From: Christian Brauner <brauner@kernel.org>
To: John Groves <John@groves.net>
Cc: Christian Brauner <brauner@kernel.org>,
John Groves <jgroves@micron.com>,
Jonathan Corbet <corbet@lwn.net>,
Dan Williams <dan.j.williams@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
Matthew Wilcox <willy@infradead.org>,
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 <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
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 [thread overview]
Message-ID: <20240227-aufhalten-funkspruch-91b2807d93a7@brauner> (raw)
In-Reply-To: <74359fdc83688fb1aac1cb2c336fbd725590a131.1708709155.git.john@groves.net>
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 <john@groves.net>
> ---
> 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
>
next prev parent reply other threads:[~2024-02-27 13:41 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-23 17:41 [RFC PATCH 00/20] Introduce the famfs shared-memory file system John Groves
2024-02-23 17:41 ` [RFC PATCH 01/20] famfs: Documentation John Groves
2024-02-23 17:41 ` [RFC PATCH 02/20] dev_dax_iomap: Add fs_dax_get() func to prepare dax for fs-dax usage John Groves
2024-02-26 12:05 ` Jonathan Cameron
2024-02-26 15:00 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 03/20] dev_dax_iomap: Move dax_pgoff_to_phys from device.c to bus.c since both need it now John Groves
2024-02-26 12:10 ` Jonathan Cameron
2024-02-26 15:13 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 04/20] dev_dax_iomap: Save the kva from memremap John Groves
2024-02-26 12:21 ` Jonathan Cameron
2024-02-26 15:48 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 05/20] dev_dax_iomap: Add dax_operations for use by fs-dax on devdax John Groves
2024-02-26 12:32 ` Jonathan Cameron
2024-02-26 16:09 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 06/20] dev_dax_iomap: Add CONFIG_DEV_DAX_IOMAP kernel build parameter John Groves
2024-02-26 12:34 ` Jonathan Cameron
2024-02-26 16:12 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 07/20] famfs: Add include/linux/famfs_ioctl.h John Groves
2024-02-24 1:39 ` Randy Dunlap
2024-02-24 2:23 ` John Groves
2024-02-24 3:27 ` Randy Dunlap
2024-02-24 23:32 ` John Groves
2024-02-24 23:40 ` Randy Dunlap
2024-02-26 12:39 ` Jonathan Cameron
2024-02-26 16:44 ` John Groves
2024-02-26 16:56 ` Jonathan Cameron
2024-02-26 18:04 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 08/20] famfs: Add famfs_internal.h John Groves
2024-02-26 12:48 ` Jonathan Cameron
2024-02-26 17:35 ` John Groves
2024-02-27 10:28 ` Jonathan Cameron
2024-02-28 1:06 ` John Groves
2024-02-27 13:38 ` Christian Brauner
2024-02-27 14:12 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 09/20] famfs: Add super_operations John Groves
2024-02-26 12:51 ` Jonathan Cameron
2024-02-26 21:47 ` John Groves
2024-02-27 10:34 ` Jonathan Cameron
2024-02-27 17:48 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 10/20] famfs: famfs_open_device() & dax_holder_operations John Groves
2024-02-26 12:56 ` Jonathan Cameron
2024-02-26 22:22 ` John Groves
2024-02-27 13:39 ` Christian Brauner [this message]
2024-02-27 18:38 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 11/20] famfs: Add fs_context_operations John Groves
2024-02-26 13:20 ` Jonathan Cameron
2024-02-26 22:43 ` John Groves
2024-02-27 13:41 ` Christian Brauner
2024-02-28 0:59 ` John Groves
2024-02-28 1:49 ` Randy Dunlap
2024-02-28 8:17 ` Christian Brauner
2024-02-28 10:07 ` Christian Brauner
2024-02-28 12:01 ` Christian Brauner
2024-02-23 17:41 ` [RFC PATCH 12/20] famfs: Add inode_operations and file_system_type John Groves
2024-02-26 13:25 ` Jonathan Cameron
2024-02-26 22:53 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 13/20] famfs: Add iomap_ops John Groves
2024-02-26 13:30 ` Jonathan Cameron
2024-02-26 23:00 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 14/20] famfs: Add struct file_operations John Groves
2024-02-26 13:32 ` Jonathan Cameron
2024-02-26 23:09 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 15/20] famfs: Add ioctl to file_operations John Groves
2024-02-26 13:44 ` Jonathan Cameron
2024-02-23 17:42 ` [RFC PATCH 16/20] famfs: Add fault counters John Groves
2024-02-23 18:23 ` Dave Hansen
2024-02-23 19:56 ` John Groves
2024-02-23 20:04 ` Dan Williams
2024-02-23 20:39 ` John Groves
2024-02-23 21:19 ` Dave Hansen
2024-02-23 23:50 ` Dan Williams
2024-02-24 3:59 ` Matthew Wilcox
2024-02-24 4:30 ` Dan Williams
2024-02-23 17:42 ` [RFC PATCH 17/20] famfs: Add module stuff John Groves
2024-02-26 13:47 ` Jonathan Cameron
2024-02-27 22:15 ` John Groves
2024-02-23 17:42 ` [RFC PATCH 18/20] famfs: Support character dax via the dev_dax_iomap patch John Groves
2024-02-26 13:52 ` Jonathan Cameron
2024-02-27 22:27 ` John Groves
2024-02-23 17:42 ` [RFC PATCH 19/20] famfs: Update MAINTAINERS file John Groves
2024-02-23 17:42 ` [RFC PATCH 20/20] famfs: Add Kconfig and Makefile plumbing John Groves
2024-02-24 1:50 ` Randy Dunlap
2024-02-24 2:24 ` John Groves
2024-02-24 0:07 ` [RFC PATCH 00/20] Introduce the famfs shared-memory file system Luis Chamberlain
2024-02-26 13:27 ` John Groves
2024-02-26 15:53 ` Luis Chamberlain
2024-02-26 21:16 ` John Groves
2024-02-27 0:58 ` Luis Chamberlain
2024-02-27 2:05 ` John Groves
2024-02-29 2:15 ` Dave Chinner
2024-02-29 14:52 ` John Groves
2024-03-11 1:29 ` Dave Chinner
2024-02-29 6:52 ` Amir Goldstein
2024-02-29 22:16 ` John Groves
2024-05-17 9:55 ` Miklos Szeredi
2024-05-19 5:59 ` Amir Goldstein
2024-05-22 2:05 ` John Groves
2024-05-22 8:58 ` Miklos Szeredi
2024-05-22 10:16 ` Amir Goldstein
2024-05-22 11:28 ` Miklos Szeredi
2024-05-22 13:41 ` Amir Goldstein
2024-05-23 2:49 ` John Groves
2024-05-23 13:57 ` Miklos Szeredi
2024-05-24 0:47 ` John Groves
2024-05-24 7:55 ` Miklos Szeredi
2024-05-25 22:54 ` Dave Chinner
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