From 03c6ecc4b4b13a3901f207152451fdd2d82e40c4 Mon Sep 17 00:00:00 2001 From: Jacopo Labardi Date: Sun, 30 Aug 2026 02:15:36 +0200 Subject: [PATCH] ntfs: fix FITRIM range alignment ntfs_trim_fs() aligns the start of a free extent up to the device discard granularity, but derives the discard length by aligning the original extent length down. When the free extent start is not discard-aligned, adding that length to the aligned start can extend the discard past the free extent and into allocated clusters. For example, with 4 KiB clusters and 32 KiB discard granularity, the free extent [4 KiB, 36 KiB) becomes the discard range [32 KiB, 64 KiB), so 28 KiB beyond the free extent may be discarded. Align the absolute end of the free extent down and derive the length from the two aligned endpoints. Skip extents that contain no full discard unit. Reproduced with a 4 KiB-cluster NTFS filesystem on scsi_debug configured for 32 KiB discard granularity and read-zero-after-trim. Before this change, FITRIM zeroed seven allocated 4 KiB clusters following an unaligned 32 KiB hole. With this change, the same data remains intact across FITRIM and remount. Fixes: 11ccc9107dc4 ("ntfs: update runlist handling and cluster allocator") Cc: stable@vger.kernel.org Assisted-by: OpenAI Codex:GPT-5.6 Sol Max Signed-off-by: Jacopo Labardi Signed-off-by: Namjae Jeon --- fs/ntfs/bitmap.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/ntfs/bitmap.c b/fs/ntfs/bitmap.c index b1436b3151b9..1840b7d84c62 100644 --- a/fs/ntfs/bitmap.c +++ b/fs/ntfs/bitmap.c @@ -64,7 +64,7 @@ int ntfs_trim_fs(struct ntfs_volume *vol, struct fstrim_range *range) end = start_buf; while (end < end_buf) { - u64 aligned_start, aligned_count; + u64 aligned_start, aligned_end, aligned_count; u64 start = find_next_zero_bit(bitmap, end_buf - start_buf, end - start_buf) + start_buf; if (start >= end_buf) @@ -74,8 +74,10 @@ int ntfs_trim_fs(struct ntfs_volume *vol, struct fstrim_range *range) start - start_buf) + start_buf; aligned_start = ALIGN(ntfs_cluster_to_bytes(vol, start), dq); - aligned_count = - ALIGN_DOWN(ntfs_cluster_to_bytes(vol, end - start), dq); + aligned_end = ALIGN_DOWN(ntfs_cluster_to_bytes(vol, end), dq); + if (aligned_start >= aligned_end) + continue; + aligned_count = aligned_end - aligned_start; if (aligned_count >= range->minlen) { ret = blkdev_issue_discard(vol->sb->s_bdev, aligned_start >> 9, aligned_count >> 9, GFP_NOFS);