[LTP] [PATCH v4] ioctl_loop06: update loopback block size validation

[Li Wang]

The kernel commit 47dd6753 ("block/bdev: lift block size restrictions to 64k")
now supports block sizes larger than PAGE_SIZE, with a new upper limit of
BLK_MAX_BLOCK_SIZE (64K). But ioctl_loop06 still assumes that PAGE_SIZE is the
maximum allowed block size, causing failures on newer kernels(>= 6.14):

  ioctl_loop06.c:74: TINFO: Using LOOP_SET_BLOCK_SIZE with arg > PAGE_SIZE
  ioctl_loop06.c:57: TFAIL: Set block size succeed unexpectedly
  ...
  ioctl_loop06.c:74: TINFO: Using LOOP_CONFIGURE with block_size > PAGE_SIZE
  ioctl_loop06.c:57: TFAIL: Set block size succeed unexpectedly

This patch updates ioctl_loop06 to use BLK_MAX_BLOCK_SIZE instead of PAGE_SIZE
for block size validation.

And, dynamically sets bs based on BLK_MAX_BLOCK_SIZE, using 1024 bytes if it's
below 1MB or scaling it otherwise. Ensures tst_fill_file() writes efficiently
while maintaining compatibility across different kernel versions.

Signed-off-by: Li Wang <liwang@redhat.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
---
 configure.ac                                  |  1 +
 include/lapi/blkdev.h                         | 19 +++++++++++++++++++
 .../kernel/syscalls/ioctl/ioctl_loop06.c      | 12 ++++++++----
 3 files changed, 28 insertions(+), 4 deletions(-)
 create mode 100644 include/lapi/blkdev.h

diff --git a/configure.ac b/configure.ac
index 0f2b6f332..5538d88d5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -52,6 +52,7 @@ AC_CHECK_HEADERS_ONCE([ \
     emmintrin.h \
     ifaddrs.h \
     keyutils.h \
+    linux/blkdev.h \
     linux/can.h \
     linux/cgroupstats.h \
     linux/cryptouser.h \
diff --git a/include/lapi/blkdev.h b/include/lapi/blkdev.h
new file mode 100644
index 000000000..3ee058ce0
--- /dev/null
+++ b/include/lapi/blkdev.h
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2025 Linux Test Project
+ *  Li Wang <liwang@redhat.com>
+ */
+
+#ifndef LAPI_BLKDEV_H__
+#define LAPI_BLKDEV_H__
+
+#ifdef HAVE_LINUX_BLKDEV_H
+#include <linux/blkdev.h>
+#endif
+
+/* Define BLK_MAX_BLOCK_SIZE for older kernels */
+#ifndef BLK_MAX_BLOCK_SIZE
+#define BLK_MAX_BLOCK_SIZE 0x00010000 /* 64K */
+#endif
+
+#endif /* LAPI_BLKDEV_H */
diff --git a/testcases/kernel/syscalls/ioctl/ioctl_loop06.c b/testcases/kernel/syscalls/ioctl/ioctl_loop06.c
index 573871bc1..35e9e79e9 100644
--- a/testcases/kernel/syscalls/ioctl/ioctl_loop06.c
+++ b/testcases/kernel/syscalls/ioctl/ioctl_loop06.c
@@ -14,7 +14,9 @@
 #include <unistd.h>
 #include <sys/types.h>
 #include <stdlib.h>
+#include "lapi/blkdev.h"
 #include "lapi/loop.h"
+#include "tst_fs.h"
 #include "tst_test.h"
 
 static char dev_path[1024];
@@ -31,7 +33,7 @@ static struct tcase {
 	"Using LOOP_SET_BLOCK_SIZE with arg < 512"},
 
 	{&invalid_value, LOOP_SET_BLOCK_SIZE,
-	"Using LOOP_SET_BLOCK_SIZE with arg > PAGE_SIZE"},
+	"Using LOOP_SET_BLOCK_SIZE with arg > BLK_MAX_BLOCK_SIZE"},
 
 	{&unalign_value, LOOP_SET_BLOCK_SIZE,
 	"Using LOOP_SET_BLOCK_SIZE with arg != power_of_2"},
@@ -40,7 +42,7 @@ static struct tcase {
 	"Using LOOP_CONFIGURE with block_size < 512"},
 
 	{&invalid_value, LOOP_CONFIGURE,
-	"Using LOOP_CONFIGURE with block_size > PAGE_SIZE"},
+	"Using LOOP_CONFIGURE with block_size > BLK_MAX_BLOCK_SIZE"},
 
 	{&unalign_value, LOOP_CONFIGURE,
 	"Using LOOP_CONFIGURE with block_size != power_of_2"},
@@ -103,10 +105,12 @@ static void setup(void)
 	if (dev_num < 0)
 		tst_brk(TBROK, "Failed to find free loop device");
 
-	tst_fill_file("test.img", 0, 1024, 1024);
+	size_t bs = (BLK_MAX_BLOCK_SIZE < TST_MB) ? 1024 : 4 * BLK_MAX_BLOCK_SIZE / 1024;
+	tst_fill_file("test.img", 0, bs, 1024);
+
 	half_value = 256;
 	pg_size = getpagesize();
-	invalid_value = pg_size * 2 ;
+	invalid_value = BLK_MAX_BLOCK_SIZE * 2;
 	unalign_value = pg_size - 1;
 
 	dev_fd = SAFE_OPEN(dev_path, O_RDWR);
-- 
2.48.1