Re: [LTP] lapi: fallback definitions for swapon syscall

Re: [LTP] lapi: fallback definitions for swapon syscall

[linuxtestproject.agent]

Hi Andrea,

On Aug 27, 2026, Andrea Cervesato wrote:
> lapi: fallback definitions for swapon syscall

Verdict - Reviewed

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[LTP] [PATCH v2 0/3] Increase coverage for swapon syscall

[Andrea Cervesato]

Complete the EINVAL coverage on invalid input data and create a new test
to verify discarding pages functionalities.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
Changes in v2:
- ensure buffer is flushed after discard using fsync()
- add messages to show what test cases we are running
- Link to v1: https://lore.kernel.org/20260827-swapon_discard_coverage-v1-0-633bcb11c181@suse.com

---
Andrea Cervesato (3):
      lapi: fallback definitions for swapon syscall
      swapon04: Add test for discard flags
      swapon02: Add test cases for invalid swapflags

 include/tse_swap.h                          |  16 +++
 runtest/syscalls                            |   1 +
 testcases/kernel/syscalls/swapon/.gitignore |   1 +
 testcases/kernel/syscalls/swapon/swapon02.c |  58 +++++---
 testcases/kernel/syscalls/swapon/swapon04.c | 204 ++++++++++++++++++++++++++++
 5 files changed, 264 insertions(+), 16 deletions(-)
---
base-commit: 9118a480cc68700f27944aab817e0202e9e6136c
change-id: 20260827-swapon_discard_coverage-34861d63fc55

Best regards,
--  
Andrea Cervesato <andrea.cervesato@suse.com>


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[LTP] [PATCH v2 1/3] lapi: fallback definitions for swapon syscall

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Introduce fallback definition inside lapi for:

- SWAP_FLAG_PREFER
- SWAP_FLAG_PRIO_MASK
- SWAP_FLAG_DISCARD
- SWAP_FLAG_DISCARD_ONCE
- SWAP_FLAG_DISCARD_PAGES

Reviewed-by: Li Wang <li.wang@linux.dev>
Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 include/tse_swap.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/tse_swap.h b/include/tse_swap.h
index c4979b3e5..25fe4ad77 100644
--- a/include/tse_swap.h
+++ b/include/tse_swap.h
@@ -14,6 +14,22 @@
 #ifndef TSE_SWAP_H__
 #define TSE_SWAP_H__
 
+#ifndef SWAP_FLAG_PREFER
+# define SWAP_FLAG_PREFER	0x8000
+#endif
+#ifndef SWAP_FLAG_PRIO_MASK
+# define SWAP_FLAG_PRIO_MASK	0x7fff
+#endif
+#ifndef SWAP_FLAG_DISCARD
+# define SWAP_FLAG_DISCARD	0x10000
+#endif
+#ifndef SWAP_FLAG_DISCARD_ONCE
+# define SWAP_FLAG_DISCARD_ONCE	0x20000
+#endif
+#ifndef SWAP_FLAG_DISCARD_PAGES
+# define SWAP_FLAG_DISCARD_PAGES 0x40000
+#endif
+
 enum swapfile_method {
     SWAPFILE_BY_SIZE,
     SWAPFILE_BY_BLKS

-- 
2.51.0


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[LTP] [PATCH v2 2/3] swapon04: Add test for discard flags

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Verify that swapon(2) discard flags (SWAP_FLAG_DISCARD,
SWAP_FLAG_DISCARD_ONCE, SWAP_FLAG_DISCARD_PAGES) correctly control
swapon-time area discard on block devices supporting discard operations.

Reviewed-by: Li Wang <li.wang@linux.dev>
Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 runtest/syscalls                            |   1 +
 testcases/kernel/syscalls/swapon/.gitignore |   1 +
 testcases/kernel/syscalls/swapon/swapon04.c | 204 ++++++++++++++++++++++++++++
 3 files changed, 206 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index 737c63e31..ca190dd97 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1676,6 +1676,7 @@ swapoff02 swapoff02
 swapon01 swapon01
 swapon02 swapon02
 swapon03 swapon03
+swapon04 swapon04
 
