Re: [PATCH v1 1/4] ntfs: bound the adjacent cluster in MFT bitmap extension

[liubaolin <liubaolin12138@163.com>]

在 2026/9/24 09:45, Xuewen Wang 写道:
> When the last MFT bitmap run reaches the volume boundary, the direct
> allocation path tests the bit for nr_clusters, an invalid LCN. A clear
> bit allows an out-of-volume allocation; a bitmap read failure aborts
> extension even if valid clusters remain available.
> 
> Check the candidate LCN before accessing $Bitmap and fall back to
> ntfs_cluster_alloc() with no locality hint when it is outside the volume.
> 
> Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>
> Signed-off-by: Xuewen Wang <wangxuewen@kylinos.cn>
> ---
>   fs/ntfs/mft.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
> index 8bb8b4085c8b..88bac85d22bc 100644
> --- a/fs/ntfs/mft.c
> +++ b/fs/ntfs/mft.c
> @@ -1377,6 +1377,11 @@ static int ntfs_mft_bitmap_extend_allocation_nolock(struct ntfs_volume *vol)
>   	lcn = rl->lcn + rl->length;
>   	ntfs_debug("Last lcn of mft bitmap attribute is 0x%llx.",
>   			(long long)lcn);
> +	/* There is no adjacent cluster if the last run ends at the volume end. */
> +	if (lcn >= vol->nr_clusters) {
> +		lcn = -1;
> +		goto alloc_cluster;
> +	}
>   	/*
>   	 * Attempt to get the cluster following the last allocated cluster by
>   	 * hand as it may be in the MFT zone so the allocator would not give it
> @@ -1413,6 +1418,7 @@ static int ntfs_mft_bitmap_extend_allocation_nolock(struct ntfs_volume *vol)
>   		kunmap_local(b);
>   		folio_put(folio);
>   		up_write(&vol->lcnbmp_lock);
> +alloc_cluster:
>   		/* Allocate a cluster from the DATA_ZONE. */
>   		rl2 = ntfs_cluster_alloc(vol, rl[1].vcn, 1, lcn, DATA_ZONE,
>   				true, false, false);

Looks good to me.

Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>