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From: Martin Steigerwald <martin@lichtvoll.de>
To: Miklos Szeredi <miklos@szeredi.hu>, NeilBrown <neilb@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>,
	Josef Bacik <josef@toxicpanda.com>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Chuck Lever <chuck.lever@oracle.com>, Chris Mason <clm@fb.com>,
	David Sterba <dsterba@suse.com>,
	linux-fsdevel@vger.kernel.org,
	Linux NFS list <linux-nfs@vger.kernel.org>,
	Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: A Third perspective on BTRFS nfsd subvol dev/inode number issues.
Date: Mon, 02 Aug 2021 09:15:09 +0200	[thread overview]
Message-ID: <3318968.VgehHcluNF@ananda> (raw)
In-Reply-To: <162787790940.32159.14588617595952736785@noble.neil.brown.name>

Hi Neil!

Wow, this is a bit overwhelming for me. However, I got a very specific 
question for userspace developers in order to probably provide valuable 
input to the KDE Baloo desktop search developers:

NeilBrown - 02.08.21, 06:18:29 CEST:
> The "obvious" choice for a replacement is the file handle provided by
> name_to_handle_at() (falling back to st_ino if name_to_handle_at isn't
> supported by the filesystem).  This returns an extensible opaque
> byte-array.  It is *already* more reliable than st_ino.  Comparing
> st_ino is only a reliable way to check if two files are the same if
> you have both of them open.  If you don't, then one of the files
> might have been deleted and the inode number reused for the other.  A
> filehandle contains a generation number which protects against this.
> 
> So I think we need to strongly encourage user-space to start using
> name_to_handle_at() whenever there is a need to test if two things are
> the same.

How could that work for Baloo's use case to see whether a file it 
encounters is already in its database or whether it is a new file.

Would Baloo compare the whole file handle or just certain fields or make a 
hash of the filehandle or what ever? Could you, in pseudo code or 
something, describe the approach you'd suggest. I'd then share it on:

Bug 438434 - Baloo appears to be indexing twice the number of files than 
are actually in my home directory

https://bugs.kde.org/438434

Best,
-- 
Martin



  parent reply	other threads:[~2021-08-02  7:15 UTC|newest]

