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quota: RFC SMP improvements for generic quota V2

From:  Dmitry Monakhov <>
Subject:  [PATCH 00/19] quota: RFC SMP improvements for generic quota V2
Date:  Fri, 22 Oct 2010 21:34:45 +0400
Message-ID:  <>
Cc:,, Dmitry Monakhov <>
Archive-link:  Article

 This patch set is my attempt to make quota code more scalable.
 Main goal of this patch-set is to split global locking to per-sb basis.
 Actually it consists of several parts
 * Fixes : trivial fixes which i hope will be accepted w/o any complain
 * Splitup global locks: Imho this part clean and simple. I hope it is
   also a sane candidate for for_testing branch.
 * More scalability for single sb : Some of this patches was already
   submitted previously, some wasn't. This part is just my first vision
   of the way we can move. This way result in real speedup, but i'm not
   shure about design solutions, please do not punch me too strong
   if you dont like that direction.

 This patch-set survived after some stress testing
  * parallel quota{on,off}
  * fssress
  * triggering ENOSPC

Performance: I've prepared some basic benchmarks results

Changes from V1
   * random fixes according to Jan's comments
     + fix spelling
     + fix deadlock on dquot_transfer, and lock_dep issues
     - list_lock patches split is still the same as before.
   *  move quota data from sb to dedicated pointer.
   *  Basic improvements fore per-sb scalability

patch against 2.6.36-rc5, linux-fs-2.6.git for_testing branch
      quota: protect getfmt call with dqonoff_mutex lock
<Splitup global locks>
      quota: Wrap common expression to  helper function
      quota: mode quota internals from sb to quota_info
      quota: Convert dq_state_lock to per-sb dq_state_lock
      quota: add quota format lock
      quota: make dquot lists per-sb
      quota: make per-sb hash array
      quota: remove global dq_list_lock
<More scalability for single sb>
      quota: rename dq_lock
      quota: make per-sb dq_data_lock
      quota: protect dquot mem info with object's lock
      quota: drop dq_data_lock where possible
      quota: relax dq_data_lock dq_lock locking consistency
      quota: protect dqget() from parallels quotaoff via RCU
      quota: remove dq_state_lock
      fs: add unlocked helpers
      quota: Some stylistic cleanup for dquot interface
      quota: remove dqptr_sem
      quota: redesign dquot reference counting

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