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From: NeilBrown <nfbrown@novell.com>
To: David Howells <dhowells@redhat.com>, linux-fsdevel@vger.kernel.org
Cc: linux-afs@vger.kernel.org, linux-nfs@vger.kernel.org,
	samba-technical@lists.samba.org, linux-kernel@vger.kernel.org,
	dhowells@redhat.com, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 1/6] statx: Add a system call to make enhanced file info available
Date: Thu, 05 May 2016 09:56:58 +1000	[thread overview]
Message-ID: <87vb2tbcmt.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <20160429125743.23636.85219.stgit@warthog.procyon.org.uk>

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On Fri, Apr 29 2016, David Howells wrote:

> Add a system call to make extended file information available, including
> file creation time, inode version and data version where available through
> the underlying filesystem.
>
>
> ========
> OVERVIEW
> ========

I think all this documentation is invaluable - thanks.
I would really like to see much of it in
    Documentation/filesystems/something.txt
rather than just in the commit log.

>
> The defined bits in the st_information field give local system data on a
> file, how it is accessed, where it is and what it does:

These bits form a channel for communication between the filesystem
developer and the application writer.  As such we should be sure that
channel actually communicates meaning...


>
> 	STATX_INFO_ENCRYPTED		File is encrypted
> 	STATX_INFO_TEMPORARY		File is temporary

What is "temporary"?  Is it a statement about quality of storage
technology (will be destroyed by reboot) or intention of creator
(created with O_TMPFILE) or something else?


> 	STATX_INFO_FABRICATED		File was made up by filesystem
> 	STATX_INFO_KERNEL_API		File is kernel API (eg: procfs/sysfs)

What is the difference between these two?  Both are synthesized by the
kernel.
Maybe the "KERNEL_API" is declared never to change its meaning, while the
fabricated one doesn't make a "stable API" promise?

What is the difference between fabricating a file from a bunch of blocks
spread over a storage device, and fabricating a file from a single field
in the super-block?


> 	STATX_INFO_REMOTE		File is remote

How far is "remote"?  Does Infiniband count?  Fibre channel?  iSCSI?
Is a file on a loop-back mounted NFS filesystem more remote than a
fibre-channel connection to the next town?

Or is this relative?  Within a filesystem there are "remote" files and
"non-remote" files and the distinction is filesystem-dependant??

> 	STATX_INFO_AUTOMOUNT		Dir is automount trigger
> 	STATX_INFO_AUTODIR		Dir provides unlisted automounts

I think this last one means that there are names in the directory which
may not appear in "readdir" but will respond to "stat".  I would prefer
the description to match the behavior without necessarily implying that
those names will be automounts.  e.g
        STATX_INFO_INCOMPLETE_READDIR   getdents may not report all
                                        names that respond to stat

> 	STATX_INFO_NONSYSTEM_OWNERSHIP	File has non-system ownership details

This probably is a well defined meaning that I just don't have the
context to understand.  For me, more words would help here.


I don't object to any of these flag.  I just want to be sure that I
understand them.
I am generally in favour this functionality going in promptly.

Thanks,
NeilBrown

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  parent reply	other threads:[~2016-05-04 23:57 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-29 12:57 [RFC][PATCH 0/6] Enhanced file stat system call David Howells
2016-04-29 12:57 ` [PATCH 1/6] statx: Add a system call to make enhanced file info available David Howells
2016-05-02 22:46   ` Andreas Dilger
2016-05-02 22:46     ` Andreas Dilger
2016-05-03 15:53   ` David Howells
2016-05-04 22:56   ` Dave Chinner
2016-05-05  0:09     ` NeilBrown
2016-05-05  0:09       ` NeilBrown
2016-05-05 19:48       ` Jeff Layton
2016-05-06 18:07         ` J. Bruce Fields
2016-05-06 18:07           ` J. Bruce Fields
2016-05-05 20:04       ` David Howells
2016-05-05 20:04         ` David Howells
2016-05-06  1:39         ` Dave Chinner
2016-05-06  1:39           ` Dave Chinner
2016-05-06  1:39           ` Dave Chinner
2016-05-06 18:29     ` J. Bruce Fields
2016-05-09  1:45       ` Dave Chinner
2016-05-09  2:46         ` J. Bruce Fields
2016-05-04 23:56   ` NeilBrown [this message]
2016-05-08  8:35   ` Christoph Hellwig
2016-05-08  8:35     ` Christoph Hellwig
2016-05-09 12:02     ` Jeff Layton
2016-05-09 12:02       ` Jeff Layton
2016-05-10  7:00       ` Christoph Hellwig
2016-05-10  7:00         ` Christoph Hellwig
2016-05-10 13:21         ` Jeff Layton
2016-05-10 13:21           ` Jeff Layton
2016-05-09 12:57   ` David Howells
2016-05-09 12:57     ` David Howells
2016-05-09 13:23     ` Trond Myklebust
2016-05-09 13:23       ` Trond Myklebust
2016-05-09 13:23       ` Trond Myklebust
2016-05-10  7:04     ` Christoph Hellwig
2016-05-10  8:25     ` David Howells
2016-05-12  9:11       ` Christoph Hellwig
2016-05-13 15:28         ` Arnd Bergmann
2016-05-13 15:28           ` Arnd Bergmann
2016-05-23  8:22           ` Christoph Hellwig
2016-05-23  9:33           ` David Howells
2016-05-18 10:55         ` David Howells
2016-05-09 13:00   ` David Howells
2016-05-09 13:00     ` David Howells
2016-05-09 13:38   ` David Howells
2016-05-10  7:08     ` Christoph Hellwig
2016-05-10  8:43     ` David Howells
2016-05-12  9:12       ` Christoph Hellwig
2016-05-09 13:40   ` David Howells
2016-04-29 12:57 ` [PATCH 2/6] statx: AFS: Return enhanced file attributes David Howells
2016-04-29 12:57 ` [PATCH 3/6] statx: Ext4: " David Howells
2016-05-02 22:48   ` Andreas Dilger
2016-05-03 20:24   ` David Howells
2016-05-03 20:24     ` David Howells
2016-05-08  8:38   ` Christoph Hellwig
2016-05-08  8:38     ` Christoph Hellwig
2016-04-29 12:58 ` [PATCH 4/6] statx: NFS: " David Howells
2016-05-02 22:48   ` Andreas Dilger
2016-04-29 12:58 ` [PATCH 5/6] statx: Make windows attributes available for CIFS, NTFS and FAT to use David Howells
2016-05-02 22:52   ` Andreas Dilger
2016-10-03 21:03     ` Steve French
2016-10-03 21:03       ` Steve French
2016-05-03 20:23   ` David Howells
2016-05-08  8:39   ` Christoph Hellwig
2016-05-08  8:39     ` Christoph Hellwig
2016-04-29 12:58 ` [PATCH 6/6] statx: CIFS: Return enhanced attributes David Howells
2016-04-30 21:05 ` [RFC][PATCH 0/6] Enhanced file stat system call Jeff Layton
2016-04-30 21:05   ` Jeff Layton
2016-05-04 13:46 ` Arnd Bergmann
2016-05-04 13:46   ` Arnd Bergmann
2016-05-05 22:54   ` Steve French
2016-05-06  2:00     ` Steve French
2016-05-09 13:09       ` Arnd Bergmann
2016-05-09 13:09         ` Arnd Bergmann
2016-05-13 14:28         ` Richard Sharpe
2016-05-13 14:28           ` Richard Sharpe
2016-05-13 15:08           ` Arnd Bergmann

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