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>
113 lines
2.9 KiB
C
113 lines
2.9 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/list.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/srcu.h>
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#include <linux/rculist.h>
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#include <linux/wait.h>
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#include <linux/fsnotify_backend.h>
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#include "fsnotify.h"
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#include <linux/atomic.h>
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/*
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* Final freeing of a group
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*/
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void fsnotify_final_destroy_group(struct fsnotify_group *group)
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{
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if (group->ops->free_group_priv)
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group->ops->free_group_priv(group);
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kfree(group);
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}
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/*
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* Trying to get rid of a group. Remove all marks, flush all events and release
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* the group reference.
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* Note that another thread calling fsnotify_clear_marks_by_group() may still
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* hold a ref to the group.
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*/
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void fsnotify_destroy_group(struct fsnotify_group *group)
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{
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/* clear all inode marks for this group */
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fsnotify_clear_marks_by_group(group);
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synchronize_srcu(&fsnotify_mark_srcu);
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/* clear the notification queue of all events */
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fsnotify_flush_notify(group);
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fsnotify_put_group(group);
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}
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/*
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* Get reference to a group.
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*/
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void fsnotify_get_group(struct fsnotify_group *group)
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{
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atomic_inc(&group->refcnt);
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}
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/*
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* Drop a reference to a group. Free it if it's through.
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*/
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void fsnotify_put_group(struct fsnotify_group *group)
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{
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if (atomic_dec_and_test(&group->refcnt))
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fsnotify_final_destroy_group(group);
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}
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/*
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* Create a new fsnotify_group and hold a reference for the group returned.
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*/
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struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
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{
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struct fsnotify_group *group;
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group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
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if (!group)
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return ERR_PTR(-ENOMEM);
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/* set to 0 when there a no external references to this group */
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atomic_set(&group->refcnt, 1);
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atomic_set(&group->num_marks, 0);
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mutex_init(&group->notification_mutex);
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INIT_LIST_HEAD(&group->notification_list);
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init_waitqueue_head(&group->notification_waitq);
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group->max_events = UINT_MAX;
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mutex_init(&group->mark_mutex);
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INIT_LIST_HEAD(&group->marks_list);
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group->ops = ops;
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fsnotify_init_event(&group->overflow_event, NULL, FS_Q_OVERFLOW);
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return group;
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}
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int fsnotify_fasync(int fd, struct file *file, int on)
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{
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struct fsnotify_group *group = file->private_data;
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return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
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}
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