[GIT PULL] percpu fixes for v4.11-rc2

[Tejun Heo]

Hello, Linus.

percpu changes for v4.11-rc2.

* The allocation path was updating pcpu_nr_empty_pop_pages without the
  required locking which can lead to incorrect handling of empty
  chunks (e.g. keeping too many around), which is buggy but shouldn't
  lead to critical failures.  Fixed by adding the locking.

* A trivial patch to drop an unused param from pcpu_get_pages().

Thanks.

The following changes since commit c1ae3cfa0e89fa1a7ecc4c99031f5e9ae99d9201:

  Linux 4.11-rc1 (2017-03-05 12:59:56 -0800)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-4.11-fixes

for you to fetch changes up to 8a1df543de8ad879d3c80bdda4c67ac4f82e7ee0:

  percpu: remove unused chunk_alloc parameter from pcpu_get_pages() (2017-03-06 15:56:55 -0500)

----------------------------------------------------------------
Tahsin Erdogan (2):
      percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages
      percpu: remove unused chunk_alloc parameter from pcpu_get_pages()

 mm/percpu-vm.c | 7 +++----
 mm/percpu.c    | 5 ++++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
index 538998a..9ac6394 100644
--- a/mm/percpu-vm.c
+++ b/mm/percpu-vm.c
@@ -21,7 +21,6 @@ static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
 
 /**
  * pcpu_get_pages - get temp pages array
- * @chunk: chunk of interest
  *
  * Returns pointer to array of pointers to struct page which can be indexed
  * with pcpu_page_idx().  Note that there is only one array and accesses
@@ -30,7 +29,7 @@ static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
  * RETURNS:
  * Pointer to temp pages array on success.
  */
-static struct page **pcpu_get_pages(struct pcpu_chunk *chunk_alloc)
+static struct page **pcpu_get_pages(void)
 {
 	static struct page **pages;
 	size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
@@ -275,7 +274,7 @@ static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
 {
 	struct page **pages;
 
-	pages = pcpu_get_pages(chunk);
+	pages = pcpu_get_pages();
 	if (!pages)
 		return -ENOMEM;
 
@@ -313,7 +312,7 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
 	 * successful population attempt so the temp pages array must
 	 * be available now.
 	 */
-	pages = pcpu_get_pages(chunk);
+	pages = pcpu_get_pages();
 	BUG_ON(!pages);
 
 	/* unmap and free */
diff --git a/mm/percpu.c b/mm/percpu.c
index 5696039..60a6488 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1011,8 +1011,11 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 		mutex_unlock(&pcpu_alloc_mutex);
 	}
 
-	if (chunk != pcpu_reserved_chunk)
+	if (chunk != pcpu_reserved_chunk) {
+		spin_lock_irqsave(&pcpu_lock, flags);
 		pcpu_nr_empty_pop_pages -= occ_pages;
+		spin_unlock_irqrestore(&pcpu_lock, flags);
+	}
 
 	if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
 		pcpu_schedule_balance_work();

-- 
tejun