Thread overview: 129+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27 22:37 [PATCH/RFC 00/11] expose btrfs subvols in mount table correctly NeilBrown
2021-07-27 22:37 ` [PATCH 07/11] exportfs: Allow filehandle lookup to cross internal mount points NeilBrown
2021-07-28 10:13   ` Amir Goldstein
2021-07-29  0:28     ` NeilBrown
2021-07-29  5:27       ` Amir Goldstein
2021-08-06  7:52         ` Miklos Szeredi
2021-08-06  8:08           ` Amir Goldstein
2021-08-06  8:18             ` Miklos Szeredi
2021-07-28 19:17   ` J. Bruce Fields
2021-07-28 22:25     ` NeilBrown
2021-07-27 22:37 ` [PATCH 04/11] VFS: export lookup_mnt() NeilBrown
2021-07-30  0:31   ` Al Viro
2021-07-30  5:33     ` NeilBrown
2021-07-27 22:37 ` [PATCH 01/11] VFS: show correct dev num in mountinfo NeilBrown
2021-07-30  0:25   ` Al Viro
2021-07-30  5:28     ` NeilBrown
2021-07-30  5:54       ` Miklos Szeredi
2021-07-30  6:13         ` NeilBrown
2021-07-30  7:18           ` Miklos Szeredi
2021-07-30  7:33             ` NeilBrown
2021-07-30  7:59               ` Miklos Szeredi
2021-08-02  4:18                 ` A Third perspective on BTRFS nfsd subvol dev/inode number issues NeilBrown
2021-08-02  5:25                   ` Al Viro
2021-08-02  5:40                     ` NeilBrown
2021-08-02  7:54                       ` Amir Goldstein
2021-08-02 13:53                         ` Josef Bacik
2021-08-03 22:29                           ` Qu Wenruo
2021-08-02 14:47                         ` Frank Filz
2021-08-02 21:24                         ` NeilBrown
2021-08-02  7:15                   ` Martin Steigerwald [this message]
2021-08-02 21:40                     ` NeilBrown
2021-08-02 12:39                   ` J. Bruce Fields
2021-08-02 20:32                     ` Patrick Goetz
2021-08-02 20:41                       ` J. Bruce Fields
2021-08-02 21:10                     ` NeilBrown
2021-08-02 21:50                       ` J. Bruce Fields
2021-08-02 21:59                         ` NeilBrown
2021-08-02 22:14                           ` J. Bruce Fields
2021-08-02 22:36                             ` NeilBrown
2021-08-03  0:15                               ` J. Bruce Fields
2021-07-27 22:37 ` [PATCH 03/11] VFS: pass lookup_flags into follow_down() NeilBrown
2021-07-27 22:37 ` [PATCH 11/11] btrfs: use automount to bind-mount all subvol roots NeilBrown
2021-07-28  8:37   ` kernel test robot
2021-07-28  8:37     ` kernel test robot
2021-07-28  8:37   ` [RFC PATCH] btrfs: btrfs_mountpoint_expiry_timeout can be static kernel test robot
2021-07-28  8:37     ` kernel test robot
2021-07-28 13:12   ` [PATCH 11/11] btrfs: use automount to bind-mount all subvol roots Christian Brauner
2021-07-29  0:43     ` NeilBrown
2021-07-29 14:38       ` Christian Brauner
2021-07-31  6:25   ` [btrfs] 5874902268: xfstests.btrfs.202.fail kernel test robot
2021-07-31  6:25     ` kernel test robot
2021-07-27 22:37 ` [PATCH 06/11] nfsd: include a vfsmount in struct svc_fh NeilBrown
2021-07-27 22:37 ` [PATCH 10/11] btrfs: introduce mapping function from location to inum NeilBrown
2021-07-27 22:37 ` [PATCH 02/11] VFS: allow d_automount to create in-place bind-mount NeilBrown
2021-07-27 22:37 ` [PATCH 09/11] nfsd: Allow filehandle lookup to cross internal mount points NeilBrown
2021-07-28 19:15   ` J. Bruce Fields
2021-07-28 22:29     ` NeilBrown
2021-07-30  0:42   ` Al Viro
2021-07-30  5:43     ` NeilBrown
2021-07-27 22:37 ` [PATCH 08/11] nfsd: change get_parent_attributes() to nfsd_get_mounted_on() NeilBrown
2021-07-27 22:37 ` [PATCH 05/11] VFS: new function: mount_is_internal() NeilBrown
2021-07-28  2:16   ` Al Viro
2021-07-28  3:32     ` NeilBrown
2021-07-30  0:34       ` Al Viro
2021-07-28  2:19 ` [PATCH/RFC 00/11] expose btrfs subvols in mount table correctly Al Viro
2021-07-28  4:58 ` Wang Yugui
2021-07-28  6:04   ` Wang Yugui
2021-07-28  7:01     ` NeilBrown
2021-07-28 12:26       ` Neal Gompa
2021-07-28 19:14         ` J. Bruce Fields
2021-07-29  1:29           ` Zygo Blaxell
2021-07-29  1:43             ` NeilBrown
2021-07-29 23:20               ` Zygo Blaxell
2021-07-28 22:50         ` NeilBrown
2021-07-29  2:37           ` Zygo Blaxell
2021-07-29  3:36             ` NeilBrown
2021-07-29 23:20               ` Zygo Blaxell
2021-07-30  2:36                 ` NeilBrown
2021-07-30  5:25                   ` Qu Wenruo
2021-07-30  5:31                     ` Qu Wenruo
2021-07-30  5:53                       ` Amir Goldstein
2021-07-30  6:00                       ` NeilBrown
2021-07-30  6:09                         ` Qu Wenruo
2021-07-30  5:58                     ` NeilBrown
2021-07-30  6:23                       ` Qu Wenruo
2021-07-30  6:53                         ` NeilBrown
2021-07-30  7:09                           ` Qu Wenruo
2021-07-30 18:15                             ` Zygo Blaxell
2021-07-30 15:17                         ` J. Bruce Fields
2021-07-30 15:48                           ` Josef Bacik
2021-07-30 16:25                             ` Forza
2021-07-30 17:43                             ` Zygo Blaxell
2021-07-30  5:28                   ` Amir Goldstein
2021-07-28 13:43       ` g.btrfs
2021-07-29  1:39         ` NeilBrown
2021-07-29  9:28           ` Graham Cobb
2021-07-28  7:06   ` NeilBrown
2021-07-28  9:36     ` Wang Yugui
2021-07-28 19:35 ` J. Bruce Fields
2021-07-28 21:30   ` Josef Bacik
2021-07-30  0:13     ` Al Viro
2021-07-30  6:08       ` NeilBrown
2021-08-13  1:45 ` [PATCH] VFS/BTRFS/NFSD: provide more unique inode number for btrfs export NeilBrown
2021-08-13 14:55   ` Josef Bacik
2021-08-15  7:39   ` Goffredo Baroncelli
2021-08-15 19:35     ` Roman Mamedov
2021-08-15 21:03       ` Goffredo Baroncelli
2021-08-15 21:53         ` NeilBrown
2021-08-17 19:34           ` Goffredo Baroncelli
2021-08-17 21:39             ` NeilBrown
2021-08-18 17:24               ` Goffredo Baroncelli
2021-08-15 22:17       ` NeilBrown
2021-08-19  8:01         ` Amir Goldstein
2021-08-20  3:21           ` NeilBrown
2021-08-20  6:23             ` Amir Goldstein
2021-08-23  4:05         ` [PATCH v2] BTRFS/NFSD: " NeilBrown
2021-08-23  8:17           ` kernel test robot
2021-08-23  8:17             ` kernel test robot
2021-08-18 14:54   ` [PATCH] VFS/BTRFS/NFSD: " Wang Yugui
2021-08-18 21:46     ` NeilBrown
2021-08-19  2:19       ` Zygo Blaxell
2021-08-20  2:54         ` NeilBrown
2021-08-22 19:29           ` Zygo Blaxell
2021-08-23  5:51             ` NeilBrown
2021-08-23 23:22             ` NeilBrown
2021-08-25  2:06               ` Zygo Blaxell
2021-08-23  0:57         ` Wang Yugui
2021-08-02  9:11 A Third perspective on BTRFS nfsd subvol dev/inode number issues Forza
2021-08-02 21:50 ` NeilBrown

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