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From: Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>
To: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: arnd-r2nGTMty4D4@public.gmane.org,
	linux-afs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	samba-technical-w/Ol4Ecudpl8XjKLYN78aQ@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 02/12] statx: Provide IOC flags for Windows fs attributes
Date: Tue, 24 Nov 2015 14:52:56 -0500	[thread overview]
Message-ID: <20151124195256.GB3482@thunk.org> (raw)
In-Reply-To: <20151120145447.18930.5308.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>

On Fri, Nov 20, 2015 at 02:54:47PM +0000, David Howells wrote:
> Provide IOC flags for Windows fs attributes so that they can be retrieved (or
> even altered) using the FS_IOC_[GS]ETFLAGS ioctl and read using statx().

We have a real problem with numberspace used by FS_IOC_[GS]ETFLAGS.
This ioctl was originally defined for use with ext2, but then later on
other file systems decided they wanted to use the same ioctl for their
file system, and so now we have the situation where some of the bits
are used in a way where they are intended to be file system
independent, and some are file system specific.  And ext[234] use
these bits as its on-disk encoding --- which given that
FS_IOC[GS]ETFLAGS was originally ext[234] specific, is understandable,
but it makes things really messy at this point.

So for example, the bits you have chosen are in conflict with ext4's use:

#define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data. */
#define EXT4_PROJINHERIT_FL		0x20000000 /* Create with parents projid */

> +#define FS_HIDDEN_FL			0x10000000 /* Windows hidden file attribute */
> +#define FS_SYSTEM_FL			0x20000000 /* Windows system file attribute */
> +#define FS_ARCHIVE_FL			0x40000000 /* Windows archive file attribute */


As a result, I would suggest that we not try to use the
FS_IOC_[GS]ETFLAGS number scheme for any new interface, so we're at
least not making a bad situation worse.

The only reason why some other file systems have chosen to use
FS_IOC_[GS]ETFLAGS, instead of defining their own ioctl, is so they
can use lsattr/chattr from e2fsprogs instead of creating their own
utility.  But for statx, there isn't a good reason use the same flags
number space.  At the very least, can we use a new flags field for the
Windows file attributes?  It's not like lsattr/chattr has the ability
to set those flags today anyway.  So we might as well use a new flags
field and a new flags numberspace for them.

						- Ted

WARNING: multiple messages have this Message-ID
From: "Theodore Ts'o" <tytso@mit.edu>
To: David Howells <dhowells@redhat.com>
Cc: arnd@arndb.de, linux-afs@vger.kernel.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	samba-technical@lists.samba.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 02/12] statx: Provide IOC flags for Windows fs attributes
Date: Tue, 24 Nov 2015 14:52:56 -0500	[thread overview]
Message-ID: <20151124195256.GB3482@thunk.org> (raw)
In-Reply-To: <20151120145447.18930.5308.stgit@warthog.procyon.org.uk>

On Fri, Nov 20, 2015 at 02:54:47PM +0000, David Howells wrote:
> Provide IOC flags for Windows fs attributes so that they can be retrieved (or
> even altered) using the FS_IOC_[GS]ETFLAGS ioctl and read using statx().

We have a real problem with numberspace used by FS_IOC_[GS]ETFLAGS.
This ioctl was originally defined for use with ext2, but then later on
other file systems decided they wanted to use the same ioctl for their
file system, and so now we have the situation where some of the bits
are used in a way where they are intended to be file system
independent, and some are file system specific.  And ext[234] use
these bits as its on-disk encoding --- which given that
FS_IOC[GS]ETFLAGS was originally ext[234] specific, is understandable,
but it makes things really messy at this point.

So for example, the bits you have chosen are in conflict with ext4's use:

#define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data. */
#define EXT4_PROJINHERIT_FL		0x20000000 /* Create with parents projid */

> +#define FS_HIDDEN_FL			0x10000000 /* Windows hidden file attribute */
> +#define FS_SYSTEM_FL			0x20000000 /* Windows system file attribute */
> +#define FS_ARCHIVE_FL			0x40000000 /* Windows archive file attribute */


As a result, I would suggest that we not try to use the
FS_IOC_[GS]ETFLAGS number scheme for any new interface, so we're at
least not making a bad situation worse.

The only reason why some other file systems have chosen to use
FS_IOC_[GS]ETFLAGS, instead of defining their own ioctl, is so they
can use lsattr/chattr from e2fsprogs instead of creating their own
utility.  But for statx, there isn't a good reason use the same flags
number space.  At the very least, can we use a new flags field for the
Windows file attributes?  It's not like lsattr/chattr has the ability
to set those flags today anyway.  So we might as well use a new flags
field and a new flags numberspace for them.

