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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1501C433FE for ; Wed, 5 Jan 2022 19:20:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5A9916B0071; Wed, 5 Jan 2022 14:20:25 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 531F26B0073; Wed, 5 Jan 2022 14:20:25 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3D3AF6B0074; Wed, 5 Jan 2022 14:20:25 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0209.hostedemail.com [216.40.44.209]) by kanga.kvack.org (Postfix) with ESMTP id 2831B6B0071 for ; Wed, 5 Jan 2022 14:20:25 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DAC6E181DA0A2 for ; Wed, 5 Jan 2022 19:20:24 +0000 (UTC) X-FDA: 78997199568.10.325C18C Received: from mail-pg1-f170.google.com (mail-pg1-f170.google.com [209.85.215.170]) by imf24.hostedemail.com (Postfix) with ESMTP id 1A49818000B for ; Wed, 5 Jan 2022 19:20:15 +0000 (UTC) Received: by mail-pg1-f170.google.com with SMTP id f8so74807pgf.8 for ; Wed, 05 Jan 2022 11:20:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Dve+wxxw9ty3Px2ty9l66SiGhuevpIEjzTRbcfS2h4g=; b=8IJNIV4LzcZk4Gk1i5TwJ2/pjHaI5I/ZxjVO81zSvC7oeyj65UIb0m9RgbG8gz6Kp0 59mKq0TZ/S9FE0NHhMPgo6Nc/C8C0i2PbWkg7IqNVvQJUIj/VMEch0dRlzvvSTuPhsbR dnICrGDtoYXsQq1BitIaSDpchHQK7QHrwe36S7aSMD0JSiKV6KmDUqRqHpc6hAr4jywd XwI146AjdrfxzR2kdmIyuvZFzDzCRmYFhNABMaWpQZpI0Gzx3na1ykEIAUjZ/aXuNKEg rv17ogtvQ6wW98kRgo5eNawBaWAq1psKDYwgPIMKF4m/zH5bqOV7s8wJvS0XTTuQvuu7 JB8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Dve+wxxw9ty3Px2ty9l66SiGhuevpIEjzTRbcfS2h4g=; b=XS9+MowV+GcYuIjVbAJmL2zAmxLlrPVVB/C5jOGoevrz+iMj3aWHDAVoVDkVwR2pvV o8j8QaxCemak7pX2nZh2urrDboV5OC/jAe+p5t/hlUEQzIHoHZMMzpn1ht51456FPQlu GT+DxZ8tufwsYFzTiHwHTKUC79Q/OvQeVthBgegGs0+eY6nFTXRw7rm7s2wNBU/UAJFM MlokbqSm0ZKzhXgKLxXVe0MHnIZ3Od27F0l6sAdfVMrp5Z29QR3rdTij4nAIRKrI0zUD EXnjWBySpiU8Oa8XtZSn5t8taRf/Egk4mvTjnKYO8YRrUgZmvBl6vPL++YLWAKbNs+tN kXVg== X-Gm-Message-State: AOAM533Ee47DwZwBAxSVshs90qwUIE3dsgR7xIrsqpXY4SbeGW4aPtVd pfKFeX2aaqIwEIPnIsKS/DjrEM4DTHx0TUbsLKpKCg== X-Google-Smtp-Source: ABdhPJz3U6I17PcLMJRT9nNHOY2Hml0MXvZXbyzvuHrppEa6CJQNVUp/+QSIaW561mi0Aw4p76wcTbR7GWuXBpuqFko= X-Received: by 2002:a63:ab01:: with SMTP id p1mr1426162pgf.437.1641410423361; Wed, 05 Jan 2022 11:20:23 -0800 (PST) MIME-Version: 1.0 References: <20211226143439.3985960-1-ruansy.fnst@fujitsu.com> <20211226143439.3985960-3-ruansy.fnst@fujitsu.com> <20220105181230.GC398655@magnolia> <20220105185626.GE398655@magnolia> In-Reply-To: <20220105185626.GE398655@magnolia> From: Dan Williams Date: Wed, 5 Jan 2022 11:20:12 -0800 Message-ID: Subject: Re: [PATCH v9 02/10] dax: Introduce holder for dax_device To: "Darrick J. Wong" Cc: Shiyang Ruan , Linux Kernel Mailing List , linux-xfs , Linux NVDIMM , Linux MM , linux-fsdevel , david , Christoph Hellwig , Jane Chu Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 1A49818000B X-Stat-Signature: uxjacpkpuhctewwfnau7owcgzksptzry Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=intel-com.20210112.gappssmtp.com header.s=20210112 header.b=8IJNIV4L; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=intel.com (policy=none); spf=none (imf24.hostedemail.com: domain of dan.j.williams@intel.com has no SPF policy when checking 209.85.215.170) smtp.mailfrom=dan.j.williams@intel.com X-Rspamd-Server: rspam02 X-HE-Tag: 1641410415-943038 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 Wed, Jan 5, 2022 at 10:56 AM Darrick J. Wong wrote: > > On Wed, Jan 05, 2022 at 10:23:08AM -0800, Dan Williams wrote: > > On Wed, Jan 5, 2022 at 10:12 AM Darrick J. Wong wrote: > > > > > > On Sun, Dec 26, 2021 at 10:34:31PM +0800, 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 > > > > instance 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 | 62 +++++++++++++++++++++++++++++++++++++++++++++ > > > > include/linux/dax.h | 29 +++++++++++++++++++++ > > > > 2 files changed, 91 insertions(+) > > > > > > > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > > > > index c46f56e33d40..94c51f2ee133 100644 > > > > --- a/drivers/dax/super.c > > > > +++ b/drivers/dax/super.c > > > > @@ -20,15 +20,20 @@ > > > > * @inode: core vfs > > > > * @cdev: optional character interface for "device dax" > > > > * @private: dax driver private data > > > > + * @holder_data: holder of a dax_device: could be filesystem or mapped device > > > > * @flags: state and boolean properties > > > > + * @ops: operations for dax_device > > > > + * @holder_ops: operations for the inner holder > > > > */ > > > > struct dax_device { > > > > struct inode inode; > > > > struct cdev cdev; > > > > void *private; > > > > struct percpu_rw_semaphore rwsem; > > > > + void *holder_data; > > > > unsigned long flags; > > > > const struct dax_operations *ops; > > > > + const struct dax_holder_operations *holder_ops; > > > > }; > > > > > > > > static dev_t dax_devt; > > > > @@ -192,6 +197,29 @@ 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, u64 off, > > > > + u64 len, int mf_flags) > > > > +{ > > > > + int rc; > > > > + > > > > + dax_read_lock(dax_dev); > > > > + if (!dax_alive(dax_dev)) { > > > > + rc = -ENXIO; > > > > + goto out; > > > > + } > > > > + > > > > + if (!dax_dev->holder_ops) { > > > > + rc = -EOPNOTSUPP; > > > > + goto out; > > > > + } > > > > + > > > > + rc = dax_dev->holder_ops->notify_failure(dax_dev, off, len, mf_flags); > > > > +out: > > > > + dax_read_unlock(dax_dev); > > > > + 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) > > > > @@ -254,6 +282,10 @@ void kill_dax(struct dax_device *dax_dev) > > > > return; > > > > dax_write_lock(dax_dev); > > > > clear_bit(DAXDEV_ALIVE, &dax_dev->flags); > > > > + > > > > + /* clear holder data */ > > > > + dax_dev->holder_ops = NULL; > > > > + dax_dev->holder_data = NULL; > > > > dax_write_unlock(dax_dev); > > > > } > > > > EXPORT_SYMBOL_GPL(kill_dax); > > > > @@ -401,6 +433,36 @@ void put_dax(struct dax_device *dax_dev) > > > > } > > > > EXPORT_SYMBOL_GPL(put_dax); > > > > > > > > +void dax_register_holder(struct dax_device *dax_dev, void *holder, > > > > + const struct dax_holder_operations *ops) > > > > +{ > > > > + if (!dax_alive(dax_dev)) > > > > + return; > > > > + > > > > + dax_dev->holder_data = holder; > > > > + dax_dev->holder_ops = ops; > > > > > > Shouldn't this return an error code if the dax device is dead or if > > > someone already registered a holder? I'm pretty sure XFS should not > > > bind to a dax device if someone else already registered for it... > > > > Agree, yes. > > > > > > > > ...unless you want to use a notifier chain for failure events so that > > > there can be multiple consumers of dax failure events? > > > > No, I would hope not. It should be 1:1 holders to dax-devices. Similar > > ownership semantics like bd_prepare_to_claim(). > > Does each partition on a pmem device still have its own dax_device? No, it never did... Just as before, each dax-device is still associated with a gendisk / whole-block_device. The recent change is that instead of needing that partition-block_device plumbed to convert a relative block number to its absolute whole-block_device offset the filesystem now handles that at iomap_begin() time. See: if (mapping_flags & IOMAP_DAX) iomap->addr += target->bt_dax_part_off; ...in xfs_bmbt_to_iomap() (in -next). I.e. bdev_dax_pgoff() is gone with the lead-in reworks.