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![KP Singh](/assets/img/avatar_default.png)
Other maps like hashmaps are already available to sleepable programs. Sleepable BPF programs run under trace RCU. Allow task, sk and inode storage to be used from sleepable programs. This allows sleepable and non-sleepable programs to provide shareable annotations on kernel objects. Sleepable programs run in trace RCU where as non-sleepable programs run in a normal RCU critical section i.e. __bpf_prog_enter{_sleepable} and __bpf_prog_exit{_sleepable}) (rcu_read_lock or rcu_read_lock_trace). In order to make the local storage maps accessible to both sleepable and non-sleepable programs, one needs to call both call_rcu_tasks_trace and call_rcu to wait for both trace and classical RCU grace periods to expire before freeing memory. Paul's work on call_rcu_tasks_trace allows us to have per CPU queueing for call_rcu_tasks_trace. This behaviour can be achieved by setting rcupdate.rcu_task_enqueue_lim=<num_cpus> boot parameter. In light of these new performance changes and to keep the local storage code simple, avoid adding a new flag for sleepable maps / local storage to select the RCU synchronization (trace / classical). Also, update the dereferencing of the pointers to use rcu_derference_check (with either the trace or normal RCU locks held) with a common bpf_rcu_lock_held helper method. Signed-off-by: KP Singh <kpsingh@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20211224152916.1550677-2-kpsingh@kernel.org
284 lines
7 KiB
C
284 lines
7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2019 Facebook
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* Copyright 2020 Google LLC.
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*/
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#include <linux/rculist.h>
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#include <linux/list.h>
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#include <linux/hash.h>
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#include <linux/types.h>
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#include <linux/spinlock.h>
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#include <linux/bpf.h>
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#include <linux/bpf_local_storage.h>
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#include <net/sock.h>
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#include <uapi/linux/sock_diag.h>
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#include <uapi/linux/btf.h>
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#include <linux/bpf_lsm.h>
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#include <linux/btf_ids.h>
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#include <linux/fdtable.h>
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#include <linux/rcupdate_trace.h>
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DEFINE_BPF_STORAGE_CACHE(inode_cache);
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static struct bpf_local_storage __rcu **
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inode_storage_ptr(void *owner)
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{
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struct inode *inode = owner;
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struct bpf_storage_blob *bsb;
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bsb = bpf_inode(inode);
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if (!bsb)
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return NULL;
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return &bsb->storage;
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}
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static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
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struct bpf_map *map,
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bool cacheit_lockit)
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{
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struct bpf_local_storage *inode_storage;
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struct bpf_local_storage_map *smap;
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struct bpf_storage_blob *bsb;
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bsb = bpf_inode(inode);
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if (!bsb)
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return NULL;
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inode_storage =
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rcu_dereference_check(bsb->storage, bpf_rcu_lock_held());
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if (!inode_storage)
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return NULL;
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smap = (struct bpf_local_storage_map *)map;
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return bpf_local_storage_lookup(inode_storage, smap, cacheit_lockit);
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}
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void bpf_inode_storage_free(struct inode *inode)
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{
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struct bpf_local_storage_elem *selem;
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struct bpf_local_storage *local_storage;
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bool free_inode_storage = false;
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struct bpf_storage_blob *bsb;
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struct hlist_node *n;
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bsb = bpf_inode(inode);
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if (!bsb)
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return;
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rcu_read_lock();
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local_storage = rcu_dereference(bsb->storage);
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if (!local_storage) {
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rcu_read_unlock();
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return;
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}
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/* Neither the bpf_prog nor the bpf-map's syscall
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* could be modifying the local_storage->list now.
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* Thus, no elem can be added-to or deleted-from the
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* local_storage->list by the bpf_prog or by the bpf-map's syscall.
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*
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* It is racing with bpf_local_storage_map_free() alone
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* when unlinking elem from the local_storage->list and
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* the map's bucket->list.
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*/
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raw_spin_lock_bh(&local_storage->lock);
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hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
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/* Always unlink from map before unlinking from
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* local_storage.
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*/
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bpf_selem_unlink_map(selem);
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free_inode_storage = bpf_selem_unlink_storage_nolock(
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local_storage, selem, false);
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}
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raw_spin_unlock_bh(&local_storage->lock);
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rcu_read_unlock();
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/* free_inoode_storage should always be true as long as
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* local_storage->list was non-empty.
