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Subject[PATCH v2 0/8] Add rcu_sync infrastructure to avoid _expedited() in percpu-rwsem
Hello,

Now that sb->s_writers was changed to use percpu_rw_semaphore let me
send v2.

Changes:

- whitespace fix in 1/8.

- remove EXPORT_SYMBOL() in 3/8, currently rcu_sync has no
modular users.

- 5/8 is new. This ugly hack pairs with another one:
"shift percpu_counter_destroy() into destroy_super_work()"
https://git.kernel.org/cgit/linux/kernel/git/viro/vfs.git/commit/?h=for-next&id=853b39a7c82826b8413048feec7bf08e98ce7a84
They both will be reverted later.

The problem is that we have 2 series routed via different
trees, RCU and VFS. We need this hack to ensure that this
series won't break alloc_super() which currently assumes that
destroy_super()->percpu_free_rwsem() is safe after kzalloc().
This way these 2 series do not depend on each other, we can
test/change/revert/etc them independently.

We will add rcu_sync_dtor() into deactivate_locked_super()
later and revert both hacks.
Oleg.

include/linux/percpu-rwsem.h | 3 +-
include/linux/rcusync.h | 56 +++++++++++++++
kernel/locking/percpu-rwsem.c | 85 ++++++++---------------
kernel/rcu/Makefile | 2 +-
kernel/rcu/sync.c | 151 +++++++++++++++++++++++++++++++++++++++++
5 files changed, 240 insertions(+), 57 deletions(-)



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