| /* |
| * Directory notifications for Linux. |
| * |
| * Copyright (C) 2000,2001,2002 Stephen Rothwell |
| * |
| * Copyright (C) 2009 Eric Paris <Red Hat Inc> |
| * dnotify was largly rewritten to use the new fsnotify infrastructure |
| * |
| * 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. |
| */ |
| #include <linux/fs.h> |
| #include <linux/module.h> |
| #include <linux/sched.h> |
| #include <linux/dnotify.h> |
| #include <linux/init.h> |
| #include <linux/spinlock.h> |
| #include <linux/slab.h> |
| #include <linux/fdtable.h> |
| #include <linux/fsnotify_backend.h> |
| |
| int dir_notify_enable __read_mostly = 1; |
| |
| static struct kmem_cache *dnotify_struct_cache __read_mostly; |
| static struct kmem_cache *dnotify_mark_cache __read_mostly; |
| static struct fsnotify_group *dnotify_group __read_mostly; |
| static DEFINE_MUTEX(dnotify_mark_mutex); |
| |
| /* |
| * dnotify will attach one of these to each inode (i_fsnotify_marks) which |
| * is being watched by dnotify. If multiple userspace applications are watching |
| * the same directory with dnotify their information is chained in dn |
| */ |
| struct dnotify_mark { |
| struct fsnotify_mark fsn_mark; |
| struct dnotify_struct *dn; |
| }; |
| |
| /* |
| * When a process starts or stops watching an inode the set of events which |
| * dnotify cares about for that inode may change. This function runs the |
| * list of everything receiving dnotify events about this directory and calculates |
| * the set of all those events. After it updates what dnotify is interested in |
| * it calls the fsnotify function so it can update the set of all events relevant |
| * to this inode. |
| */ |
| static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark) |
| { |
| __u32 new_mask, old_mask; |
| struct dnotify_struct *dn; |
| struct dnotify_mark *dn_mark = container_of(fsn_mark, |
| struct dnotify_mark, |
| fsn_mark); |
| |
| assert_spin_locked(&fsn_mark->lock); |
| |
| old_mask = fsn_mark->mask; |
| new_mask = 0; |
| for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next) |
| new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT); |
| fsn_mark->mask = new_mask; |
| |
| if (old_mask == new_mask) |
| return; |
| |
| if (fsn_mark->i.inode) |
| fsnotify_recalc_inode_mask(fsn_mark->i.inode); |
| } |
| |
| /* |
| * Mains fsnotify call where events are delivered to dnotify. |
| * Find the dnotify mark on the relevant inode, run the list of dnotify structs |
| * on that mark and determine which of them has expressed interest in receiving |
| * events of this type. When found send the correct process and signal and |
| * destroy the dnotify struct if it was not registered to receive multiple |
| * events. |
| */ |
| static int dnotify_handle_event(struct fsnotify_group *group, |
| struct fsnotify_event *event) |
| { |
| struct fsnotify_mark *fsn_mark = NULL; |
| struct dnotify_mark *dn_mark; |
| struct inode *to_tell; |
| struct dnotify_struct *dn; |
| struct dnotify_struct **prev; |
| struct fown_struct *fown; |
| __u32 test_mask = event->mask & ~FS_EVENT_ON_CHILD; |
| |
| to_tell = event->to_tell; |
| |
| fsn_mark = fsnotify_find_mark(group, to_tell); |
| if (unlikely(!fsn_mark)) |
| return 0; |
| dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
| |
| spin_lock(&fsn_mark->lock); |
| prev = &dn_mark->dn; |
| while ((dn = *prev) != NULL) { |
| if ((dn->dn_mask & test_mask) == 0) { |
| prev = &dn->dn_next; |
| continue; |
| } |
| fown = &dn->dn_filp->f_owner; |
| send_sigio(fown, dn->dn_fd, POLL_MSG); |
| if (dn->dn_mask & FS_DN_MULTISHOT) |
| prev = &dn->dn_next; |
| else { |
| *prev = dn->dn_next; |
| kmem_cache_free(dnotify_struct_cache, dn); |
| dnotify_recalc_inode_mask(fsn_mark); |
| } |
| } |
| |
| spin_unlock(&fsn_mark->lock); |
| fsnotify_put_mark(fsn_mark); |
| |
| return 0; |
| } |
| |
| /* |
| * Given an inode and mask determine if dnotify would be interested in sending |
| * userspace notification for that pair. |
| */ |
| static bool dnotify_should_send_event(struct fsnotify_group *group, |
| struct inode *inode, struct vfsmount *mnt, |
| __u32 mask, void *data, int data_type) |
| { |
| struct fsnotify_mark *fsn_mark; |
| bool send; |
| |
