linux-kernel - Re: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12]

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Date:   Wed, 17 Oct 2018 14:15:01 +0100
From:   David Howells <dhowells@...hat.com>
To:     Alan Jenkins <alan.christopher.jenkins@...il.com>
Cc:     dhowells@...hat.com, Al Viro <viro@...IV.linux.org.uk>,
        linux-api@...r.kernel.org, torvalds@...ux-foundation.org,
        ebiederm@...ssion.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, mszeredi@...hat.com
Subject: Re: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12]

Alan Jenkins <alan.christopher.jenkins@...il.com> wrote:

> Sorry, I guess SB_NOUSER was the wrong word.  I was trying find if anything
> stopped things like
> 
> int memfd = memfd_create("foo", 0);
> int fsfd = fspick(memfd, "", FSPICK_EMPTY_PATH);
> 
> fsconfig(fsfd, FSCONFIG_SET_FLAG, "ro", NULL, 0);
> fsconfig(fsfd, FSCONFIG_SET_STRING, "size", "100M", 0);
> fsconfig(fsfd, FSCONFIG_CMD_RECONFIGURE, NULL, NULL, 0);
> 
> So far I'm getting -EBUSY if I try to apply the "ro", -EINVAL if I try to
> apply the "size=100M".  But if I don't apply either, then
> FSCONFIG_CMD_RECONFIGURE succeeds.

I should probably check that the picked point is actually a mountpoint.

David