From patchwork Mon Jul 4 04:34:32 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chandan Rajendra X-Patchwork-Id: 9211601 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 C17A860467 for ; Mon, 4 Jul 2016 04:35:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B680E2862D for ; Mon, 4 Jul 2016 04:35:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AB87D2863D; Mon, 4 Jul 2016 04:35:55 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI 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 3732E2862D for ; Mon, 4 Jul 2016 04:35:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752776AbcGDEfv (ORCPT ); Mon, 4 Jul 2016 00:35:51 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:7558 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752444AbcGDEfs (ORCPT ); Mon, 4 Jul 2016 00:35:48 -0400 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u644XfGb013901 for ; Mon, 4 Jul 2016 00:35:48 -0400 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0a-001b2d01.pphosted.com with ESMTP id 23x9ppexue-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 04 Jul 2016 00:35:47 -0400 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 4 Jul 2016 00:35:44 -0400 X-IBM-Helo: d01dlp02.pok.ibm.com X-IBM-MailFrom: chandan@linux.vnet.ibm.com Received: from b01cxnp23034.gho.pok.ibm.com (b01cxnp23034.gho.pok.ibm.com [9.57.198.29]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 966A46E803C; Mon, 4 Jul 2016 00:35:25 -0400 (EDT) Received: from b01ledav006.gho.pok.ibm.com (b01ledav006.gho.pok.ibm.com [9.57.199.111]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u644ZkHd10289652; Mon, 4 Jul 2016 04:35:46 GMT Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ECE69AC040; Mon, 4 Jul 2016 00:35:43 -0400 (EDT) Received: from localhost.in.ibm.com (unknown [9.124.208.86]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTP id EC846AC03A; Mon, 4 Jul 2016 00:35:41 -0400 (EDT) From: Chandan Rajendra To: clm@fb.com, jbacik@fb.com, dsterba@suse.com Cc: Chandan Rajendra , linux-btrfs@vger.kernel.org Subject: [PATCH V20 12/19] Revert "btrfs: fix lockups from btrfs_clear_path_blocking" Date: Mon, 4 Jul 2016 10:04:32 +0530 X-Mailer: git-send-email 2.5.5 In-Reply-To: <1467606879-14181-1-git-send-email-chandan@linux.vnet.ibm.com> References: <1467606879-14181-1-git-send-email-chandan@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16070404-0040-0000-0000-000000B8DD3E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16070404-0041-0000-0000-00000492FB03 Message-Id: <1467606879-14181-13-git-send-email-chandan@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2016-07-04_02:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1607040043 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.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 0a56d1b..394ad8e 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 */ @@ -2922,7 +2932,7 @@ 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); @@ -3054,7 +3064,7 @@ 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) {