[LTP] [PATCH] fcntl36: fix 32-bit sporadic failures

[Jan Stancek]

fcntl36 testcase has been observed to sporadically fail, when
running 32-bit user-space on 64-bit kernel.

Strace shows that region length is 0 for some commands:
  fcntl64(6, F_SETLK, {l_type=F_UNLCK, l_whence=SEEK_SET, l_start=5120, l_len=0}

This is because testcase is passing struct flock64, but
command is F_SETLK, not F_SETLK64.

So, kernel treats argument for POSIX command as 32-bit "struct flock":

  static long do_compat_fcntl64(unsigned int fd, unsigned int cmd,
  ...
        case F_SETLK:
        case F_SETLKW:
                err = get_compat_flock(&flock, compat_ptr(arg));
		...

in contrast to F_OFD_* commands, where argument  is treated
as "struct flock64":
        case F_SETLK64:
        case F_SETLKW64:
        case F_OFD_SETLK:
        case F_OFD_SETLKW:
                err = get_compat_flock64(&flock, compat_ptr(arg));
		...

Switch argument of POSIX commands to 'struct flock' and leave it to
glibc to pick correct syscall and command.

I tested fcntl36 and fcntl36_64 on x86_64 kernel (as 64bit + 32bit binary)
and i386 kernel by running 100 iterations.

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
No kernel bug, problem was found in my reproducer.
Can anyone confirm this fixes 32-bit arm too?

 testcases/kernel/syscalls/fcntl/fcntl36.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/syscalls/fcntl/fcntl36.c b/testcases/kernel/syscalls/fcntl/fcntl36.c
index 3246d13892cd..81bd5a647e4c 100644
--- a/testcases/kernel/syscalls/fcntl/fcntl36.c
+++ b/testcases/kernel/syscalls/fcntl/fcntl36.c
@@ -127,7 +127,7 @@ static void *fn_posix_w(void *arg)
 	int fd = SAFE_OPEN(fname, O_RDWR);
 	long wt = pa->cnt;
 
-	struct flock64 lck = {
+	struct flock lck = {
 		.l_whence = SEEK_SET,
 		.l_start  = pa->offset,
 		.l_len    = pa->length,
@@ -227,7 +227,7 @@ static void *fn_posix_r(void *arg)
 	int i;
 	int fd = SAFE_OPEN(fname, O_RDWR);
 
-	struct flock64 lck = {
+	struct flock lck = {
 		.l_whence = SEEK_SET,
 		.l_start  = pa->offset,
 		.l_len    = pa->length,
-- 
1.8.3.1