In commit 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for
debug") an internal macro GET_SUBPAGE_BITMAP() is introduced to grab the
bitmap of each attribute.
But that commit is using bitmap_cut() which will do the left shift of
the larger bitmap, causing incorrect values.
Thankfully this bitmap_cut() is only called for debug usage, and so far
it's not yet causing problem.
Fix it to use bitmap_read() to only grab the desired sub-bitmap.
Fixes: 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for debug")
CC: stable@xxxxxxxxxxxxxxx # 6.6+
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index 631d96f1e905..f8795c3d2270 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -902,8 +902,14 @@ void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct fol
}
#define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst) \
- bitmap_cut(dst, subpage->bitmaps, 0, \
- subpage_info->name##_offset, subpage_info->bitmap_nr_bits)
+{ \
+ const int bitmap_nr_bits = subpage_info->bitmap_nr_bits; \
+ \
+ ASSERT(bitmap_nr_bits < BITS_PER_LONG); \
+ *dst = bitmap_read(subpage->bitmaps, \
+ subpage_info->name##_offset, \
+ bitmap_nr_bits); \
+}
void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
struct folio *folio, u64 start, u32 len)
