From patchwork Tue Apr 26 13:27:11 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chandan Rajendra X-Patchwork-Id: 8938751 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 09EDB9F1C1 for ; Tue, 26 Apr 2016 13:28:39 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 26A98200DB for ; Tue, 26 Apr 2016 13:28:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D689620148 for ; Tue, 26 Apr 2016 13:28:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752082AbcDZN21 (ORCPT ); Tue, 26 Apr 2016 09:28:27 -0400 Received: from e28smtp03.in.ibm.com ([125.16.236.3]:39772 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbcDZN2S (ORCPT ); Tue, 26 Apr 2016 09:28:18 -0400 Received: from localhost by e28smtp03.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 26 Apr 2016 18:58:11 +0530 X-IBM-Helo: d28relay05.in.ibm.com X-IBM-MailFrom: chandan@linux.vnet.ibm.com X-IBM-RcptTo: linux-btrfs@vger.kernel.org Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay05.in.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u3QDSC9g49741900 for ; Tue, 26 Apr 2016 18:58:12 +0530 Received: from d28av02.in.ibm.com (localhost [127.0.0.1]) by d28av02.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u3QDS7ik009951 for ; Tue, 26 Apr 2016 18:58:09 +0530 Received: from localhost.in.ibm.com ([9.79.189.70]) by d28av02.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id u3QDRjCq008918; Tue, 26 Apr 2016 18:58:07 +0530 From: Chandan Rajendra To: linux-btrfs@vger.kernel.org Cc: Chandan Rajendra , dsterba@suse.cz, clm@fb.com, jbacik@fb.com, chandan@mykolab.com Subject: [PATCH V18 12/18] Revert "btrfs: fix lockups from btrfs_clear_path_blocking" Date: Tue, 26 Apr 2016 18:57:11 +0530 Message-Id: <1461677237-7703-13-git-send-email-chandan@linux.vnet.ibm.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1461677237-7703-1-git-send-email-chandan@linux.vnet.ibm.com> References: <1461677237-7703-1-git-send-email-chandan@linux.vnet.ibm.com> X-TM-AS-MML: disable x-cbid: 16042613-0009-0000-0000-00000C5C3460 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The patch "Btrfs: subpage-blocksize: Prevent writes to an extent buffer when PG_writeback flag is set" requires btrfs_try_tree_write_lock() to be a true try lock w.r.t to both spinning and blocking locks. During 2015's Vault Conference Btrfs meetup, Chris Mason had suggested that he will write up a suitable locking function to be used when writing dirty pages that map metadata blocks. Until we have a suitable locking function available, this patch temporarily disables the commit f82c458a2c3ffb94b431fc6ad791a79df1b3713e. --- fs/btrfs/ctree.c | 14 ++++++++++++-- fs/btrfs/locking.c | 24 +++--------------------- fs/btrfs/locking.h | 2 -- 3 files changed, 15 insertions(+), 25 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 7d76add..4a753c9 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -81,6 +81,13 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p, { int i; +#ifdef CONFIG_DEBUG_LOCK_ALLOC + /* lockdep really cares that we take all of these spinlocks + * in the right order. If any of the locks in the path are not + * currently blocking, it is going to complain. So, make really + * really sure by forcing the path to blocking before we clear + * the path blocking. + */ if (held) { btrfs_set_lock_blocking_rw(held, held_rw); if (held_rw == BTRFS_WRITE_LOCK) @@ -89,6 +96,7 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p, held_rw = BTRFS_READ_LOCK_BLOCKING; } btrfs_set_path_blocking(p); +#endif for (i = BTRFS_MAX_LEVEL - 1; i >= 0; i--) { if (p->nodes[i] && p->locks[i]) { @@ -100,8 +108,10 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p, } } +#ifdef CONFIG_DEBUG_LOCK_ALLOC if (held) btrfs_clear_lock_blocking_rw(held, held_rw); +#endif } /* this also releases the path */ @@ -2904,7 +2914,7 @@ cow_done: } p->locks[level] = BTRFS_WRITE_LOCK; } else { - err = btrfs_tree_read_lock_atomic(b); + err = btrfs_try_tree_read_lock(b); if (!err) { btrfs_set_path_blocking(p); btrfs_tree_read_lock(b); @@ -3036,7 +3046,7 @@ again: } level = btrfs_header_level(b); - err = btrfs_tree_read_lock_atomic(b); + err = btrfs_try_tree_read_lock(b); if (!err) { btrfs_set_path_blocking(p); btrfs_tree_read_lock(b); diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index d13128c..8b50e60 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -132,26 +132,6 @@ again: } /* - * take a spinning read lock. - * returns 1 if we get the read lock and 0 if we don't - * this won't wait for blocking writers - */ -int btrfs_tree_read_lock_atomic(struct extent_buffer *eb) -{ - if (atomic_read(&eb->blocking_writers)) - return 0; - - read_lock(&eb->lock); - if (atomic_read(&eb->blocking_writers)) { - read_unlock(&eb->lock); - return 0; - } - atomic_inc(&eb->read_locks); - atomic_inc(&eb->spinning_readers); - return 1; -} - -/* * returns 1 if we get the read lock and 0 if we don't * this won't wait for blocking writers */ @@ -182,7 +162,9 @@ int btrfs_try_tree_write_lock(struct extent_buffer *eb) atomic_read(&eb->blocking_readers)) return 0; - write_lock(&eb->lock); + if (!write_trylock(&eb->lock)) + return 0; + if (atomic_read(&eb->blocking_writers) || atomic_read(&eb->blocking_readers)) { write_unlock(&eb->lock); diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index c44a9d5..b81e0e9 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -35,8 +35,6 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw); void btrfs_assert_tree_locked(struct extent_buffer *eb); int btrfs_try_tree_read_lock(struct extent_buffer *eb); int btrfs_try_tree_write_lock(struct extent_buffer *eb); -int btrfs_tree_read_lock_atomic(struct extent_buffer *eb); - static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw) {