Re: [PATCH v1 4/4] ntfs: account for direct MFT bitmap cluster allocation

[liubaolin]

在 2026/9/24 09:45, Xuewen Wang 写道:
> The MFT bitmap extension fast path sets $Bitmap directly, bypassing
> ntfs_cluster_alloc() and its free_clusters and lcn_empty_bits_per_page
> updates. Successful extensions overreport free space, and rollback adds
> back counts that were never deducted.
>
> Update both counts under lcnbmp_lock and the bitmap folio lock. Require
> a nonzero page count and space remaining after delayed-allocation
> reservations; otherwise use the regular allocator. The page check also
> prevents underflow when the initial scan recorded zero after a read error.
>
> Fixes: 6251f0b0de7d ("ntfs: update super block operations")
> Suggested-by: Baolin Liu <liubaolin@xxxxxxxxxx>
> Reviewed-by: Baolin Liu <liubaolin@xxxxxxxxxx>
> Signed-off-by: Xuewen Wang <wangxuewen@xxxxxxxxxx>
> ---
>   fs/ntfs/mft.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
> index 489a5935202c..e01e367a588d 100644
> --- a/fs/ntfs/mft.c
> +++ b/fs/ntfs/mft.c
> @@ -1404,10 +1404,18 @@ static int ntfs_mft_bitmap_extend_allocation_nolock(struct ntfs_volume *vol)
>   	folio_lock(folio);
>   	b = (u8 *)kmap_local_folio(folio, 0) + (ll & ~PAGE_MASK);
>   	tb = 1 << (lcn & 7ull);
> -	if (*b != 0xff && !(*b & tb)) {
> +	/*
> +	 * A page skipped by the initial scan has no free bits recorded.
> +	 * Honor that and the space reserved for delayed allocation.
> +	 */
> +	if (*b != 0xff && !(*b & tb) &&
> +	    vol->lcn_empty_bits_per_page[ll >> PAGE_SHIFT] &&
> +	    ntfs_available_clusters_count(vol, 1) > 0) {
>   		/* Next cluster is free, allocate it. */
>   		*b |= tb;
>   		folio_mark_dirty(folio);
> +		ntfs_dec_free_clusters(vol, 1);
> +		ntfs_set_lcn_empty_bits(vol, ll >> PAGE_SHIFT, 1, 1);
>   		folio_unlock(folio);
>   		kunmap_local(b);
>   		folio_put(folio);

Looks good to me.

Reviewed-by: Baolin Liu <liubaolin@xxxxxxxxxx>