This is a note to let you know that I've just added the patch titled
btrfs: subpage: fix the bitmap dump which can cause bitmap corruption
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-subpage-fix-the-bitmap-dump-which-can-cause-bi.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0ee6c631ddf129206d318890c6460cdceb05603e
Author: Qu Wenruo <wqu@xxxxxxxx>
Date: Fri Aug 30 16:35:48 2024 +0930
btrfs: subpage: fix the bitmap dump which can cause bitmap corruption
[ Upstream commit 77b0b98bb743f5d04d8f995ba1936e1143689d4a ]
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>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index 1b999c6e41930..b98d42ca55647 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -713,8 +713,14 @@ void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
}
#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 page *page, u64 start, u32 len)
