Re: [LTP] [PATCH v1 1/1] swap: Add exfat to filesystems requiring tst_fill_file

[Namjae Jeon]

On Tue, Aug 25, 2026 at 10:46 PM Cyril Hrubis <chrubis@xxxxxxx> wrote:
>
> Hi!
Hi Cyril, Petr,
> > > That does not make much sense, if swap_activate was added to kernel,
> > > pre-filling the fallocated file shouldn't be needed anymore.
> >
> > Good catch, you're right. I'm also confused, before v7.2 swap worked on exfat,
> > now even with 82a81a7352bc ("exfat: add iomap buffered I/O support") [2]
> > and your fix 03a43677ca91 ("exfat: add swap_activate support") [3] is not
> > working. Obviously the fix was not good enough.
>
> There were two bugs I suppose, one is that fallocate() support for exfat broke
> the swapon on fallocated file. The second bug was introduced later when
> exfat was rewritten to use iomap. The iomap case was fixed in the patch
> above, however it looks like the original bug caused by fallocate()
> implementation for exfat is still there.
Can you check if an attached patch improves this issue?
Thanks.
From 5679a624816454c8e7683842eb0ab3f1adf0dcca Mon Sep 17 00:00:00 2001
From: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Date: Wed, 26 Aug 2026 09:14:14 +0900
Subject: [PATCH] exfat: map allocated extents for swap activation

exFAT reports allocated ranges beyond valid_size as IOMAP_HOLE when
IOMAP_REPORT is set. iomap_swapfile_activate() also uses IOMAP_REPORT
while collecting physical extents for a swap file, so it treats the
preallocated tail as unallocated and rejects the file with -EINVAL.

Use swap-specific iomap operations that suppress IOMAP_REPORT before
mapping the file. This reports physically allocated ranges as
IOMAP_UNWRITTEN during swap activation without changing the
byte-accurate SEEK_HOLE and SEEK_DATA behavior of the regular iomap
operations.

Fixes: 03a43677ca91 ("exfat: add swap_activate support")
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
---
 fs/exfat/iomap.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/fs/exfat/iomap.c b/fs/exfat/iomap.c
index 0c805bf6676a..bf8baf78a9b8 100644
--- a/fs/exfat/iomap.c
+++ b/fs/exfat/iomap.c
@@ -155,6 +155,22 @@ const struct iomap_ops exfat_iomap_ops = {
 	.iomap_begin = exfat_iomap_begin,
 };
 
+static int exfat_swap_iomap_begin(struct inode *inode, loff_t offset,
+		loff_t length, unsigned int flags, struct iomap *iomap,
+		struct iomap *srcmap)
+{
+	/*
+	 * Swap activation needs the physical mappings of preallocated
+	 * ranges. Do not report the VDL tail as a hole.
+	 */
+	return __exfat_iomap_begin(inode, offset, length,
+			flags & ~IOMAP_REPORT, iomap, false);
+}
+
+static const struct iomap_ops exfat_swap_iomap_ops = {
+	.iomap_begin = exfat_swap_iomap_begin,
+};
+
 /*
  * exfat_write_iomap_end - Update the state after write
  *
@@ -274,5 +290,6 @@ const struct iomap_read_ops exfat_iomap_bio_read_ops = {
 int exfat_iomap_swap_activate(struct swap_info_struct *sis,
 			       struct file *file, sector_t *span)
 {
-	return iomap_swapfile_activate(sis, file, span, &exfat_iomap_ops);
+	return iomap_swapfile_activate(sis, file, span,
+				       &exfat_swap_iomap_ops);
 }
-- 
2.34.1