From: Manu Bretelle <chantr4@gmail.com>
To: Yonghong Song <yonghong.song@linux.dev>
Cc: Kui-Feng Lee <sinquersw@gmail.com>,
ast@kernel.org, bpf@vger.kernel.org, andrii@kernel.org,
daniel@iogearbox.net, martin.lau@linux.dev, song@kernel.org,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
haoluo@google.com, jolsa@kernel.org, mykolal@fb.com,
shuah@kernel.org
Subject: Re: [PATCH bpf-next] selftests/bpf: umount children of TDIR in test_bpffs
Date: Fri, 27 Oct 2023 14:09:46 -0700 [thread overview]
Message-ID: <ZTwnGrDL9vwWlXJ7@surya> (raw)
In-Reply-To: <6e4e46a2-77de-45d0-a1ec-b5622e1d75e0@linux.dev>
On Thu, Oct 26, 2023 at 11:08:35PM -0700, Yonghong Song wrote:
>
> On 10/24/23 10:41 PM, Manu Bretelle wrote:
> > On Tue, Oct 24, 2023 at 02:29:19PM -0700, Kui-Feng Lee wrote:
> > >
> > > On 10/24/23 13:18, Manu Bretelle wrote:
> > > > Currently this tests tries to umount /sys/kernel/debug (TDIR) but the
> > > > system it is running on may have mounts below.
> > > >
> > > > For example, danobi/vmtest [0] VMs have
> > > > mount -t tracefs tracefs /sys/kernel/debug/tracing
> > > > as part of their init.
> > > >
> > > > This change list mounts and will umount any mounts below TDIR before
> > > > umounting TDIR itself.
> > > >
> > > > Note that it is not umounting recursively, so in the case of a sub-mount
> > > > of TDIR having another sub-mount, this will fail as mtab is ordered.
> > > Should we move TID to a random path likes "/sys/kernel/debug-<pid>/"?
> > >
> > Fair point, I suppose we would want to keep TDIR a defined string as it does
> > simplify the gymnastic involved through the rest of the script, but yeah
> > looking at the original commit:
> > edb65ee5aa25 (selftests/bpf: Add bpffs preload test)
> >
> > I don't see any reason to use an alternate directory and rather mkdir it vs
> > umounting the original one.
> > so something like
> >
> > #define TDIR "/sys/kernel/test_bpffs"
> >
> > Would probably do.
> >
> > Alexei could confirm his original intent probably.
>
>
> Maybe/sys/kernel/tracing should work too? Not sure whether it is universally
> available or not.
>
>
I think we just need an existing directory (whichever) to mount tmpfs on, and Alexei previous
comment seems to confirm that. But importantly, nothing that has sub-mounts
if we don't want to get into the business of recursively umounting sub-mounts.
I will just pick up a name which is random enough to not realistically exist on
a system, mkdir it instead of the existing umount(TDIR) and we should be good.
> >
> > > > Test:
> > > >
> > > > Originally:
> > > >
> > > > $ vmtest -k $KERNEL_REPO/arch/x86_64/boot/bzImage "./test_progs -vv -a test_bpffs"
> > > > => bzImage
> > > > ===> Booting
> > > > ===> Setting up VM
> > > > ===> Running command
> > > > [ 2.138818] bpf_testmod: loading out-of-tree module taints kernel.
> > > > [ 2.140913] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
> > > > bpf_testmod.ko is already unloaded.
> > > > Loading bpf_testmod.ko...
> > > > Successfully loaded bpf_testmod.ko.
> > > > test_test_bpffs:PASS:clone 0 nsec
> > > > fn:PASS:unshare 0 nsec
> > > > fn:PASS:mount / 0 nsec
> > > > fn:FAIL:umount /sys/kernel/debug unexpected error: -1 (errno 16)
> > > > bpf_testmod.ko is already unloaded.
> > > > Loading bpf_testmod.ko...
> > > > Successfully loaded bpf_testmod.ko.
> > > > test_test_bpffs:PASS:clone 0 nsec
> > > > test_test_bpffs:PASS:waitpid 0 nsec
> > > > test_test_bpffs:FAIL:bpffs test failed 255#282 test_bpffs:FAIL
> > > > Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
> > > > Successfully unloaded bpf_testmod.ko.
> > > > Command failed with exit code: 1
> > > >
> > > > After this change:
> > > >
> > > > $ vmtest -k $KERNEL_REPO/arch/x86_64/boot/bzImage "./test_progs -vv -a test_bpffs"
> > > > => bzImage
> > > > ===> Booting
> > > > ===> Setting up VM
> > > > ===> Running command
> > > > [ 2.035210] bpf_testmod: loading out-of-tree module taints kernel.
> > > > [ 2.036510] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
> > > > bpf_testmod.ko is already unloaded.
> > > > Loading bpf_testmod.ko...
> > > > Successfully loaded bpf_testmod.ko.
