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From: David Howells <dhowells@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: dhowells@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>,
	Matthew Wilcox <willy@infradead.org>, Ian Kent <raven@themaw.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 0/3] vfs: Use an xarray instead of inserted bookmarks to scan mount list
Date: Mon, 15 Mar 2021 13:41:48 +0000	[thread overview]
Message-ID: <2857440.1615815708@warthog.procyon.org.uk> (raw)
In-Reply-To: <CAJfpegsb9XrUct5zawN+kS_DSfowBf2BnrZzG+cQXUvsGZZuow@mail.gmail.com>

Miklos Szeredi <miklos@szeredi.hu> 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.

David


  parent reply	other threads:[~2021-03-15 13:42 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 [this message]
2021-03-15 14:22   ` Miklos Szeredi

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