From: Bobby Eshleman <redacted>

Refactor sock_devmem_dontneed() in preparation for supporting both
autorelease and manual token release modes.

Split the function into two parts:
- sock_devmem_dontneed(): handles input validation, token allocation,
  and copying from userspace
- sock_devmem_dontneed_autorelease(): performs the actual token release
  via xarray lookup and page pool put

This separation allows a future commit to add a parallel
sock_devmem_dontneed_manual_release() function that uses a different
token tracking mechanism (per-niov reference counting) without
duplicating the input validation logic.

The refactoring is purely mechanical with no functional change. Only
intended to minimize the noise in subsequent patches.

Signed-off-by: Bobby Eshleman <redacted>
---
 net/core/sock.c | 52 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index a99132cc0965..e7b378753763 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c

@@ -1082,30 +1082,13 @@ static int sock_reserve_memory(struct sock *sk, int bytes)
 #define MAX_DONTNEED_FRAGS 1024

 static noinline_for_stack int
-sock_devmem_dontneed(struct sock *sk, sockptr_t optval, unsigned int optlen)
+sock_devmem_dontneed_autorelease(struct sock *sk, struct dmabuf_token *tokens,