From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B1D513AA4C; Tue, 27 Feb 2024 13:41:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709041300; cv=none; b=omMQyGXnVUD+KsfWpE5O20ZYKGyzQ6bt1usE3Hcww/owHpdF3EmIh9KtfEYfWCszSMfmd0fQ314L+IU3LIv4OU5OTGrridjoUuuDPhA5zqvR/bDGryrR+vLGnvq6v57vlULQJjOMg8QrUAPuZ73z1jiaN0MVIi+wtZorlTwMxHw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709041300; c=relaxed/simple; bh=ZeSUM3z3GiUVvHCrkzq+QtV/032258+nd5zG5NeETjk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cKfg1zKx/kr5nnDEpJALpC6x8ywy1VCYfBXZMhjfjO1kdO4PCv8lzliHWeRAAVUF/RcJOfnNI6fBRhvIP4/JEreYQ5zvVVooMQ0zzm0tU32ix+LI7zvAWppOC7kasKIAQqexrisX6eK6JpjCQlI9PMnvm9UmN+Idma5abSQu4mk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nOlo8Z/R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nOlo8Z/R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99E5CC43394; Tue, 27 Feb 2024 13:41:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709041299; bh=ZeSUM3z3GiUVvHCrkzq+QtV/032258+nd5zG5NeETjk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nOlo8Z/R8XdRFHQ9eNWITjtSX+KKIe8oYY4tEdnmje2PGhHvGIXTVCWTmv991gE5y OcGTD38890/yrE0qoUSqyMzZTr4HbzO+3GuYEYUzbxbi1lYHmef95LQWKFxLfSjKmk 0G+ebJc6Tp4fTxZOED7YKpvDdlVEn/GfaUPWl5QzGb1XTe/HVhLMA8ZbQLnR+0wkuz K3HPfMGsgzDerzFlS5+c0kOKgGh6TM3hrx1Nytcm9dkDfrieFEsGJLXcZB80JYTvMZ sye/K3BpPRsmGlEuaTXqyVMWEex4BWh8JBAI890MxtETG4ELs2vPPR5Bx1mMxhVgY0 PRa7sBaAFoXqg== From: Christian Brauner To: John Groves Cc: Christian Brauner , John Groves , Jonathan Corbet , Dan Williams , Vishal Verma , Dave Jiang , Alexander Viro , Jan Kara , Matthew Wilcox , linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, john@jagalactic.com, Dave Chinner , Christoph Hellwig , dave.hansen@linux.intel.com, gregory.price@memverge.com Subject: Re: [RFC PATCH 10/20] famfs: famfs_open_device() & dax_holder_operations Date: Tue, 27 Feb 2024 14:39:20 +0100 Message-ID: <20240227-aufhalten-funkspruch-91b2807d93a7@brauner> X-Mailer: git-send-email 2.43.0 In-Reply-To: <74359fdc83688fb1aac1cb2c336fbd725590a131.1708709155.git.john@groves.net> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4531; i=brauner@kernel.org; h=from:subject:message-id; bh=ZeSUM3z3GiUVvHCrkzq+QtV/032258+nd5zG5NeETjk=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMaTefVbbFrY/zvbXyYiz8ct0Fa9WT52cm84y/dcD5ZRch 9eFkWvcO0pZGMS4GGTFFFkc2k3C5ZbzVGw2ytSAmcPKBDKEgYtTACYi387I8PxSN4tJ7K7M99va o9umi8pFib9szmKPXn6vUfny9F6vVQy/mN/Ln0vb/4WHkXHVhpufFP4L3LU02X//SQxPzGbBsIf PWQE= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit On Fri, Feb 23, 2024 at 11:41:54AM -0600, John Groves wrote: > Famfs works on both /dev/pmem and /dev/dax devices. This commit introduces > the function that opens a block (pmem) device and the struct > dax_holder_operations that are needed for that ABI. > > In this commit, support for opening character /dev/dax is stubbed. A > later commit introduces this capability. > > Signed-off-by: John Groves > --- > fs/famfs/famfs_inode.c | 83 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 83 insertions(+) > > diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c > index 3329aff000d1..82c861998093 100644 > --- a/fs/famfs/famfs_inode.c > +++ b/fs/famfs/famfs_inode.c > @@ -68,5 +68,88 @@ static const struct super_operations famfs_ops = { > .show_options = famfs_show_options, > }; > > +/*************************************************************************************** > + * dax_holder_operations