[LTP] [PATCH v2 1/2] lib: limit the size of tmpfs in LTP

[Li Wang <liwang@redhat.com>]

LTP mount and make use of the whole tmpfs of the test system,
generally, it's fine. But if a test (e.g fallocate06) try to
fill full in the filesystem, it takes too long to complete
testing on a large memory system.

This patch adds a new function limit_tmpfs_mount_size with
appending '-o size=xxM' to the mount options in prepare_device()
which helps limit the tmpfs mount size.

Suggested-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Li Wang <liwang@redhat.com>
---

Notes:
    V1 --> V2
        * state limit_tmpfs_mount_size as a static function
        * make use of the loop device size directly since
          it already gets a proper size in tst_acquire_device_
        * do NOT modify the tst_test->mnt_data

 lib/tst_test.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/lib/tst_test.c b/lib/tst_test.c
index 55449c80b..93761868e 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -882,8 +882,35 @@ static void prepare_and_mount_dev_fs(const char *mntpoint)
 	}
 }
 
+static char *limit_tmpfs_mount_size(const char *mnt_data,
+			char *buf, size_t buf_size, const char *fs_type)
+{
+	int fd;
+	uint64_t dev_size;
+
+	if (strcmp(fs_type, "tmpfs"))
+		return mnt_data;
+
+	fd = SAFE_OPEN(tdev.dev, O_RDONLY);
+	SAFE_IOCTL(fd, BLKGETSIZE64, &dev_size);
+	SAFE_CLOSE(fd);
+
+	dev_size = dev_size/1024/1024;
+
+	if (mnt_data)
+		snprintf(buf, buf_size, "%s,size=%luM", mnt_data, dev_size);
+	else
+		snprintf(buf, buf_size, "size=%luM", dev_size);
+
+	tst_res(TINFO, "Limiting tmpfs size to %luMB", dev_size);
+
+	return buf;
+}
+
 static void prepare_device(void)
 {
+	char *mnt_data, buf[1024];
+
 	if (tst_test->format_device) {
 		SAFE_MKFS(tdev.dev, tdev.fs_type, tst_test->dev_fs_opts,
 			  tst_test->dev_extra_opts);
@@ -896,8 +923,11 @@ static void prepare_device(void)
 	}
 
 	if (tst_test->mount_device) {
+		mnt_data = limit_tmpfs_mount_size(tst_test->mnt_data,
+				buf, sizeof(buf), tdev.fs_type);
+
 		SAFE_MOUNT(tdev.dev, tst_test->mntpoint, tdev.fs_type,
-			   tst_test->mnt_flags, tst_test->mnt_data);
+			   tst_test->mnt_flags, mnt_data);
 		mntpoint_mounted = 1;
 	}
 }
-- 
2.31.1