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btrfs: subpage: fix the bitmap dump which can cause bitmap corruption

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[ Upstream commit 77b0b98bb7 ]

In commit 75258f20fb ("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: 75258f20fb ("btrfs: subpage: dump extra subpage bitmaps for debug")
CC: stable@vger.kernel.org # 6.6+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Qu Wenruo 2024-08-30 16:35:48 +09:30 committed by Greg Kroah-Hartman
parent 459b724c3c
commit 0131bf19a1
1 changed files with 8 additions and 2 deletions
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10
fs/btrfs/subpage.c
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@ -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)