[PATCH RFC 0/13] fs: generic filesystem shutdown handling

[Jan Kara <jack@suse.cz>]

Hello,

this patch series implements generic handling of filesystem shutdown. The idea
is very simple: Have a superblock flag, which when set, will make VFS refuse
modifications to the filesystem. The patch series consists of several parts.
Patches 1-6 cleanup handling of SB_I_ flags which is currently messy (different
flags seem to have different locks protecting them although they are modified
by plain stores). Patches 7-12 gradually convert code to be able to handle
errors from sb_start_write() / sb_start_pagefault(). Patch 13 then shows how
filesystems can use this generic flag. Additionally, we could remove some
shutdown checks from within ext4 code and rely on checks in VFS but I didn't
want to complicate the series with ext4 specific things.

Also, as Dave suggested, we can lift *_IOC_{SHUTDOWN|GOINGDOWN} ioctl handling
to VFS (currently in 5 filesystems) and just call new ->shutdown op for
the filesystem abort handling itself. But that is kind of independent thing
and this series is long enough as is.

So what do people think?

								Honza