[PATCH 15/24] mm/list_lru.c: Rename kvfree_rcu() to local variant

[PATCH 15/24] mm/list_lru.c: Rename kvfree_rcu() to local variant

[Uladzislau Rezki (Sony)]

Rename kvfree_rcu() function to the kvfree_rcu_local() one. The aim is
to introduce the public API that would conflict with this one. So we
temporarily rename it and remove it in a later commit.

Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: rcu@vger.kernel.org
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 mm/list_lru.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 4d5294c39bba..42c95bcb53ca 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -373,14 +373,14 @@ static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
 	struct list_lru_memcg *memcg_lrus;
 	/*
 	 * This is called when shrinker has already been unregistered,
-	 * and nobody can use it. So, there is no need to use kvfree_rcu().
+	 * and nobody can use it. So, there is no need to use kvfree_rcu_local().
 	 */
 	memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
 	__memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
 	kvfree(memcg_lrus);
 }
 
-static void kvfree_rcu(struct rcu_head *head)
+static void kvfree_rcu_local(struct rcu_head *head)
 {
 	struct list_lru_memcg *mlru;
 
@@ -419,7 +419,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 	rcu_assign_pointer(nlru->memcg_lrus, new);
 	spin_unlock_irq(&nlru->lock);
 
-	call_rcu(&old->rcu, kvfree_rcu);
+	call_rcu(&old->rcu, kvfree_rcu_local);
 	return 0;
 }
 
-- 
2.20.1

Re: [PATCH 15/24] mm/list_lru.c: Rename kvfree_rcu() to local variant

[Uladzislau Rezki]

[-- Attachment #1: Type: text/plain, Size: 2051 bytes --]

Hello.

I apologize. Please ignore this patch and email. Wanted to send it to one
person,
instead git send-email also handled some emails from commit footer.

--
Vlad Rezki

On Mon, Apr 27, 2020 at 1:11 PM Uladzislau Rezki (Sony) <urezki@gmail.com>
wrote:

> Rename kvfree_rcu() function to the kvfree_rcu_local() one. The aim is
> to introduce the public API that would conflict with this one. So we
> temporarily rename it and remove it in a later commit.
>
> Cc: linux-mm@kvack.org
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: rcu@vger.kernel.org
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
>  mm/list_lru.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 4d5294c39bba..42c95bcb53ca 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -373,14 +373,14 @@ static void memcg_destroy_list_lru_node(struct
> list_lru_node *nlru)
>         struct list_lru_memcg *memcg_lrus;
>         /*
>          * This is called when shrinker has already been unregistered,
> -        * and nobody can use it. So, there is no need to use kvfree_rcu().
> +        * and nobody can use it. So, there is no need to use
> kvfree_rcu_local().
>          */
>         memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
>         __memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
>         kvfree(memcg_lrus);
>  }
>
> -static void kvfree_rcu(struct rcu_head *head)
> +static void kvfree_rcu_local(struct rcu_head *head)
>  {
>         struct list_lru_memcg *mlru;
>
> @@ -419,7 +419,7 @@ static int memcg_update_list_lru_node(struct
> list_lru_node *nlru,
>         rcu_assign_pointer(nlru->memcg_lrus, new);
>         spin_unlock_irq(&nlru->lock);
>
> -       call_rcu(&old->rcu, kvfree_rcu);
> +       call_rcu(&old->rcu, kvfree_rcu_local);
>         return 0;
>  }
>
> --
> 2.20.1
>
>

-- 
Uladzislau Rezki

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[PATCH 18/24] mm/list_lru.c: Remove kvfree_rcu_local() function

[Uladzislau Rezki (Sony)]

Since there is newly introduced kvfree_rcu() API, there is no need in
queuing and using call_rcu() to kvfree() an object after the GP.

Remove kvfree_rcu_local() function and replace call_rcu() by new
kvfree_rcu() API that does the same but in more efficient way.

Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: rcu@vger.kernel.org
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 mm/list_lru.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 42c95bcb53ca..a0b08b27a9b9 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/memcontrol.h>
+#include <linux/rcupdate.h>
 #include "slab.h"
 
 #ifdef CONFIG_MEMCG_KMEM
@@ -373,21 +374,13 @@ static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
 	struct list_lru_memcg *memcg_lrus;
 	/*
 	 * This is called when shrinker has already been unregistered,
-	 * and nobody can use it. So, there is no need to use kvfree_rcu_local().
+	 * and nobody can use it. So, there is no need to use kvfree_rcu().
 	 */
 	memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
 	__memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
 	kvfree(memcg_lrus);
 }
 
-static void kvfree_rcu_local(struct rcu_head *head)
-{
-	struct list_lru_memcg *mlru;
-
-	mlru = container_of(head, struct list_lru_memcg, rcu);
-	kvfree(mlru);
-}
-
 static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 				      int old_size, int new_size)
 {
@@ -419,7 +412,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 	rcu_assign_pointer(nlru->memcg_lrus, new);
 	spin_unlock_irq(&nlru->lock);
 
-	call_rcu(&old->rcu, kvfree_rcu_local);
+	kvfree_rcu(old, rcu);
 	return 0;
 }
 
-- 
2.20.1

Re: [PATCH 18/24] mm/list_lru.c: Remove kvfree_rcu_local() function

[Uladzislau Rezki]

[-- Attachment #1: Type: text/plain, Size: 2504 bytes --]

Hello.

I apologize. Please ignore this patch and email. Wanted to send it to one
person,
instead git send-email also handled some emails from commit footer.

--
Vlad Rezki

On Mon, Apr 27, 2020 at 1:11 PM Uladzislau Rezki (Sony) <urezki@gmail.com>
wrote:

> Since there is newly introduced kvfree_rcu() API, there is no need in
> queuing and using call_rcu() to kvfree() an object after the GP.
>
> Remove kvfree_rcu_local() function and replace call_rcu() by new
> kvfree_rcu() API that does the same but in more efficient way.
>
> Cc: linux-mm@kvack.org
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: rcu@vger.kernel.org
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
>  mm/list_lru.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 42c95bcb53ca..a0b08b27a9b9 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -12,6 +12,7 @@
>  #include <linux/slab.h>
>  #include <linux/mutex.h>
>  #include <linux/memcontrol.h>
> +#include <linux/rcupdate.h>
>  #include "slab.h"
>
>  #ifdef CONFIG_MEMCG_KMEM
> @@ -373,21 +374,13 @@ static void memcg_destroy_list_lru_node(struct
> list_lru_node *nlru)
>         struct list_lru_memcg *memcg_lrus;
>         /*
>          * This is called when shrinker has already been unregistered,
> -        * and nobody can use it. So, there is no need to use
> kvfree_rcu_local().
> +        * and nobody can use it. So, there is no need to use kvfree_rcu().
>          */
>         memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
>         __memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
>         kvfree(memcg_lrus);
>  }
>
> -static void kvfree_rcu_local(struct rcu_head *head)
> -{
> -       struct list_lru_memcg *mlru;
> -
> -       mlru = container_of(head, struct list_lru_memcg, rcu);
> -       kvfree(mlru);
> -}
> -
>  static int memcg_update_list_lru_node(struct list_lru_node *nlru,
>                                       int old_size, int new_size)
>  {
> @@ -419,7 +412,7 @@ static int memcg_update_list_lru_node(struct
> list_lru_node *nlru,
>         rcu_assign_pointer(nlru->memcg_lrus, new);
>         spin_unlock_irq(&nlru->lock);
>
> -       call_rcu(&old->rcu, kvfree_rcu_local);
> +       kvfree_rcu(old, rcu);
>         return 0;
>  }
>
> --
> 2.20.1
>
>

-- 
Uladzislau Rezki

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[PATCH 00/24] Introduce kvfree_rcu(1 or 2 arguments)

[Uladzislau Rezki (Sony)]

Motivation
----------
There were some discussions and demand in having kvfree_rcu()
interface for different purposes. Basically to have a simple
interface like:

<snip>
    void *ptr = kvmalloc(some_bytes, GFP_KERNEL);
        if (ptr)
            kvfree_rcu(ptr);
<snip>

For example, please have a look at ext4 discussion here:
    https://lkml.org/lkml/2020/2/19/1372

due to lack of the interface that is in question, the ext4 specific
workaround has been introduced, to kvfree() after a grace period:

<snip>
void ext4_kvfree_array_rcu(void *to_free)
{
	struct ext4_rcu_ptr *ptr = kzalloc(sizeof(*ptr), GFP_KERNEL);

	if (ptr) {
		ptr->ptr = to_free;
		call_rcu(&ptr->rcu, ext4_rcu_ptr_callback);
		return;
	}
	synchronize_rcu();
	kvfree(ptr);
}
<snip>

there are also similar places there which could be replaced by the new
interface, that is much more efficient then just call synchronize_rcu()
and release a memory.

