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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 268A6C433E1 for ; Thu, 27 Aug 2020 07:25:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EFFD022BEA for ; Thu, 27 Aug 2020 07:25:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728109AbgH0HZL (ORCPT ); Thu, 27 Aug 2020 03:25:11 -0400 Received: from mx2.suse.de ([195.135.220.15]:41702 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728070AbgH0HZK (ORCPT ); Thu, 27 Aug 2020 03:25:10 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 03E1EAC2B; Thu, 27 Aug 2020 07:25:40 +0000 (UTC) Subject: Re: [PATCH 01/19] char_dev: replace cdev_map with an xarray To: Christoph Hellwig , Jens Axboe Cc: Greg Kroah-Hartman , "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 References: <20200826062446.31860-1-hch@lst.de> <20200826062446.31860-2-hch@lst.de> From: Hannes Reinecke Openpgp: preference=signencrypt Autocrypt: addr=hare@suse.de; prefer-encrypt=mutual; keydata= mQINBE6KyREBEACwRN6XKClPtxPiABx5GW+Yr1snfhjzExxkTYaINHsWHlsLg13kiemsS6o7 qrc+XP8FmhcnCOts9e2jxZxtmpB652lxRB9jZE40mcSLvYLM7S6aH0WXKn8bOqpqOGJiY2bc 6qz6rJuqkOx3YNuUgiAxjuoYauEl8dg4bzex3KGkGRuxzRlC8APjHlwmsr+ETxOLBfUoRNuE b4nUtaseMPkNDwM4L9+n9cxpGbdwX0XwKFhlQMbG3rWA3YqQYWj1erKIPpgpfM64hwsdk9zZ QO1krgfULH4poPQFpl2+yVeEMXtsSou915jn/51rBelXeLq+cjuK5+B/JZUXPnNDoxOG3j3V VSZxkxLJ8RO1YamqZZbVP6jhDQ/bLcAI3EfjVbxhw9KWrh8MxTcmyJPn3QMMEp3wpVX9nSOQ tzG72Up/Py67VQe0x8fqmu7R4MmddSbyqgHrab/Nu+ak6g2RRn3QHXAQ7PQUq55BDtj85hd9 W2iBiROhkZ/R+Q14cJkWhzaThN1sZ1zsfBNW0Im8OVn/J8bQUaS0a/NhpXJWv6J1ttkX3S0c QUratRfX4D1viAwNgoS0Joq7xIQD+CfJTax7pPn9rT////hSqJYUoMXkEz5IcO+hptCH1HF3 qz77aA5njEBQrDRlslUBkCZ5P+QvZgJDy0C3xRGdg6ZVXEXJOQARAQABtCpIYW5uZXMgUmVp bmVja2UgKFN1U0UgTGFicykgPGhhcmVAc3VzZS5kZT6JAkEEEwECACsCGwMFCRLMAwAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheABQJOisquAhkBAAoJEGz4yi9OyKjPOHoQAJLeLvr6JNHx GPcHXaJLHQiinz2QP0/wtsT8+hE26dLzxb7hgxLafj9XlAXOG3FhGd+ySlQ5wSbbjdxNjgsq FIjqQ88/Lk1NfnqG5aUTPmhEF+PzkPogEV7Pm5Q17ap22VK623MPaltEba+ly6/pGOODbKBH ak3gqa7Gro5YCQzNU0QVtMpWyeGF7xQK76DY/atvAtuVPBJHER+RPIF7iv5J3/GFIfdrM+wS BubFVDOibgM7UBnpa7aohZ9RgPkzJpzECsbmbttxYaiv8+EOwark4VjvOne8dRaj50qeyJH6 HLpBXZDJH5ZcYJPMgunghSqghgfuUsd5fHmjFr3hDb5EoqAfgiRMSDom7wLZ9TGtT6viDldv hfWaIOD5UhpNYxfNgH6Y102gtMmN4o2P6g3UbZK1diH13s9DA5vI2mO2krGz2c5BOBmcctE5 