linux-kernel - [PATCH] initramfs: Fix initramfs rebuilds w/ compression after disabling

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Date:   Fri, 29 Sep 2017 20:39:35 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "Francisco Blas Izquierdo Riera (klondike)" <klondike@...ndike.es>,
        Nicholas Piggin <npiggin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] initramfs: Fix initramfs rebuilds w/ compression after disabling

This is a follow-up to commit 57ddfdaa9a72 ("initramfs: fix disabling of
initramfs (and its compression)"). This particular commit fixed the use case
where we build the kernel with an initramfs with no compression, and then we
build the kernel with no initramfs.

Now this still left us with the same case as described here:
http://lkml.kernel.org/r/20170521033337.6197-1-f.fainelli@gmail.com
not working with initramfs compression. This can be seen by the following
steps/timestamps:

https://www.spinics.net/lists/kernel/msg2598153.html

.initramfs_data.cpio.gz.cmd is correct:

cmd_usr/initramfs_data.cpio.gz := /bin/bash
./scripts/gen_initramfs_list.sh -o usr/initramfs_data.cpio.gz  -u 1000
-g 1000  /home/fainelli/work/uclinux-rootfs/romfs
/home/fainelli/work/uclinux-rootfs/misc/initramfs.dev

and was generated the first time we did generate the gzip initramfs, so the
command has not changed, nor its arguments, so we just don't call it, no
initramfs cpio is re-generated as a consequence.

The fix for this problem is just to properly keep track of the
.initramfs_cpio_data.d file by suffixing it with the compression extension.
This takes care of properly tracking dependencies such that the initramfs get
(re)generated any time files are added/deleted etc.

Fixes: db2aa7fd15e8 ("initramfs: allow again choice of the embedded initramfs compression algorithm")
Fixes: 9e3596b0c653 ("kbuild: initramfs cleanup, set target from Kconfig")
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 usr/Makefile | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/usr/Makefile b/usr/Makefile
index 0b87e71c00fc..2d7d7f4b91f1 100644
--- a/usr/Makefile
+++ b/usr/Makefile
@@ -7,6 +7,7 @@ PHONY += klibcdirs
 
 suffix_y = $(subst $\",,$(CONFIG_INITRAMFS_COMPRESSION))
 datafile_y = initramfs_data.cpio$(suffix_y)
+datafile_d_y = .$(datafile_y).d
 AFLAGS_initramfs_data.o += -DINITRAMFS_IMAGE="usr/$(datafile_y)"
 
 
@@ -29,12 +30,12 @@ ramfs-args  := \
         $(if $(CONFIG_INITRAMFS_ROOT_UID), -u $(CONFIG_INITRAMFS_ROOT_UID)) \
         $(if $(CONFIG_INITRAMFS_ROOT_GID), -g $(CONFIG_INITRAMFS_ROOT_GID))
 
-# .initramfs_data.cpio.d is used to identify all files included
+# $(datafile_d_y) is used to identify all files included
 # in initramfs and to detect if any files are added/removed.
 # Removed files are identified by directory timestamp being updated
 # The dependency list is generated by gen_initramfs.sh -l
-ifneq ($(wildcard $(obj)/.initramfs_data.cpio.d),)
-	include $(obj)/.initramfs_data.cpio.d
+ifneq ($(wildcard $(obj)/$(datafile_d_y)),)
+	include $(obj)/$(datafile_d_y)
 endif
 
 quiet_cmd_initfs = GEN     $@
@@ -52,5 +53,5 @@ $(deps_initramfs): klibcdirs
 # 3) If gen_init_cpio are newer than initramfs_data.cpio
 # 4) arguments to gen_initramfs.sh changes
 $(obj)/$(datafile_y): $(obj)/gen_init_cpio $(deps_initramfs) klibcdirs
-	$(Q)$(initramfs) -l $(ramfs-input) > $(obj)/.initramfs_data.cpio.d
+	$(Q)$(initramfs) -l $(ramfs-input) > $(obj)/$(datafile_d_y)
 	$(call if_changed,initfs)
-- 
2.11.0