init: open output files from cpio unpacking with O_LARGEFILE

If a member of a cpio archive for an initrd or initrams is larger than
2Gb, we'll eventually fail to write to that file when we get to that
limit, unless O_LARGEFILE is set.

The problem can be seen with this recipe, assuming that BLK_DEV_RAM
is not configured:

cd /tmp
dd if=/dev/zero of=BIGFILE bs=1048576 count=2200
echo BIGFILE | cpio -o -H newc -R root:root > initrd.img
kexec -l /boot/vmlinuz-$(uname -r) --initrd=initrd.img --reuse-cmdline
kexec -e

The console will show 'Initramfs unpacking failed: write error'.  With
the patch, the error is gone.

Link: https://lkml.kernel.org/r/20240323152934.3307391-1-jsperbeck@google.comSigned-off-by: John Sperbeck <jsperbeck@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

init/initramfs.c

@@ -367,7 +367,7 @@ static int __init do_name(void)
 	if (S_ISREG(mode)) {
 		int ml = maybe_link();
 		if (ml >= 0) {
-			int openflags = O_WRONLY|O_CREAT;
+			int openflags = O_WRONLY|O_CREAT|O_LARGEFILE;
 			if (ml != 1)
 				openflags |= O_TRUNC;
 			wfile = filp_open(collected, openflags, mode);