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

Hi Namjae,

> On Tue, Aug 25, 2026 at 10:46 PM Cyril Hrubis <[email protected]> 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.

LGTM.

Tested-by: Petr Vorel <[email protected]>

Tested on rapido-linux with:
CONFIG_EXFAT_FS=y
CONFIG_EXFAT_DEFAULT_IOCHARSET="utf8"

Hopefully Jan will test it as well, built as module.

Kind regards,
Petr

> From 5679a624816454c8e7683842eb0ab3f1adf0dcca Mon Sep 17 00:00:00 2001
> From: Namjae Jeon <[email protected]>
> 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 <[email protected]>
> ---
>  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);
>  }