Re: [PATCH] exfat: implement swap activate

[David Timber]

On 6/18/26 18:33, Andrea Cervesato wrote:
> From: Andrea Cervesato <andrea.cervesato@xxxxxxxx>
>
> exfat's fallocate allocates clusters without updating valid_size,
> leaving them invisible to bmap(). Extend valid_size to i_size so
> that generic_swapfile_activate() can map all blocks.
>
> This bug has been found during a Linux Test Project regression test
> using swapon/swapoff testing suite.
>
> Signed-off-by: Andrea Cervesato <andrea.cervesato@xxxxxxxx>
> Fixes: bf1797960c20 ("exfat: add fallocate FALLOC_FL_ALLOCATE_RANGE support")
> Link: https://patchwork.ozlabs.org/project/ltp/patch/20260608155241.270875-1-japo@xxxxxxxxxxxxx/
> ---
> bf1797960c20 - ("exfat: add fallocate FALLOC_FL_ALLOCATE_RANGE support")
> introduces fallocate() support in exfat, but omits the swap activate
> implementation, causing EINVAL inside Linux Test Project swapon/swapoff
> testing suites which are testing these syscalls with many filesystems,
> including exfat.
>
> This turned out to be a bug inside the kernel. The patch implements
> swap activate in order to ensure that exfat valid_size is correctly
> updated and the generic_swapfile_activate() doesn't fail with EINVAL
> due to valid_size=0, which is passed to bmap().
> ---
>  fs/exfat/exfat_fs.h |  1 +
>  fs/exfat/file.c     |  2 +-
>  fs/exfat/inode.c    | 23 +++++++++++++++++++++++
>  3 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
> index aff4dcd4e75a55296d536c19306813a566d6f0bb..18382c661d4358f8b80e6f7b5032a356a5905614 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -489,6 +489,7 @@ int exfat_trim_fs(struct inode *inode, struct fstrim_range *range);
>  
>  /* file.c */
>  extern const struct file_operations exfat_file_operations;
> +int exfat_extend_valid_size(struct inode *inode, loff_t new_valid_size);
>  int __exfat_truncate(struct inode *inode);
>  void exfat_truncate(struct inode *inode);
>  int exfat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> diff --git a/fs/exfat/file.c b/fs/exfat/file.c
> index 91e5511945d11b12658908dc6287fabd572d1d6a..12ed28c3ff896fb545bad58b47cccf808b48618d 100644
> --- a/fs/exfat/file.c
> +++ b/fs/exfat/file.c
> @@ -642,7 +642,7 @@ int exfat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
>  	return blkdev_issue_flush(inode->i_sb->s_bdev);
>  }
>  
> -static int exfat_extend_valid_size(struct inode *inode, loff_t new_valid_size)
> +int exfat_extend_valid_size(struct inode *inode, loff_t new_valid_size)
>  {
>  	int err;
>  	loff_t pos;
> diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
> index 1ea4c740fef9ef6932a75e122e1b0130c85533b2..5a395851062e4a14b456fa79546541227d8427e6 100644
> --- a/fs/exfat/inode.c
> +++ b/fs/exfat/inode.c
> @@ -11,6 +11,7 @@
>  #include <linux/time.h>
>  #include <linux/writeback.h>
>  #include <linux/uio.h>
> +#include <linux/swap.h>
>  #include <linux/random.h>
>  #include <linux/iversion.h>
>  
> @@ -534,6 +535,27 @@ int exfat_block_truncate_page(struct inode *inode, loff_t from)
>  	return block_truncate_page(inode->i_mapping, from, exfat_get_block);
>  }
>  
> +static int exfat_swap_activate(struct swap_info_struct *sis,
> +			       struct file *file, sector_t *span)
> +{
> +	struct inode *inode = file_inode(file);
> +	struct exfat_inode_info *ei = EXFAT_I(inode);
> +	int ret;
> +
> +	/*
> +	 * exfat's fallocate allocates clusters without updating valid_size,
> +	 * leaving them invisible to bmap(). Extend valid_size to i_size so
> +	 * that generic_swapfile_activate() can map all blocks.
> +	 */
> +	if (ei->valid_size < i_size_read(inode)) {
Also, if we want to do this, please ensure that ei->valid_size is cached
in by locking the inode or etc before referencing it.

I'll see if I can make exfat_extend_valid_size() interruptible by
placing missing fatal_signal_pending(current) check in both stable and
iomap branches.

Davo