Subject: Crash in -next due to 'drivers/of: Fix depth when unflattening devicetree'

From: Guenter Roeck <[email-masked]>
Date: Wed, 18 May 2016 20:11:12 -0700

Hi,

some of my ppc qemu tests crash with the following log message.

VFS: Cannot open root device "hda" or unknown-block(0,0): error -6
Please append a correct "root=" boot option; here are the available partitions:
0100            4096 ram0  (driver?)
0101            4096 ram1  (driver?)
0102            4096 ram2  (driver?)
0103            4096 ram3  (driver?)
0104            4096 ram4  (driver?)
0105            4096 ram5  (driver?)
0106            4096 ram6  (driver?)
0107            4096 ram7  (driver?)
0108            4096 ram8  (driver?)
0109            4096 ram9  (driver?)
010a            4096 ram10  (driver?)
010b            4096 ram11  (driver?)
010c            4096 ram12  (driver?)
010d            4096 ram13  (driver?)
010e            4096 ram14  (driver?)
010f            4096 ram15  (driver?)
1600            8383 hdc  driver: ide-gd
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

A complete boot log is available at
http://kerneltests.org/builders/qemu-ppc-next/builds/408/steps/qemubuildcommand/logs/stdio

Bisect points to commit 'drivers/of: Fix depth when unflattening devicetree'.
Reverting this commit fixes the problem. Bisect log is attached.

The scripts and root file system used for the test are available at
https://github.com/groeck/linux-build-test/tree/master/rootfs/ppc

Failing tests are 

powerpc:mac99:nosmp:ppc_book3s_defconfig
powerpc:g3beige:nosmp:ppc_book3s_defconfig
powerpc:mac99:smp:ppc_book3s_defconfig

Guenter

---
# bad: [1af872fb6cfb3c701d8819466a4672f85c3f17a3] dcssblk: fix the direct_access prototype to add 'size'
# good: [2dcd0af568b0cf583645c8a317dd12e344b1c72a] Linux 4.6
git bisect start 'HEAD' 'v4.6'
# good: [586cf328ff7e7c0c32f89d6f2063c81143802c01] Merge remote-tracking branch 'net-next/master'
git bisect good 586cf328ff7e7c0c32f89d6f2063c81143802c01
# bad: [69bf2b19c358d937a3f40c07a08bc73476d43c02] Merge remote-tracking branch 'tty/tty-next'
git bisect bad 69bf2b19c358d937a3f40c07a08bc73476d43c02
# good: [c81e18989b12bdb70a056b05b94620eefd2aed7b] Merge remote-tracking branch 'drm/drm-next'
git bisect good c81e18989b12bdb70a056b05b94620eefd2aed7b
# good: [4668e9adc5722b6fdf887d0bc70e9f5998507689] Merge remote-tracking branch 'vfio/next'
git bisect good 4668e9adc5722b6fdf887d0bc70e9f5998507689
# bad: [8ab5e17d29971673f08ce9cabfa6170e2f56fe07] Merge remote-tracking branch 'ftrace/for-next'
git bisect bad 8ab5e17d29971673f08ce9cabfa6170e2f56fe07
# bad: [a792d9ada26755882a5ea1e958bc582fe6f2d7bc] Merge remote-tracking branch 'dt-rh/for-next'
git bisect bad a792d9ada26755882a5ea1e958bc582fe6f2d7bc
# good: [03da37387a3aa07e45d077043f48e7dc29206b62] Merge remote-tracking branch 'trivial/for-next'
git bisect good 03da37387a3aa07e45d077043f48e7dc29206b62
# good: [8f97c2814b5448d91a3c67081f7d978c097feabe] Documentation: dt: interrupt-controller: fix spelling mistakes
git bisect good 8f97c2814b5448d91a3c67081f7d978c097feabe
# good: [947c82cbf01c9c6012cb96e385b5f6d6d1e1decb] drivers/of: Rename unflatten_dt_node()
git bisect good 947c82cbf01c9c6012cb96e385b5f6d6d1e1decb
# bad: [047eb65024c00807ff8f0407580f088b23cf908e] of/unittest: Remove unnecessary module.h header inclusion
git bisect bad 047eb65024c00807ff8f0407580f088b23cf908e
# good: [bb91f923d176578257aed682047653cc33148413] drivers/of: Export of_detach_node()
git bisect good bb91f923d176578257aed682047653cc33148413
# bad: [ac78f9bdcf3836cafcd114a76a9473380a3faef5] drivers/of: Fix depth when unflattening devicetree
git bisect bad ac78f9bdcf3836cafcd114a76a9473380a3faef5
# good: [b9c43856f21d97ffdfdd642acf2eb0b52d3b1555] of: dynamic: changeset prop-update revert fix
git bisect good b9c43856f21d97ffdfdd642acf2eb0b52d3b1555
# first bad commit: [ac78f9bdcf3836cafcd114a76a9473380a3faef5] drivers/of: Fix depth when unflattening devicetree