linux-kernel - Re: [PATCH 04/25] vfs: Implement parameter value retrieval with fsinfo() [ver #13]

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Message-ID: <24127.1560897289@warthog.procyon.org.uk>
Date:   Tue, 18 Jun 2019 23:34:49 +0100
From:   David Howells <dhowells@...hat.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        Ian Kent <raven@...maw.net>,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: Re: [PATCH 04/25] vfs: Implement parameter value retrieval with fsinfo() [ver #13]

Miklos Szeredi <miklos@...redi.hu> wrote:

> Again, don't blindly transform s_flags into options, because some of
> them may have been internally manipulated by the filesystem.

In what filesystems do I need to undo this manipulation?

> You could do a helper for filesystems that does the the common ones
> (ro/sync/dirsync) but all of that *should* go through the filesystem.

I don't agree, but since you keep insisting, I've changed the helper function
that renders these so that it now takes s_flags as an argument and is called
from generic_fsinfo() if the filesystem doesn't handle FSINFO_ATTR_PARAMETERS.

Therefore, every filesystem that handles FSINFO_ATTR_PARAMETERS, *must* call
the function itself (or do the noting directly) otherwise these parameters
will not get rendered.

The helper function has been exported, and the calling filesystem can give any
s_flags it likes.  All the filesystems so far just use
path->dentry->d_sb->s_flags.

> Same goes for vfs_parse_sb_flag() btw.   It should be moved into each
> filesystem's ->parse_param() and not be a mandatory thing.

I disagree.  Every filesystem *must* be able to accept these standard flags,
even if it then ignores them.

David