From patchwork Mon Apr 16 18:02:33 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Whitcroft X-Patchwork-Id: 152958 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from chlorine.canonical.com (chlorine.canonical.com [91.189.94.204]) by ozlabs.org (Postfix) with ESMTP id 46E98B708E for ; Tue, 17 Apr 2012 04:03:00 +1000 (EST) Received: from localhost ([127.0.0.1] helo=chlorine.canonical.com) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1SJqGJ-0000Zi-Th; Mon, 16 Apr 2012 18:02:51 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1SJqGD-0000Xg-Nf for kernel-team@lists.ubuntu.com; Mon, 16 Apr 2012 18:02:45 +0000 Received: from 79-78-218-124.dynamic.dsl.as9105.com ([79.78.218.124] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1SJqGD-0000Jf-1W; Mon, 16 Apr 2012 18:02:45 +0000 From: Andy Whitcroft To: kernel-team@lists.ubuntu.com Subject: [PATCH 03/10] fsnotify: use reference counting for groups Date: Mon, 16 Apr 2012 19:02:33 +0100 Message-Id: <1334599360-15346-4-git-send-email-apw@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1334599360-15346-1-git-send-email-apw@canonical.com> References: <1334599360-15346-1-git-send-email-apw@canonical.com> Cc: Andy Whitcroft X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.13 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: kernel-team-bounces@lists.ubuntu.com Errors-To: kernel-team-bounces@lists.ubuntu.com From: Lino Sanfilippo Get a group ref for each mark that is added to the groups list and release that ref when the mark is freed in fsnotify_put_mark(). We also use get a group reference for duplicated marks and for private event data. Now we dont free a group any more when the number of marks becomes 0 but when the groups ref count does. Since this will only happen when all marks are removed from a groups mark list, we dont have to set the groups number of marks to 1 at group creation. Beside clearing all marks in fsnotify_destroy_group() we do also flush the groups event queue. This is since events may hold references to groups (due to private event data) and we have to put those references first before we get a chance to put the final ref, which will result in a call to fsnotify_final_destroy_group(). Signed-off-by: Lino Sanfilippo Signed-off-by: Eric Paris (cherry-picked from commit 0f948ec4aff7eb629b08e7dd3d9761be17a1ae9e git://git.infradead.org/users/eparis/notify.git) BugLink: http://bugs.launchpad.net/bugs/922906 Signed-off-by: Andy Whitcroft --- fs/notify/group.c | 28 ++++++++++------------------ fs/notify/inotify/inotify_fsnotify.c | 2 ++ fs/notify/inotify/inotify_user.c | 1 + fs/notify/mark.c | 24 ++++++++++++++---------- 4 files changed, 27 insertions(+), 28 deletions(-) diff --git a/fs/notify/group.c b/fs/notify/group.c index 59a6b53..37569ec 100644 --- a/fs/notify/group.c +++ b/fs/notify/group.c @@ -34,9 +34,6 @@ */ void fsnotify_final_destroy_group(struct fsnotify_group *group) { - /* clear the notification queue of all events */ - fsnotify_flush_notify(group); - if (group->ops->free_group_priv) group->ops->free_group_priv(group); @@ -44,12 +41,10 @@ void fsnotify_final_destroy_group(struct fsnotify_group *group) } /* - * Trying to get rid of a group. We need to first get rid of any outstanding - * allocations and then free the group. Remember that fsnotify_clear_marks_by_group - * could miss marks that are being freed by inode and those marks could still - * hold a reference to this group (via group->num_marks) If we get into that - * situtation, the fsnotify_final_destroy_group will get called when that final - * mark is freed. + * Trying to get rid of a group. Remove all marks, flush all events and release + * the group reference. + * Note that another thread calling fsnotify_clear_marks_by_group() may still + * hold a ref to the group. */ void fsnotify_destroy_group(struct fsnotify_group *group) { @@ -58,9 +53,10 @@ void fsnotify_destroy_group(struct fsnotify_group *group) synchronize_srcu(&fsnotify_mark_srcu); - /* past the point of no return, matches the initial value of 1 */ - if (atomic_dec_and_test(&group->num_marks)) - fsnotify_final_destroy_group(group); + /* clear