Please have a look at another places in the kernel where people do not
embed the rcu_head into their stuctures for some reason and do like:

<snip>
    synchronize_rcu();
    kfree(p);
<snip>

<snip>
urezki@pc638:~/data/coding/linux-rcu.git$ find ./ -name "*.c" | xargs grep -C 1 -rn "synchronize_rcu" | grep kfree
./fs/nfs/sysfs.c-113-           kfree(old);
./fs/ext4/super.c-1708- kfree(old_qname);
./kernel/trace/ftrace.c-5079-                   kfree(direct);
./kernel/trace/ftrace.c-5156-                   kfree(direct);
./kernel/trace/trace_probe.c-1087-      kfree(link);
./kernel/module.c-3910- kfree(mod->args);
./net/core/sysctl_net_core.c-143-                               kfree(cur);
./arch/x86/mm/mmio-mod.c-314-           kfree(found_trace);
./drivers/mfd/dln2.c-183-               kfree(i);
./drivers/block/drbd/drbd_state.c-2074-         kfree(old_conf);
./drivers/block/drbd/drbd_nl.c-1689-    kfree(old_disk_conf);
./drivers/block/drbd/drbd_nl.c-2522-    kfree(old_net_conf);
./drivers/block/drbd/drbd_nl.c-2935-            kfree(old_disk_conf);
./drivers/block/drbd/drbd_receiver.c-3805-      kfree(old_net_conf);
./drivers/block/drbd/drbd_receiver.c-4177-                      kfree(old_disk_conf);
./drivers/ipack/carriers/tpci200.c-189- kfree(slot_irq);
./drivers/crypto/nx/nx-842-pseries.c-1010-      kfree(old_devdata);
./drivers/net/ethernet/myricom/myri10ge/myri10ge.c-3583-        kfree(mgp->ss);
./drivers/net/ethernet/mellanox/mlx5/core/fpga/tls.c:286:       synchronize_rcu(); /* before kfree(flow) */
./drivers/net/ethernet/mellanox/mlxsw/core.c-1574-      kfree(rxl_item);
./drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c-6642- kfree(adapter->mbox_log);
./drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c-6644- kfree(adapter);
./drivers/infiniband/hw/hfi1/sdma.c-1337-       kfree(dd->per_sdma);
./drivers/infiniband/core/device.c:2164:                         * synchronize_rcu before the netdev is kfreed, so we
./drivers/misc/vmw_vmci/vmci_context.c-692-             kfree(notifier);
./drivers/misc/vmw_vmci/vmci_event.c-213-       kfree(s);
./drivers/staging/fwserial/fwserial.c-2122-     kfree(peer);
urezki@pc638:~/data/coding/linux-rcu.git$
<snip>

so all of it can be replaced by the introduced interface and that
is actually aim and motivation. All that can replaced by the single
kvfree_rcu() logic.

As for double argument of the kvfree_rcu() we have only one user
so far, it is "mm/list_lru.c". But it costs nothing to add it.

Description
-----------
This small series introduces kvfree_rcu() macro that is used
for free memory after a grace period. It can be called either
with one or two arguments. kvfree_rcu() as it derives from its
name can handle two types of pointers, SLAB and vmalloc ones.

As a result we get two ways how to use kvfree_rcu() macro, see
below two examples.

a) kvfree_rcu(ptr, rhf);
    struct X {
        struct rcu_head rhf;
        unsigned char data[100];
    };

    void *ptr = kvmalloc(sizeof(struct X), GFP_KERNEL);
    if (ptr)
        kvfree_rcu(ptr, rhf);

b) kvfree_rcu(ptr);
    void *ptr = kvmalloc(some_bytes, GFP_KERNEL);
    if (ptr)
        kvfree_rcu(ptr);

Last one, we name it headless variant, only needs one argument,
means it does not require any rcu_head to be present within the
type of ptr. There is a restriction the (b) context has to fall
into might_sleep() annotation. To check that, please activate
the CONFIG_DEBUG_ATOMIC_SLEEP option in your kernel.

