From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f45.google.com (mail-qg0-f45.google.com [209.85.192.45]) by kanga.kvack.org (Postfix) with ESMTP id B1FA06B0073 for ; Thu, 28 May 2015 14:51:13 -0400 (EDT) Received: by qgf2 with SMTP id 2so20487905qgf.3 for ; Thu, 28 May 2015 11:51:13 -0700 (PDT) Received: from mail-qg0-x22d.google.com (mail-qg0-x22d.google.com. [2607:f8b0:400d:c04::22d]) by mx.google.com with ESMTPS id q5si3311515qce.7.2015.05.28.11.51.13 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 May 2015 11:51:13 -0700 (PDT) Received: by qgfa63 with SMTP id a63so20535363qgf.0 for ; Thu, 28 May 2015 11:51:12 -0700 (PDT) From: Tejun Heo Subject: [PATCH 7/9] writeback: add lockdep annotation to inode_to_wb() Date: Thu, 28 May 2015 14:50:55 -0400 Message-Id: <1432839057-17609-8-git-send-email-tj@kernel.org> In-Reply-To: <1432839057-17609-1-git-send-email-tj@kernel.org> References: <1432839057-17609-1-git-send-email-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, khlebnikov@yandex-team.ru, Tejun Heo With the previous three patches, all operations which acquire wb from inode are either under one of inode->i_lock, mapping->tree_lock or wb->list_lock or protected by unlocked_inode_to_wb transaction. This will be depended upon by foreign inode wb switching. This patch adds lockdep assertion to inode_to_wb() so that usages outside the above list locks can be caught easily. There are three exceptions. * locked_inode_to_wb_and_lock_list() is holding wb->list_lock but the wb may not be the inode's. Ensuring that is the function's role after all. Updated to deref inode->i_wb directly. * inode_wb_stat_unlocked_begin() is usually protected by combination of !I_WB_SWITCH and rcu_read_lock(). Updated to deref inode->i_wb directly. * inode_congested() wants to test whether inode->i_wb is set before starting the transaction. Added inode_to_wb_is_valid() which tests inode->i_wb directly. v5: might_lock() removed. It annotates that the lock is grabbed w/ irq enabled which isn't the case and triggering lockdep warning spuriously. v4: might_lock() added to unlocked_inode_to_wb_begin(). v3: inode_congested() conversion added. v2: locked_inode_to_wb_and_lock_list() was missing in the first version. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Wu Fengguang Cc: Greg Thelen --- fs/fs-writeback.c | 5 +++-- include/linux/backing-dev.h | 34 ++++++++++++++++++++++++++++++++-- 2 files changed, 35 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 25458fa..6b99dee 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -285,7 +285,8 @@ locked_inode_to_wb_and_lock_list(struct inode *inode) spin_lock(&wb->list_lock); wb_put(wb); /* not gonna deref it anymore */ - if (likely(wb == inode_to_wb(inode))) + /* i_wb may have changed inbetween, can't use inode_to_wb() */ + if (likely(wb == inode->i_wb)) return wb; /* @inode already has ref */ spin_unlock(&wb->list_lock); @@ -622,7 +623,7 @@ int inode_congested(struct inode *inode, int cong_bits) * Once set, ->i_wb never becomes NULL while the inode is alive. * Start transaction iff ->i_wb is visible. */ - if (inode && inode_to_wb(inode)) { + if (inode && inode_to_wb_is_valid(inode)) { struct bdi_writeback *wb; bool locked, congested; diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 73ffa32..dfce808 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -322,13 +322,33 @@ wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp) } /** + * inode_to_wb_is_valid - test whether an inode has a wb associated + * @inode: inode of interest + * + * Returns %true if @inode has a wb associated. May be called without any + * locking. + */ +static inline bool inode_to_wb_is_valid(struct inode *inode) +{ + return inode->i_wb; +} + +/** * inode_to_wb - determine the wb of an inode * @inode: inode of interest * - * Returns the wb @inode is currently associated with. + * Returns the wb @inode is currently associated with. The caller must be + * holding either @inode->i_lock, @inode->i_mapping->tree_lock, or the + * associated wb's list_lock. */ static inline struct bdi_writeback *inode_to_wb(struct inode *inode) { +#ifdef CONFIG_LOCKDEP + WARN_ON_ONCE(debug_locks && + (!lockdep_is_held(&inode->i_lock) && + !lockdep_is_held(&inode->i_mapping->tree_lock) && + !lockdep_is_held(&inode->i_wb->list_lock))); +#endif return inode->i_wb; } @@ -360,7 +380,12 @@ unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp) if (unlikely(*lockedp)) spin_lock_irq(&inode->i_mapping->tree_lock); - return inode_to_wb(inode); + + /* + * Protected by either !I_WB_SWITCH + rcu_read_lock() or tree_lock. + * inode_to_wb() will bark. Deref directly. + */ + return inode->i_wb; } /** @@ -459,6 +484,11 @@ wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp) return &bdi->wb; } +static inline bool inode_to_wb_is_valid(struct inode *inode) +{ + return true; +} + static inline struct bdi_writeback *inode_to_wb(struct inode *inode) { return &inode_to_bdi(inode)->wb; -- 2.4.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org