diff mbox series

[bpf-next,1/2] bpf: Reduce the scope of rcu_read_lock when updating fd map

Message ID 20231113141207.1459002-2-houtao@huaweicloud.com (mailing list archive)
State New, archived
Delegated to: BPF
Headers show
Series bpf: Use GFP_KERNEL in bpf_event_entry_gen() | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1146 this patch: 1146
netdev/cc_maintainers success CCed 12 of 12 maintainers
netdev/build_clang success Errors and warnings before: 1162 this patch: 1162
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1173 this patch: 1173
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 24 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
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Commit Message

Hou Tao Nov. 13, 2023, 2:12 p.m. UTC 
From: Hou Tao <houtao1@huawei.com>

There is no rcu-read-lock requirement for ops->map_fd_get_ptr() or
ops->map_fd_put_ptr(), so doesn't use rcu-read-lock for these two
callbacks.

For bpf_fd_array_map_update_elem(), accessing array->ptrs doesn't need
rcu-read-lock because array->ptrs will not be freed until the map-in-map
is released. For bpf_fd_htab_map_update_elem(), htab_map_update_elem()
requires rcu-read-lock to be held, so only use rcu_read_lock() during
the invocation of htab_map_update_elem().

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 kernel/bpf/hashtab.c | 2 ++
 kernel/bpf/syscall.c | 4 ----
 2 files changed, 2 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index fd8d4b0addfca..7d1457360c99b 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -2523,7 +2523,9 @@  int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
 	if (IS_ERR(ptr))
 		return PTR_ERR(ptr);
 
+	rcu_read_lock();
 	ret = htab_map_update_elem(map, key, &ptr, map_flags);
+	rcu_read_unlock();
 	if (ret)
 		map->ops->map_fd_put_ptr(ptr);
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0ed286b8a0f0f..eff8f241af5da 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -180,15 +180,11 @@  static int bpf_map_update_value(struct bpf_map *map, struct file *map_file,
 		err = bpf_percpu_cgroup_storage_update(map, key, value,
 						       flags);
 	} else if (IS_FD_ARRAY(map)) {
-		rcu_read_lock();
 		err = bpf_fd_array_map_update_elem(map, map_file, key, value,
 						   flags);
-		rcu_read_unlock();
 	} else if (map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
-		rcu_read_lock();
 		err = bpf_fd_htab_map_update_elem(map, map_file, key, value,
 						  flags);
-		rcu_read_unlock();
 	} else if (map->map_type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY) {
 		/* rcu_read_lock() is not needed */
 		err = bpf_fd_reuseport_array_update_elem(map, key, value,