[LTP] [PATCH V4 4/6] libswap: add function to prealloc contiguous file

[Li Wang]

The improve makes several key updates to the swap file handling
in the libswap.c file:

It incorporates support for the Btrfs filesystem, which is now
recognized as a valid filesystem for swap files.

A new function, set_nocow_attr, is added to apply the FS_NOCOW_FL
flag to files on Btrfs filesystems.

Introduces a new prealloc_contiguous_file function. This method
preallocates a contiguous block of space for the swap file during
its creation, rather than filling the file with data as was done
previously.

Modifications to the make_swapfile function are made to utilize
prealloc_contiguous_file for creating the swap file, ensuring
the file is created with contiguous space on the filesystem.

Signed-off-by: Li Wang <liwang@redhat.com>
---
 libs/libltpswap/libswap.c | 54 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/libs/libltpswap/libswap.c b/libs/libltpswap/libswap.c
index 8c2ce6cd7..e606e3f03 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
@@ -13,6 +14,7 @@
 #include "lapi/syscalls.h"
 
 static const char *const swap_supported_fs[] = {
+	"btrfs",
 	"ext2",
 	"ext3",
 	"ext4",
@@ -23,6 +25,50 @@ static const char *const swap_supported_fs[] = {
 	NULL
 };
 
+static void set_nocow_attr(const char *filename)
+{
+	int fd;
+	int attrs;
+
+	tst_res(TINFO, "FS_NOCOW_FL attribute set on %s", filename);
+
+	fd = SAFE_OPEN(filename, O_RDONLY);
+
+	SAFE_IOCTL(fd, FS_IOC_GETFLAGS, &attrs);
+
+	attrs |= FS_NOCOW_FL;
+
+	SAFE_IOCTL(fd, FS_IOC_SETFLAGS, &attrs);
+
+	SAFE_CLOSE(fd);
+}
+
+static int prealloc_contiguous_file(const char *path, size_t bs, size_t bcount)
+{
+	int fd;
+
+	fd = open(path, O_CREAT|O_WRONLY|O_TRUNC, 0600);
+	if (fd < 0)
+		return -1;
+
+	/* Btrfs file need set 'nocow' attribute */
+	if (tst_fs_type(path) == TST_BTRFS_MAGIC)
+		set_nocow_attr(path);
+
+	if (tst_prealloc_size_fd(fd, bs, bcount)) {
+		close(fd);
+		unlink(path);
+		return -1;
+	}
+
+	if (close(fd) < 0) {
+		unlink(path);
+		return -1;
+	}
+
+	return 0;
+}
+
 /*
  * Make a swap file
  */
@@ -32,9 +78,15 @@ int make_swapfile(const char *swapfile, int safe)
 		tst_brk(TBROK, "Insufficient disk space to create swap file");
 
 	/* create file */
-	if (tst_fill_file(swapfile, 0, sysconf(_SC_PAGESIZE), 10) != 0)
+	if (prealloc_contiguous_file(swapfile, sysconf(_SC_PAGESIZE), 10) != 0)
 		tst_brk(TBROK, "Failed to create swapfile");
 
+	/* Full the file to make old xfs happy*/
+	if (tst_fs_type(swapfile) == TST_XFS_MAGIC) {
+		if (tst_fill_file(swapfile, 0, sysconf(_SC_PAGESIZE), 10) != 0)
+			tst_brk(TBROK, "Failed to create swapfile");
+	}
+
 	/* make the file swapfile */
 	const char *argv[2 + 1];
 
-- 
2.40.1