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*/
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if (free_inode_storage)
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kfree_rcu(local_storage, rcu);
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}
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static void *bpf_fd_inode_storage_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_local_storage_data *sdata;
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struct file *f;
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int fd;
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fd = *(int *)key;
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f = fget_raw(fd);
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if (!f)
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return ERR_PTR(-EBADF);
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sdata = inode_storage_lookup(f->f_inode, map, true);
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fput(f);
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return sdata ? sdata->data : NULL;
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}
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static int bpf_fd_inode_storage_update_elem(struct bpf_map *map, void *key,
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void *value, u64 map_flags)
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{
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struct bpf_local_storage_data *sdata;
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struct file *f;
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int fd;
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fd = *(int *)key;
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f = fget_raw(fd);
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if (!f)
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return -EBADF;
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if (!inode_storage_ptr(f->f_inode)) {
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fput(f);
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return -EBADF;
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}
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sdata = bpf_local_storage_update(f->f_inode,
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(struct bpf_local_storage_map *)map,
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value, map_flags);
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fput(f);
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return PTR_ERR_OR_ZERO(sdata);
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}
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static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
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{
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struct bpf_local_storage_data *sdata;
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sdata = inode_storage_lookup(inode, map, false);
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if (!sdata)
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return -ENOENT;
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bpf_selem_unlink(SELEM(sdata));
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return 0;
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}
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static int bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)
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{
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struct file *f;
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int fd, err;
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fd = *(int *)key;
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f = fget_raw(fd);
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if (!f)
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return -EBADF;
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err = inode_storage_delete(f->f_inode, map);
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fput(f);
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return err;
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}
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BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
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void *, value, u64, flags)
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{
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struct bpf_local_storage_data *sdata;
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WARN_ON_ONCE(!bpf_rcu_lock_held());
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if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
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return (unsigned long)NULL;
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/* explicitly check that the inode_storage_ptr is not
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* NULL as inode_storage_lookup returns NULL in this case and
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* bpf_local_storage_update expects the owner to have a
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* valid storage pointer.
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*/
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if (!inode || !inode_storage_ptr(inode))
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return (unsigned long)NULL;
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sdata = inode_storage_lookup(inode, map, true);
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if (sdata)
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return (unsigned long)sdata->data;
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/* This helper must only called from where the inode is guaranteed
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* to have a refcount and cannot be freed.
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*/
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if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
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sdata = bpf_local_storage_update(
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inode, (struct bpf_local_storage_map *)map, value,
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BPF_NOEXIST);
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return IS_ERR(sdata) ? (unsigned long)NULL :
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(unsigned long)sdata->data;
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}
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return (unsigned long)NULL;
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}
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BPF_CALL_2(bpf_inode_storage_delete,
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struct bpf_map *, map, struct inode *, inode)
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{
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WARN_ON_ONCE(!bpf_rcu_lock_held());
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if (!inode)
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return -EINVAL;
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/* This helper must only called from where the inode is guaranteed
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* to have a refcount and cannot be freed.
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*/
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return inode_storage_delete(inode, map);
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}
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static int notsupp_get_next_key(struct bpf_map *map, void *key,
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void *next_key)
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{
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return -ENOTSUPP;
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}
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static struct bpf_map *inode_storage_map_alloc(union bpf_attr *attr)
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{
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struct bpf_local_storage_map *smap;
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smap = bpf_local_storage_map_alloc(attr);
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if (IS_ERR(smap))
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return ERR_CAST(smap);
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smap->cache_idx = bpf_local_storage_cache_idx_get(&inode_cache);
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return &smap->map;
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}
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static void inode_storage_map_free(struct bpf_map *map)
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{
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struct bpf_local_storage_map *smap;
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smap = (struct bpf_local_storage_map *)map;
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bpf_local_storage_cache_idx_free(&inode_cache, smap->cache_idx);
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bpf_local_storage_map_free(smap, NULL);
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}
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static int inode_storage_map_btf_id;
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const struct bpf_map_ops inode_storage_map_ops = {
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.map_meta_equal = bpf_map_meta_equal,
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.map_alloc_check = bpf_local_storage_map_alloc_check,
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.map_alloc = inode_storage_map_alloc,
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.map_free = inode_storage_map_free,
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.map_get_next_key = notsupp_get_next_key,
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.map_lookup_elem = bpf_fd_inode_storage_lookup_elem,
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.map_update_elem = bpf_fd_inode_storage_update_elem,
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.map_delete_elem = bpf_fd_inode_storage_delete_elem,
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.map_check_btf = bpf_local_storage_map_check_btf,
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.map_btf_name = "bpf_local_storage_map",
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.map_btf_id = &inode_storage_map_btf_id,
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.map_owner_storage_ptr = inode_storage_ptr,
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};
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BTF_ID_LIST_SINGLE(bpf_inode_storage_btf_ids, struct, inode)
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const struct bpf_func_proto bpf_inode_storage_get_proto = {
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.func = bpf_inode_storage_get,
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.gpl_only = false,
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.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_BTF_ID,
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.arg2_btf_id = &bpf_inode_storage_btf_ids[0],
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.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
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.arg4_type = ARG_ANYTHING,
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};
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const struct bpf_func_proto bpf_inode_storage_delete_proto = {
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.func = bpf_inode_storage_delete,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_BTF_ID,
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.arg2_btf_id = &bpf_inode_storage_btf_ids[0],
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};
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