diff mbox series

[v2,bpf-next] bpf: Fix usage of trace RCU in local storage.

Message ID 20220418155158.2865678-1-kpsingh@kernel.org (mailing list archive)
State Accepted
Commit dcf456c9a095a6e71f53d6f6f004133ee851ee70
Delegated to: BPF
Headers show
Series [v2,bpf-next] bpf: Fix usage of trace RCU in local storage. | expand

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Context Check Description
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Single patches do not need cover letters
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 76 this patch: 76
netdev/cc_maintainers warning 9 maintainers not CCed: songliubraving@fb.com davem@davemloft.net netdev@vger.kernel.org pabeni@redhat.com joannelkoong@gmail.com john.fastabend@gmail.com yhs@fb.com haoluo@google.com kuba@kernel.org
netdev/build_clang fail Errors and warnings before: 25 this patch: 25
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 76 this patch: 76
netdev/checkpatch warning CHECK: Alignment should match open parenthesis CHECK: Lines should not end with a '('
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-PR success PR summary
bpf/vmtest-bpf-next-VM_Test-2 success Logs for Kernel LATEST on z15 + selftests
bpf/vmtest-bpf-next-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest + selftests

Commit Message

KP Singh April 18, 2022, 3:51 p.m. UTC 
bpf_{sk,task,inode}_storage_free() do not need to use
call_rcu_tasks_trace as no BPF program should be accessing the owner
as it's being destroyed. The only other reader at this point is
bpf_local_storage_map_free() which uses normal RCU.

The only path that needs trace RCU are:

* bpf_local_storage_{delete,update} helpers
* map_{delete,update}_elem() syscalls

Fixes: 0fe4b381a59e ("bpf: Allow bpf_local_storage to be used by sleepable programs")
Signed-off-by: KP Singh <kpsingh@kernel.org>
---
 include/linux/bpf_local_storage.h |  4 ++--
 kernel/bpf/bpf_inode_storage.c    |  4 ++--
 kernel/bpf/bpf_local_storage.c    | 29 +++++++++++++++++++----------
 kernel/bpf/bpf_task_storage.c     |  4 ++--
 net/core/bpf_sk_storage.c         |  6 +++---
 5 files changed, 28 insertions(+), 19 deletions(-)

Comments

Martin KaFai Lau April 19, 2022, 7:41 p.m. UTC | #1 
On Mon, Apr 18, 2022 at 03:51:58PM +0000, KP Singh wrote:
> bpf_{sk,task,inode}_storage_free() do not need to use
> call_rcu_tasks_trace as no BPF program should be accessing the owner
> as it's being destroyed. The only other reader at this point is
> bpf_local_storage_map_free() which uses normal RCU.
> 
> The only path that needs trace RCU are:
> 
> * bpf_local_storage_{delete,update} helpers
> * map_{delete,update}_elem() syscalls
Acked-by: Martin KaFai Lau <kafai@fb.com>
patchwork-bot+netdevbpf@kernel.org April 20, 2022, 2:20 a.m. UTC | #2 
Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon, 18 Apr 2022 15:51:58 +0000 you wrote:
> bpf_{sk,task,inode}_storage_free() do not need to use
> call_rcu_tasks_trace as no BPF program should be accessing the owner
> as it's being destroyed. The only other reader at this point is
> bpf_local_storage_map_free() which uses normal RCU.
> 
> The only path that needs trace RCU are:
> 
> [...]

Here is the summary with links:
  - [v2,bpf-next] bpf: Fix usage of trace RCU in local storage.
    https://git.kernel.org/bpf/bpf-next/c/dcf456c9a095

You are awesome, thank you!
diff mbox series

Patch

diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index 493e63258497..7ea18d4da84b 100644
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -143,9 +143,9 @@  void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
 
 bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
 				     struct bpf_local_storage_elem *selem,
-				     bool uncharge_omem);
+				     bool uncharge_omem, bool use_trace_rcu);
 
-void bpf_selem_unlink(struct bpf_local_storage_elem *selem);
+void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu);
 
 void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 			struct bpf_local_storage_elem *selem);
diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c
index 96be8d518885..10424a1cda51 100644
--- a/kernel/bpf/bpf_inode_storage.c
+++ b/kernel/bpf/bpf_inode_storage.c
@@ -90,7 +90,7 @@  void bpf_inode_storage_free(struct inode *inode)
 		 */
 		bpf_selem_unlink_map(selem);
 		free_inode_storage = bpf_selem_unlink_storage_nolock(
-			local_storage, selem, false);
+			local_storage, selem, false, false);
 	}
 	raw_spin_unlock_bh(&local_storage->lock);
 	rcu_read_unlock();
@@ -149,7 +149,7 @@  static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
 	if (!sdata)
 		return -ENOENT;
 
