7053aee26a
Currently fsnotify framework creates one event structure for each notification event and links this event into all interested notification groups. This is done so that we save memory when several notification groups are interested in the event. However the need for event structure shared between inotify & fanotify bloats the event structure so the result is often higher memory consumption. Another problem is that fsnotify framework keeps path references with outstanding events so that fanotify can return open file descriptors with its events. This has the undesirable effect that filesystem cannot be unmounted while there are outstanding events - a regression for inotify compared to a situation before it was converted to fsnotify framework. For fanotify this problem is hard to avoid and users of fanotify should kind of expect this behavior when they ask for file descriptors from notified files. This patch changes fsnotify and its users to create separate event structure for each group. This allows for much simpler code (~400 lines removed by this patch) and also smaller event structures. For example on 64-bit system original struct fsnotify_event consumes 120 bytes, plus additional space for file name, additional 24 bytes for second and each subsequent group linking the event, and additional 32 bytes for each inotify group for private data. After the conversion inotify event consumes 48 bytes plus space for file name which is considerably less memory unless file names are long and there are several groups interested in the events (both of which are uncommon). Fanotify event fits in 56 bytes after the conversion (fanotify doesn't care about file names so its events don't have to have it allocated). A win unless there are four or more fanotify groups interested in the event. The conversion also solves the problem with unmount when only inotify is used as we don't have to grab path references for inotify events. [hughd@google.com: fanotify: fix corruption preventing startup] Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: Eric Paris <eparis@parisplace.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
299 lines
8.8 KiB
C
299 lines
8.8 KiB
C
/*
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/dcache.h>
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#include <linux/fs.h>
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#include <linux/gfp.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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#include <linux/srcu.h>
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#include <linux/fsnotify_backend.h>
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#include "fsnotify.h"
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#include "../mount.h"
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/*
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* Clear all of the marks on an inode when it is being evicted from core
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*/
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void __fsnotify_inode_delete(struct inode *inode)
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{
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fsnotify_clear_marks_by_inode(inode);
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}
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EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
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void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
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{
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fsnotify_clear_marks_by_mount(mnt);
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}
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/*
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* Given an inode, first check if we care what happens to our children. Inotify
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* and dnotify both tell their parents about events. If we care about any event
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* on a child we run all of our children and set a dentry flag saying that the
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* parent cares. Thus when an event happens on a child it can quickly tell if
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* if there is a need to find a parent and send the event to the parent.
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*/
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void __fsnotify_update_child_dentry_flags(struct inode *inode)
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{
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struct dentry *alias;
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int watched;
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if (!S_ISDIR(inode->i_mode))
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return;
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/* determine if the children should tell inode about their events */
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watched = fsnotify_inode_watches_children(inode);
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spin_lock(&inode->i_lock);
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/* run all of the dentries associated with this inode. Since this is a
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* directory, there damn well better only be one item on this list */
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hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
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struct dentry *child;
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/* run all of the children of the original inode and fix their
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* d_flags to indicate parental interest (their parent is the
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* original inode) */
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spin_lock(&alias->d_lock);
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list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
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if (!child->d_inode)
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continue;
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spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
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if (watched)
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child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
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else
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child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
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spin_unlock(&child->d_lock);
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}
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spin_unlock(&alias->d_lock);
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}
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spin_unlock(&inode->i_lock);
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}
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/* Notify this dentry's parent about a child's events. */
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int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
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{
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struct dentry *parent;
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struct inode *p_inode;
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int ret = 0;
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if (!dentry)
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dentry = path->dentry;
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if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
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return 0;
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parent = dget_parent(dentry);
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p_inode = parent->d_inode;
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if (unlikely(!fsnotify_inode_watches_children(p_inode)))
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__fsnotify_update_child_dentry_flags(p_inode);
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else if (p_inode->i_fsnotify_mask & mask) {
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/* we are notifying a parent so come up with the new mask which
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* specifies these are events which came from a child. */
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mask |= FS_EVENT_ON_CHILD;
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if (path)
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ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
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dentry->d_name.name, 0);
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else
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ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
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dentry->d_name.name, 0);
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}
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dput(parent);
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return ret;
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}
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EXPORT_SYMBOL_GPL(__fsnotify_parent);
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static int send_to_group(struct inode *to_tell,
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struct fsnotify_mark *inode_mark,
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struct fsnotify_mark *vfsmount_mark,
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__u32 mask, void *data,
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int data_is, u32 cookie,
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const unsigned char *file_name)
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{
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struct fsnotify_group *group = NULL;
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__u32 inode_test_mask = 0;
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__u32 vfsmount_test_mask = 0;
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if (unlikely(!inode_mark && !vfsmount_mark)) {
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BUG();
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return 0;
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}
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/* clear ignored on inode modification */
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if (mask & FS_MODIFY) {
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if (inode_mark &&
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!(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
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inode_mark->ignored_mask = 0;
