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c5cbbec54f
linux/include
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Tejun Heo c5cbbec54f writeback: flush inode cgroup wb switches instead of pinning super_block 
commit a1a0e23e49 upstream.

If cgroup writeback is in use, inodes can be scheduled for
asynchronous wb switching.  Before 5ff8eaac16 ("writeback: keep
superblock pinned during cgroup writeback association switches"), this
could race with umount leading to super_block being destroyed while
inodes are pinned for wb switching.  5ff8eaac16 fixed it by bumping
s_active while wb switches are in flight; however, this allowed
in-flight wb switches to make umounts asynchronous when the userland
expected synchronosity - e.g. fsck immediately following umount may
fail because the device is still busy.

This patch removes the problematic super_block pinning and instead
makes generic_shutdown_super() flush in-flight wb switches.  wb
switches are now executed on a dedicated isw_wq so that they can be
flushed and isw_nr_in_flight keeps track of the number of in-flight wb
switches so that flushing can be avoided in most cases.

v2: Move cgroup_writeback_umount() further below and add MS_ACTIVE
    check in inode_switch_wbs() as Jan an Al suggested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Tahsin Erdogan <tahsin@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Link: http://lkml.kernel.org/g/CAAeU0aNCq7LGODvVGRU-oU_o-6enii5ey0p1c26D1ZzYwkDc5A@mail.gmail.com
Fixes: 5ff8eaac16 ("writeback: keep superblock pinned during cgroup writeback association switches")
Reviewed-by: Jan Kara <jack@suse.cz>
Tested-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-03-09 15:34:52 -08:00
..
acpi Merge branch 'acpi-pci' 2015-11-07 01:30:10 +01:00
asm-generic cputime: Prevent 32bit overflow in time[val|spec]_to_cputime() 2016-03-03 15:07:16 -08:00
clocksource
crypto crypto: af_alg - Allow af_af_alg_release_parent to be called on nokey path 2016-02-17 12:31:03 -08:00
drm drm: add helper to check for wc memory support 2016-03-03 15:07:21 -08:00
dt-bindings ARM: DT updates for v4.4 2015-11-10 15:06:26 -08:00
keys
kvm KVM: arm/arm64: arch_timer: Preserve physical dist. active state on LR.active 2015-11-24 18:07:40 +01:00
linux writeback: flush inode cgroup wb switches instead of pinning super_block 2016-03-09 15:34:52 -08:00
math-emu
media
memory
misc
net tcp/dccp: fix another race at listener dismantle 2016-03-03 15:07:07 -08:00
pcmcia
ras
rdma IB/mad: Require CM send method for everything except ClassPortInfo 2015-12-08 12:19:11 -05:00
rxrpc
scsi Merge branch 'mkp-fixes' into fixes 2015-12-03 09:32:33 -08:00
soc ARM: SoC driver updates for v4.4 2015-11-10 15:00:03 -08:00
sound ALSA: rawmidi: Make snd_rawmidi_transmit() race-free 2016-02-17 12:30:58 -08:00
target target: Fix WRITE_SAME/DISCARD conversion to linux 512b sectors 2016-03-09 15:34:51 -08:00
trace Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux 2015-11-11 09:03:01 -08:00
uapi uapi: update install list after nvme.h rename 2016-03-03 15:07:24 -08:00
video gpu: ipu-v3: drop unused dmfc field from client platform data 2015-11-24 11:30:15 +01:00
xen xen: Add RING_COPY_REQUEST() 2015-12-18 10:00:17 -05:00
Kbuild