iS+JWiCizOqia5Op+B/tUNye/YIXSC4oMR++Fgt30OEafB8twxydMAE3HmY+foawCpGq06yM vAguLzvm7f6wAPesDAO9vxRNC5y7JeN4Kytl561ciTICmBR80Pdgs/Obj2DwM6dvHquQbQrU Op4XtD3eGUW4qgD99DrMXqCcSXX/uay9kOG+fQBfK39jkPKZEuEV2QdpE4Pry36SUGfohSNq xXW+bMc6P+irTT39VWFUJMcSuQINBE6KyREBEACvEJggkGC42huFAqJcOcLqnjK83t4TVwEn JRisbY/VdeZIHTGtcGLqsALDzk+bEAcZapguzfp7cySzvuR6Hyq7hKEjEHAZmI/3IDc9nbdh EgdCiFatah0XZ/p4vp7KAelYqbv8YF/ORLylAdLh9rzLR6yHFqVaR4WL4pl4kEWwFhNSHLxe 55G56/dxBuoj4RrFoX3ynerXfbp4dH2KArPc0NfoamqebuGNfEQmDbtnCGE5zKcR0zvmXsRp qU7+caufueZyLwjTU+y5p34U4PlOO2Q7/bdaPEdXfpgvSpWk1o3H36LvkPV/PGGDCLzaNn04 BdiiiPEHwoIjCXOAcR+4+eqM4TSwVpTn6SNgbHLjAhCwCDyggK+3qEGJph+WNtNU7uFfscSP k4jqlxc8P+hn9IqaMWaeX9nBEaiKffR7OKjMdtFFnBRSXiW/kOKuuRdeDjL5gWJjY+IpdafP KhjvUFtfSwGdrDUh3SvB5knSixE3qbxbhbNxmqDVzyzMwunFANujyyVizS31DnWC6tKzANkC k15CyeFC6sFFu+WpRxvC6fzQTLI5CRGAB6FAxz8Hu5rpNNZHsbYs9Vfr/BJuSUfRI/12eOCL IvxRPpmMOlcI4WDW3EDkzqNAXn5Onx/b0rFGFpM4GmSPriEJdBb4M4pSD6fN6Y/Jrng/Bdwk SQARAQABiQIlBBgBAgAPBQJOiskRAhsMBQkSzAMAAAoJEGz4yi9OyKjPgEwQAIP/gy/Xqc1q OpzfFScswk3CEoZWSqHxn/fZasa4IzkwhTUmukuIvRew+BzwvrTxhHcz9qQ8hX7iDPTZBcUt ovWPxz+3XfbGqE+q0JunlIsP4N+K/I10nyoGdoFpMFMfDnAiMUiUatHRf9Wsif/nT6oRiPNJ T0EbbeSyIYe+ZOMFfZBVGPqBCbe8YMI+JiZeez8L9JtegxQ6O3EMQ//1eoPJ5mv5lWXLFQfx f4rAcKseM8DE6xs1+1AIsSIG6H+EE3tVm+GdCkBaVAZo2VMVapx9k8RMSlW7vlGEQsHtI0FT c1XNOCGjaP4ITYUiOpfkh+N0nUZVRTxWnJqVPGZ2Nt7xCk7eoJWTSMWmodFlsKSgfblXVfdM 9qoNScM3u0b9iYYuw/ijZ7VtYXFuQdh0XMM/V6zFrLnnhNmg0pnK6hO1LUgZlrxHwLZk5X8F uD/0MCbPmsYUMHPuJd5dSLUFTlejVXIbKTSAMd0tDSP5Ms8Ds84z5eHreiy1ijatqRFWFJRp ZtWlhGRERnDH17PUXDglsOA08HCls0PHx8itYsjYCAyETlxlLApXWdVl9YVwbQpQ+i693t/Y PGu8jotn0++P19d3JwXW8t6TVvBIQ1dRZHx1IxGLMn+CkDJMOmHAUMWTAXX2rf5tUjas8/v2 azzYF4VRJsdl+d0MCaSy8mUh Message-ID: Date: Thu, 27 Aug 2020 09:25:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200826062446.31860-2-hch@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-raid-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 8/26/20 8:24 AM, 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 > --- > 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); > - > return 0; > + > +out_unwind: > + while (--i >= 0) > + xa_erase(&cdev_map, dev + i); > + mutex_unlock(&chrdevs_lock); > + return error; > } > > /** Do you really need the mutex? Wouldn't xa_store_range() be better and avoid the mutex? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer