From patchwork Thu Sep 1 01:21:14 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Kent X-Patchwork-Id: 9308187 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E5723607D6 for ; Thu, 1 Sep 2016 01:21:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D57B9290E9 for ; Thu, 1 Sep 2016 01:21:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CA25F29109; Thu, 1 Sep 2016 01:21:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 93ECA290E9 for ; Thu, 1 Sep 2016 01:21:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754574AbcIABVU (ORCPT ); Wed, 31 Aug 2016 21:21:20 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:38474 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752513AbcIABVT (ORCPT ); Wed, 31 Aug 2016 21:21:19 -0400 Received: from compute7.internal (compute7.nyi.internal [10.202.2.47]) by mailout.nyi.internal (Postfix) with ESMTP id 03BE32058E; Wed, 31 Aug 2016 21:21:17 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute7.internal (MEProxy); Wed, 31 Aug 2016 21:21:18 -0400 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=themaw.net; h=cc :content-transfer-encoding:content-type:date:from:message-id :mime-version:subject:to:x-sasl-enc:x-sasl-enc; s=mesmtp; bh=KtH lV35PswOZnqSBDzB0k7YERxs=; b=SeCaQOKkvMHfvTuwVIBo2qLgWrbKoPZmTRO UnYPJmBMAlNb3UPTc/RM9/YOHYyyFr4+zOiNTFD1Z1NVOXn5VGWDtg+EvFpaVwyd 8leXLi+qG+HTqLgYc0SEX4orShaNlcd2WaYG0LtCOHKEpcjFNZH4LQd5uy7HvTUJ cESDBG20= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-sasl-enc :x-sasl-enc; s=smtpout; bh=KtHlV35PswOZnqSBDzB0k7YERxs=; b=m+uun 2H7whDWe3/Dbn0CYibkaCISFvH0ep6t1ofP6xZy36mKbEWH8CSD4Ax3heUVst9v4 1tnQ7byMT2jeSBdlZvghUrzOqNZGO4oGyQmL5EWl6y9KB4yNgVZZvBDGwIH0jh+l J66tSF7gEPJOpGoPVmTQG8i7xKQ58nGjZu55uk= X-Sasl-enc: UGucAtbLtOugFExojmJSuD2pL9Bqd+mQQgExpraFUGoX 1472692877 Received: from pluto.themaw.net (220-253-166-124.dyn.iinet.net.au [220.253.166.124]) by mail.messagingengine.com (Postfix) with ESMTPA id 47D6ACCE66; Wed, 31 Aug 2016 21:21:17 -0400 (EDT) Received: from pluto.themaw.net (localhost [127.0.0.1]) by pluto.themaw.net (Postfix) with ESMTP id 4CF95A0061; Thu, 1 Sep 2016 09:21:14 +0800 (AWST) Subject: [PATCH] autofs - use dentry flags to block walks during expire From: Ian Kent To: Al Viro Cc: linux-fsdevel , Takashi Iwai , autofs mailing list , Kernel Mailing List Date: Thu, 01 Sep 2016 09:21:14 +0800 Message-ID: <20160901012114.6476.57874.stgit@pluto.themaw.net> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Somewhere along the way the autofs expire operation has changed to hold a spin lock over expired dentry selection. The autofs indirect mount expired dentry selection is complicated and quite lengthy so it isn't appropriate to hold a spin lock over the operation. Commit 47be6184 added a might_sleep() to dput() causing a BUG() about this usage to be issued. But the spin lock doesn't need to be held over this check, the autofs dentry info. flags are enough to block walks into dentrys during the expire. I've left the direct mount expire as it is (for now) becuase it is much simpler and quicker than the indirect mount expire and adding spin lock release and re-aquires would do nothing more than add overhead. Signed-off-by: Ian Kent --- fs/autofs4/expire.c | 55 +++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 42 insertions(+), 13 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c index b493909..2d8e176 100644 --- a/fs/autofs4/expire.c +++ b/fs/autofs4/expire.c @@ -417,6 +417,7 @@ static struct dentry *should_expire(struct dentry *dentry, } return NULL; } + /* * Find an eligible tree to time-out * A tree is eligible if :- @@ -432,6 +433,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb, struct dentry *root = sb->s_root; struct dentry *dentry; struct dentry *expired; + struct dentry *found; struct autofs_info *ino; if (!root) @@ -442,31 +444,46 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb, dentry = NULL; while ((dentry = get_next_positive_subdir(dentry, root))) { + int flags = how; + spin_lock(&sbi->fs_lock); ino = autofs4_dentry_ino(dentry); - if (ino->flags & AUTOFS_INF_WANT_EXPIRE) - expired = NULL; - else - expired = should_expire(dentry, mnt, timeout, how); - if (!expired) { + if (ino->flags & AUTOFS_INF_WANT_EXPIRE) { spin_unlock(&sbi->fs_lock); continue; } + spin_unlock(&sbi->fs_lock); + + expired = should_expire(dentry, mnt, timeout, flags); + if (!expired) + continue; + + spin_lock(&sbi->fs_lock); ino = autofs4_dentry_ino(expired); ino->flags |= AUTOFS_INF_WANT_EXPIRE; spin_unlock(&sbi->fs_lock); synchronize_rcu(); - spin_lock(&sbi->fs_lock); - if (should_expire(expired, mnt, timeout, how)) { - if (expired != dentry) - dput(dentry); - goto found; - } + /* Make sure a reference is not taken on found if + * things have changed. + */ + flags &= ~AUTOFS_EXP_LEAVES; + found = should_expire(expired, mnt, timeout, how); + if (!found || found != expired) + /* Something has changed, continue */ + goto next; + + if (expired != dentry) + dput(dentry); + + spin_lock(&sbi->fs_lock); + goto found; +next: + spin_lock(&sbi->fs_lock); ino->flags &= ~AUTOFS_INF_WANT_EXPIRE; + spin_unlock(&sbi->fs_lock); if (expired != dentry) dput(expired); - spin_unlock(&sbi->fs_lock); } return NULL; @@ -483,6 +500,7 @@ int autofs4_expire_wait(struct dentry *dentry, int rcu_walk) struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); struct autofs_info *ino = autofs4_dentry_ino(dentry); int status; + int state; /* Block on any pending expire */ if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE)) @@ -490,8 +508,19 @@ int autofs4_expire_wait(struct dentry *dentry, int rcu_walk) if (rcu_walk) return -ECHILD; +retry: spin_lock(&sbi->fs_lock); - if (ino->flags & AUTOFS_INF_EXPIRING) { + state = ino->flags & (AUTOFS_INF_WANT_EXPIRE | AUTOFS_INF_EXPIRING); + if (state == AUTOFS_INF_WANT_EXPIRE) { + spin_unlock(&sbi->fs_lock); + /* + * Possibly being selected for expire, wait until + * it's selected or not. + */ + schedule_timeout(HZ/10); + goto retry; + } + if (state & AUTOFS_INF_EXPIRING) { spin_unlock(&sbi->fs_lock); pr_debug("waiting for expire %p name=%pd\n", dentry, dentry);