[PATCH] fs/ntfs3: end trim runs at fully allocated bitmap windows

[Hungyu Lin <dennylin0707@gmail.com>]

ntfs_trim_fs() keeps a free run pending across bitmap windows. When
the cached free-bit count of a window is zero, the loop skips it without
ending the pending run. Free clusters at the start of a later window
are then added to the old length despite the allocated gap.

For example, two eight-cluster holes separated by fully allocated bitmap
windows can be submitted as one sixteen-cluster discard starting at the
first hole. This discards allocated clusters while leaving the actual
second hole untrimmed.

Finish a qualifying pending run and reset its length before skipping a
fully allocated window. Preserve the minimum-length check and the cached
window optimization, matching the analogous handling in wnd_rescan().

Fixes: 3f3b442b5ad2 ("fs/ntfs3: Add bitmap")
Cc: stable@vger.kernel.org
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
 fs/ntfs3/bitmap.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs3/bitmap.c b/fs/ntfs3/bitmap.c
index 60b362f388d960558cd8ea65680df266e26dabd5..8875e6feff9c9715933545dc2fc173a191302ddc 100644
--- a/fs/ntfs3/bitmap.c
+++ b/fs/ntfs3/bitmap.c
@@ -1447,8 +1447,16 @@ int ntfs_trim_fs(struct ntfs_sb_info *sbi, struct fstrim_range *range)
 		if (lcn_wnd > lcn_to)
 			break;
 
-		if (!wnd->free_bits[iw])
+		if (!wnd->free_bits[iw]) {
+			if (len >= minlen) {
+				err = ntfs_discard(sbi, lcn, len);
+				if (err)
+					goto out;
+				done += len;
+			}
+			len = 0;
 			continue;
+		}
 
 		if (iw + 1 == wnd->nwnd)
 			wbits = wnd->bits_last;

base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.43.0