[PATCH net v2 2/2] net: clarify SO_DEVMEM_DONTNEED behavior in documentation

From: Mina Almasry
Date: Thu Nov 07 2024 - 16:11:01 EST


Document new behavior when the number of frags passed is too big.

Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
---
Documentation/networking/devmem.rst | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/Documentation/networking/devmem.rst b/Documentation/networking/devmem.rst
index a55bf21f671c..d95363645331 100644
--- a/Documentation/networking/devmem.rst
+++ b/Documentation/networking/devmem.rst
@@ -225,6 +225,15 @@ The user must ensure the tokens are returned to the kernel in a timely manner.
Failure to do so will exhaust the limited dmabuf that is bound to the RX queue
and will lead to packet drops.

+The user must pass no more than 128 tokens, with no more than 1024 total frags
+among the token->token_count across all the tokens. If the user provides more
+than 1024 frags, the kernel will free up to 1024 frags and return early.
+
+The kernel returns the number of actual frags freed. The number of frags freed
+can be less than the tokens provided by the user in case of:
+
+(a) an internal kernel leak bug.
+(b) the user passed more than 1024 frags.

Implementation & Caveats
========================
--
2.47.0.277.g8800431eea-goog