2022-03-28 23:03:00

by Petr Vorel

[permalink] [raw]
Subject: [PATCH v2 1/1] lib: Retry safe_clone() on ENOSPC|EUSERS

In some tests we are creating the namespaces faster than they are being
asynchronously cleaned up in the kernel:

$ sudo ./userns08 -i 10
userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
userns08.c:36: TBROK: clone3 failed: ENOSPC (28)

Thus retrying the clone() on ENOSPC (or EUSERS for kernel < 4.9).

Suggested-by: Cyril Hrubis <[email protected]>
Signed-off-by: Petr Vorel <[email protected]>
---
changes v1->v2:
* use TST_RETRY_FN_EXP_BACKOFF() (Cyril)

NOTE: 0.1s seems to be safe, although using TST_RETRY_FUNC() with 1s
(the default) would be of course OK.

Kind regards,
Petr

lib/tst_test.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/tst_test.c b/lib/tst_test.c
index 384c73e163..2e89d954ec 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -436,6 +436,9 @@ pid_t safe_fork(const char *filename, unsigned int lineno)
return pid;
}

+/* too fast creating namespaces => retrying */
+#define TST_CHECK_ENOSPC(x) ((x) >= 0 || !(errno == ENOSPC || errno == EUSERS))
+
pid_t safe_clone(const char *file, const int lineno,
const struct tst_clone_args *args)
{
@@ -444,7 +447,7 @@ pid_t safe_clone(const char *file, const int lineno,
if (!tst_test->forks_child)
tst_brk(TBROK, "test.forks_child must be set!");

- pid = tst_clone(args);
+ pid = TST_RETRY_FN_EXP_BACKOFF(tst_clone(args), TST_CHECK_ENOSPC, 0.1);

switch (pid) {
case -1:
--
2.35.1