2 files changed, 75 insertions, 52 deletions

diff --git a/Documentation/ABI/testing/sysfs-kernel-slab b/Documentation/ABI/testing/sysfs-kernel-slab
index 6dcf75e594fb..8b093f8222d3 100644
--- a/Documentation/ABI/testing/sysfs-kernel-slab
+++ b/Documentation/ABI/testing/sysfs-kernel-slab
@@ -45,8 +45,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The alloc_fastpath file is read-only and specifies how many
-                objects have been allocated using the fast path.
+                The alloc_fastpath file shows how many objects have been
+                allocated using the fast path.  It can be written to clear the
+                current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/alloc_from_partial
@@ -55,9 +56,10 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The alloc_from_partial file is read-only and specifies how
-                many times a cpu slab has been full and it has been refilled
-                by using a slab from the list of partially used slabs.
+                The alloc_from_partial file shows how many times a cpu slab has
+                been full and it has been refilled by using a slab from the list
+                of partially used slabs.  It can be written to clear the current
+                count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/alloc_refill
@@ -66,9 +68,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The alloc_refill file is read-only and specifies how many
-                times the per-cpu freelist was empty but there were objects
-                available as the result of remote cpu frees.
+                The alloc_refill file shows how many times the per-cpu freelist
+                was empty but there were objects available as the result of
+                remote cpu frees.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/alloc_slab
@@ -77,8 +79,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The alloc_slab file is read-only and specifies how many times
-                a new slab had to be allocated from the page allocator.
+                The alloc_slab file is shows how many times a new slab had to
+                be allocated from the page allocator.  It can be written to
+                clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/alloc_slowpath
@@ -87,9 +90,10 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The alloc_slowpath file is read-only and specifies how many
-                objects have been allocated using the slow path because of a
-                refill or allocation from a partial or new slab.
+                The alloc_slowpath file shows how many objects have been
+                allocated using the slow path because of a refill or
+                allocation from a partial or new slab.  It can be written to
+                clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/cache_dma
@@ -117,10 +121,11 @@ KernelVersion:	2.6.31
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file cpuslab_flush is read-only and specifies how many
-                times a cache's cpu slabs have been flushed as the result of
-                destroying or shrinking a cache, a cpu going offline, or as
-                the result of forcing an allocation from a certain node.
+                The file cpuslab_flush shows how many times a cache's cpu slabs
+                have been flushed as the result of destroying or shrinking a
+                cache, a cpu going offline, or as the result of forcing an
+                allocation from a certain node.  It can be written to clear the
+                current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/ctor
@@ -139,8 +144,8 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file deactivate_empty is read-only and specifies how many
-                times an empty cpu slab was deactivated.
+                The deactivate_empty file shows how many times an empty cpu slab
+                was deactivated.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/deactivate_full
@@ -149,8 +154,8 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file deactivate_full is read-only and specifies how many
-                times a full cpu slab was deactivated.
+                The deactivate_full file shows how many times a full cpu slab
+                was deactivated.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/deactivate_remote_frees
@@ -159,9 +164,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file deactivate_remote_frees is read-only and specifies how
-                many times a cpu slab has been deactivated and contained free
-                objects that were freed remotely.
+                The deactivate_remote_frees file shows how many times a cpu slab
+                has been deactivated and contained free objects that were freed
+                remotely.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/deactivate_to_head
@@ -170,9 +175,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file deactivate_to_head is read-only and specifies how
-                many times a partial cpu slab was deactivated and added to the
-                head of its node's partial list.
+                The deactivate_to_head file shows how many times a partial cpu
+                slab was deactivated and added to the head of its node's partial
+                list.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/deactivate_to_tail
@@ -181,9 +186,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file deactivate_to_tail is read-only and specifies how
-                many times a partial cpu slab was deactivated and added to the
-                tail of its node's partial list.
+                The deactivate_to_tail file shows how many times a partial cpu
+                slab was deactivated and added to the tail of its node's partial
+                list.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/destroy_by_rcu
@@ -201,9 +206,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file free_add_partial is read-only and specifies how many
-                times an object has been freed in a full slab so that it had to
-                added to its node's partial list.
+                The free_add_partial file shows how many times an object has
+                been freed in a full slab so that it had to added to its node's
+                partial list.  It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/free_calls
@@ -222,9 +227,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The free_fastpath file is read-only and specifies how many
-                objects have been freed using the fast path because it was an
-                object from the cpu slab.
+                The free_fastpath file shows how many objects have been freed
+                using the fast path because it was an object from the cpu slab.
+                It can be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/free_frozen
@@ -233,9 +238,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The free_frozen file is read-only and specifies how many
-                objects have been freed to a frozen slab (i.e. a remote cpu
-                slab).
+                The free_frozen file shows how many objects have been freed to
+                a frozen slab (i.e. a remote cpu slab).  It can be written to
+                clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/free_remove_partial
@@ -244,9 +249,10 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file free_remove_partial is read-only and specifies how
-                many times an object has been freed to a now-empty slab so
-                that it had to be removed from its node's partial list.
+                The free_remove_partial file shows how many times an object has
+                been freed to a now-empty slab so that it had to be removed from
+                its node's partial list.  It can be written to clear the current
+                count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/free_slab
@@ -255,8 +261,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The free_slab file is read-only and specifies how many times an
-                empty slab has been freed back to the page allocator.
+                The free_slab file shows how many times an empty slab has been
+                freed back to the page allocator.  It can be written to clear
+                the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/free_slowpath
@@ -265,9 +272,9 @@ KernelVersion:	2.6.25
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The free_slowpath file is read-only and specifies how many
-                objects have been freed using the slow path (i.e. to a full or
-                partial slab).
+                The free_slowpath file shows how many objects have been freed
+                using the slow path (i.e. to a full or partial slab).  It can
+                be written to clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/hwcache_align
@@ -346,10 +353,10 @@ KernelVersion:	2.6.26
 Contact:        Pekka Enberg <penberg@cs.helsinki.fi>,
                 Christoph Lameter <cl@linux-foundation.org>
 Description:
-                The file order_fallback is read-only and specifies how many
-                times an allocation of a new slab has not been possible at the
-                cache's order and instead fallen back to its minimum possible
-                order.
+                The order_fallback file shows how many times an allocation of a
+                new slab has not been possible at the cache's order and instead
+                fallen back to its minimum possible order.  It can be written to
+                clear the current count.
                 Available when CONFIG_SLUB_STATS is enabled.
 