for block dax > + */ > + > +static int > +famfs_blk_dax_notify_failure( > + struct dax_device *dax_devp, > + u64 offset, > + u64 len, > + int mf_flags) > +{ > + > + pr_err("%s: dax_devp %llx offset %llx len %lld mf_flags %x\n", > + __func__, (u64)dax_devp, (u64)offset, (u64)len, mf_flags); > + return -EOPNOTSUPP; > +} > + > +const struct dax_holder_operations famfs_blk_dax_holder_ops = { > + .notify_failure = famfs_blk_dax_notify_failure, > +}; > + > +static int > +famfs_open_char_device( > + struct super_block *sb, > + struct fs_context *fc) > +{ > + pr_err("%s: Root device is %s, but your kernel does not support famfs on /dev/dax\n", > + __func__, fc->source); > + return -ENODEV; > +} > + > +/** > + * famfs_open_device() > + * > + * Open the memory device. If it looks like /dev/dax, call famfs_open_char_device(). > + * Otherwise try to open it as a block/pmem device. > + */ > +static int > +famfs_open_device( I'm confused why that function is added here but it's completely unclear in what wider context it's called. This is really hard to follow. > + struct super_block *sb, > + struct fs_context *fc) > +{ > + struct famfs_fs_info *fsi = sb->s_fs_info; > + struct dax_device *dax_devp; > + u64 start_off = 0; > + struct bdev_handle *handlep; > + > + if (fsi->dax_devp) { > + pr_err("%s: already mounted\n", __func__); > + return -EALREADY; > + } > + > + if (strstr(fc->source, "/dev/dax")) /* There is probably a better way to check this */ > + return famfs_open_char_device(sb, fc); > + > + if (!strstr(fc->source, "/dev/pmem")) { /* There is probably a better way to check this */ Yeah, this is not just a bit ugly but also likely wrong because: sudo mount --bind /dev/pmem /opt/muhaha fsconfig(fd_fs, FSCONFIG_SET_STRING, "source", "/opt/muhaha", [...]) or a simple mknod to create that device somewhere else. You likely want: lookup_bdev(fc->source, &dev); if (!DEVICE_NUMBER_SOMETHING_SOMETHING_SANE(dev)) return invalfc(fc, "SOMETHING SOMETHING... bdev_open_by_dev(dev, ....) (This reminds me that I should get back to making it possible to specify "source" as a file descriptor instead of a mere string with the new mount api...) > + pr_err("%s: primary backing dev (%s) is not pmem\n", > + __func__, fc->source); > + return -EINVAL; > + } > + > + handlep = bdev_open_by_path(fc->source, FAMFS_BLKDEV_MODE, fsi, &fs_holder_ops); Hm, I suspected that FAMFS_BLKDEV_MODE would be wrong based on: https://lore.kernel.org/r/13556dbbd8d0f51bc31e3bdec796283fe85c6baf.1708709155.git.john@groves.net It's defined as FMODE_READ | FMODE_WRITE which is wrong. But these helpers want BLOCK_OPEN_READ | BLOCK_OPEN_WRITE. > + if (IS_ERR(handlep->bdev)) { @bdev_handle will be gone as of v6.9 so you might want to wait until then to resend. > + pr_err("%s: failed blkdev_get_by_path(%s)\n", __func__, fc->source); > + return PTR_ERR(handlep->bdev); > + } > + > + dax_devp = fs_dax_get_by_bdev(handlep->bdev, &start_off, > + fsi /* holder */, > + &famfs_blk_dax_holder_ops); > + if (IS_ERR(dax_devp)) { > + pr_err("%s: unable to get daxdev from handlep->bdev\n", __func__); > + bdev_release(handlep); > + return -ENODEV; > + } > + fsi->bdev_handle = handlep; > + fsi->dax_devp = dax_devp; > + > + pr_notice("%s: root device is block dax (%s)\n", __func__, fc->source); > + return 0; > +} > + > + > > MODULE_LICENSE("GPL"); > -- > 2.43.0 >