From 2fe1d55134fce05c17ea118a2e37a4af771887bc Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Thu, 22 Sep 2016 17:24:20 -0700 Subject: Btrfs: fix free space tree bitmaps on big-endian systems MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In convert_free_space_to_{bitmaps,extents}(), we buffer the free space bitmaps in memory and copy them directly to/from the extent buffers with {read,write}_extent_buffer(). The extent buffer bitmap helpers use byte granularity, which is equivalent to a little-endian bitmap. This means that on big-endian systems, the in-memory bitmaps will be written to disk byte-swapped. To fix this, use byte-granularity for the bitmaps in memory. Fixes: a5ed91828518 ("Btrfs: implement the free space B-tree") Cc: stable@vger.kernel.org # 4.5+ Tested-by: Holger Hoffstätte Tested-by: Chandan Rajendra Signed-off-by: Omar Sandoval Signed-off-by: David Sterba --- fs/btrfs/extent_io.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'fs/btrfs/extent_io.h') diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index 28cd88fccc7e..1cf4e4226fc8 100644 --- a/fs/btrfs/extent_io.h +++ b/fs/btrfs/extent_io.h @@ -59,6 +59,28 @@ */ #define EXTENT_PAGE_PRIVATE 1 +/* + * The extent buffer bitmap operations are done with byte granularity instead of + * word granularity for two reasons: + * 1. The bitmaps must be little-endian on disk. + * 2. Bitmap items are not guaranteed to be aligned to a word and therefore a + * single word in a bitmap may straddle two pages in the extent buffer. + */ +#define BIT_BYTE(nr) ((nr) / BITS_PER_BYTE) +#define BYTE_MASK ((1 << BITS_PER_BYTE) - 1) +#define BITMAP_FIRST_BYTE_MASK(start) \ + ((BYTE_MASK << ((start) & (BITS_PER_BYTE - 1))) & BYTE_MASK) +#define BITMAP_LAST_BYTE_MASK(nbits) \ + (BYTE_MASK >> (-(nbits) & (BITS_PER_BYTE - 1))) + +static inline int le_test_bit(int nr, const u8 *addr) +{ + return 1U & (addr[BIT_BYTE(nr)] >> (nr & (BITS_PER_BYTE-1))); +} + +extern void le_bitmap_set(u8 *map, unsigned int start, int len); +extern void le_bitmap_clear(u8 *map, unsigned int start, int len); + struct extent_state; struct btrfs_root; struct btrfs_io_bio; -- cgit v1.2.3