Re: [PATCH V14 02/12] famfs: Module operations, fs_context, and mount

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The mount path explicitly rejects concurrent mounts of the same backing device, contradicting the commit message claim that multiple mounts should share the superblock.
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commit c082254e4802428a0767926c0085c3cbeace41cb
Author: John Groves <john@groves.net>
famfs: Module operations, fs_context, and mount

This commit introduces the initial module operations for famfs, including
filesystem registration, mount parameter parsing, superblock initialization,
and DAX device lookup.

> diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
> new file mode 100644
> index 0000000000000..5a13903da61b7
> --- /dev/null
> +++ b/fs/famfs/famfs_inode.c

[ ... ]

> +static int
> +famfs_get_tree(struct fs_context *fc)
> +{
> +	struct famfs_fs_info *fsi = fc->s_fs_info;
> +	struct super_block *sb;
> +	struct inode *inode;
> +	dev_t daxdevno;
> +	int err;

[ ... ]

> +	/* This will set sb->s_dev=daxdevno */
> +	sb = sget_dev(fc, daxdevno);
> +	if (IS_ERR(sb)) {
> +		pr_debug("%s: sget_dev error\n", __func__);
> +		return PTR_ERR(sb);
> +	}
> +
> +	if (sb->s_root) {
> +		pr_debug("%s: found a matching superblock for %s\n",
> +			__func__, fc->source);
> +
> +		/* We don't expect to find a match by dev_t; if we do, it must
> +		 * already be mounted, so we bail
> +		 */
> +		err = -EBUSY;
> +		goto deactivate_out;

[Severity: Medium]
Does returning -EBUSY here intentionally prevent sharing the superblock
across multiple mounts?

The commit message states: "so a second mount of the same device shares one
super, much as a block filesystem keys on its block device." However, this
check appears to explicitly reject concurrent mounts of the same DAX backing
device rather than sharing the existing superblock.

> +	} else {
> +		pr_debug("%s: initializing new superblock for %s\n",
> +			__func__, fc->source);
> +		famfs_fill_super(sb, fc);
> +	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/010001a04e801a4e-8eb212cd-b263-4043-ab65-33e480d2d7d4-000000@email.amazonses.com?part=2