[PATCH net-next v2] selftests: tls: size splice_short pipe by page size

[PATCH net-next v2] selftests: tls: size splice_short pipe by page size

[Nirmoy Das]

splice_short grows its pipe with (MAX_FRAGS + 1) * 0x1000 so it can
queue one short vmsplice() buffer for each fragment before draining the
pipe. That assumes 4K pipe buffers.

On 64K-page kernels the request is rounded to 262144 bytes, which
provides only four pipe buffers. The fifth one-byte vmsplice() blocks in
pipe_wait_writable and the test times out before it reaches the TLS path.

Request enough bytes for the same number of pipe buffers using the
runtime page size, and assert that the kernel granted at least that much.
If an unprivileged run cannot raise the pipe above the system
pipe-max-size limit, skip the test because it cannot exercise the
intended path.

Fixes: 3667e9b442b9 ("selftests: tls: add test for short splice due to full skmsg")
Assisted-by: Codex:gpt-5
Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
---
v2: Remove redundant ASSERT_GE(ret, 0) (Simon Horman).

 tools/testing/selftests/net/tls.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/tls.c b/tools/testing/selftests/net/tls.c
index 30a236b8e9f73..d805a7dfbdd51 100644
--- a/tools/testing/selftests/net/tls.c
+++ b/tools/testing/selftests/net/tls.c
@@ -997,6 +997,8 @@ TEST_F(tls, splice_short)
 	char sendbuf[0x100];
 	char sendchar = 'S';
 	int pipefds[2];
+	int pipe_sz;
+	int ret;
 	int i;
 
 	sendchar_iov.iov_base = &sendchar;
@@ -1005,7 +1007,11 @@ TEST_F(tls, splice_short)
 	memset(sendbuf, 's', sizeof(sendbuf));
 
 	ASSERT_GE(pipe2(pipefds, O_NONBLOCK), 0);
-	ASSERT_GE(fcntl(pipefds[0], F_SETPIPE_SZ, (MAX_FRAGS + 1) * 0x1000), 0);
+	pipe_sz = (MAX_FRAGS + 1) * getpagesize();
+	ret = fcntl(pipefds[0], F_SETPIPE_SZ, pipe_sz);
+	if (ret < 0 && errno == EPERM)
+		SKIP(return, "insufficient pipe capacity");
+	ASSERT_GE(ret, pipe_sz);
 
 	for (i = 0; i < MAX_FRAGS; i++)
 		ASSERT_GE(vmsplice(pipefds[1], &sendchar_iov, 1, 0), 0);

base-commit: 47186409c092cd7dd70350999186c700233e854d
-- 
2.43.0

Re: [PATCH net-next v2] selftests: tls: size splice_short pipe by page size

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 24 Jun 2026 06:44:16 -0700 you wrote:
> splice_short grows its pipe with (MAX_FRAGS + 1) * 0x1000 so it can
> queue one short vmsplice() buffer for each fragment before draining the
> pipe. That assumes 4K pipe buffers.
> 
> On 64K-page kernels the request is rounded to 262144 bytes, which
> provides only four pipe buffers. The fifth one-byte vmsplice() blocks in
> pipe_wait_writable and the test times out before it reaches the TLS path.
> 
> [...]

Here is the summary with links:
  - [net-next,v2] selftests: tls: size splice_short pipe by page size
    https://git.kernel.org/netdev/net/c/3e52f56875c6

You are awesome, thank you!
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