From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8ACD2C433E1 for ; Wed, 26 Aug 2020 08:18:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 612C520866 for ; Wed, 26 Aug 2020 08:18:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598429932; bh=+vJV+mRF0Lzjjr3fr3A1d25Ht5edbPCfJqUZ9mJTuZc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=oE6mzfzUHRnUQxInmMuPQWr3Pfv6384gNu1LL6jUzpyrrwBsWJf7EESc/nfaVYZ+I h90RQACMmvHFZK/oOhyHJRO0Bq9AZGYY2qnU2UNcmy/h4sIz+pHkyPKfzIyNxIDaMf fVdczJdIANCgjlbW2gqJ1Rkft3963qlS9XETMoyg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726794AbgHZISv (ORCPT ); Wed, 26 Aug 2020 04:18:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:40140 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbgHZISu (ORCPT ); Wed, 26 Aug 2020 04:18:50 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 23DE520678; Wed, 26 Aug 2020 08:18:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598429929; bh=+vJV+mRF0Lzjjr3fr3A1d25Ht5edbPCfJqUZ9mJTuZc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GEU0Xm/bx8cP15xViHXthdwpTyen+TUGLxiTYu1aQr59txHczphF0iSJ6zUYeHWWX KeG6A4r//Wu1oZzMeekzFUdHP4041f9NyizugHYCE97ojW+tbEj5IjPyO+fOYOD9T4 Wjw7xvPDwkn7MCG9zkXnTpGNV75HhW6BJRy8Z9QE= Date: Wed, 26 Aug 2020 10:19:05 +0200 From: Greg Kroah-Hartman To: Christoph Hellwig Cc: Jens Axboe , "Rafael J. Wysocki" , Denis Efremov , "David S. Miller" , Song Liu , Al Viro , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, linux-raid@vger.kernel.org, linux-scsi@vger.kernel.org, linux-m68k@lists.linux-m68k.org Subject: Re: [PATCH 01/19] char_dev: replace cdev_map with an xarray Message-ID: <20200826081905.GB1796103@kroah.com> References: <20200826062446.31860-1-hch@lst.de> <20200826062446.31860-2-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200826062446.31860-2-hch@lst.de> Sender: linux-ide-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ide@vger.kernel.org On Wed, Aug 26, 2020 at 08:24:28AM +0200, Christoph Hellwig wrote: > None of the complicated overlapping regions bits of the kobj_map are > required for the character device lookup, so just a trivial xarray > instead. > > Signed-off-by: Christoph Hellwig Really? This is ok to use and just as fast? If so, wonderful, it would be great to clean up kobj_map users. But I don't think you got all of the needed bits here: > --- > fs/char_dev.c | 94 +++++++++++++++++++++++++-------------------------- > fs/dcache.c | 1 - > fs/internal.h | 5 --- > 3 files changed, 46 insertions(+), 54 deletions(-) > > diff --git a/fs/char_dev.c b/fs/char_dev.c > index ba0ded7842a779..6c4d6c4938f14b 100644 > --- a/fs/char_dev.c > +++ b/fs/char_dev.c > @@ -17,7 +17,6 @@ > #include > > #include > -#include > #include > #include > #include > @@ -25,8 +24,7 @@ > > #include "internal.h" > > -static struct kobj_map *cdev_map; > - > +static DEFINE_XARRAY(cdev_map); > static DEFINE_MUTEX(chrdevs_lock); > > #define CHRDEV_MAJOR_HASH_SIZE 255 > @@ -367,6 +365,29 @@ void cdev_put(struct cdev *p) > } > } > > +static struct cdev *cdev_lookup(dev_t dev) > +{ > + struct cdev *cdev; > + > +retry: > + mutex_lock(&chrdevs_lock); > + cdev = xa_load(&cdev_map, dev); > + if (!cdev) { > + mutex_unlock(&chrdevs_lock); > + > + if (request_module("char-major-%d-%d", > + MAJOR(dev), MINOR(dev)) > 0) > + /* Make old-style 2.4 aliases work */ > + request_module("char-major-%d", MAJOR(dev)); > + goto retry; > + } > + > + if (!cdev_get(cdev)) > + cdev = NULL; > + mutex_unlock(&chrdevs_lock); > + return cdev; > +} > + > /* > * Called every time a character special file is opened > */ > @@ -380,13 +401,10 @@ static int chrdev_open(struct inode *inode, struct file *filp) > spin_lock(&cdev_lock); > p = inode->i_cdev; > if (!p) { > - struct kobject *kobj; > - int idx; > spin_unlock(&cdev_lock); > - kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); > - if (!kobj) > + new = cdev_lookup(inode->i_rdev); > + if (!new) > return -ENXIO; > - new = container_of(kobj, struct cdev, kobj); > spin_lock(&cdev_lock); > /* Check i_cdev again in case somebody beat us to it while > we dropped the lock. */ > @@ -454,18 +472,6 @@ const struct file_operations def_chr_fops = { > .llseek = noop_llseek, > }; > > -static struct kobject *exact_match(dev_t dev, int *part, void *data) > -{ > - struct cdev *p = data; > - return &p->kobj; > -} > - > -static int exact_lock(dev_t dev, void *data) > -{ > - struct cdev *p = data; > - return cdev_get(p) ? 0 : -1; > -} > - > /** > * cdev_add() - add a char device to the system > * @p: the cdev structure for the device > @@ -478,7 +484,7 @@ static int exact_lock(dev_t dev, void *data) > */ > int cdev_add(struct cdev *p, dev_t dev, unsigned count) > { > - int error; > + int error, i; > > p->dev = dev; > p->count = count; > @@ -486,14 +492,22 @@ int cdev_add(struct cdev *p, dev_t dev, unsigned count) > if (WARN_ON(dev == WHITEOUT_DEV)) > return -EBUSY; > > - error = kobj_map(cdev_map, dev, count, NULL, > - exact_match, exact_lock, p); > - if (error) > - return error; > + mutex_lock(&chrdevs_lock); > + for (i = 0; i < count; i++) { > + error = xa_insert(&cdev_map, dev + i, p, GFP_KERNEL); > + if (error) > + goto out_unwind; > + } > + mutex_unlock(&chrdevs_lock); > > kobject_get(p->kobj.parent); Can't you drop this kobject_get() too? And also the "struct kobj" in struct cdev can be gone as well, as the kobj_map was the only "real" user of this structure. I know some drivers liked to touch that field as well, but it never actually did anything for them, so it was pointless, but it will take some 'make allmodconfig' builds to flush them out. thanks, greg k-h