[RFC PATCH 11/19] xdp: convert to use vm_account

From: Alistair Popple
Date: Tue Jan 24 2023 - 00:46:41 EST


Switch to using the new vm_account struct to charge pinned pages and
enforce the rlimit. This will allow a future change to also charge a
cgroup for limiting the number of pinned pages.

Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Cc: "Björn Töpel" <bjorn@xxxxxxxxxx>
Cc: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Cc: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
Cc: Jonathan Lemon <jonathan.lemon@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Cc: bpf@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
include/net/xdp_sock.h | 2 +-
net/xdp/xdp_umem.c | 38 +++++++++++++-------------------------
2 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 3057e1a..b0d3c16 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -25,7 +25,7 @@ struct xdp_umem {
u32 chunk_size;
u32 chunks;
u32 npgs;
- struct user_struct *user;
+ struct vm_account vm_account;
refcount_t users;
u8 flags;
bool zc;
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 4681e8e..4b5fb2f 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -29,12 +29,10 @@ static void xdp_umem_unpin_pages(struct xdp_umem *umem)
umem->pgs = NULL;
}

-static void xdp_umem_unaccount_pages(struct xdp_umem *umem)
+static void xdp_umem_unaccount_pages(struct xdp_umem *umem, u32 npgs)
{
- if (umem->user) {
- atomic_long_sub(umem->npgs, &umem->user->locked_vm);
- free_uid(umem->user);
- }
+ vm_unaccount_pinned(&umem->vm_account, npgs);
+ vm_account_release(&umem->vm_account);
}

static void xdp_umem_addr_unmap(struct xdp_umem *umem)
@@ -54,13 +52,15 @@ static int xdp_umem_addr_map(struct xdp_umem *umem, struct page **pages,

static void xdp_umem_release(struct xdp_umem *umem)
{
+ u32 npgs = umem->npgs;
+
umem->zc = false;
ida_free(&umem_ida, umem->id);

xdp_umem_addr_unmap(umem);
xdp_umem_unpin_pages(umem);

- xdp_umem_unaccount_pages(umem);
+ xdp_umem_unaccount_pages(umem, npgs);
kfree(umem);
}

@@ -127,24 +127,13 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem, unsigned long address)

static int xdp_umem_account_pages(struct xdp_umem *umem)
{
- unsigned long lock_limit, new_npgs, old_npgs;
-
- if (capable(CAP_IPC_LOCK))
- return 0;
-
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- umem->user = get_uid(current_user());
+ vm_account_init(&umem->vm_account, current,
+ current_user(), VM_ACCOUNT_USER);
+ if (vm_account_pinned(&umem->vm_account, umem->npgs)) {
+ vm_account_release(&umem->vm_account);
+ return -ENOBUFS;
+ }

- do {
- old_npgs = atomic_long_read(&umem->user->locked_vm);
- new_npgs = old_npgs + umem->npgs;
- if (new_npgs > lock_limit) {
- free_uid(umem->user);
- umem->user = NULL;
- return -ENOBUFS;
- }
- } while (atomic_long_cmpxchg(&umem->user->locked_vm, old_npgs,
- new_npgs) != old_npgs);
return 0;
}

@@ -204,7 +193,6 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
umem->chunks = chunks;
umem->npgs = (u32)npgs;
umem->pgs = NULL;
- umem->user = NULL;
umem->flags = mr->flags;

INIT_LIST_HEAD(&umem->xsk_dma_list);
@@ -227,7 +215,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
out_unpin:
xdp_umem_unpin_pages(umem);
out_account:
- xdp_umem_unaccount_pages(umem);
+ xdp_umem_unaccount_pages(umem, npgs);
return err;
}

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git-series 0.9.1