linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: David Howells <dhowells@redhat.com>
Cc: viro@zeniv.linux.org.uk, torvalds@linux-foundation.org,
	raven@themaw.net, mszeredi@redhat.com, christian@brauner.io,
	jannh@google.com, darrick.wong@oracle.com, kzak@redhat.com,
	jlayton@redhat.com, linux-api@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 06/18] fsinfo: Add a uniquifier ID to struct mount [ver #21]
Date: Tue, 4 Aug 2020 12:41:08 +0200	[thread overview]
Message-ID: <20200804104108.GC32719@miu.piliscsaba.redhat.com> (raw)
In-Reply-To: <159646183662.1784947.5709738540440380373.stgit@warthog.procyon.org.uk>

On Mon, Aug 03, 2020 at 02:37:16PM +0100, David Howells wrote:
> Add a uniquifier ID to struct mount that is effectively unique over the
> kernel lifetime to deal around mnt_id values being reused.  This can then
> be exported through fsinfo() to allow detection of replacement mounts that
> happen to end up with the same mount ID.
> 
> The normal mount handle is still used for referring to a particular mount.
> 
> The mount notification is then changed to convey these unique mount IDs
> rather than the mount handle.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> 
>  fs/mount.h        |    3 +++
>  fs/mount_notify.c |    4 ++--
>  fs/namespace.c    |    3 +++
>  3 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/mount.h b/fs/mount.h
> index 85456a5f5a3a..1037781be055 100644
> --- a/fs/mount.h
> +++ b/fs/mount.h
> @@ -79,6 +79,9 @@ struct mount {
>  	int mnt_expiry_mark;		/* true if marked for expiry */
>  	struct hlist_head mnt_pins;
>  	struct hlist_head mnt_stuck_children;
> +#ifdef CONFIG_FSINFO
> +	u64	mnt_unique_id;		/* ID unique over lifetime of kernel */
> +#endif

Not sure if it's worth making conditional.

>  #ifdef CONFIG_MOUNT_NOTIFICATIONS
>  	struct watch_list *mnt_watchers; /* Watches on dentries within this mount */
>  #endif
> diff --git a/fs/mount_notify.c b/fs/mount_notify.c
> index 44f570e4cebe..d8ba66ed5f77 100644
> --- a/fs/mount_notify.c
> +++ b/fs/mount_notify.c
> @@ -90,7 +90,7 @@ void notify_mount(struct mount *trigger,
>  	n.watch.type	= WATCH_TYPE_MOUNT_NOTIFY;
>  	n.watch.subtype	= subtype;
>  	n.watch.info	= info_flags | watch_sizeof(n);
> -	n.triggered_on	= trigger->mnt_id;
> +	n.triggered_on	= trigger->mnt_unique_id;
>  
>  	switch (subtype) {
>  	case NOTIFY_MOUNT_EXPIRY:
> @@ -102,7 +102,7 @@ void notify_mount(struct mount *trigger,
>  	case NOTIFY_MOUNT_UNMOUNT:
>  	case NOTIFY_MOUNT_MOVE_FROM:
>  	case NOTIFY_MOUNT_MOVE_TO:
> -		n.auxiliary_mount	= aux->mnt_id;
> +		n.auxiliary_mount = aux->mnt_unique_id;

Hmm, so we now have two ID's:

 - one can be used to look up the mount
 - one is guaranteed to be unique

With this change the mount cannot be looked up with FSINFO_FLAGS_QUERY_MOUNT,
right?

Should we be merging the two ID's into a single one which has both properties?

