From: Neil Brown <neilb@suse.de>
To: Bastien ROUCARIES <roucaries.bastien@gmail.com>
Cc: Andreas Dilger <andreas.dilger@oracle.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
"adilger@sun.com" <adilger@sun.com>,
"corbet@lwn.net" <corbet@lwn.net>,
"npiggin@kernel.dk" <npiggin@kernel.dk>,
"hooanon05@yahoo.co.jp" <hooanon05@yahoo.co.jp>,
"bfields@fieldses.org" <bfields@fieldses.org>,
"miklos@szeredi.hu" <miklos@szeredi.hu>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"sfrench@us.ibm.com" <sfrench@us.ibm.com>,
"philippe.deniel@CEA.FR" <philippe.deniel@cea.fr>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -V18 04/13] vfs: Allow handle based open on symlinks
Date: Wed, 25 Aug 2010 12:04:13 +1000 [thread overview]
Message-ID: <20100825120413.7d5c5994@notabene> (raw)
In-Reply-To: <AANLkTi=vYJDT_6YrfugE1N-k0Sj+abQBw7vQeG1GPhUP@mail.gmail.com>
On Tue, 24 Aug 2010 11:41:10 +0200
Bastien ROUCARIES <roucaries.bastien@gmail.com> wrote:
> On Mon, Aug 23, 2010 at 1:06 AM, Neil Brown <neilb@suse.de> wrote:
> > On Sat, 21 Aug 2010 01:13:52 -0600
> > Andreas Dilger <andreas.dilger@oracle.com> wrote:
> >
> >> On 2010-08-20, at 18:09, Neil Brown <neilb@suse.de> wrote:
> >> > How about a new AT flag: AT_FILE_HANDLE
> >> >
> >> > Meaning is that the 'dirfd' is used only to identify a filesystem (vfsmnt) and
> >> > the 'name' pointer actually points to a filehandle fragment interpreted in
> >> > that filesystem.
>
> Why ot creating a special file system for this kind of operation ?
> I mean a vfsmnt filesystem, with each directory on the root is a
> symlink to the root of the real vfsmnt root ?
>
> I could be even be in proc space like /proc/self/vfsmnt
>
> path_to_handle will return a relative path from this directory like
> 0x75843558/somehandle (if X is on /usr/bin/X and usr is mounted by
> filesystem 0x75843558)
> path_to_fshandle() will return 0x75843558
>
> opening file handle will be just a matter to thus open
> /proc/self/vfsmount/0x75843558/somehandle
>
> Permission will be determined by vfsmount filesystem.
>
> No need to create new syscall all te handle to filename will be handle
> by the vfsmount filesystem
>
> We could even use at existing command. The dirfd will need to be only
> /proc/self/vfsmnt (and if you need to get a fd without mounting /proc
> create a syscall to get this fd).
>
> Does sound plausible ?
>
I don't think so.
I'm not 100% certain what you are proposing, but I think the basic idea is a
virtual filesystem where giving a textual filehandle as a name gives access
to the file with that filehandle.
This could only work by creating a virtual symlink from the name to the
object in whichever filesystem - somewhat like /proc/self/fd/*.
This could be used to open the file, not to create a hard-link or read a
symlink which are two of the issues we are struggling with.
Maybe I have misunderstood you though.
NeilBrown
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next prev parent reply other threads:[~2010-08-25 2:04 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-20 1:51 [PATCH -V18 0/13] Generic name to handle and open by handle syscalls Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 01/13] exportfs: Return the minimum required handle size Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 02/13] vfs: Add name to file handle conversion support Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 03/13] vfs: Add open by file handle support Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 04/13] vfs: Allow handle based open on symlinks Aneesh Kumar K.V
2010-08-20 2:13 ` Aneesh Kumar K. V
2010-08-20 6:53 ` Aneesh Kumar K. V
2010-08-20 8:30 ` Christoph Hellwig
2010-08-20 9:53 ` Neil Brown
2010-08-20 11:51 ` Al Viro
2010-08-21 0:09 ` Neil Brown
2010-08-21 7:13 ` Andreas Dilger
2010-08-21 9:32 ` Aneesh Kumar K. V
2010-08-22 23:06 ` Neil Brown
2010-08-23 1:24 ` Aneesh Kumar K. V
2010-08-23 1:52 ` Neil Brown
2010-08-24 10:40 ` Aneesh Kumar K. V
2010-08-23 2:49 ` Aneesh Kumar K. V
2010-08-25 2:06 ` Neil Brown
2010-08-24 9:41 ` Bastien ROUCARIES
2010-08-25 2:04 ` Neil Brown [this message]
2010-08-25 9:13 ` Bastien ROUCARIES
2010-08-21 8:30 ` Nick Piggin
2010-08-21 9:42 ` Aneesh Kumar K. V
2010-08-22 2:02 ` Aneesh Kumar K. V
2010-08-24 7:21 ` Nick Piggin
2010-08-24 10:34 ` Aneesh Kumar K. V
2010-08-24 13:19 ` J. Bruce Fields
2010-08-22 23:17 ` Neil Brown
2010-08-24 7:29 ` Nick Piggin
2010-08-21 9:31 ` Aneesh Kumar K. V
2010-08-20 13:25 ` Peter Zijlstra
2010-08-20 23:47 ` Neil Brown
2010-08-20 14:38 ` Aneesh Kumar K. V
2010-08-20 1:51 ` [PATCH -V18 05/13] vfs: Support null pathname in readlink Aneesh Kumar K.V
2010-08-20 8:32 ` Christoph Hellwig
2010-08-20 10:04 ` Neil Brown
2010-08-20 14:43 ` Aneesh Kumar K. V
2010-08-20 1:51 ` [PATCH -V18 06/13] vfs: Support null pathname in faccessat Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 07/13] vfs: Support null pathname in linkat Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 08/13] x86: Add new syscalls for x86_32 Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 09/13] x86: Add new syscalls for x86_64 Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 10/13] unistd.h: Add new syscalls numbers to asm-generic Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 11/13] vfs: Export file system uuid via /proc/<pid>/mountinfo Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 12/13] ext3: Copy fs UUID to superblock Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 13/13] ext4: " Aneesh Kumar K.V
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