Patch: romfs_lookup always failed in linux-2.6.25-rc3-git3

From: "Adam J. Richter" <adam@yggdrasil.com>
To: dhowells@redhat.com
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Patch: romfs_lookup always failed in linux-2.6.25-rc3-git3
Date: Mon, 3 Mar 2008 09:36:20 -0800	[thread overview]
Message-ID: <20080303173620.GA9243@freya.fugue.com> (raw)

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Hi David,

	romfs_lookup worked in 2.6.24.2, but always fails in
linux-2.6.25-rc3-git3.  fs/romfs/inode.c is the same in at least
2.6.25-rc3 through 2.6.25-rc3-git4 and the latest sources from git, so
these versions almost certainly have the same problem.

	The bug appears to be from a well meaning but botched attempt
to eliminate a goto from romfs_lookup.  Previously, a goto statement
was used to skip over "inode = NULL;" when the lookup succeeded.  In
the 2.6.25-rc3 version, inode is set to NULL even when an inode was
found, so the result is the the lookup always appears to fail.

	 The attached patch fixes the problem while still eliminating
the goto.  The patch adds one line and replaces one line.  It only
looks big because I've set the number of context lines to 10 for
better readability.  I have tested it in on a romfs initial ramdisk
which on which I had experienced the problem.

	If this patch looks OK to you, can you please submit it
upstream?

P.S. romfs_lookup casts a valid pointer to an int and then back again
with res = PTR_ERR(inode);...return ERR_PTR(res).  This may break on
arhictectures where sizeof(int) < sizeof(pointer).  If I want to submit
a subsequent fix for this, are you the person I should the patch to?

Adam Richter

[-- Attachment #2: romfs.diff --]
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diff -U 8 -r linux-2.6.25-rc3-git3/fs/romfs/inode.c linux/fs/romfs/inode.c

--- linux-2.6.25-rc3-git3/fs/romfs/inode.c	2008-03-03 09:05:38.000000000 -0800
+++ linux/fs/romfs/inode.c	2008-03-03 09:06:03.000000000 -0800
@@ -342,16 +342,17 @@
 	unsigned long offset, maxoff;
 	int fslen, res;
 	struct inode *inode;
 	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
 	struct romfs_inode ri;
 	const char *name;		/* got from dentry */
 	int len;
 
+	inode = NULL;
 	res = -EACCES;			/* placeholder for "no data here" */
 	offset = dir->i_ino & ROMFH_MASK;
 	lock_kernel();
 	if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
 		goto out;
 
 	maxoff = romfs_maxsize(dir->i_sb);
 	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
@@ -404,17 +405,17 @@
 	 * it's a bit funky, _lookup needs to return an error code
 	 * (negative) or a NULL, both as a dentry.  ENOENT should not
 	 * be returned, instead we need to create a negative dentry by
 	 * d_add(dentry, NULL); and return 0 as no error.
 	 * (Although as I see, it only matters on writable file
 	 * systems).
 	 */
 
-out0:	inode = NULL;
+out0:
 	res = 0;
 	d_add (dentry, inode);
 
 out:	unlock_kernel();
 	return ERR_PTR(res);
 }
 
 /*