 #Exclusive syscall() for POWER6 machines only
 switch01 endian_switch01
diff --git a/testcases/kernel/syscalls/swapon/.gitignore b/testcases/kernel/syscalls/swapon/.gitignore
index 729226b11..db03b81ea 100644
--- a/testcases/kernel/syscalls/swapon/.gitignore
+++ b/testcases/kernel/syscalls/swapon/.gitignore
@@ -1,3 +1,4 @@
 /swapon01
 /swapon02
 /swapon03
+/swapon04
diff --git a/testcases/kernel/syscalls/swapon/swapon04.c b/testcases/kernel/syscalls/swapon/swapon04.c
new file mode 100644
index 000000000..419edbc05
--- /dev/null
+++ b/testcases/kernel/syscalls/swapon/swapon04.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) Linux Test Project, 2026
+ */
+
+/*\
+ * Check that :manpage:`swapon(2)` discard flags control swapon-time area discard:
+ *
+ * - With 0 (no flags), the swap area is not discarded at swapon.
+ * - With SWAP_FLAG_DISCARD, the swap area is discarded at swapon.
+ * - With SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE, the swap area is discarded at swapon.
+ * - With SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_PAGES, swapon-time area discard
+ *   is disabled (page-cluster discard only).
+ * - With SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | SWAP_FLAG_DISCARD_PAGES,
+ *   SWAP_FLAG_DISCARD_ONCE takes precedence and discards the swap area at swapon.
+ * - With SWAP_FLAG_DISCARD_ONCE or SWAP_FLAG_DISCARD_PAGES alone (without the
+ *   SWAP_FLAG_DISCARD master enable bit), discard is not enabled.
+ *
+ * [Algorithm]
+ *
+ * - Create a backing file on the test filesystem and fill it completely.
+ * - Attach the backing file to a loop device supporting discard.
+ * - For each test case, populate the backing file and format it with mkswap.
+ * - Record the allocated block count before swapon().
+ * - Call swapon() with the test case flags.
+ * - Verify whether the allocated block count dropped (discarded) or remained.
+ * - Call swapoff() to reset the swap device state.
+ */
+
+#define _GNU_SOURCE
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "tst_test.h"
+#include "tse_swap.h"
+#include "lapi/syscalls.h"
+#include "lapi/fallocate.h"
+
+#define MNTPOINT "mntpoint"
+#define BACKING_FILE MNTPOINT "/swap_backing_file"
+#define SWAP_SIZE_MB 16
+
+static char loop_dev[PATH_MAX];
+static int loop_dev_id = -1;
+static int loop_attached;
+static int swap_active;
+static size_t max_header_blocks;
+
+static struct tcase {
+	int flags;
+	int exp_discard;
+	const char *desc;
+} tcases[] = {
+	{
+		.desc = "0 (no flags)",
+	},
+	{
+		.flags = SWAP_FLAG_DISCARD,
+		.exp_discard = 1,
+		.desc = "SWAP_FLAG_DISCARD",
+	},
+	{
+		.flags = SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE,
+		.exp_discard = 1,
+		.desc = "SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE",
+	},
+	{
+		.flags = SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_PAGES,
+		.desc = "SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_PAGES",
+	},
+	{
+		.flags = SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | SWAP_FLAG_DISCARD_PAGES,
+		.exp_discard = 1,
+		.desc = "SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | SWAP_FLAG_DISCARD_PAGES",
+	},
+	{
+		.flags = SWAP_FLAG_DISCARD_ONCE,
+		.desc = "SWAP_FLAG_DISCARD_ONCE (alone without master flag)",
+	},
+	{
+		.flags = SWAP_FLAG_DISCARD_PAGES,
