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

[Hyunchul Lee]

On Sun, Oct 04, 2026 at 10:48:22AM +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")
> Signed-off-by: Hongling Zeng <zenghongling@xxxxxxxxxx>
> ---
>  fs/ntfs/file.c | 29 +++++++++++++++++++++++++++--
>  1 file changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
> index 3ec82715a588..b5b30e44ac51 100644
> --- a/fs/ntfs/file.c
> +++ b/fs/ntfs/file.c
> @@ -678,14 +678,39 @@ static ssize_t ntfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  				&ntfs_iomap_folio_ops, NULL);
>  out:
>  	if (ret < 0 && ret != -EIOCBQUEUED) {
> +		int undo_err = 0;
> +
>  		if (ni->initialized_size != old_init_size) {
> +			int init_err;
> +
>  			mutex_lock(&ni->mrec_lock);
> -			ntfs_attr_set_initialized_size(ni, old_init_size);
> +			init_err = ntfs_attr_set_initialized_size(ni,
> +					old_init_size);

I think the rollback needs to distinguish resident and compressed
attributes.
If the data attribute is still resident,
ntfs_attr_set_initialized_size() always return -EINVAL.


>  			mutex_unlock(&ni->mrec_lock);
> +			if (init_err && !undo_err)
> +				undo_err = init_err;
>  		}
>  		if (ni->data_size != old_data_size) {
> +			int data_err;
> +
>  			truncate_setsize(vi, old_data_size);
> -			ntfs_attr_truncate(ni, old_data_size);

> +			data_err = ntfs_attr_truncate(ni, old_data_size);

And ntfs_attr_truncate() always return -EOPNOTSUPP for a compressed
attribute.

> +			if (data_err && !undo_err)
> +				undo_err = data_err;
> +		}
> +		if (undo_err) {
> +			/*
> +			 * The extension is recorded in the dirty MFT
> +			 * record already, so a failed rollback leaves the
> +			 * new sizes on disk while the VFS inode keeps
> +			 * reporting the old ones.  Record the error: the
> +			 * next persistence point persists it as
> +			 * VOLUME_IS_DIRTY.  Run chkdsk.
> +			 */
> +			NVolSetErrors(vol);
> +			ntfs_error(vi->i_sb,
> +				   "Failed to roll back the size update: %d",
> +				   undo_err);
>  		}
>  	}
>  out_lock:
> -- 
> 2.25.1
> 

-- 
Thanks,
Hyunchul