/* * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> * * 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/dcache.h> #include <linux/fs.h> #include <linux/gfp.h> #include <linux/init.h> #include <linux/module.h> #include <linux/mount.h> #include <linux/srcu.h> #include <linux/fsnotify_backend.h> #include "fsnotify.h" /* * Clear all of the marks on an inode when it is being evicted from core */ void __fsnotify_inode_delete(struct inode *inode) { fsnotify_clear_marks_by_inode(inode); } EXPORT_SYMBOL_GPL(__fsnotify_inode_delete); void __fsnotify_vfsmount_delete(struct vfsmount *mnt) { fsnotify_clear_marks_by_mount(mnt); } /** * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes. * @sb: superblock being unmounted. * * Called during unmount with no locks held, so needs to be safe against * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block. */ void fsnotify_unmount_inodes(struct super_block *sb) { struct inode *inode, *iput_inode = NULL; spin_lock(&sb->s_inode_list_lock); list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { /* * 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; } __iget(inode); spin_unlock(&inode->i_lock); spin_unlock(&sb->s_inode_list_lock); if (iput_inode) iput(iput_inode); /* 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 = inode; spin_lock(&sb->s_inode_list_lock); } spin_unlock(&sb->s_inode_list_lock); if (iput_inode) iput(iput_inode); } /* * Given an inode, first check if we care what happens to our children. Inotify * and dnotify both tell their parents about events. If we care about any event * on a child we run all of our children and set a dentry flag saying that the * parent cares. Thus when an event happens on a child it can quickly tell if * if there is a need to find a parent and send the event to the parent. */ void __fsnotify_update_child_dentry_flags(struct inode *inode) { struct dentry *alias; int watched; if (!S_ISDIR(inode->i_mode)) return; /* determine if the children should tell inode about their events */ watched = fsnotify_inode_watches_children(inode); spin_lock(&inode->i_lock); /* run all of the dentries associated with this inode. Since this is a * directory, there damn well better only be one item on this list */ hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { struct dentry *child; /* run all of the children of the original inode and fix their * d_flags to indicate parental interest (their parent is the * original inode) */ spin_lock(&alias->d_lock); list_for_each_entry(child, &alias->d_subdirs, d_child) { if (!child->d_inode) continue; spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); if (watched) child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; else child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; spin_unlock(&child->d_lock); } spin_unlock(&alias->d_lock); } spin_unlock(&inode->i_lock); } /* Notify this dentry's parent about a child's events. */ int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask) { struct dentry *parent; struct inode *p_inode; int ret = 0; if (!dentry) dentry = path->dentry; if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED)) return 0; parent = dget_parent(dentry); p_inode = parent->d_inode; if (unlikely(!fsnotify_inode_watches_children(p_inode))) __fsnotify_update_child_dentry_flags(p_inode); else if (p_inode->i_fsnotify_mask & mask) { struct name_snapshot name; /* we are notifying a parent so come up with the new mask which * specifies these are events which came from a child. */ mask |= FS_EVENT_ON_CHILD; take_dentry_name_snapshot(&name, dentry); if (path) ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH, name.name, 0); else ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE, name.name, 0); release_dentry_name_snapshot(&name); } dput(parent); return ret; } EXPORT_SYMBOL_GPL(__fsnotify_parent); static int send_to_group(struct inode *to_tell, struct fsnotify_mark *inode_mark, struct fsnotify_mark *vfsmount_mark, __u32 mask, const void *data, int data_is, u32 cookie, const unsigned char *file_name, struct fsnotify_iter_info *iter_info) { struct fsnotify_group *group = NULL; __u32 inode_test_mask = 0; __u32 vfsmount_test_mask = 0; if (unlikely(!inode_mark && !vfsmount_mark)) { BUG(); return 0; } /* clear ignored on inode modification */ if (mask & FS_MODIFY) { if (inode_mark && !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) inode_mark->ignored_mask = 0; if (vfsmount_mark && !