						- Ted

  parent reply	other threads:[~2015-11-24 19:52 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-20 14:54 [RFC][PATCH 00/12] Enhanced file stat system call David Howells
2015-11-20 14:54 ` [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding David Howells
     [not found]   ` <20151120145434.18930.89755.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-24 17:37     ` Andreas Dilger
2015-11-24 17:37       ` Andreas Dilger
2015-11-24 19:36   ` Theodore Ts'o
     [not found]     ` <20151124193646.GA3482-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2015-11-24 20:10       ` Arnd Bergmann
2015-11-24 20:10         ` Arnd Bergmann
2015-11-29  2:45         ` Theodore Ts'o
2015-11-29  2:45           ` Theodore Ts'o
     [not found]           ` <20151129024555.GA31968-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2015-11-29 21:30             ` Arnd Bergmann
2015-11-29 21:30               ` Arnd Bergmann
2015-11-30 14:16               ` Theodore Ts'o
     [not found]                 ` <20151130141605.GA4316-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2015-11-30 14:37                   ` Arnd Bergmann
2015-11-30 14:37                     ` Arnd Bergmann
2015-11-30 14:46                 ` Elmar Stellnberger
2015-11-26 15:28       ` David Howells
2015-11-26 15:28         ` David Howells
2015-11-20 14:54 ` [PATCH 02/12] statx: Provide IOC flags for Windows fs attributes David Howells
     [not found]   ` <20151120145447.18930.5308.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-24 19:52     ` Theodore Ts'o [this message]
2015-11-24 19:52       ` Theodore Ts'o
2015-11-26 15:35   ` David Howells
     [not found]   ` <7976.1448552129-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-26 16:01     ` David Howells
2015-11-26 16:01       ` David Howells
2015-11-26 22:10     ` Andreas Dilger
2015-11-26 22:10       ` Andreas Dilger
2015-11-20 14:54 ` [PATCH 03/12] statx: Add a system call to make enhanced file info available David Howells
     [not found]   ` <20151120145457.18930.79678.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-24 20:21     ` Dave Chinner
2015-11-24 20:21       ` Dave Chinner
2015-12-04 12:06     ` Pavel Machek
2015-12-04 12:06       ` Pavel Machek
2015-12-21 23:21   ` David Howells
2015-11-20 14:55 ` [PATCH 04/12] statx: AFS: Return enhanced file attributes David Howells
2015-11-20 14:55 ` [PATCH 05/12] statx: Ext4: " David Howells
2015-11-20 14:55 ` [PATCH 06/12] statx: NFS: " David Howells
2015-11-20 14:55 ` [PATCH 07/12] statx: CIFS: Return enhanced attributes David Howells
2015-11-24 17:33   ` Steve French
2015-11-24 17:34   ` Steve French
2015-11-24 17:34     ` Steve French
2015-11-20 14:56 ` [PATCH 08/12] fsinfo: Add a system call to make enhanced filesystem info available David Howells
2015-11-20 14:56 ` [PATCH 09/12] fsinfo: Ext4: Return information through the filesystem info syscall David Howells
2015-11-20 14:56 ` [PATCH 10/12] fsinfo: AFS: " David Howells
2015-11-20 14:56 ` [PATCH 11/12] fsinfo: NFS: " David Howells
     [not found] ` <20151120145422.18930.72662.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-20 14:56   ` [PATCH 12/12] fsinfo: CIFS: " David Howells
2015-11-20 14:56     ` David Howells
2015-11-24  8:11   ` [RFC][PATCH 00/12] Enhanced file stat system call Christoph Hellwig
2015-11-24  8:11     ` Christoph Hellwig
2015-11-20 16:19 ` Martin Steigerwald
2015-11-24  8:13   ` Christoph Hellwig
2015-11-24  8:48     ` Martin Steigerwald
2015-11-24  8:50       ` Christoph Hellwig
2015-11-20 16:28 ` David Howells
2015-11-20 16:28   ` David Howells
2015-11-20 16:35   ` Martin Steigerwald
     [not found]   ` <4495.1448036915-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-25 17:51     ` J. Bruce Fields
2015-11-25 17:51       ` J. Bruce Fields
     [not found]       ` <20151125175153.GA30335-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2015-11-25 19:30         ` Andreas Dilger
2015-11-25 19:30           ` Andreas Dilger
2015-11-20 16:50 ` Casey Schaufler
     [not found]   ` <564F4F4E.8060603-iSGtlc1asvQWG2LlvL+J4A@public.gmane.org>
2015-11-24  8:15     ` Christoph Hellwig
2015-11-24  8:15       ` Christoph Hellwig
2015-11-24 14:43       ` Casey Schaufler
2015-11-24 16:28   ` Andreas Dilger
2015-11-26 15:19 ` David Howells
2015-11-26 22:06   ` Andreas Dilger

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