-	bpf_selem_unlink(SELEM(sdata));
+	bpf_selem_unlink(SELEM(sdata), true);
 
 	return 0;
 }
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 01aa2b51ec4d..8ce40fd869f6 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -106,7 +106,7 @@  static void bpf_selem_free_rcu(struct rcu_head *rcu)
  */
 bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
 				     struct bpf_local_storage_elem *selem,
-				     bool uncharge_mem)
+				     bool uncharge_mem, bool use_trace_rcu)
 {
 	struct bpf_local_storage_map *smap;
 	bool free_local_storage;
@@ -150,11 +150,16 @@  bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
 	    SDATA(selem))
 		RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
 
-	call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
+	if (use_trace_rcu)
+		call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
+	else
+		kfree_rcu(selem, rcu);
+
 	return free_local_storage;
 }
 
-static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
+static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
+				       bool use_trace_rcu)
 {
 	struct bpf_local_storage *local_storage;
 	bool free_local_storage = false;
@@ -169,12 +174,16 @@  static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
 	raw_spin_lock_irqsave(&local_storage->lock, flags);
 	if (likely(selem_linked_to_storage(selem)))
 		free_local_storage = bpf_selem_unlink_storage_nolock(
-			local_storage, selem, true);
+			local_storage, selem, true, use_trace_rcu);
 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 
-	if (free_local_storage)
-		call_rcu_tasks_trace(&local_storage->rcu,
+	if (free_local_storage) {
+		if (use_trace_rcu)
+			call_rcu_tasks_trace(&local_storage->rcu,
 				     bpf_local_storage_free_rcu);
+		else
+			kfree_rcu(local_storage, rcu);
+	}
 }
 
 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
@@ -214,14 +223,14 @@  void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 	raw_spin_unlock_irqrestore(&b->lock, flags);
 }
 
-void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
+void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu)
 {
 	/* Always unlink from map before unlinking from local_storage
 	 * because selem will be freed after successfully unlinked from
 	 * the local_storage.
 	 */
 	bpf_selem_unlink_map(selem);
-	__bpf_selem_unlink_storage(selem);
+	__bpf_selem_unlink_storage(selem, use_trace_rcu);
 }
 
 struct bpf_local_storage_data *
@@ -466,7 +475,7 @@  bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 	if (old_sdata) {
 		bpf_selem_unlink_map(SELEM(old_sdata));
 		bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
-						false);
+						false, true);
 	}
 
 unlock:
@@ -548,7 +557,7 @@  void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
 				migrate_disable();
 				__this_cpu_inc(*busy_counter);
 			}
-			bpf_selem_unlink(selem);
+			bpf_selem_unlink(selem, false);
 			if (busy_counter) {
 				__this_cpu_dec(*busy_counter);
 				migrate_enable();
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index 6638a0ecc3d2..57904263a710 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -102,7 +102,7 @@  void bpf_task_storage_free(struct task_struct *task)
 		 */
 		bpf_selem_unlink_map(selem);
 		free_task_storage = bpf_selem_unlink_storage_nolock(
-			local_storage, selem, false);
+			local_storage, selem, false, false);
 	}
 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	bpf_task_storage_unlock();
@@ -192,7 +192,7 @@  static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
 	if (!sdata)
 		return -ENOENT;
 
-	bpf_selem_unlink(SELEM(sdata));
+	bpf_selem_unlink(SELEM(sdata), true);
 
 	return 0;
 }
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index e3ac36380520..83d7641ef67b 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -40,7 +40,7 @@  static int bpf_sk_storage_del(struct sock *sk, struct bpf_map *map)
 	if (!sdata)
 		return -ENOENT;
 
-	bpf_selem_unlink(SELEM(sdata));
+	bpf_selem_unlink(SELEM(sdata), true);
 
 	return 0;
 }
@@ -75,8 +75,8 @@  void bpf_sk_storage_free(struct sock *sk)
 		 * sk_storage.
 		 */
 		bpf_selem_unlink_map(selem);
-		free_sk_storage = bpf_selem_unlink_storage_nolock(sk_storage,
-								  selem, true);
+		free_sk_storage = bpf_selem_unlink_storage_nolock(
+			sk_storage, selem, true, false);
 	}
 	raw_spin_unlock_bh(&sk_storage->lock);
 	rcu_read_unlock();