From patchwork Wed Apr 1 18:56:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Trond Myklebust X-Patchwork-Id: 11469453 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3450F92C for ; Wed, 1 Apr 2020 18:59:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0986F20784 for ; Wed, 1 Apr 2020 18:59:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585767543; bh=OmgAVK6bTWzuG2IQfmjq1oW6E74fa81T2HCJUHpmPpM=; h=From:To:Subject:Date:In-Reply-To:References:List-ID:From; b=kyMIRO5hjWSWi8AbHMeqaZBKG0bhup+6Y2UX3OOo83qi0UAaf5vUeK9eQs+4ywm2g 2cBA/4ZioW7OcQz2zFJ9xGVT2SFc+nJKXloBjtJ9zfWxiSsjGJ5TXKmv3zdvztk/ty bPnwn6QlGuNp4tSvFok4wEJ3Oy3ssmwg/I2g3JNo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732208AbgDAS7C (ORCPT ); Wed, 1 Apr 2020 14:59:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:36664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726785AbgDAS7C (ORCPT ); Wed, 1 Apr 2020 14:59:02 -0400 Received: from localhost.localdomain (c-68-36-133-222.hsd1.mi.comcast.net [68.36.133.222]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 41599206F5 for ; Wed, 1 Apr 2020 18:59:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585767541; bh=OmgAVK6bTWzuG2IQfmjq1oW6E74fa81T2HCJUHpmPpM=; h=From:To:Subject:Date:In-Reply-To:References:From; b=AExqx48NC9Oo/qSb8aHn459jCHk6NvwkaWxPiq7RHe1in43AGkKJOIr+uAuiOHtDo UPwGjtjgR2skm0ox37hZkFo6s4WQb1ZSoaSfkEnV3gGM2DU8FEin1DxONX5Nd0yIYS c1uA7OUHupwkzbbANplQw6F1MDn4T2jgHDSn7QV0= From: trondmy@kernel.org To: linux-nfs@vger.kernel.org Subject: [PATCH 02/10] NFS: Fix races nfs_page_group_destroy() vs nfs_destroy_unlinked_subrequests() Date: Wed, 1 Apr 2020 14:56:44 -0400 Message-Id: <20200401185652.1904777-3-trondmy@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200401185652.1904777-2-trondmy@kernel.org> References: <20200401185652.1904777-1-trondmy@kernel.org> <20200401185652.1904777-2-trondmy@kernel.org> MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Trond Myklebust When a subrequest is being detached from the subgroup, we want to ensure that it is not holding the group lock, or in the process of waiting for the group lock. Fixes: 5b2b5187fa85 ("NFS: Fix nfs_page_group_destroy() and nfs_lock_and_join_requests() race cases") Signed-off-by: Trond Myklebust --- fs/nfs/pagelist.c | 67 +++++++++++++++++++++++++++------------- fs/nfs/write.c | 10 ++++-- include/linux/nfs_page.h | 2 ++ 3 files changed, 55 insertions(+), 24 deletions(-) diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c index be5e209399ea..0e3f0f241d83 100644 --- a/fs/nfs/pagelist.c +++ b/fs/nfs/pagelist.c @@ -133,47 +133,70 @@ nfs_async_iocounter_wait(struct rpc_task *task, struct nfs_lock_context *l_ctx) EXPORT_SYMBOL_GPL(nfs_async_iocounter_wait); /* - * nfs_page_group_lock - lock the head of the page group - * @req - request in group that is to be locked + * nfs_page_set_headlock - set the request PG_HEADLOCK + * @req: request that is to be locked * - * this lock must be held when traversing or modifying the page - * group list + * this lock must be held when modifying req->wb_head * * return 0 on success, < 0 on error */ int -nfs_page_group_lock(struct nfs_page *req) +nfs_page_set_headlock(struct nfs_page *req) { - struct nfs_page *head = req->wb_head; - - WARN_ON_ONCE(head != head->wb_head); - - if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags)) + if (!test_and_set_bit(PG_HEADLOCK, &req->wb_flags)) return 