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) vfsmount_mark->ignored_mask = 0; } /* does the inode mark tell us to do something? */ if (inode_mark) { group = inode_mark->group; inode_test_mask = (mask & ~FS_EVENT_ON_CHILD); inode_test_mask &= inode_mark->mask; inode_test_mask &= ~inode_mark->ignored_mask; } /* does the vfsmount_mark tell us to do something? */ if (vfsmount_mark) { vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD); group = vfsmount_mark->group; vfsmount_test_mask &= vfsmount_mark->mask; vfsmount_test_mask &= ~vfsmount_mark->ignored_mask; if (inode_mark) vfsmount_test_mask &= ~inode_mark->ignored_mask; } pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p" " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x" " data=%p data_is=%d cookie=%d\n", __func__, group, to_tell, mask, inode_mark, inode_test_mask, vfsmount_mark, vfsmount_test_mask, data, data_is, cookie); if (!inode_test_mask && !vfsmount_test_mask) return 0; return group->ops->handle_event(group, to_tell, inode_mark, vfsmount_mark, mask, data, data_is, file_name, cookie, iter_info); } static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp) { struct fsnotify_mark_connector *conn; struct hlist_node *node = NULL; conn = srcu_dereference(*connp, &fsnotify_mark_srcu); if (conn) node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu); return hlist_entry_safe(node, struct fsnotify_mark, obj_list); } static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark) { struct hlist_node *node = NULL; if (mark) node = srcu_dereference(mark->obj_list.next, &fsnotify_mark_srcu); return hlist_entry_safe(node, struct fsnotify_mark, obj_list); } /* * This is the main call to fsnotify. The VFS calls into hook specific functions * in linux/fsnotify.h. Those functions then in turn call here. Here will call * out to all of the registered fsnotify_group. Those groups can then use the * notification event in whatever means they feel necessary. */ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, const unsigned char *file_name, u32 cookie) { struct fsnotify_iter_info iter_info = {}; struct mount *mnt; int ret = 0; /* global tests shouldn't care about events on child only the specific event */ __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD); if (data_is == FSNOTIFY_EVENT_PATH) mnt = real_mount(((const struct path *)data)->mnt); else mnt = NULL; /* * Optimization: srcu_read_lock() has a memory barrier which can * be expensive. It protects walking the *_fsnotify_marks lists. * However, if we do not walk the lists, we do not have to do * SRCU because we have no references to any objects and do not * need SRCU to keep them "alive". */ if (!to_tell->i_fsnotify_marks && (!mnt || !mnt->mnt_fsnotify_marks)) return 0; /* * if this is a modify event we may need to clear the ignored masks * otherwise return if neither the inode nor the vfsmount care about * this type of event. */ if (!(mask & FS_MODIFY) && !(test_mask & to_tell->i_fsnotify_mask) && !(mnt && test_mask & mnt->mnt_fsnotify_mask)) return 0; iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); if ((mask & FS_MODIFY) || (test_mask & to_tell->i_fsnotify_mask)) { iter_info.inode_mark = fsnotify_first_mark(&to_tell->i_fsnotify_marks); } if (mnt && ((mask & FS_MODIFY) || (test_mask & mnt->mnt_fsnotify_mask))) { iter_info.inode_mark = fsnotify_first_mark(&to_tell->i_fsnotify_marks); iter_info.vfsmount_mark = fsnotify_first_mark(&mnt->mnt_fsnotify_marks); } /* * We need to merge inode & vfsmount mark lists so that inode mark * ignore masks are properly reflected for mount mark notifications. * That's why this traversal is so complicated... */ while (iter_info.inode_mark || iter_info.vfsmount_mark) { struct fsnotify_mark *inode_mark = iter_info.inode_mark; struct fsnotify_mark *vfsmount_mark = iter_info.vfsmount_mark; if (inode_mark && vfsmount_mark) { int cmp = fsnotify_compare_groups(inode_mark->group, vfsmount_mark->group); if (cmp > 0) inode_mark = NULL; else if (cmp < 0) vfsmount_mark = NULL; } ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask, data, data_is, cookie, file_name, &iter_info); if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS)) goto out; if (inode_mark) iter_info.inode_mark = fsnotify_next_mark(iter_info.inode_mark); if (vfsmount_mark) iter_info.vfsmount_mark = fsnotify_next_mark(iter_info.vfsmount_mark); } ret = 0; out: srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx); return ret; } EXPORT_SYMBOL_GPL(fsnotify); extern struct kmem_cache *fsnotify_mark_connector_cachep; static __init int fsnotify_init(void) { int ret; BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23); ret = init_srcu_struct(&fsnotify_mark_srcu); if (ret) panic("initializing fsnotify_mark_srcu"); fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector, SLAB_PANIC); return 0; } core_initcall(fsnotify_init);