>  		break;
>  
>  	default:
> diff --git a/fs/namespace.c b/fs/namespace.c
> index b2b9920ffd3c..1db8a64cd76f 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -115,6 +115,9 @@ static int mnt_alloc_id(struct mount *mnt)
>  	if (res < 0)
>  		return res;
>  	mnt->mnt_id = res;
> +#ifdef CONFIG_FSINFO
> +	mnt->mnt_unique_id = atomic64_inc_return(&vfs_unique_counter);
> +#endif
>  	return 0;
>  }
>  
> 
> 

  reply	other threads:[~2020-08-04 10:41 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-03 13:36 [PATCH 00/18] VFS: Filesystem information " David Howells
2020-08-03 13:36 ` [PATCH 01/18] fsinfo: Introduce a non-repeating system-unique superblock ID " David Howells
2020-08-04  9:34   ` Miklos Szeredi
2020-08-03 13:36 ` [PATCH 02/18] fsinfo: Add fsinfo() syscall to query filesystem information " David Howells
2020-08-04 10:16   ` Miklos Szeredi
2020-08-04 11:34   ` David Howells
2020-08-27 11:27   ` Michael Kerrisk (man-pages)
2020-08-03 13:36 ` [PATCH 03/18] fsinfo: Provide a bitmap of the features a filesystem supports " David Howells
2020-08-03 13:37 ` [PATCH 04/18] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
2020-08-03 13:37 ` [PATCH 05/18] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
2020-08-04 10:33   ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 06/18] fsinfo: Add a uniquifier ID to struct mount " David Howells
2020-08-04 10:41   ` Miklos Szeredi [this message]
2020-08-04 12:32     ` Ian Kent
2020-08-05 14:13   ` David Howells
2020-08-05 14:46     ` Miklos Szeredi
2020-08-05 15:30     ` David Howells
2020-08-05 19:33       ` Matthew Wilcox
2020-08-06  5:43         ` Ian Kent
2020-08-03 13:37 ` [PATCH 07/18] fsinfo: Allow mount information to be queried " David Howells
2020-08-03 13:37 ` [PATCH 08/18] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
2020-08-04 13:38   ` Miklos Szeredi
2020-08-05 15:37   ` David Howells
2020-08-05 17:19     ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 09/18] watch_queue: Mount event counters " David Howells
2020-08-03 13:37 ` [PATCH 10/18] fsinfo: Provide notification overrun handling support " David Howells
2020-08-04 13:56   ` Miklos Szeredi
2020-08-05  2:05     ` Ian Kent
2020-08-05  2:46       ` Ian Kent
2020-08-05  7:45         ` Miklos Szeredi
2020-08-05 11:23           ` Ian Kent
2020-08-05 11:27             ` Miklos Szeredi
2020-08-06  1:47               ` Ian Kent
2020-08-05 16:06   ` David Howells
2020-08-05 17:26     ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 11/18] fsinfo: sample: Mount listing program " David Howells
2020-08-03 13:38 ` [PATCH 12/18] fsinfo: Add API documentation " David Howells
2020-08-03 13:38 ` [PATCH 13/18] fsinfo: Add support for AFS " David Howells
2020-08-03 13:38 ` [PATCH 14/18] fsinfo: Add support to ext4 " David Howells
2020-08-03 13:38 ` [PATCH 15/18] fsinfo: Add an attribute that lists all the visible mounts in a namespace " David Howells
2020-08-04 14:05   ` Miklos Szeredi
2020-08-05  0:59     ` Ian Kent
2020-08-05 16:44   ` David Howells
2020-08-03 13:38 ` [PATCH 16/18] errseq: add a new errseq_scrape function " David Howells
2020-08-03 13:38 ` [PATCH 17/18] vfs: allow fsinfo to fetch the current state of s_wb_err " David Howells
2020-08-03 13:39 ` [PATCH 18/18] samples: add error state information to test-fsinfo.c " David Howells
2020-08-04 15:39 ` [PATCH 00/18] VFS: Filesystem information " James Bottomley
2020-08-04 19:18   ` Miklos Szeredi
2020-08-05 17:13 ` David Howells

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200804104108.GC32719@miu.piliscsaba.redhat.com \
    --to=miklos@szeredi.hu \
    --cc=christian@brauner.io \
    --cc=darrick.wong@oracle.com \
    --cc=dhowells@redhat.com \
    --cc=jannh@google.com \
    --cc=jlayton@redhat.com \
    --cc=kzak@redhat.com \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=mszeredi@redhat.com \
    --cc=raven@themaw.net \
    --cc=torvalds@linux-foundation.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [PATCH 06/18] fsinfo: Add a uniquifier ID to struct mount [ver #21]' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).