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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 6F991C4320E for ; Fri, 20 Aug 2021 16:11:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5C47B60EE4 for ; Fri, 20 Aug 2021 16:11:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232726AbhHTQM2 (ORCPT ); Fri, 20 Aug 2021 12:12:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58934 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231502AbhHTQMT (ORCPT ); Fri, 20 Aug 2021 12:12:19 -0400 Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A621C08ED6F for ; Fri, 20 Aug 2021 09:06:34 -0700 (PDT) Received: by mail-pg1-x529.google.com with SMTP id n18so9626425pgm.12 for ; Fri, 20 Aug 2021 09:06:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SE1PBWc7mAk6yXDwwX3HHPm6R0g9oeMCDvjQB1FSRU4=; b=qYalQzoW2Ggwdbv3kEUgyzgEYSvY12zzfUROr1+BzqCFxig1iNFSX1WjFq9gGf8qwb RLSCrRhomWIzKnh9gEpB6S+i3uPQYcDisaRNTg1c6SZvnnC8rCRCfumKRT6L7fH/1P37 +zW0nAHwXhnhLpUFFCPDuTHWmlUXf+4CnmFxja9S4eBXm6oRYFHW4+GcrVo4fVlT7yjw Y0n63ldEWM68CSxELu9A6tHjrShCuAjb5kkOm7v4dtrVpJ6G1MvoNXZhrHbSNZPol3FU 2lyLCf9JfLM5anzTGAgvT2ovm2qtdFPG9BrPN8aF3hnxb5CodCg/svyxL8kbWdXo7Okb T5Ow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SE1PBWc7mAk6yXDwwX3HHPm6R0g9oeMCDvjQB1FSRU4=; b=FThasiLZg6hxzXTqBnx4ZpLoxIEO83cPihBDw5+yDahZ4RLt382QQB2M0VBQNmpSex nRPbosu8bLPS/h01/Zisk8OEgIq/DK/1Cn9suBayTMAG8g9jo5lgcDD114HElYra5MbE CPdeG2bKHUTmRrqW3WByLU4K+ICPkJz1YJNq6R2wk8zvFC83MNuLjCCmwXSBgG903VUv ki29Gk7ZsCB0lSzCDjbICyvI09opZKmFg+esI1GX2C/VlYrDa73q8gtJHOFeo7cSCCn3 4kj8W2ki4dJFsIMoca1x1Pf6m6+/B9Zb7NoewsCiQv+mg0ApcqBJW0ZEJrlxeqAeC7l/ Sp8Q== X-Gm-Message-State: AOAM533lK+T74B8HkTtgZ2REiQKvj4UHFfEMSwggTOfSl4sz7IOu/dB3 vQZkSSCyUhCDeogOCl937RAN19+bwOqKMShmU7tQJg== X-Google-Smtp-Source: ABdhPJzZwGSABeBQxV85uUQDyE877kBWKar9nuSTal+efpWConcEcwK48D/jgozGf+NtNUk6MXi23elgGDtpJtSZv9s= X-Received: by 2002:a05:6a00:16c6:b029:32d:e190:9dd0 with SMTP id l6-20020a056a0016c6b029032de1909dd0mr20235683pfc.70.1629475593581; Fri, 20 Aug 2021 09:06:33 -0700 (PDT) MIME-Version: 1.0 References: <20210730100158.3117319-1-ruansy.fnst@fujitsu.com> <20210730100158.3117319-3-ruansy.fnst@fujitsu.com> In-Reply-To: <20210730100158.3117319-3-ruansy.fnst@fujitsu.com> From: Dan Williams Date: Fri, 20 Aug 2021 09:06:22 -0700 Message-ID: Subject: Re: [PATCH RESEND v6 2/9] dax: Introduce holder for dax_device To: Shiyang Ruan Cc: Linux Kernel Mailing List , linux-xfs , Linux NVDIMM , Linux MM , linux-fsdevel , device-mapper development , "Darrick J. Wong" , david , Christoph Hellwig , Alasdair Kergon , Mike Snitzer Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 30, 2021 at 3:02 AM Shiyang Ruan wrote: > > To easily track filesystem from a pmem device, we introduce a holder for > dax_device structure, and also its operation. This holder is used to > remember who is using this dax_device: > - When it is the backend of a filesystem, the holder will be the > superblock of this filesystem. > - When this pmem device is one of the targets in a mapped device, the > holder will be this mapped device. In this case, the mapped device > has its own dax_device and it will follow the first rule. So that we > can finally track to the filesystem we needed. > > The holder and holder_ops will be set when filesystem is being mounted, > or an target device is being activated. > > Signed-off-by: Shiyang Ruan > --- > drivers/dax/super.c | 46 +++++++++++++++++++++++++++++++++++++++++++++ > include/linux/dax.h | 17 +++++++++++++++++ > 2 files changed, 63 insertions(+) > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > index 5fa6ae9dbc8b..00c32dfa5665 100644 > --- a/drivers/dax/super.c > +++ b/drivers/dax/super.c > @@ -214,6 +214,8 @@ enum dax_device_flags { > * @cdev: optional character interface for "device dax" > * @host: optional name for lookups where the device path is not available > * @private: dax driver private data > + * @holder_rwsem: prevent unregistration while holder_ops is in progress > + * @holder_data: holder of a dax_device: could be filesystem or mapped device > * @flags: state and boolean properties > */ > struct dax_device { > @@ -222,8 +224,11 @@ struct dax_device { > struct cdev cdev; > const char *host; > void *private; > + struct rw_semaphore holder_rwsem; Given the rarity of notification failures and the infrequency of registration events I think it would be ok for this to be a global lock rather than per-device. In fact there is already a global dax lock, see dax_read_lock(). Let's convert that from srcu to rwsem and add a dax_write_lock(). > + void *holder_data; > unsigned long flags; > const struct dax_operations *ops; > + const struct dax_holder_operations *holder_ops; > }; > > static ssize_t write_cache_show(struct device *dev, > @@ -373,6 +378,25 @@ int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, > } > EXPORT_SYMBOL_GPL(dax_zero_page_range); > > +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, > + size_t size, void *data) > +{ > + int rc; > + > + if (!dax_dev) > + return -ENXIO; There also needs to be a dax_dev->alive check, which is only valid to be checked under dax_read_lock(). Who would ever pass NULL to this function? > + > + if (!dax_dev->holder_data) > + return -EOPNOTSUPP; > + > + down_read(&dax_dev->holder_rwsem); > + rc = dax_dev->holder_ops->notify_failure(dax_dev, offset, > + size, data); > + up_read(&dax_dev->holder_rwsem); > + return rc; > +} > +EXPORT_SYMBOL_GPL(dax_holder_notify_failure); > + > #ifdef CONFIG_ARCH_HAS_PMEM_API > void arch_wb_cache_pmem(void *addr, size_t size); > void dax_flush(struct dax_device *dax_dev, void *addr, size_t size) > @@ -603,6 +627,7 @@ struct dax_device *alloc_dax(void *private, const char *__host, > dax_add_host(dax_dev, host); > dax_dev->ops = ops; > dax_dev->private = private; > + init_rwsem(&dax_dev->holder_rwsem); > if (flags & DAXDEV_F_SYNC) > set_dax_synchronous(dax_dev); > > @@ -624,6 +649,27 @@ void put_dax(struct dax_device *dax_dev) > } > EXPORT_SYMBOL_GPL(put_dax); > > +void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops) > +{ > + if (!dax_dev) Same questions about NULL dax dev and ->alive checking. > + return; > + down_write(&dax_dev->holder_rwsem); > + dax_dev->holder_data = holder; > + dax_dev->holder_ops = ops; > + up_write(&dax_dev->holder_rwsem); > +} > +EXPORT_SYMBOL_GPL(dax_set_holder); > + > +void *dax_get_holder(struct dax_device *dax_dev) > +{ > + if (!dax_dev) > + return NULL; Where is this API used? This result is not valid unless the caller is holding the read lock. > + > + return dax_dev->holder_data; > +} > +EXPORT_SYMBOL_GPL(dax_get_holder); > + > /** > * dax_get_by_host() - temporary lookup mechanism for filesystem-dax > * @host: alternate name for the device registered by a dax driver > diff --git a/include/linux/dax.h b/include/linux/dax.h > index b52f084aa643..6f4b5c97ceb0 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -38,10 +38,17 @@ struct dax_operations { > int (*zero_page_range)(struct dax_device *, pgoff_t, size_t); > }; > > +struct dax_holder_operations { > + int (*notify_failure)(struct dax_device *, loff_t, size_t, void *); > +}; > + > extern struct attribute_group dax_attribute_group; > > #if IS_ENABLED(CONFIG_DAX) > struct dax_device *dax_get_by_host(const char *host); > +void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops); > +void *dax_get_holder(struct dax_device *dax_dev); > struct dax_device *alloc_dax(void *private, const char *host, > const struct dax_operations *ops, unsigned long flags); > void put_dax(struct dax_device *dax_dev); > @@ -77,6 +84,14 @@ static inline struct dax_device *dax_get_by_host(const char *host) > { > return NULL; > } > +static inline void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops) > +{ > +} > +static inline void *dax_get_holder(struct dax_device *dax_dev) > +{ > + return NULL; > +} > static inline struct dax_device *alloc_dax(void *private, const char *host, > const struct dax_operations *ops, unsigned long flags) > { > @@ -226,6 +241,8 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, > size_t bytes, struct iov_iter *i); > int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, > size_t nr_pages); > +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, > + size_t size, void *data); > void dax_flush(struct dax_device *dax_dev, void *addr, size_t size); > > ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter, > -- > 2.32.0 > > >