| /* !dir_notify_enable should never get here, don't waste time checking |
| if (!dir_notify_enable) |
| return 0; */ |
| |
| /* not a dir, dnotify doesn't care */ |
| if (!S_ISDIR(inode->i_mode)) |
| return false; |
| |
| fsn_mark = fsnotify_find_mark(group, inode); |
| if (!fsn_mark) |
| return false; |
| |
| mask = (mask & ~FS_EVENT_ON_CHILD); |
| send = (mask & fsn_mark->mask); |
| |
| fsnotify_put_mark(fsn_mark); /* matches fsnotify_find_mark */ |
| |
| return send; |
| } |
| |
| static void dnotify_free_mark(struct fsnotify_mark *fsn_mark) |
| { |
| struct dnotify_mark *dn_mark = container_of(fsn_mark, |
| struct dnotify_mark, |
| fsn_mark); |
| |
| BUG_ON(dn_mark->dn); |
| |
| kmem_cache_free(dnotify_mark_cache, dn_mark); |
| } |
| |
| static struct fsnotify_ops dnotify_fsnotify_ops = { |
| .handle_event = dnotify_handle_event, |
| .should_send_event = dnotify_should_send_event, |
| .free_group_priv = NULL, |
| .freeing_mark = NULL, |
| .free_event_priv = NULL, |
| }; |
| |
| /* |
| * Called every time a file is closed. Looks first for a dnotify mark on the |
| * inode. If one is found run all of the ->dn structures attached to that |
| * mark for one relevant to this process closing the file and remove that |
| * dnotify_struct. If that was the last dnotify_struct also remove the |
| * fsnotify_mark. |
| */ |
| void dnotify_flush(struct file *filp, fl_owner_t id) |
| { |
| struct fsnotify_mark *fsn_mark; |
| struct dnotify_mark *dn_mark; |
| struct dnotify_struct *dn; |
| struct dnotify_struct **prev; |
| struct inode *inode; |
| |
| inode = filp->f_path.dentry->d_inode; |
| if (!S_ISDIR(inode->i_mode)) |
| return; |
| |
| fsn_mark = fsnotify_find_mark(dnotify_group, inode); |
| if (!fsn_mark) |
| return; |
| dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
| |
| mutex_lock(&dnotify_mark_mutex); |
| |
| spin_lock(&fsn_mark->lock); |
| prev = &dn_mark->dn; |
| while ((dn = *prev) != NULL) { |
| if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { |
| *prev = dn->dn_next; |
| kmem_cache_free(dnotify_struct_cache, dn); |
| dnotify_recalc_inode_mask(fsn_mark); |
| break; |
| } |
| prev = &dn->dn_next; |
| } |
| |
| spin_unlock(&fsn_mark->lock); |
| |
| /* nothing else could have found us thanks to the dnotify_mark_mutex */ |
| if (dn_mark->dn == NULL) |
| fsnotify_destroy_mark(fsn_mark); |
| |
| fsnotify_recalc_group_mask(dnotify_group); |
| |
| mutex_unlock(&dnotify_mark_mutex); |
| |
| fsnotify_put_mark(fsn_mark); |
| } |
| |
| /* this conversion is done only at watch creation */ |
| static __u32 convert_arg(unsigned long arg) |
| { |
| __u32 new_mask = FS_EVENT_ON_CHILD; |
| |
| if (arg & DN_MULTISHOT) |
| new_mask |= FS_DN_MULTISHOT; |
| if (arg & DN_DELETE) |
| new_mask |= (FS_DELETE | FS_MOVED_FROM); |
| if (arg & DN_MODIFY) |
| new_mask |= FS_MODIFY; |
| if (arg & DN_ACCESS) |
| new_mask |= FS_ACCESS; |
| if (arg & DN_ATTRIB) |
| new_mask |= FS_ATTRIB; |
| if (arg & DN_RENAME) |
| new_mask |= FS_DN_RENAME; |
| if (arg & DN_CREATE) |
| new_mask |= (FS_CREATE | FS_MOVED_TO); |
| |
| return new_mask; |
| } |
| |
| /* |
| * If multiple processes watch the same inode with dnotify there is only one |
| * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct |
| * onto that mark. This function either attaches the new dnotify_struct onto |
| * that list, or it |= the mask onto an existing dnofiy_struct. |
| */ |
| static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark, |
| fl_owner_t id, int fd, struct file *filp, __u32 mask) |
| { |
| struct dnotify_struct *odn; |
| |
| odn = dn_mark->dn; |
| while (odn != NULL) { |
| /* adding more events to existing dnofiy_struct? */ |
| if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { |
| odn->dn_fd = fd; |
| odn->dn_mask |= mask; |
| return -EEXIST; |
| } |
| odn = odn->dn_next; |
| } |
| |
| dn->dn_mask = mask; |
| dn->dn_fd = fd; |
| dn->dn_filp = filp; |
| dn->dn_owner = id; |
| dn->dn_next = dn_mark->dn; |
| dn_mark->dn = dn; |
| |
| return 0; |
| } |
| |
| /* |
| * When a process calls fcntl to attach a dnotify watch to a directory it ends |
| * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be |
| * attached to the fsnotify_mark. |
| */ |
| int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) |
| { |
| struct dnotify_mark *new_dn_mark, *dn_mark; |
| struct fsnotify_mark *new_fsn_mark, *fsn_mark; |
| struct dnotify_struct *dn; |
| struct inode *inode; |
| fl_owner_t id = current->files; |
| struct file *f; |
| int destroy = 0, error = 0; |
| __u32 mask; |
| |
| /* we use these to tell if we need to kfree */ |
| new_fsn_mark = NULL; |
| dn = NULL; |
| |
| if (!dir_notify_enable) { |
| error = -EINVAL; |
| goto out_err; |
| } |
| |
| /* a 0 mask means we are explicitly removing the watch */ |
| if ((arg & ~DN_MULTISHOT) == 0) { |
| dnotify_flush(filp, id); |
| error = 0; |
| goto out_err; |
| } |
| |
| /* dnotify only works on directories */ |
| inode = filp->f_path.dentry->d_inode; |
| if (!S_ISDIR(inode->i_mode)) { |
| error = -ENOTDIR; |
| goto out_err; |
| } |
| |
| /* expect most fcntl to add new rather than augment old */ |
| dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL); |
| if (!dn) { |
| error = -ENOMEM; |
| goto out_err; |
| } |
| |
| /* new fsnotify mark, we expect most fcntl calls to add a new mark */ |
| new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL); |
| if (!new_dn_mark) { |
| error = -ENOMEM; |
| goto out_err; |
| } |
| |
| /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */ |
| mask = convert_arg(arg); |
| |
| /* set up the new_fsn_mark and new_dn_mark */ |
| new_fsn_mark = &new_dn_mark->fsn_mark; |
| fsnotify_init_mark(new_fsn_mark, dnotify_free_mark); |
| new_fsn_mark->mask = mask; |
| new_dn_mark->dn = NULL; |
| |
| /* this is needed to prevent the fcntl/close race described below */ |
| mutex_lock(&dnotify_mark_mutex); |
| |
| /* add the new_fsn_mark or find an old one. */ |
| fsn_mark = fsnotify_find_mark(dnotify_group, inode); |
| if (fsn_mark) { |
| dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
| spin_lock(&fsn_mark->lock); |
| } else { |
| fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, 0); |
| spin_lock(&new_fsn_mark->lock); |
| fsn_mark = new_fsn_mark; |
| dn_mark = new_dn_mark; |
| /* we used new_fsn_mark, so don't free it */ |
| new_fsn_mark = NULL; |
| } |
| |
| rcu_read_lock(); |
| f = fcheck(fd); |
| rcu_read_unlock(); |
| |
| /* if (f != filp) means that we lost a race and another task/thread |
| * actually closed the fd we are still playing with before we grabbed |
| * the dnotify_mark_mutex and fsn_mark->lock. Since closing the fd is the |
| * only time we clean up the marks we need to get our mark off |
| * the list. */ |
| if (f != filp) { |
| /* if we added ourselves, shoot ourselves, it's possible that |
| * the flush actually did shoot this fsn_mark. That's fine too |
| * since multiple calls to destroy_mark is perfectly safe, if |
| * we found a dn_mark already attached to the inode, just sod |
| * off silently as the flush at close time dealt with it. |
| */ |
| if (dn_mark == new_dn_mark) |
| destroy = 1; |
| goto out; |
| } |
| |
| error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); |
| if (error) { |
| /* if we added, we must shoot */ |
| if (dn_mark == new_dn_mark) |
| destroy = 1; |
| goto out; |
| } |
| |
| error = attach_dn(dn, dn_mark, id, fd, filp, mask); |
| /* !error means that we attached the dn to the dn_mark, so don't free it */ |
| if (!error) |
| dn = NULL; |
| /* -EEXIST means that we didn't add this new dn and used an old one. |
| * that isn't an error (and the unused dn should be freed) */ |
| else if (error == -EEXIST) |
| error = 0; |
| |
| dnotify_recalc_inode_mask(fsn_mark); |
| out: |
| spin_unlock(&fsn_mark->lock); |
| |
| if (destroy) |
| fsnotify_destroy_mark(fsn_mark); |
| |
| fsnotify_recalc_group_mask(dnotify_group); |
| |
| mutex_unlock(&dnotify_mark_mutex); |
| fsnotify_put_mark(fsn_mark); |
| out_err: |
| if (new_fsn_mark) |
| fsnotify_put_mark(new_fsn_mark); |
| if (dn) |
| kmem_cache_free(dnotify_struct_cache, dn); |
| return error; |
| } |
| |
| static int __init dnotify_init(void) |
| { |
| dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC); |
| dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC); |
| |
| dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops); |
| if (IS_ERR(dnotify_group)) |
| panic("unable to allocate fsnotify group for dnotify\n"); |
| return 0; |
| } |
| |
| module_init(dnotify_init) |