[LTP] [PATCH 4/4] libswap: add Btrfs noCOW attribute setting for swap files

Li Wang
2024-01-22T07:31:06Z

The patch aims to ensure swap files on Btrfs filesystems are created
with the appropriate FS_NOCOW_FL attribute, which is necessary to
disable CoW (Copy-on-Write) for swap files, perthe btrfs(5) manual page.
This change is gated behind a kernel version check to ensure compatibility
with the system's capabilities.

Signed-off-by: Li Wang <liwang@redhat.com>
---
libs/libltpswap/libswap.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)

diff --git a/libs/libltpswap/libswap.c b/libs/libltpswap/libswap.c
index 623f2fb3c..0b1d9a227 100644
--- a/libs/libltpswap/libswap.c
+++ b/libs/libltpswap/libswap.c
@@ -4,6 +4,7 @@
* Author: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
*/

+#include <linux/fs.h>
#include <errno.h>

#define TST_NO_DEFAULT_MAIN
@@ -23,11 +24,37 @@ static const char *const swap_supported_fs[] = {
NULL
};

+static void set_nocow_attr(const char *filename)
+{
+ int fd;
+ int attrs;
+
+ fd = SAFE_OPEN(filename, O_RDONLY);
+
+ if (ioctl(fd, FS_IOC_GETFLAGS, &attrs) == -1) {
+ tst_res(TFAIL | TERRNO, "Error getting attributes");
+ close(fd);
+ return;
+ }
+
+ attrs |= FS_NOCOW_FL;
+
+ if (ioctl(fd, FS_IOC_SETFLAGS, &attrs) == -1)
+ tst_res(TFAIL | TERRNO, "Error setting FS_NOCOW_FL attribute");
+ else
+ tst_res(TINFO, "FS_NOCOW_FL attribute set on %s\n", filename);
+
+ close(fd);
+}
+
/*
* Make a swap file
*/
int make_swapfile(const char *swapfile, int safe)
{
+ long fs_type = tst_fs_type(swapfile);
+ const char *fstype = tst_fs_type_name(fs_type);
+
if (!tst_fs_has_free(".", sysconf(_SC_PAGESIZE) * 10, TST_BYTES))
tst_brk(TBROK, "Insufficient disk space to create swap file");

@@ -35,6 +62,14 @@ int make_swapfile(const char *swapfile, int safe)
if (tst_fill_file(swapfile, 0, sysconf(_SC_PAGESIZE), 10) != 0)
tst_brk(TBROK, "Failed to create swapfile");

+ /* Btrfs file need set 'nocow' attribute */
+ if (strcmp(fstype, "btrfs") == 0) {
+ if (tst_kvercmp(5, 0, 0) > 0)
+ set_nocow_attr(swapfile);
+ else
+ tst_brk(TCONF, "Swapfile on %s not implemented", fstype);
+ }
+
/* make the file swapfile */
const char *argv[2 + 1];
argv[0] = "mkswap";
--
2.40.1