cachestat01: Reduce required space on 64kb page size

ppc64le (6.10.1 on Tumbleweed) fails due 64kb page size requiring more
space:

cachestat01.c:39: TINFO: Number of pages: 4096
cachestat01.c:56: TPASS: cachestat(fd, cs_range, cs, 0) passed
cachestat01.c:59: TPASS: cs->nr_cache + cs->nr_evicted == num_pages (4096)
cachestat01.c:38: TINFO: Disable file synchronization
cachestat01.c:39: TINFO: Number of pages: 8192
cachestat01.c:46: TBROK: write(3,0x1000ddb0aa0,65536) failed: ENOSPC (28)

Therefore use calculation, which enables maximum number of pages 1 << 14
only for 4kb page size, for 64kb set the maximum number of pages 1 << 11
(13 would trigger ENOSPC on XFS and Btrfs, 12 would work, but using 11
to be future proof in case of metadata size changes or page size
increases).

Link: https://lore.kernel.org/ltp/[email protected]/
Fixes: 93b28ee ("Add cachestat01 test")
Reviewed-by: Cyril Hrubis <[email protected]>
Signed-off-by: Petr Vorel <[email protected]>

testcases/kernel/syscalls/cachestat/cachestat01.c

@@ -26,7 +26,7 @@
 #define MNTPOINT "mntpoint"
 #define FILENAME MNTPOINT "/myfile.bin"
 
-static int page_size;
+static int page_size, num_shift;
 static char *page_data;
 static struct cachestat *cs;
 static struct cachestat_range *cs_range;
@@ -67,14 +67,14 @@ static void test_cached_pages(const unsigned int use_sync, const int num_pages)
 
 static void run(unsigned int use_sync)
 {
-	for (int i = 0; i < 15; i++)
+	for (int i = 0; i < num_shift; i++)
 		test_cached_pages(use_sync, 1 << i);
 }
 
 static void setup(void)
 {
 	page_size = (int)sysconf(_SC_PAGESIZE);
-
+	num_shift = MIN(tst_device->size*1024*2.5/page_size, 15);
 	page_data = SAFE_MALLOC(page_size);
 	memset(page_data, 'a', page_size);
 }