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ntfs: account for direct MFT bitmap cluster allocation

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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: 6251f0b0de ("ntfs: update super block operations")
Suggested-by: Baolin Liu <liubaolin@kylinos.cn>
Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>
Signed-off-by: Xuewen Wang <wangxuewen@kylinos.cn>
Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Xuewen Wang 2026-09-24 09:45:14 +08:00 committed by Namjae Jeon
parent 0c3f2944e9
commit 109c9b0f67
1 changed files with 9 additions and 1 deletions
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10
fs/ntfs/mft.c
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@ -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);