the notification queue of all events */ + fsnotify_flush_notify(group); + + fsnotify_put_group(group); } /* @@ -77,7 +73,7 @@ void fsnotify_get_group(struct fsnotify_group *group) void fsnotify_put_group(struct fsnotify_group *group) { if (atomic_dec_and_test(&group->refcnt)) - fsnotify_destroy_group(group); + fsnotify_final_destroy_group(group); } EXPORT_SYMBOL(fsnotify_put_group); @@ -94,11 +90,7 @@ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) /* set to 0 when there a no external references to this group */ atomic_set(&group->refcnt, 1); - /* - * hits 0 when there are no external references AND no marks for - * this group - */ - atomic_set(&group->num_marks, 1); + atomic_set(&group->num_marks, 0); mutex_init(&group->notification_mutex); INIT_LIST_HEAD(&group->notification_list); diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c index e3cbd74..74977fb 100644 --- a/fs/notify/inotify/inotify_fsnotify.c +++ b/fs/notify/inotify/inotify_fsnotify.c @@ -118,6 +118,7 @@ static int inotify_handle_event(struct fsnotify_group *group, fsn_event_priv = &event_priv->fsnotify_event_priv_data; + fsnotify_get_group(group); fsn_event_priv->group = group; event_priv->wd = wd; @@ -210,6 +211,7 @@ void inotify_free_event_priv(struct fsnotify_event_private_data *fsn_event_priv) event_priv = container_of(fsn_event_priv, struct inotify_event_private_data, fsnotify_event_priv_data); + fsnotify_put_group(fsn_event_priv->group); kmem_cache_free(event_priv_cachep, event_priv); } diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index dbafbfc..246250f 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -531,6 +531,7 @@ void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark, fsn_event_priv = &event_priv->fsnotify_event_priv_data; + fsnotify_get_group(group); fsn_event_priv->group = group; event_priv->wd = i_mark->wd; diff --git a/fs/notify/mark.c b/fs/notify/mark.c index 54f36db..5b784aa 100644 --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -109,8 +109,11 @@ void fsnotify_get_mark(struct fsnotify_mark *mark) void fsnotify_put_mark(struct fsnotify_mark *mark) { - if (atomic_dec_and_test(&mark->refcnt)) + if (atomic_dec_and_test(&mark->refcnt)) { + if (mark->group) + fsnotify_put_group(mark->group); mark->free_mark(mark); + } } EXPORT_SYMBOL(fsnotify_put_mark); @@ -126,12 +129,13 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark) spin_lock(&mark->lock); + fsnotify_get_group(mark->group); group = mark->group; /* something else already called this function on this mark */ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) { spin_unlock(&mark->lock); - return; + goto put_group; } mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; @@ -178,19 +182,15 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark) if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) iput(inode); - /* * We don't necessarily have a ref on mark from caller so the above iput * may have already destroyed it. Don't touch from now on. */ - /* - * it's possible that this group tried to destroy itself, but this - * this mark was simultaneously being freed by inode. If that's the - * case, we finish freeing the group here. - */ - if (unlikely(atomic_dec_and_test(&group->num_marks))) - fsnotify_final_destroy_group(group); + atomic_dec(&group->num_marks); + +put_group: + fsnotify_put_group(group); } EXPORT_SYMBOL(fsnotify_destroy_mark); @@ -236,6 +236,7 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE; + fsnotify_get_group(group); mark->group = group; list_add(&mark->g_list, &group->marks_list); atomic_inc(&group->num_marks); @@ -267,6 +268,7 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, err: mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; list_del_init(&mark->g_list); + fsnotify_put_group(group); mark->group = NULL; atomic_dec(&group->num_marks); @@ -320,6 +322,8 @@ void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *ol assert_spin_locked(&old->lock); new->i.inode = old->i.inode; new->m.mnt = old->m.mnt; + if (old->group) + fsnotify_get_group(old->group); new->group = old->group; new->mask = old->mask; new->free_mark = old->free_mark;