+		.desc = "SWAP_FLAG_DISCARD_PAGES (alone without master flag)",
+	},
+};
+
+static void setup(void)
+{
+	char discard_path[PATH_MAX];
+	unsigned long discard_max_bytes = 0;
+	size_t page_size, blk_size, alloc_units;
+	struct stat st;
+	int fd;
+
+	if (access("/proc/swaps", F_OK))
+		tst_brk(TCONF, "swap is not supported by kernel");
+
+	fd = SAFE_OPEN(BACKING_FILE, O_RDWR | O_CREAT | O_TRUNC, 0600);
+	TEST(fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, 4096));
+
+	if (TST_RET != 0) {
+		SAFE_CLOSE(fd);
+
+		if (TST_ERR == EOPNOTSUPP || TST_ERR == ENOSYS) {
+			tst_brk(TCONF, "Filesystem %s does not support FALLOC_FL_PUNCH_HOLE",
+				tst_device->fs_type);
+		}
+
+		tst_brk(TBROK | TERRNO, "fallocate() error");
+	}
+
+	SAFE_FTRUNCATE(fd, SWAP_SIZE_MB * TST_MB);
+	SAFE_CLOSE(fd);
+
+	loop_dev_id = tst_find_free_loopdev(loop_dev, sizeof(loop_dev));
+	if (loop_dev_id < 0)
+		tst_brk(TBROK, "No free loop device found");
+
+	if (tst_attach_device(loop_dev, BACKING_FILE))
+		tst_brk(TBROK, "Failed to attach %s to %s", loop_dev, BACKING_FILE);
+	loop_attached = 1;
+
+	snprintf(discard_path, sizeof(discard_path),
+		 "/sys/block/loop%d/queue/discard_max_bytes", loop_dev_id);
+	if (FILE_SCANF(discard_path, "%lu", &discard_max_bytes) != 0 || discard_max_bytes == 0) {
+		tst_brk(TCONF, "Loop device %s does not support discard on %s",
+			loop_dev, tst_device->fs_type);
+	}
+
+	SAFE_STAT(BACKING_FILE, &st);
+
+	page_size = getpagesize();
+	blk_size = st.st_blksize;
+	alloc_units = page_size > blk_size ? page_size : blk_size;
+
+	/* Minimum 512-byte blocks for 1 page + small tolerance for filesystem metadata */
+	max_header_blocks = (alloc_units / 512) * 2;
+}
+
+static void verify_swapon(unsigned int n)
+{
+	struct tcase *tc = &tcases[n];
+	int fd;
+	struct stat st;
+	blkcnt_t blocks_before, blocks_after;
+	const char *const mkswap_argv[] = {"mkswap", loop_dev, NULL};
+
+	tst_res(TINFO, "Testing swapon(%s, %s)", loop_dev, tc->desc);
+
+	tst_fill_file(BACKING_FILE, 'A', TST_MB, SWAP_SIZE_MB);
+
+	fd = SAFE_OPEN(BACKING_FILE, O_RDONLY);
+	SAFE_FSYNC(fd);
+	SAFE_CLOSE(fd);
+
+	tst_cmd(mkswap_argv, "/dev/null", "/dev/null", TST_CMD_TCONF_ON_MISSING);
+
+	SAFE_STAT(BACKING_FILE, &st);
+	blocks_before = st.st_blocks;
+
+	if (!blocks_before)
+		tst_brk(TBROK, "Backing file has 0 allocated blocks");
+
+	TEST(tst_syscall(__NR_swapon, loop_dev, tc->flags));
+	if (TST_RET != 0) {
+		tst_res(TFAIL | TTERRNO, "swapon(%s, %s)", loop_dev, tc->desc);
+		return;
+	}
+	swap_active = 1;
+
+	SAFE_STAT(BACKING_FILE, &st);
+	blocks_after = st.st_blocks;
+
+	if (tc->exp_discard)
+		TST_EXP_LE_LU(blocks_after, max_header_blocks);
+	else
+		TST_EXP_EQ_LI(blocks_after, blocks_before);
+
+	if (tst_syscall(__NR_swapoff, loop_dev) != 0)
+		tst_brk(TBROK | TTERRNO, "swapoff(%s) failed", loop_dev);
+	swap_active = 0;
+}
+
+static void cleanup(void)
+{
+	if (swap_active && tst_syscall(__NR_swapoff, loop_dev) != 0)
+		tst_res(TWARN | TTERRNO, "swapoff(%s) failed", loop_dev);
+	swap_active = 0;
+
+	if (loop_attached)
+		tst_detach_device(loop_dev);
+	loop_attached = 0;
+}
+
+static struct tst_test test = {
+	.needs_root = 1,
+	.mount_device = 1,
+	.mntpoint = MNTPOINT,
+	.all_filesystems = 1,
+	.setup = setup,
+	.cleanup = cleanup,
+	.test = verify_swapon,
+	.tcnt = ARRAY_SIZE(tcases),
+};

