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d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rNJnohOxZ2tYY4zBbKafxSC+YdJTy0xKZFu1jw0GLL8=; b=jz0lW51oSBoKfEXHbDTVc8XbVEGyXqQM/hNotujqVRMxIRRSkIvQxK5FRB9vo77E8B A71E0P1TtMD67Mkjr5Jst3IV8XDP7lYrIAkszqxLn9TFBMRkTrhzk6cw8upqs+h9rYwb ffuyL9eYp6AT4NUr2mI0UYIvxufIStpdrG0F5cI3FB4t0wsbUMAbFDO9q5d4oSwzW03+ nmmLw13pRD75DId6Sl5J0pu3DLkam8F38jYhNU7QpkDvjjdset8OPEhJWmupkIvxt3er AKJa0EZUvL+Le/tW8A38iJCLi5cHfBVibh/uQfzmlFpK+Ia/htHM975MoG51iNFG1nNO G+Kg== X-Gm-Message-State: AOAM531Dm2mjSfYdY/PH2j9kgoWAEbAa9lGJOPG5GewkkCv8ZKhRl0Hf LucOFRzPrAGf/De0yE+zA/RMy4mN4FXdKyrblKM= X-Google-Smtp-Source: ABdhPJxr0pA1sWecskM1s00zJ4Ngz6Niuik3lr7xF711vE6whdBcrVDMILrb+V3mN6IAFLZ9Y81yE5GkGVAcRJ0Petc= X-Received: by 2002:a92:2810:: with SMTP id l16mr430910ilf.9.1597957399896; Thu, 20 Aug 2020 14:03:19 -0700 (PDT) MIME-Version: 1.0 References: <5f3edc64.qkHsk6Qli55TwDHw%lkp@intel.com> <20200820134006.ce03bfbb54650fd99de0f09c@linux-foundation.org> In-Reply-To: <20200820134006.ce03bfbb54650fd99de0f09c@linux-foundation.org> From: Amir Goldstein Date: Fri, 21 Aug 2020 00:03:08 +0300 Message-ID: Subject: Re: [linux-next:master] BUILD REGRESSION 605cbf3d5f20470ec303b79feda3202935f4a142 To: Andrew Morton Cc: kernel test robot , Linux Memory Management List , Jan Kara Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: E33BC18038E6F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Aug 20, 2020 at 11:40 PM Andrew Morton wrote: > > On Fri, 21 Aug 2020 04:26:12 +0800 kernel test robot wrote: > > > tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > > branch HEAD: 605cbf3d5f20470ec303b79feda3202935f4a142 Add linux-next specific files for 20200820 > > > > Error/Warning in current branch: > > > > fs/notify/fsnotify.c:460 fsnotify() warn: variable dereferenced before check 'inode' (see line 449) > > Yes, this: > > : if (!inode) { > : /* Dirent event - report on TYPE_INODE to dir */ > : inode = dir; > : } else if (mask & FS_EVENT_ON_CHILD) { > : /* > : * Event on child - report on TYPE_INODE to dir if it is > : * watching children and on TYPE_CHILD to child. > : */ > : child = inode; > : inode = dir; > : } > > `inode' is non-NULL here. > > : sb = inode->i_sb; > > So this is OK. > > : /* > : * Optimization: srcu_read_lock() has a memory barrier which can > : * be expensive. It protects walking the *_fsnotify_marks lists. > : * However, if we do not walk the lists, we do not have to do > : * SRCU because we have no references to any objects and do not > : * need SRCU to keep them "alive". > : */ > : if (!sb->s_fsnotify_marks && > : (!mnt || !mnt->mnt_fsnotify_marks) && > : (!inode || !inode->i_fsnotify_marks) && > > So !inode is always false. > > : (!child || !child->i_fsnotify_marks)) > : return 0; > > I assume we can just zap the "!inode ||". Amir & Jan, can you > please take a look? > Andrew, This warning was brought to our attention. We both agreed that we like the code as it is with the unneeded !inode check. https://lore.kernel.org/linux-fsdevel/20200730192537.GB13525@quack2.suse.cz/ Thanks, Amir.