linux-toradex.git/include/linux/percpu_counter.h, branch v4.11-rc3

percpu_counter: batch size aware __percpu_counter_compare()

2015-05-28T21:39:34+00:00

XFS uses non-stanard batch sizes for avoiding frequent global
counter updates on it's allocated inode counters, as they increment
or decrement in batches of 64 inodes. Hence the standard percpu
counter batch of 32 means that the counter is effectively a global
counter. Currently Xfs uses a batch size of 128 so that it doesn't
take the global lock on every single modification.

However, Xfs also needs to compare accurately against zero, which
means we need to use percpu_counter_compare(), and that has a
hard-coded batch size of 32, and hence will spuriously fail to
detect when it is supposed to use precise comparisons and hence
the accounting goes wrong.

Add __percpu_counter_compare() to take a custom batch size so we can
use it sanely in XFS and factor percpu_counter_compare() to use it.

Signed-off-by: Dave Chinner 
Acked-by: Tejun Heo 
Signed-off-by: Dave Chinner

percpu_counter: add @gfp to percpu_counter_init()

2014-09-08T00:51:29+00:00

Percpu allocator now supports allocation mask.  Add @gfp to
percpu_counter_init() so that !GFP_KERNEL allocation masks can be used
with percpu_counters too.

We could have left percpu_counter_init() alone and added
percpu_counter_init_gfp(); however, the number of users isn't that
high and introducing _gfp variants to all percpu data structures would
be quite ugly, so let's just do the conversion.  This is the one with
the most users.  Other percpu data structures are a lot easier to
convert.

This patch doesn't make any functional difference.

Signed-off-by: Tejun Heo 
Acked-by: Jan Kara 
Acked-by: "David S. Miller" 
Cc: x86@kernel.org
Cc: Jens Axboe 
Cc: "Theodore Ts'o" 
Cc: Alexander Viro 
Cc: Andrew Morton

percpu_counter.h: comment code for better readability

2013-02-05T10:54:06+00:00

Help people reading the percpu_counter code, to notice the ifdef
else statement that seperates CONFIG_SMP.

Signed-off-by: Jesper Dangaard Brouer 
Acked-by: Tejun Heo 
Signed-off-by: Jiri Kosina

locking, percpu_counter: Annotate ::lock as raw

2011-09-13T09:11:47+00:00

The percpu_counter::lock can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Ingo Molnar

percpu_counter: change return value and add comments

2011-05-25T15:39:54+00:00

The percpu_counter_*_positive() API in UP case doesn't check if return
value is positive.  Add comments to explain why we don't.  Also if count <
0, returns 0 instead of 1 for *read_positive().

[akpm@linux-foundation.org: tweak comment]
Signed-off-by: Shaohua Li 
Acked-by: Eric Dumazet 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ext4: fix kernel oops if the journal superblock has a non-zero j_errno

2010-10-28T01:30:13+00:00

Commit 84061e0 fixed an accounting bug only to introduce the
possibility of a kernel OOPS if the journal has a non-zero j_errno
field indicating that the file system had detected a fs inconsistency.
After the journal replay, if the journal superblock indicates that the
file system has an error, this indication is transfered to the file
system and then ext4_commit_super() is called to write this to the
disk.

But since the percpu counters are now initialized after the journal
replay, the call to ext4_commit_super() will cause a kernel oops since
it needs to use the percpu counters the ext4 superblock structure.

The fix is to skip setting the ext4 free block and free inode fields
if the percpu counter has not been set.

Thanks to Ken Sumrall for reporting and analyzing the root causes of
this bug.

Addresses-Google-Bug: #3054080

Signed-off-by: "Theodore Ts'o"

tmpfs: add accurate compare function to percpu_counter library

2010-08-10T03:44:58+00:00

Add percpu_counter_compare that allows for a quick but accurate comparison
of percpu_counter with a given value.

A rough count is provided by the count field in percpu_counter structure,
without accounting for the other values stored in individual cpu counters.

The actual count is a sum of count and the cpu counters.  However, count
field is never different from the actual value by a factor of
batch*num_online_cpu.  We do not need to get actual count for comparison
if count is different from the given value by this factor and allows for
quick comparison without summing up all the per cpu counters.

Signed-off-by: Tim Chen 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2010-03-03T15:34:18+00:00

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu: add __percpu sparse annotations to what's left
  percpu: add __percpu sparse annotations to fs
  percpu: add __percpu sparse annotations to core kernel subsystems
  local_t: Remove leftover local.h
  this_cpu: Remove pageset_notifier
  this_cpu: Page allocator conversion
  percpu, x86: Generic inc / dec percpu instructions
  local_t: Move local.h include to ringbuffer.c and ring_buffer_benchmark.c
  module: Use this_cpu_xx to dynamically allocate counters
  local_t: Remove cpu_local_xx macros
  percpu: refactor the code in pcpu_[de]populate_chunk()
  percpu: remove compile warnings caused by __verify_pcpu_ptr()
  percpu: make accessors check for percpu pointer in sparse
  percpu: add __percpu for sparse.
  percpu: make access macros universal
  percpu: remove per_cpu__ prefix.

percpu: add __percpu sparse annotations to core kernel subsystems

2010-02-17T02:17:38+00:00

Add __percpu sparse annotations to core subsystems.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.

Signed-off-by: Tejun Heo 
Reviewed-by: Christoph Lameter 
Acked-by: Paul E. McKenney 
Cc: Jens Axboe 
Cc: linux-mm@kvack.org
Cc: Rusty Russell 
Cc: Dipankar Sarma 
Cc: Peter Zijlstra 
Cc: Andrew Morton 
Cc: Eric Biederman

percpu_counter: Make __percpu_counter_add an inline function on UP

2010-02-08T07:57:36+00:00

Even though batch isn't used on UP, we may want to pass one in
to keep the SMP and UP code paths similar. Convert
__percpu_counter_add to an inline function so we wont get
variable unused warnings if we do.

Signed-off-by: Anton Blanchard 
Cc: KOSAKI Motohiro 
Cc: Peter Zijlstra 
Cc: Martin Schwidefsky 
Cc: "Luck, Tony" 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Ingo Molnar