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if (vfsmount_mark &&
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!(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
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vfsmount_mark->ignored_mask = 0;
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}
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/* does the inode mark tell us to do something? */
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if (inode_mark) {
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group = inode_mark->group;
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inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
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inode_test_mask &= inode_mark->mask;
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inode_test_mask &= ~inode_mark->ignored_mask;
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}
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/* does the vfsmount_mark tell us to do something? */
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if (vfsmount_mark) {
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vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
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group = vfsmount_mark->group;
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vfsmount_test_mask &= vfsmount_mark->mask;
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vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
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if (inode_mark)
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vfsmount_test_mask &= ~inode_mark->ignored_mask;
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}
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pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
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" inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
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" data=%p data_is=%d cookie=%d\n",
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__func__, group, to_tell, mask, inode_mark,
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inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
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data_is, cookie);
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if (!inode_test_mask && !vfsmount_test_mask)
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return 0;
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if (group->ops->should_send_event(group, to_tell, inode_mark,
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vfsmount_mark, mask, data,
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data_is) == false)
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return 0;
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return group->ops->handle_event(group, to_tell, inode_mark,
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vfsmount_mark, mask, data, data_is,
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file_name);
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}
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/*
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* This is the main call to fsnotify. The VFS calls into hook specific functions
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* in linux/fsnotify.h. Those functions then in turn call here. Here will call
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* out to all of the registered fsnotify_group. Those groups can then use the
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* notification event in whatever means they feel necessary.
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*/
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int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
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const unsigned char *file_name, u32 cookie)
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{
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struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
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struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
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struct fsnotify_group *inode_group, *vfsmount_group;
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struct mount *mnt;
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int idx, ret = 0;
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/* global tests shouldn't care about events on child only the specific event */
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__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
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if (data_is == FSNOTIFY_EVENT_PATH)
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mnt = real_mount(((struct path *)data)->mnt);
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else
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mnt = NULL;
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/*
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* if this is a modify event we may need to clear the ignored masks
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* otherwise return if neither the inode nor the vfsmount care about
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* this type of event.
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*/
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if (!(mask & FS_MODIFY) &&
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!(test_mask & to_tell->i_fsnotify_mask) &&
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!(mnt && test_mask & mnt->mnt_fsnotify_mask))
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return 0;
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idx = srcu_read_lock(&fsnotify_mark_srcu);
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if ((mask & FS_MODIFY) ||
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(test_mask & to_tell->i_fsnotify_mask))
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inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
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&fsnotify_mark_srcu);
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if (mnt && ((mask & FS_MODIFY) ||
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(test_mask & mnt->mnt_fsnotify_mask))) {
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vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
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&fsnotify_mark_srcu);
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inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
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&fsnotify_mark_srcu);
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}
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while (inode_node || vfsmount_node) {
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inode_group = vfsmount_group = NULL;
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if (inode_node) {
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inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
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struct fsnotify_mark, i.i_list);
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inode_group = inode_mark->group;
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}
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if (vfsmount_node) {
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vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
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struct fsnotify_mark, m.m_list);
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vfsmount_group = vfsmount_mark->group;
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}
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if (inode_group > vfsmount_group) {
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/* handle inode */
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ret = send_to_group(to_tell, inode_mark, NULL, mask,
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data, data_is, cookie, file_name);
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/* we didn't use the vfsmount_mark */
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vfsmount_group = NULL;
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} else if (vfsmount_group > inode_group) {
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ret = send_to_group(to_tell, NULL, vfsmount_mark, mask,
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data, data_is, cookie, file_name);
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inode_group = NULL;
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} else {
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ret = send_to_group(to_tell, inode_mark, vfsmount_mark,
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mask, data, data_is, cookie,
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file_name);
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}
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if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
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goto out;
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if (inode_group)
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inode_node = srcu_dereference(inode_node->next,
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&fsnotify_mark_srcu);
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if (vfsmount_group)
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vfsmount_node = srcu_dereference(vfsmount_node->next,
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&fsnotify_mark_srcu);
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}
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ret = 0;
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out:
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srcu_read_unlock(&fsnotify_mark_srcu, idx);
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return ret;
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}
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EXPORT_SYMBOL_GPL(fsnotify);
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static __init int fsnotify_init(void)
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{
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int ret;
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BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
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ret = init_srcu_struct(&fsnotify_mark_srcu);
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if (ret)
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panic("initializing fsnotify_mark_srcu");
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return 0;
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}
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core_initcall(fsnotify_init);
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