Re: add file system helpers that take kernel pointers for the init code v4
From: Qian Cai
Date: Mon Aug 03 2020 - 10:56:29 EST
On Tue, Jul 28, 2020 at 06:33:53PM +0200, Christoph Hellwig wrote:
> Hi Al and Linus,
> currently a lot of the file system calls in the early in code (and the
> devtmpfs kthread) rely on the implicit set_fs(KERNEL_DS) during boot.
> This is one of the few last remaining places we need to deal with to kill
> off set_fs entirely, so this series adds new helpers that take kernel
> pointers. These helpers are in init/ and marked __init and thus will
> be discarded after bootup. A few also need to be duplicated in devtmpfs,
> though unfortunately.
Reverting this series from next-20200803 fixed the crash below on shutdown.
[ 7303.287890][ T1] systemd-shutdown: All loop devices detached.
[ 7303.287930][ T1] systemd-shutdown: Detaching DM devices.
[ 7303.441674][ T1] printk: shutdown: 9 output lines suppressed due to ratelimiting
[ 7303.443999][ T1] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000100
[ 7303.444027][ T1] CPU: 120 PID: 1 Comm: shutdown Not tainted 5.8.0-next-20200803 #2
[ 7303.444053][ T1] Call Trace:
[ 7303.444069][ T1] [c000000015d27b70] [c0000000006f3778] dump_stack+0xfc/0x174 (unreliable)
[ 7303.444103][ T1] [c000000015d27bc0] [c0000000000c9328] panic+0x214/0x4ac
[ 7303.444140][ T1] [c000000015d27c60] [c0000000000d4d28] do_exit+0xda8/0xee0
[ 7303.444178][ T1] [c000000015d27d60] [c0000000000d4f1c] do_group_exit+0x5c/0xd0
list_empty at include/linux/list.h:282
(inlined by) thread_group_empty at include/linux/sched/signal.h:671
(inlined by) do_group_exit at kernel/exit.c:888
[ 7303.444205][ T1] [c000000015d27da0] [c0000000000d4fac] sys_exit_group+0x1c/0x20
sys_exit_group at kernel/exit.c:914
[ 7303.444234][ T1] [c000000015d27dc0] [c00000000002c628] system_call_exception+0xf8/0x1d0
[ 7303.444262][ T1] [c000000015d27e20] [c00000000000d0a8] system_call_common+0xe8/0x218
[ 7304.936912][ T1] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000100 ]---
> The series sits on top of my previous
> "decruft the early init / initrd / initramfs code v2"
> Git tree:
> git://git.infradead.org/users/hch/misc.git init_path
> Changes since v3:
> - rename fs/for_init.c to fs/init.c
> - document the purpose of the routines in fs/init.c with a comment
> - don't mark devtmpfs __init as that will cause it to get overwritten
> by initmem poisoning
> - add an init_dup helper to make Al more happy than with the version
> commit to the "decruft the early init / initrd / initramfs code v2"
> Changes since v2:
> - move to fs/for_init.c
> - reuse the init routines in devtmpfs after refactoring devtmpfsd
> (and thus the broken error handling in the previous version)
> - actually use kern_path in a place where user_path_at sneaked back in
> Changes since v1:
> - avoid most core VFS changes
> - renamed the functions and move them to init/ and devtmpfs
> - drop a bunch of cleanups that can be submitted independently now