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From: Miklos Szeredi <>
To: David Howells <>
Cc: Alexander Viro <>,
	Matthew Wilcox <>, Ian Kent <>,
	Linus Torvalds <>,,
Subject: Re: [RFC][PATCH 0/3] vfs: Use an xarray instead of inserted bookmarks to scan mount list
Date: Mon, 15 Mar 2021 15:22:47 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Mon, Mar 15, 2021 at 2:41 PM David Howells <> wrote:
> Miklos Szeredi <> wrote:
> > >  (2) We can use the file position to represent the mnt_id and can jump to
> > >      it directly - ie. using seek() to jump to a mount object by its ID.
> >
> > What happens if the mount at the current position is removed?
> umount_tree() requires the namespace_sem to be writelocked, so that should be
> fine as the patches currently read-lock that whilst doing /proc/*/mount*
> I'm assuming that kern_unmount() won't be a problem as it is there to deal
> with mounts made by kern_mount() which don't get added to the mount list
> (mnt_ns is MNT_NS_INTERNAL).  kern_unmount_array() seems to be the same
> because overlayfs gives it mounts generated by clone_private_mount().  It
> might be worth putting a WARN_ON() in kern_unmount() to require this.
> When reading through proc, m_start() calls xas_find() which returns the entry
> at the starting index or, if not present, the next higher entry.

This will break the property of new mounts always being added to the
end of the list.  That's likely a regression for nerural based parsers
(i.e. people), probably less so for machine parsers.


> David

      reply	other threads:[~2021-03-15 14:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-15 12:07 [RFC][PATCH 0/3] vfs: Use an xarray instead of inserted bookmarks to scan mount list David Howells
2021-03-15 12:07 ` [PATCH 1/3] vfs: Use an xarray in the mount namespace to handle /proc/mounts list David Howells
2021-03-15 12:07 ` [PATCH 2/3] vfs: Use the mounts_to_id array to do /proc/mounts and co David Howells
2021-03-15 12:54   ` Matthew Wilcox
2021-03-15 12:08 ` [PATCH 3/3] vfs: Remove mount list trawling cursor stuff David Howells
2021-03-15 12:46 ` [RFC][PATCH 0/3] vfs: Use an xarray instead of inserted bookmarks to scan mount list Matthew Wilcox
2021-03-15 13:14 ` Miklos Szeredi
2021-03-15 13:17   ` Matthew Wilcox
2021-03-15 13:41 ` David Howells
2021-03-15 14:22   ` Miklos Szeredi [this message]

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