Re: [PATCH v2] ntfs: handle a failed size rollback in the write error path

[Hyunchul Lee <hyc.lee@gmail.com>]

Hi Hongling,

On Mon, Oct 19, 2026 at 02:49:18PM +0800, Hongling Zeng wrote:
> ntfs_file_write_iter() extends the data and initialized sizes before
> it copies the user data and restores them when the write then fails.
> The restoration is best-effort: both results are discarded, even
> though the extension is already recorded in the dirty MFT record.
> When the restoration fails too, the extended sizes reach the disk
> while the VFS inode keeps reporting the old ones: after a remount the
> file appears grown again, with an uninitialized tail where the failed
> write never put any data, and nothing records the failure.
> 
> Keep both undo results: on failure, set NVolSetErrors(), which the next
> persistence point persists as VOLUME_IS_DIRTY, and log a message for
> the errors= policy.
> 
> Fixes: 9c87959601e8 ("ntfs: update file operations")
> Suggested-by: Hyunchul Lee <hyc.lee@gmail.com>
> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> ---
> Changes in v2:
> - do not roll the initialized size back on a resident data attribute,
>   where ntfs_attr_set_initialized_size() always fails with -EINVAL and
>   the data size rollback restores both coupled sizes.
> ---
>  fs/ntfs/file.c | 46 +++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 37 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
> index d810ca5904bd..597fd70ed30b 100644
> --- a/fs/ntfs/file.c
> +++ b/fs/ntfs/file.c
> @@ -934,22 +934,50 @@ ssize_t ntfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  				&ntfs_iomap_folio_ops, NULL);
>  out:
>  	if (ret < 0 && ret != -EIOCBQUEUED) {
> -		if (ni->initialized_size != old_init_size) {
> -			struct ntfs_inode *mrec_ni =
> -				ntfs_base_inode(ni);
> +		int undo_err = 0;
> +		int init_err = 0;
> +
> +		/* ntfs_attr_set_initialized_size() rejects a resident one. */
> +		if (ni->initialized_size != old_init_size &&
> +		    NInoNonResident(ni)) {
> +			struct ntfs_inode *mrec_ni = ntfs_base_inode(ni);
>  
>  			mutex_lock(&mrec_ni->mrec_lock);
> -			ntfs_attr_set_initialized_size(ni, old_init_size);
> +			init_err = ntfs_attr_set_initialized_size(ni,
> +					old_init_size);
>  			mutex_unlock(&mrec_ni->mrec_lock);
> +			if (init_err && !undo_err)
> +				undo_err = init_err;
>  		}
>  		if (ni->data_size != old_data_size) {
> -			struct ntfs_inode *mrec_ni =
> -				ntfs_base_inode(ni);
> +			struct ntfs_inode *mrec_ni = ntfs_base_inode(ni);
> +			int data_err = 0;
>  
>  			truncate_setsize(vi, old_data_size);
> -			mutex_lock(&mrec_ni->mrec_lock);
> -			ntfs_attr_truncate(ni, old_data_size);
> -			mutex_unlock(&mrec_ni->mrec_lock);
> +			/*
> +			 * ntfs_attr_truncate() rejects a compressed one.
> +			 * Skip it also after a failed initialized size
> +			 * rollback: the shrunk data size would stay below
> +			 * the initialized size, which the loader rejects.
> +			 */
> +			if (!NInoCompressed(ni) && !init_err) {
> +				mutex_lock(&mrec_ni->mrec_lock);
> +				data_err = ntfs_attr_truncate(ni,
> +						old_data_size);
> +				mutex_unlock(&mrec_ni->mrec_lock);
> +			}
> +			if (data_err && !undo_err)
> +				undo_err = data_err;
> +		}
> +		if (ni->data_size != old_data_size && NInoCompressed(ni))
> +			ntfs_warning(vi->i_sb,

For compressed-file, the code only emits a warning, which causes the
VOLUME_IS_DIRTY persistence to be bypassed even though the MFT data size
remains expanded.

I think that we should report the compressed rollback as an error.

-- 
Thanks,
Hyunchul