linux-kernel - [PATCH] initramfs: Fix initramfs to work with hardlinked init.

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Message-ID: <20090406034420.GB13424@vmware.com>
Date:	Sun, 5 Apr 2009 20:44:20 -0700
From:	Randy Robertson <rmrobert@...are.com>
To:	linux-kernel@...r.kernel.org
Cc:	David Howells <dhowells@...hat.com>
Subject: [PATCH] initramfs: Fix initramfs to work with hardlinked init.

Change cb6ff208076b5f434db1b8c983429269d719cef5 seems to have broken
booting from initramfs with /sbin/init being a hardlink.  It seems like
the logic required for XIP on nommu, i.e. ftruncate to reported cpio
header file size (body_len) is broken for hardlinks, which have
a reported size of 0, and the truncate thus nukes the contents of the
file (in my case busybox), making boot impossible and ending with runaway
loop modprobe binfmt-0000 - and of course 0000 is not a valid binary format.

My fix is to only call ftruncate if size is non-zero which fixes things
for me, but I'm not certain whether this will break XIP for those files
on nommu systems, although I would guess not.

Signed-off-by: Randy Robertson <rmrobert@...are.com>
---
diff --git a/init/initramfs.c b/init/initramfs.c
index d9c941c..4675f62 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -317,7 +317,8 @@ static int __init do_name(void)
			if (wfd >= 0) {
				sys_fchown(wfd, uid, gid);
				sys_fchmod(wfd, mode);
-			       sys_ftruncate(wfd, body_len);
+			       if (body_len)
+				       sys_ftruncate(wfd, body_len);
				vcollected = kstrdup(collected, GFP_KERNEL);
				state = CopyFile;
			}
--
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