This series is based on:
git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git
"origin/rcu/dev" branch, what is the same as Paul's almost
latest dev.2020.04.13c branch.

Appreciate for any comments and feedback.

Joel Fernandes (Google) (5):
  rcu/tree: Keep kfree_rcu() awake during lock contention
  rcu/tree: Skip entry into the page allocator for PREEMPT_RT
  rcu/tree: Use consistent style for comments
  rcu/tree: Simplify debug_objects handling
  rcu/tree: Make kvfree_rcu() tolerate any alignment

Sebastian Andrzej Siewior (1):
  rcu/tree: Use static initializer for krc.lock

Uladzislau Rezki (Sony) (18):
  rcu/tree: Repeat the monitor if any free channel is busy
  rcu/tree: Simplify KFREE_BULK_MAX_ENTR macro
  rcu/tree: move locking/unlocking to separate functions
  rcu/tree: cache specified number of objects
  rcu/tree: add rcutree.rcu_min_cached_objs description
  rcu/tree: Maintain separate array for vmalloc ptrs
  rcu/tiny: support vmalloc in tiny-RCU
  rcu: Rename rcu_invoke_kfree_callback/rcu_kfree_callback
  rcu: Rename __is_kfree_rcu_offset() macro
  rcu: Rename kfree_call_rcu() to the kvfree_call_rcu().
  mm/list_lru.c: Rename kvfree_rcu() to local variant
  rcu: Introduce 2 arg kvfree_rcu() interface
  mm/list_lru.c: Remove kvfree_rcu_local() function
  rcu/tree: Support reclaim for head-less object
  rcu/tiny: move kvfree_call_rcu() out of header
  rcu/tiny: support reclaim for head-less object
  rcu: Introduce 1 arg kvfree_rcu() interface
  lib/test_vmalloc.c: Add test cases for kvfree_rcu()

 .../admin-guide/kernel-parameters.txt         |   8 +
 include/linux/rcupdate.h                      |  53 +-
 include/linux/rcutiny.h                       |   6 +-
 include/linux/rcutree.h                       |   2 +-
 include/trace/events/rcu.h                    |   8 +-
 kernel/rcu/tiny.c                             | 168 ++++++-
 kernel/rcu/tree.c                             | 454 +++++++++++++-----
 lib/test_vmalloc.c                            | 103 +++-
 mm/list_lru.c                                 |  11 +-
 9 files changed, 662 insertions(+), 151 deletions(-)

-- 
2.20.1

[PATCH 18/24] mm/list_lru.c: Remove kvfree_rcu_local() function

[Uladzislau Rezki (Sony)]

Since there is newly introduced kvfree_rcu() API, there is no need in
queuing and using call_rcu() to kvfree() an object after the GP.

Remove kvfree_rcu_local() function and replace call_rcu() by new
kvfree_rcu() API that does the same but in more efficient way.

Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: rcu@vger.kernel.org
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 mm/list_lru.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 42c95bcb53ca..a0b08b27a9b9 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/memcontrol.h>
+#include <linux/rcupdate.h>
 #include "slab.h"
 
 #ifdef CONFIG_MEMCG_KMEM
@@ -373,21 +374,13 @@ static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
 	struct list_lru_memcg *memcg_lrus;
 	/*
 	 * This is called when shrinker has already been unregistered,
-	 * and nobody can use it. So, there is no need to use kvfree_rcu_local().
+	 * and nobody can use it. So, there is no need to use kvfree_rcu().
 	 */
 	memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
 	__memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
 	kvfree(memcg_lrus);
 }
 
-static void kvfree_rcu_local(struct rcu_head *head)
-{
-	struct list_lru_memcg *mlru;
-
-	mlru = container_of(head, struct list_lru_memcg, rcu);
-	kvfree(mlru);
-}
-
 static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 				      int old_size, int new_size)
 {
@@ -419,7 +412,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 	rcu_assign_pointer(nlru->memcg_lrus, new);
 	spin_unlock_irq(&nlru->lock);
 
-	call_rcu(&old->rcu, kvfree_rcu_local);
+	kvfree_rcu(old, rcu);
 	return 0;
 }
 
-- 
2.20.1