0; - set_bit(PG_CONTENDED1, &head->wb_flags); + set_bit(PG_CONTENDED1, &req->wb_flags); smp_mb__after_atomic(); - return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK, + return wait_on_bit_lock(&req->wb_flags, PG_HEADLOCK, TASK_UNINTERRUPTIBLE); } /* - * nfs_page_group_unlock - unlock the head of the page group - * @req - request in group that is to be unlocked + * nfs_page_clear_headlock - clear the request PG_HEADLOCK + * @req: request that is to be locked */ void -nfs_page_group_unlock(struct nfs_page *req) +nfs_page_clear_headlock(struct nfs_page *req) { - struct nfs_page *head = req->wb_head; - - WARN_ON_ONCE(head != head->wb_head); - smp_mb__before_atomic(); - clear_bit(PG_HEADLOCK, &head->wb_flags); + clear_bit(PG_HEADLOCK, &req->wb_flags); smp_mb__after_atomic(); - if (!test_bit(PG_CONTENDED1, &head->wb_flags)) + if (!test_bit(PG_CONTENDED1, &req->wb_flags)) return; - wake_up_bit(&head->wb_flags, PG_HEADLOCK); + wake_up_bit(&req->wb_flags, PG_HEADLOCK); +} + +/* + * nfs_page_group_lock - lock the head of the page group + * @req: request in group that is to be locked + * + * this lock must be held when traversing or modifying the page + * group list + * + * return 0 on success, < 0 on error + */ +int +nfs_page_group_lock(struct nfs_page *req) +{ + int ret; + + ret = nfs_page_set_headlock(req); + if (ret || req->wb_head == req) + return ret; + return nfs_page_set_headlock(req->wb_head); +} + +/* + * nfs_page_group_unlock - unlock the head of the page group + * @req: request in group that is to be unlocked + */ +void +nfs_page_group_unlock(struct nfs_page *req) +{ + if (req != req->wb_head) + nfs_page_clear_headlock(req->wb_head); + nfs_page_clear_headlock(req); } /* diff --git a/fs/nfs/write.c b/fs/nfs/write.c index 626e99cbb50e..a6d7926b0653 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -428,22 +428,28 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list, destroy_list = (subreq->wb_this_page == old_head) ? NULL : subreq->wb_this_page; + /* Note: lock subreq in order to change subreq->wb_head */ + nfs_page_set_headlock(subreq); WARN_ON_ONCE(old_head != subreq->wb_head); /* make sure old group is not used */ subreq->wb_this_page = subreq; + subreq->wb_head = subreq; clear_bit(PG_REMOVE, &subreq->wb_flags); /* Note: races with nfs_page_group_destroy() */ if (!kref_read(&subreq->wb_kref)) { /* Check if we raced with nfs_page_group_destroy() */ - if (test_and_clear_bit(PG_TEARDOWN, &subreq->wb_flags)) + if (test_and_clear_bit(PG_TEARDOWN, &subreq->wb_flags)) { + nfs_page_clear_headlock(subreq); nfs_free_request(subreq); + } else + nfs_page_clear_headlock(subreq); continue; } + nfs_page_clear_headlock(subreq); - subreq->wb_head = subreq; nfs_release_request(old_head); if (test_and_clear_bit(PG_INODE_REF, &subreq->wb_flags)) { diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h index 0bbd587fac6a..7e9419d74b86 100644 --- a/include/linux/nfs_page.h +++ b/include/linux/nfs_page.h @@ -142,6 +142,8 @@ extern void nfs_unlock_and_release_request(struct nfs_page *); extern int nfs_page_group_lock(struct nfs_page *); extern void nfs_page_group_unlock(struct nfs_page *); extern bool nfs_page_group_sync_on_bit(struct nfs_page *, unsigned int); +extern int nfs_page_set_headlock(struct nfs_page *req); +extern void nfs_page_clear_headlock(struct nfs_page *req); extern bool nfs_async_iocounter_wait(struct rpc_task *, struct nfs_lock_context *); /*