[LTP] [PATCH v2 1/7] libltpswap: Add get_maxswapfiles api

[Yang Xu]

Current, the kernel constant MAX_SWAPFILES value is calculated as below
------------------------------------
//#ifdef CONFIG_DEVICE_PRIVATE
//#define SWP_DEVICE_NUM 4
//#else
//#define SWP_DEVICE_NUM 0
//#endif

//#ifdef CONFIG_MIGRATION
//#define SWP_MIGRATION_NUM 3
//#else
//#define SWP_MIGRATION_NUM 0

//#ifdef CONFIG_MEMORY_FAILURE
//#define SWP_HWPOISON_NUM 1
//#else
//#define SWP_HWPOISON_NUM 0
//#endif

//#define SWP_PTE_MARKER_NUM 1
//#define MAX_SWAPFILES_SHIFT   5

//#define MAX_SWAPFILES \
//      ((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \
//      SWP_MIGRATION_NUM - SWP_HWPOISON_NUM - \
//      SWP_PTE_MARKER_NUM)
------------------------------------

Also, man-pages missed something after 5.14 kernel. I have sent two patches[1][2] to
add it. The kernel patches modify this kernel constant in[3][4][5][6].

[1]https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=26f3ec74e
[2]https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=6bf3937fc
[3]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/swap.h?id=5042db43cc
[4]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/swap.h?id=b756a3b5e
[5]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/swap.h?id=679d10331
[6]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/swap.h?id=6c287605f

Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
---
 include/libswap.h         |  6 ++++++
 libs/libltpswap/libswap.c | 44 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/include/libswap.h b/include/libswap.h
index d4b5301a5..2cab1047d 100644
--- a/include/libswap.h
+++ b/include/libswap.h
@@ -21,4 +21,10 @@ int make_swapfile(const char *swapfile, int safe);
  * we are testing on.
  */
 void is_swap_supported(const char *filename);
+
+/*
+ * Get kernel constant MAX_SWAPFILES value
+ */
+unsigned int get_maxswapfiles(void);
+
 #endif /* __LIBSWAP_H__ */
diff --git a/libs/libltpswap/libswap.c b/libs/libltpswap/libswap.c
index d014325e5..658ecede7 100644
--- a/libs/libltpswap/libswap.c
+++ b/libs/libltpswap/libswap.c
@@ -11,6 +11,8 @@
 #include "tst_test.h"
 #include "libswap.h"
 #include "lapi/syscalls.h"
+#include "tst_kconfig.h"
+#include "tst_safe_stdio.h"
 
 /*
  * Make a swap file
@@ -65,3 +67,45 @@ void is_swap_supported(const char *filename)
 	if (TST_RET == -1)
 		tst_brk(TFAIL | TTERRNO, "swapoff on %s failed", fstype);
 }
+
+/*
+ * Get kernel constant MAX_SWAPFILES value
+ */
+unsigned int get_maxswapfiles(void)
+{
+	unsigned int max_swapfile = 32;
+	unsigned int swp_migration_num = 0, swp_hwpoison_num = 0, swp_device_num = 0, swp_pte_marker_num = 0;
+	struct tst_kconfig_var migration_kconfig = TST_KCONFIG_INIT("CONFIG_MIGRATION");
+	struct tst_kconfig_var memory_kconfig = TST_KCONFIG_INIT("CONFIG_MEMORY_FAILURE");
+	struct tst_kconfig_var device_kconfig = TST_KCONFIG_INIT("CONFIG_DEVICE_PRIVATE");
+	struct tst_kconfig_var marker_kconfig = TST_KCONFIG_INIT("CONFIG_PTE_MARKER");
+
+	tst_kconfig_read(&migration_kconfig, 1);
+	tst_kconfig_read(&memory_kconfig, 1);
+	tst_kconfig_read(&device_kconfig, 1);
+	tst_kconfig_read(&marker_kconfig, 1);
+
+	if (migration_kconfig.choice == 'y') {
+		if (tst_kvercmp(5, 19, 0) < 0)
+			swp_migration_num = 2;
+		else
+			swp_migration_num = 3;
+	}
+
+	if (memory_kconfig.choice == 'y')
+		swp_hwpoison_num = 1;
+
+	if (device_kconfig.choice == 'y') {
+		if (tst_kvercmp(4, 14, 0) >= 0)
+			swp_device_num = 2;
+		if (tst_kvercmp(5, 14, 0) >= 0)
+			swp_device_num = 4;
+	}
+
+	if (marker_kconfig.choice == 'y') {
+		if (tst_kvercmp(5, 19, 0) >= 0)
+			swp_pte_marker_num = 1;
+	}
+
+	return max_swapfile - swp_migration_num - swp_hwpoison_num - swp_device_num - swp_pte_marker_num;
+}
-- 
2.27.0