify_struct **prev;
   69         struct inode *inode;
   70         fl_owner_t id = current->files;
   71 
   72         if ((arg & ~DN_MULTISHOT) == 0) {
   73                 dnotify_flush(filp, id);
   74                 return 0;
   75         }
   76         if (!dir_notify_enable)
   77                 return -EINVAL;
   78         inode = filp->f_dentry->d_inode;
   79         if (!S_ISDIR(inode->i_mode))
   80                 return -ENOTDIR;
   81         dn = kmem_cache_alloc(dn_cache, SLAB_KERNEL);
   82         if (dn == NULL)
   83                 return -ENOMEM;
   84         write_lock(&dn_lock);
   85         prev = &inode->i_dnotify;
   86         while ((odn = *prev) != NULL) {
   87                 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
   88                         odn->dn_fd = fd;
   89                         odn->dn_mask |= arg;
   90                         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
   91                         kmem_cache_free(dn_cache, dn);
   92                         goto out;
   93                 }
   94                 prev = &odn->dn_next;
   95         }
   96         filp->f_owner.pid = current->pid;
   97         filp->f_owner.uid = current->uid;
   98         filp->f_owner.euid = current->euid;
   99         dn->dn_mask = arg;
  100         dn->dn_fd = fd;
  101         dn->dn_filp = filp;
  102         dn->dn_owner = id;
  103         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
  104         dn->dn_next = inode->i_dnotify;
  105         inode->i_dnotify = dn;
  106 out:
  107         write_unlock(&dn_lock);
  108         return 0;
  109 }
  110 
  111 void __inode_dir_notify(struct inode *inode, unsigned long event)
  112 {
  113         struct dnotify_struct * dn;
  114         struct dnotify_struct **prev;
  115         struct fown_struct *    fown;
  116         int                     changed = 0;
  117 
  118         write_lock(&dn_lock);
  119         prev = &inode->i_dnotify;
  120         while ((dn = *prev) != NULL) {
  121                 if ((dn->dn_mask & event) == 0) {
  122                         prev = &dn->dn_next;
  123                         continue;
  124                 }
  125                 fown = &dn->dn_filp->f_owner;
  126                 if (fown->pid)
  127                         send_sigio(fown, dn->dn_fd, POLL_MSG);
  128                 if (dn->dn_mask & DN_MULTISHOT)
  129                         prev = &dn->dn_next;
  130                 else {
  131                         *prev = dn->dn_next;
  132                         changed = 1;
  133                         kmem_cache_free(dn_cache, dn);
  134                 }
  135         }
  136         if (changed)
  137                 redo_inode_mask(inode);
  138         write_unlock(&dn_lock);
  139 }
  140 
  141 static int __init dnotify_init(void)
  142 {
  143         dn_cache = kmem_cache_create("dnotify_cache",
  144                 sizeof(struct dnotify_struct), 0, 0, NULL, NULL);
  145         if (!dn_cache)
  146                 panic("cannot create dnotify slab cache");
  147         return 0;
  148 }
  149 
  150 module_init(dnotify_init)

Cache object: 67d3d4a98329727f0b20b4eeeb7009b8


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