Commit 403e935f authored by Amery Hung's avatar Amery Hung Committed by Martin KaFai Lau
Browse files

bpf: Convert bpf_selem_unlink to failable 



To prepare changing both bpf_local_storage_map_bucket::lock and
bpf_local_storage::lock to rqspinlock, convert bpf_selem_unlink() to
failable. It still always succeeds and returns 0 until the change
happens. No functional change.

Open code bpf_selem_unlink_storage() in the only caller,
bpf_selem_unlink(), since unlink_map and unlink_storage must be done
together after all the necessary locks are acquired.

For bpf_local_storage_map_free(), ignore the return from
bpf_selem_unlink() for now. A later patch will allow it to unlink selems
even when failing to acquire locks.

Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAmery Hung <ameryhung@gmail.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260205222916.1788211-5-ameryhung@gmail.com
parent fd103ffc

include/linux/bpf_local_storage.h

+1 −1
Original line number Diff line number Diff line
@@ -176,7 +176,7 @@ int bpf_local_storage_map_check_btf(const struct bpf_map *map, 
void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,

				   struct bpf_local_storage_elem *selem);



void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);

int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);



int bpf_selem_link_map(struct bpf_local_storage_map *smap,

		       struct bpf_local_storage *local_storage,

kernel/bpf/bpf_cgrp_storage.c

+1 −2
Original line number Diff line number Diff line
@@ -118,8 +118,7 @@ static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map) 
	if (!sdata)

		return -ENOENT;



	bpf_selem_unlink(SELEM(sdata), false);

	return 0;

	return bpf_selem_unlink(SELEM(sdata), false);

}



static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)

kernel/bpf/bpf_inode_storage.c

+1 −3
Original line number Diff line number Diff line
@@ -110,9 +110,7 @@ static int inode_storage_delete(struct inode *inode, struct bpf_map *map) 
	if (!sdata)

		return -ENOENT;



	bpf_selem_unlink(SELEM(sdata), false);



	return 0;

	return bpf_selem_unlink(SELEM(sdata), false);

}



static long bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)

kernel/bpf/bpf_local_storage.c

+34 −37
Original line number Diff line number Diff line
@@ -308,33 +308,6 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor 
	return free_local_storage;

}



static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,

				     bool reuse_now)

{

	struct bpf_local_storage *local_storage;

	bool free_local_storage = false;

	HLIST_HEAD(selem_free_list);

	unsigned long flags;



	if (unlikely(!selem_linked_to_storage_lockless(selem)))

		/* selem has already been unlinked from sk */

		return;



	local_storage = rcu_dereference_check(selem->local_storage,

					      bpf_rcu_lock_held());



	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, &selem_free_list);

	raw_spin_unlock_irqrestore(&local_storage->lock, flags);



	bpf_selem_free_list(&selem_free_list, reuse_now);



	if (free_local_storage)

		bpf_local_storage_free(local_storage, reuse_now);

}



void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,

				   struct bpf_local_storage_elem *selem)

{
@@ -386,19 +359,43 @@ static void bpf_selem_link_map_nolock(struct bpf_local_storage_map_bucket *b, 
	hlist_add_head_rcu(&selem->map_node, &b->list);

}



void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)

int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)

{

	int err;

	struct bpf_local_storage *local_storage;

	bool free_local_storage = false;

	HLIST_HEAD(selem_free_list);

	unsigned long flags;

	int err = 0;



	if (unlikely(!selem_linked_to_storage_lockless(selem)))

		/* selem has already been unlinked from sk */

		return 0;



	local_storage = rcu_dereference_check(selem->local_storage,

					      bpf_rcu_lock_held());



	raw_spin_lock_irqsave(&local_storage->lock, flags);

	if (likely(selem_linked_to_storage(selem))) {

		/* Always unlink from map before unlinking from local_storage

		 * because selem will be freed after successfully unlinked from

		 * the local_storage.

		 */

		err = bpf_selem_unlink_map(selem);

		if (err)

		return;

			goto out;



		free_local_storage = bpf_selem_unlink_storage_nolock(

			local_storage, selem, &selem_free_list);

	}

out:

	raw_spin_unlock_irqrestore(&local_storage->lock, flags);



	bpf_selem_unlink_storage(selem, reuse_now);

	bpf_selem_free_list(&selem_free_list, reuse_now);



	if (free_local_storage)

		bpf_local_storage_free(local_storage, reuse_now);



	return err;

}



void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage,

kernel/bpf/bpf_task_storage.c

+1 −3
Original line number Diff line number Diff line
@@ -167,9 +167,7 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map, 
	if (!nobusy)

		return -EBUSY;



	bpf_selem_unlink(SELEM(sdata), false);



	return 0;

	return bpf_selem_unlink(SELEM(sdata), false);

}



static long bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)