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	Mon, 24 Feb 2025 02:53:30 +0000
Date: Mon, 24 Feb 2025 02:53:30 +0000
From: Al Viro <viro@zeniv.linux.org.uk>
To: NeilBrown <neilb@suse.de>
Cc: Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	Miklos Szeredi <miklos@szeredi.hu>, Xiubo Li <xiubli@redhat.com>,
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	netfs@lists.linux.dev
Subject: Re: [PATCH 4/6] fuse: return correct dentry for ->mkdir
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 <174036397835.74271.9038146946135155196@noble.neil.brown.name>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Mon, Feb 24, 2025 at 01:26:18PM +1100, NeilBrown wrote:

> Probably now.  It would require S_IFDIR to be passed in the mode to
> vfs_mknod().  I don't think any current callers do that, but I don't see
> any code in vfs_mknod() to prevent it.

Not allowed (and that's caller's responsibility to enforce).  Local filesystems
would break horribly if that ever happened.

->mknod() instance _may_ be a convenient helper for ->mkdir() et.al. to call,
but even for ramfs it won't coincide with ->mkdir() (wrong i_nlink, for one
thing).

If that's not documented, it really should be.

vfs_mknod() may be called for block devices, character devices, FIFOs and
sockets.  Nothing else is allowed.