[PATCH net v2 0/2] vsock/virtio: collapse receive queue under memory pressure

[Stefano Garzarella <sgarzare@redhat.com>]

This series contains a patch (the first one) that is part of work I'm
doing to improve the tracking of memory used by AF_VSOCK sockets.
The second patch is a test for our suite that highlights the issue.

Since Brien reported an issue with his environment (based on Linux 6.12.y)
related to the work I’m doing, I extracted this patch and tried to make it
as easy as possible to backport. Brien tested it by backporting it to
6.12.y, which now contains the backport of the 059b7dbd20a6
("vsock/virtio: fix potential unbounded skb queue").

This patch primarily fixes STREAM sockets, but also partially fixes
SEQPACKET (with the exception of EOMs, which are kept in separate skbs to
avoid overcomplicating the code).

The rest of the work, I feel, is more net-next material and still needs
some work to be completed.

Changelog
---------

v2:
- defined MAX_COLLAPSE_LEN macro instead of using a variable [Paolo]
- added a threshold to avoid walking all the queue while collapsing
  [Paolo]
- collapsed the queue before calling virtio_transport_inc_rx_pkt().
  While working on the threshold, I figured out that the check I was
  introducing can also be used to proactively trigger the collapse, so I
  moved the call to virtio_transport_collapse_rx_queue() before acquiring
  the rx_lock to have also a better diff to simplify backports
- improved code readability (removed `out` label, `keep` initialization,
  etc.) [Paolo + other small stuff]
- Brien kindly retested this version as well (thank you so much)

v1: https://lore.kernel.org/netdev/20260626134823.206676-1-sgarzare@redhat.com/

Thanks,
Stefano

Stefano Garzarella (2):
  vsock/virtio: collapse receive queue under memory pressure
  vsock/test: add test for small packets under pressure

 net/vmw_vsock/virtio_transport_common.c | 165 +++++++++++++++++++++++-
 tools/testing/vsock/vsock_test.c        |  87 +++++++++++++
 2 files changed, 251 insertions(+), 1 deletion(-)

-- 
2.55.0