linux-kernel - Re: [PATCH -V16 07/12] vfs: Support null pathname in linkat

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Date:	Mon, 12 Jul 2010 16:28:53 +0530
From:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	hch@...radead.org, viro@...iv.linux.org.uk, adilger@....com,
	corbet@....net, neilb@...e.de, npiggin@...e.de,
	hooanon05@...oo.co.jp, bfields@...ldses.org,
	linux-fsdevel@...r.kernel.org, sfrench@...ibm.com,
	philippe.deniel@....FR, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V16 07/12] vfs: Support null pathname in linkat

On Mon, 12 Jul 2010 10:05:39 +0200, Miklos Szeredi <miklos@...redi.hu> wrote:
> On Mon, 12 Jul 2010, Aneesh Kumar K.V wrote:
> > This enables to use linkat to create hardlinks from a
> > file descriptor pointing to the file. This can be used
> > with open_by_handle syscall that returns a file descriptor.
> 
> This needs more thought, filesystems don't usually tolerate
> resurrecting a file which has already been unlinked (i_nlink == 0).
> 

We get -ENOENT error when we do that on ext*

open("test", O_RDONLY)                  = 3
unlink("test")                          = 0
linkat(3, NULL, AT_FDCWD, "test3", 0)   = -1 ENOENT (No such file or directory)

ext4_link does the below

/*
 * Return -ENOENT if we've raced with unlink and i_nlink is 0.  Doing
 * otherwise has the potential to corrupt the orphan inode list.
 */
if (inode->i_nlink == 0)
	return -ENOENT;

I can move this check to VFS so that we do it for all file systems. 

-aneesh
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