From patchwork Thu Aug 9 02:04:41 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10560695 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2ED9E14E5 for ; Thu, 9 Aug 2018 02:07:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1200E29EC6 for ; Thu, 9 Aug 2018 02:07:50 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 03D552AC8E; Thu, 9 Aug 2018 02:07:50 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, 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 8A9FA2AC8A for ; Thu, 9 Aug 2018 02:07:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727623AbeHIEaF (ORCPT ); Thu, 9 Aug 2018 00:30:05 -0400 Received: from mx2.suse.de ([195.135.220.15]:60492 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725757AbeHIEaF (ORCPT ); Thu, 9 Aug 2018 00:30:05 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 71A68AE06; Thu, 9 Aug 2018 02:07:40 +0000 (UTC) From: NeilBrown To: Jeff Layton , Alexander Viro Date: Thu, 09 Aug 2018 12:04:41 +1000 Subject: [PATCH 2/5] fs/locks: allow a lock request to block other requests. Cc: "J. Bruce Fields" , Martin Wilck , linux-fsdevel@vger.kernel.org, Frank Filz , linux-kernel@vger.kernel.org Message-ID: <153378028110.1220.8149340480666080233.stgit@noble> In-Reply-To: <153378012255.1220.6754153662007899557.stgit@noble> References: <153378012255.1220.6754153662007899557.stgit@noble> 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 Currently, a lock can block pending requests, but all pending requests are equal. If lots of pending requests are mutually exclusive, this means they will all be woken up and all but one will fail. This can hurt performance. So we will allow pending requests to block other requests. Only the first request will be woken, and it will wake the others. This patch doesn't implement this fully, but prepares the way. - It acknowledges that a request might be blocking other requests, and when the request is converted to a lock, those blocked requests are moved across. - When a request is removed, all blocked requests are woken. - When deadlock-detection looks for the lock which blocks a given request, we follow the chain of ->fl_blocker all the way to the top. Signed-off-by: NeilBrown --- fs/locks.c | 58 ++++++++++++++++++++++++++++++++++++++++------------------ 1 file changed, 40 insertions(+), 18 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 322491e70e41..b4812da2a374 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -408,9 +408,19 @@ void locks_copy_lock(struct file_lock *new, struct file_lock *fl) fl->fl_ops->fl_copy_lock(new, fl); } } - EXPORT_SYMBOL(locks_copy_lock); +static void locks_move_blocks(struct file_lock *new, struct file_lock *fl) +{ + struct file_lock *f; + + spin_lock(&blocked_lock_lock); + list_splice_init(&fl->fl_blocked, &new->fl_blocked); + list_for_each_entry(f, &fl->fl_blocked, fl_block) + f->fl_blocker = new; + spin_unlock(&blocked_lock_lock); +} + static inline int flock_translate_cmd(int cmd) { if (cmd & LOCK_MAND) return cmd & (LOCK_MAND | LOCK_RW); @@ -681,9 +691,25 @@ static void __locks_delete_block(struct file_lock *waiter) waiter->fl_blocker = NULL; } +static void __locks_wake_up_blocks(struct file_lock *blocker) +{ + while (!list_empty(&blocker->fl_blocked)) { + struct file_lock *waiter; + + waiter = list_first_entry(&blocker->fl_blocked, + struct file_lock, fl_block); + __locks_delete_block(waiter); + if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) + waiter->fl_lmops->lm_notify(waiter); + else + wake_up(&waiter->fl_wait); + } +} + static void locks_delete_block(struct file_lock *waiter) { spin_lock(&blocked_lock_lock); + __locks_wake_up_blocks(waiter); __locks_delete_block(waiter); spin_unlock(&blocked_lock_lock); } @@ -735,17 +761,7 @@ static void locks_wake_up_blocks(struct file_lock *blocker) return; spin_lock(&blocked_lock_lock); - while (!list_empty(&blocker->fl_blocked)) { - struct file_lock *waiter; - - waiter = list_first_entry(&blocker->fl_blocked, - struct file_lock, fl_block); - __locks_delete_block(waiter); - if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) - waiter->fl_lmops->lm_notify(waiter); - else - wake_up(&waiter->fl_wait); - } + __locks_wake_up_blocks(blocker); spin_unlock(&blocked_lock_lock); } @@ -888,8 +904,11 @@ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl) struct file_lock *fl; hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) { - if (posix_same_owner(fl, block_fl)) - return fl->fl_blocker; + if (posix_same_owner(fl, block_fl)) { + while (fl->fl_blocker) + fl = fl->fl_blocker; + return fl; + } } return NULL; } @@ -982,6 +1001,7 @@ static int flock_lock_inode(struct inode *inode, struct file_lock *request) if (request->fl_flags & FL_ACCESS) goto out; locks_copy_lock(new_fl, request); + locks_move_blocks(new_fl, request); locks_insert_lock_ctx(new_fl, &ctx->flc_flock); new_fl = NULL; error = 0; @@ -1174,6 +1194,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, goto out; } locks_copy_lock(new_fl, request); + locks_move_blocks(new_fl, request); locks_insert_lock_ctx(new_fl, &fl->fl_list); fl = new_fl; new_fl = NULL; @@ -2582,13 +2603,14 @@ void locks_remove_file(struct file *filp) int posix_unblock_lock(struct file_lock *waiter) { - int status = 0; + int status = -ENOENT; spin_lock(&blocked_lock_lock); - if (waiter->fl_blocker) + if (waiter->fl_blocker) { + __locks_wake_up_blocks(waiter); __locks_delete_block(waiter); - else - status = -ENOENT; + status = 0; + } spin_unlock(&blocked_lock_lock); return status; }