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net/rds: reinitialize to_be_dropped on rds_send_xmit() restart

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The to_be_dropped list is declared once at the top of rds_send_xmit()
but the function can loop via "goto restart" after each batch.  The
code currently relies on rds_send_remove_from_sock() having emptied
the list entry by entry (via list_del_init()) at the end of the
previous batch; nothing in rds_send_xmit() itself guarantees the list
head is empty when a new batch starts.

Re-initialize the list on every restart, and warn once if it is ever
found non-empty there: entries left on the list at that point would
keep their message reference, their RDS_MSG_ON_SOCK accounting and
their pending RDS_RDMA_DROPPED notification, so a silent re-init
would orphan them.  This is hardening: no user-visible bug is known
in the current code.

This mirrors Oracle UEK commit "net/rds: rds_send_xmit should
INIT_LIST_HEAD(&to_be_dropped) on restart".

Signed-off-by: Gerd Rausch <gerd.rausch@oracle.com>
Signed-off-by: Sharath Srinivasan <sharath.srinivasan@oracle.com>
[achender: port to net-next (keep the existing LIST_HEAD declaration and
 add only the restart re-init); warn if the restart invariant is
 violated; update commit message]
Assisted-by: Claude-Code:claude-fable-5
Signed-off-by: Allison Henderson <achender@kernel.org>
Link: https://patch.msgid.link/20260809005103.82371-2-achender@kernel.org
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Sharath Srinivasan 2026-08-08 17:51:02 -07:00 committed by Paolo Abeni
parent 2f886609bd
commit a364a7c168
1 changed files with 8 additions and 0 deletions
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8
net/rds/send.c
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@ -200,6 +200,14 @@ int rds_send_xmit(struct rds_conn_path *cp)
restart:
batch_count = 0;
/* The drop processing after over_batch relies on
* rds_send_remove_from_sock() emptying to_be_dropped entry by
* entry; warn if that post-condition ever stops holding, and
* re-initialize the list head.
*/
WARN_ON_ONCE(!list_empty(&to_be_dropped));
INIT_LIST_HEAD(&to_be_dropped);
/*
* sendmsg calls here after having queued its message on the send
* queue. We only have one task feeding the connection at a time. If