> > > > test_test_bpffs:PASS:clone 0 nsec
> > > > fn:PASS:unshare 0 nsec
> > > > fn:PASS:mount / 0 nsec
> > > > fn:PASS:accessing /etc/mtab 0 nsec
> > > > fn:PASS:umount /sys/kernel/debug/tracing 0 nsec
> > > > fn:PASS:umount /sys/kernel/debug 0 nsec
> > > > fn:PASS:mount tmpfs 0 nsec
> > > > fn:PASS:mkdir /sys/kernel/debug/fs1 0 nsec
> > > > fn:PASS:mkdir /sys/kernel/debug/fs2 0 nsec
> > > > fn:PASS:mount bpffs /sys/kernel/debug/fs1 0 nsec
> > > > fn:PASS:mount bpffs /sys/kernel/debug/fs2 0 nsec
> > > > fn:PASS:reading /sys/kernel/debug/fs1/maps.debug 0 nsec
> > > > fn:PASS:reading /sys/kernel/debug/fs2/progs.debug 0 nsec
> > > > fn:PASS:creating /sys/kernel/debug/fs1/a 0 nsec
> > > > fn:PASS:creating /sys/kernel/debug/fs1/a/1 0 nsec
> > > > fn:PASS:creating /sys/kernel/debug/fs1/b 0 nsec
> > > > fn:PASS:create_map(ARRAY) 0 nsec
> > > > fn:PASS:pin map 0 nsec
> > > > fn:PASS:stat(/sys/kernel/debug/fs1/a) 0 nsec
> > > > fn:PASS:renameat2(/fs1/a, /fs1/b, RENAME_EXCHANGE) 0 nsec
> > > > fn:PASS:stat(/sys/kernel/debug/fs1/b) 0 nsec
> > > > fn:PASS:b should have a's inode 0 nsec
> > > > fn:PASS:access(/sys/kernel/debug/fs1/b/1) 0 nsec
> > > > fn:PASS:stat(/sys/kernel/debug/fs1/map) 0 nsec
> > > > fn:PASS:renameat2(/fs1/c, /fs1/b, RENAME_EXCHANGE) 0 nsec
> > > > fn:PASS:stat(/sys/kernel/debug/fs1/b) 0 nsec
> > > > fn:PASS:b should have c's inode 0 nsec
> > > > fn:PASS:access(/sys/kernel/debug/fs1/c/1) 0 nsec
> > > > fn:PASS:renameat2(RENAME_NOREPLACE) 0 nsec
> > > > fn:PASS:access(/sys/kernel/debug/fs1/b) 0 nsec
> > > > bpf_testmod.ko is already unloaded.
> > > > Loading bpf_testmod.ko...
> > > > Successfully loaded bpf_testmod.ko.
> > > > test_test_bpffs:PASS:clone 0 nsec
> > > > test_test_bpffs:PASS:waitpid 0 nsec
> > > > test_test_bpffs:PASS:bpffs test 0 nsec
> > > > #282 test_bpffs:OK
> > > > Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
> > > > Successfully unloaded bpf_testmod.ko.
> > > >
> > > > [0] https://github.com/danobi/vmtest
> > > >
> > > > Signed-off-by: Manu Bretelle <chantr4@gmail.com>
> > > > ---
> > > > .../selftests/bpf/prog_tests/test_bpffs.c | 28 +++++++++++++++++++
> > > > 1 file changed, 28 insertions(+)
> > > >
> > > > diff --git a/tools/testing/selftests/bpf/prog_tests/test_bpffs.c b/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
> > > > index 214d9f4a94a5..001bf694c269 100644
> > > > --- a/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
> > > > +++ b/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
> > > > @@ -3,12 +3,14 @@
> > > > #define _GNU_SOURCE
> > > > #include <stdio.h>
> > > > #include <sched.h>
> > > > +#include <mntent.h>
> > > > #include <sys/mount.h>
> > > > #include <sys/stat.h>
> > > > #include <sys/types.h>
> > > > #include <test_progs.h>
> > > > #define TDIR "/sys/kernel/debug"
> > > > +#define MTAB "/etc/mtab"
> > > > static int read_iter(char *file)
> > > > {
> > > > @@ -32,6 +34,8 @@ static int read_iter(char *file)
> > > > static int fn(void)
> > > > {
> > > > + /* A buffer to store logging messages */
> > > > + char buf[1024];
> > > > struct stat a, b, c;
> > > > int err, map;
> > > > @@ -43,6 +47,30 @@ static int fn(void)
> > > > if (!ASSERT_OK(err, "mount /"))
> > > > goto out;
> > > > + /* TDIR may have mounts below. unount them first */
> > > > + FILE *mtab = setmntent(MTAB, "r");
> > > > +
> > > > + if (!ASSERT_TRUE(mtab != NULL, "accessing " MTAB)) {
> > > > + err = errno;
> > > > + goto out;
> > > > + }
> > > > +
> > > > + struct mntent *mnt = NULL;
> > > > +
> > > > + while ((mnt = getmntent(mtab)) != NULL) {
> > > > + if (strlen(mnt->mnt_dir) > strlen(TDIR) &&
> > > > + strncmp(TDIR, mnt->mnt_dir, strlen(TDIR)) == 0) {
> > > > + snprintf(buf, sizeof(buf) - 1, "umount %s", mnt->mnt_dir);
> > > > + err = umount(mnt->mnt_dir);
> > > > + if (!ASSERT_OK(err, buf)) {
> > > > + endmntent(mtab);
> > > > + goto out;
> > > > + }
> > > > + }
> > > > + }
> > > > + // Ignore any error here
> > > > + endmntent(mtab);
> > > > +
> > > > err = umount(TDIR);
> > > > if (!ASSERT_OK(err, "umount " TDIR))
> > > > goto out;
prev parent reply other threads:[~2023-10-27 21:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-24 20:18 [PATCH bpf-next] selftests/bpf: umount children of TDIR in test_bpffs Manu Bretelle
2023-10-24 21:29 ` Kui-Feng Lee
2023-10-25 5:41 ` Manu Bretelle
2023-10-26 21:35 ` Alexei Starovoitov
2023-10-28 0:56 ` Manu Bretelle
2023-10-27 6:08 ` Yonghong Song
2023-10-27 21:09 ` Manu Bretelle [this message]
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