-- 
2.51.0


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[LTP] [PATCH v2 3/3] swapon02: Add test cases for invalid swapflags

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Add test cases verifying that swapon(2) returns EINVAL when swapflags
contains undefined or invalid flag bits.

Reviewed-by: Li Wang <li.wang@linux.dev>
Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 testcases/kernel/syscalls/swapon/swapon02.c | 58 +++++++++++++++++++++--------
 1 file changed, 42 insertions(+), 16 deletions(-)

diff --git a/testcases/kernel/syscalls/swapon/swapon02.c b/testcases/kernel/syscalls/swapon/swapon02.c
index d3e528c94..9d30f8527 100644
--- a/testcases/kernel/syscalls/swapon/swapon02.c
+++ b/testcases/kernel/syscalls/swapon/swapon02.c
@@ -5,10 +5,11 @@
  */
 
 /*\
- * This test case checks whether swapon(2) system call returns:
+ * This test case checks whether :manpage:`swapon(2)` system call returns:
  *
  * - ENOENT when the path does not exist
  * - EINVAL when the path exists but is invalid
+ * - EINVAL when swapflags contains invalid or undefined flag bits
  * - EPERM when user is not a superuser
  * - EBUSY when the specified path is already being used as a swap area
  */
@@ -20,10 +21,10 @@
 #include "tse_swap.h"
 
 #define MNTPOINT	"mntpoint"
-#define TEST_FILE	MNTPOINT"/testswap"
-#define NOTSWAP_FILE	MNTPOINT"/notswap"
-#define SWAP_FILE	MNTPOINT"/swapfile"
-#define USED_FILE	MNTPOINT"/alreadyused"
+#define TEST_FILE	MNTPOINT "/testswap"
+#define NOTSWAP_FILE	MNTPOINT "/notswap"
+#define SWAP_FILE	MNTPOINT "/swapfile"
+#define USED_FILE	MNTPOINT "/alreadyused"
 
 static uid_t nobody_uid;
 static int do_swapoff;
@@ -32,11 +33,40 @@ static struct tcase {
 	char *err_desc;
 	int exp_errno;
 	char *path;
+	int flags;
 } tcases[] = {
-	{"Path does not exist", ENOENT, "./doesnotexist"},
-	{"Invalid path", EINVAL, NOTSWAP_FILE},
-	{"Permission denied", EPERM, SWAP_FILE},
-	{"File already used", EBUSY, USED_FILE},
+	{
+		.err_desc = "Path does not exist",
+		.exp_errno = ENOENT,
+		.path = "./doesnotexist",
+	},
+	{
+		.err_desc = "Invalid path",
+		.exp_errno = EINVAL,
+		.path = NOTSWAP_FILE,
+	},
+	{
+		.err_desc = "Permission denied",
+		.exp_errno = EPERM,
+		.path = SWAP_FILE,
+	},
+	{
+		.err_desc = "File already used",
+		.exp_errno = EBUSY,
+		.path = USED_FILE,
+	},
+	{
+		.err_desc = "Invalid swapflags (undefined flag bits)",
+		.exp_errno = EINVAL,
+		.path = SWAP_FILE,
+		.flags = 0x80000,
+	},
+	{
+		.err_desc = "Invalid swapflags (high bits set)",
+		.exp_errno = EINVAL,
+		.path = SWAP_FILE,
+		.flags = ~0,
+	},
 };
 
 static void setup(void)
@@ -66,20 +96,16 @@ static void cleanup(void)
 
 static void verify_swapon(unsigned int i)
 {
-	struct tcase *tc = tcases + i;
+	struct tcase *tc = &tcases[i];
+
 	if (tc->exp_errno == EPERM)
 		SAFE_SETEUID(nobody_uid);
 
-	TST_EXP_FAIL(tst_syscall(__NR_swapon, tc->path, 0), tc->exp_errno,
+	TST_EXP_FAIL(tst_syscall(__NR_swapon, tc->path, tc->flags), tc->exp_errno,
 		     "swapon(2) fail with %s", tc->err_desc);
 
 	if (tc->exp_errno == EPERM)
 		SAFE_SETEUID(0);
-
-	if (TST_RET != -1) {
-		tst_res(TFAIL, "swapon(2) failed unexpectedly, expected: %s",
-			tst_strerrno(tc->exp_errno));
-	}
 }
 
 static struct tst_test test = {

-- 
2.51.0


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Re: [LTP] [PATCH v2 2/3] swapon04: Add test for discard flags