 What:           /sys/kernel/slab/cache/partial
diff --git a/mm/slub.c b/mm/slub.c
index 4996fc719552..ac0ca4c0d054 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4371,12 +4371,28 @@ static int show_stat(struct kmem_cache *s, char *buf, enum stat_item si)
         return len + sprintf(buf + len, "\n");
 }
 
+static void clear_stat(struct kmem_cache *s, enum stat_item si)
+{
+        int cpu;
+
+        for_each_online_cpu(cpu)
+                get_cpu_slab(s, cpu)->stat[si] = 0;
+}
+
 #define STAT_ATTR(si, text)                                     \
 static ssize_t text##_show(struct kmem_cache *s, char *buf)     \
 {                                                               \
         return show_stat(s, buf, si);                           \
 }                                                               \
-SLAB_ATTR_RO(text);                                             \
+static ssize_t text##_store(struct kmem_cache *s,               \
+                                const char *buf, size_t length) \
+{                                                               \
+        if (buf[0] != '0')                                      \
+                return -EINVAL;                                 \
+        clear_stat(s, si);                                      \
+        return length;                                          \
+}                                                               \
+SLAB_ATTR(text);                                                \
 
 STAT_ATTR(ALLOC_FASTPATH, alloc_fastpath);
 STAT_ATTR(ALLOC_SLOWPATH, alloc_slowpath);