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bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check

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Similar to the earlier change in bpf_task_storage_get_recur.
This patch changes bpf_task_storage_delete_recur such that it
does the lookup first.  It only returns -EBUSY if it needs to
take the spinlock to do the deletion when potential deadlock
is detected.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20221025184524.3526117-7-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Martin KaFai Lau 2022-10-25 11:45:21 -07:00 • committed by Alexei Starovoitov
parent 4279adb094
commit fda64ae0bb
1 changed files with 11 additions and 7 deletions
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18
kernel/bpf/bpf_task_storage.c
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@ -184,7 +184,8 @@ out:
return err; return err;
} }
static int task_storage_delete(struct task_struct *task, struct bpf_map *map) static int task_storage_delete(struct task_struct *task, struct bpf_map *map,
bool nobusy)
{ {
struct bpf_local_storage_data *sdata; struct bpf_local_storage_data *sdata;
@ -192,6 +193,9 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
if (!sdata) if (!sdata)
return -ENOENT; return -ENOENT;
if (!nobusy)
return -EBUSY;
bpf_selem_unlink(SELEM(sdata), true); bpf_selem_unlink(SELEM(sdata), true);
return 0; return 0;
@ -220,7 +224,7 @@ static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
} }
bpf_task_storage_lock(); bpf_task_storage_lock();
err = task_storage_delete(task, map); err = task_storage_delete(task, map, true);
bpf_task_storage_unlock(); bpf_task_storage_unlock();
out: out:
put_pid(pid); put_pid(pid);
@ -289,21 +293,21 @@ BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *, BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *,
task) task)
{ {
bool nobusy;
int ret; int ret;
WARN_ON_ONCE(!bpf_rcu_lock_held()); WARN_ON_ONCE(!bpf_rcu_lock_held());
if (!task) if (!task)
return -EINVAL; return -EINVAL;
if (!bpf_task_storage_trylock()) nobusy = bpf_task_storage_trylock();
return -EBUSY;
/* This helper must only be called from places where the lifetime of the task /* This helper must only be called from places where the lifetime of the task
* is guaranteed. Either by being refcounted or by being protected * is guaranteed. Either by being refcounted or by being protected
* by an RCU read-side critical section. * by an RCU read-side critical section.
*/ */
ret = task_storage_delete(task, map); ret = task_storage_delete(task, map, nobusy);
bpf_task_storage_unlock(); if (nobusy)
bpf_task_storage_unlock();
return ret; return ret;
} }