[Li Wang]

Andrea Cervesato wrote:

> +static void verify_swapon(unsigned int n)
> +{
> +	struct tcase *tc = &tcases[n];
> +	int fd;
> +	struct stat st;
> +	blkcnt_t blocks_before, blocks_after;
> +	const char *const mkswap_argv[] = {"mkswap", loop_dev, NULL};
> +
> +	tst_res(TINFO, "Testing swapon(%s, %s)", loop_dev, tc->desc);
> +
> +	tst_fill_file(BACKING_FILE, 'A', TST_MB, SWAP_SIZE_MB);
> +

Or, we need to confirm with an XFS developer/expert whether this
should be treated as a minor bug or is worth fixing on 6.6.

If not, then the code comment below is needed.

	/*
	 * Flush the backing file to disk before formatting it with mkswap.

	 * XFS uses delayed allocation, and without fsync the blocks written
	 * by tst_fill_file() may remain as unwritten extents in page cache.
	 * If swapon(2) with SWAP_FLAG_DISCARD is called while such extents
	 * are still pending, the discard request may not cover the whole
	 * swap area, causing the test to fail spuriously.
	 *
	 * This is especially visible on kernel 6.6, where the XFS/swap
	 * discard path does not force delalloc extents to be resolved.
	 */

> +	fd = SAFE_OPEN(BACKING_FILE, O_RDONLY);
> +	SAFE_FSYNC(fd);
> +	SAFE_CLOSE(fd);

-- 
Regards,
Li Wang

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Re: [LTP] lapi: fallback definitions for swapon syscall

[linuxtestproject.agent]

Hi Andrea,

On Aug 28, 2026, Andrea Cervesato wrote:
> lapi: fallback definitions for swapon syscall

--- [PATCH 1/3] ---

> lapi: fallback definitions for swapon syscall
>
> Introduce fallback definition inside lapi for:

Could the subject and body name include/tse_swap.h rather than lapi? The
fallback definitions are not added under include/lapi/, so the current
component and location do not match the patch.

--- [PATCH 3/3] ---

> +	TST_EXP_FAIL(tst_syscall(__NR_swapon, tc->path, tc->flags), tc->exp_errno,
>  		     "swapon(2) fail with %s", tc->err_desc);
>
>  static void cleanup(void)
>  {
>  	if (do_swapoff && tst_syscall(__NR_swapoff, USED_FILE))
>  		tst_res(TWARN | TERRNO, "swapoff(alreadyused) failed");
>  }

Could an unexpected successful swapon() of SWAP_FILE be tracked and undone?
This is the failure mode these new cases are intended to detect, but
TST_EXP_FAIL() only reports TFAIL. The swap area remains active, the next
case gets EBUSY, and cleanup only disables USED_FILE, so the test filesystem
cannot be unmounted.

Verdict - Needs revision

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

-- 
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Re: [LTP] lapi: fallback definitions for swapon syscall

[Andrea Cervesato via ltp]

> --- [PATCH 1/3] ---
> 
> > lapi: fallback definitions for swapon syscall
> >
> > Introduce fallback definition inside lapi for:
> 
> Could the subject and body name include/tse_swap.h rather than lapi? The
> fallback definitions are not added under include/lapi/, so the current
> component and location do not match the patch.
> 
> --- [PATCH 3/3] ---
> 
> > +	TST_EXP_FAIL(tst_syscall(__NR_swapon, tc->path, tc->flags), tc->exp_errno,
> >  		     "swapon(2) fail with %s", tc->err_desc);
> >
> >  static void cleanup(void)
> >  {
> >  	if (do_swapoff && tst_syscall(__NR_swapoff, USED_FILE))
> >  		tst_res(TWARN | TERRNO, "swapoff(alreadyused) failed");
> >  }
> 
> Could an unexpected successful swapon() of SWAP_FILE be tracked and undone?
> This is the failure mode these new cases are intended to detect, but
> TST_EXP_FAIL() only reports TFAIL. The swap area remains active, the next
> case gets EBUSY, and cleanup only disables USED_FILE, so the test filesystem
> cannot be unmounted.

These are both correct, I will fix them in the next version.

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

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