Commit 2fe1d551 authored by Omar Sandoval's avatar Omar Sandoval Committed by David Sterba
Browse files

Btrfs: fix free space tree bitmaps on big-endian systems 



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: a5ed9182 ("Btrfs: implement the free space B-tree")
Cc: stable@vger.kernel.org # 4.5+
Tested-by: default avatarHolger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: default avatarChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 08895a8b

fs/btrfs/extent_io.c

+46 −18
Original line number Diff line number Diff line
@@ -5524,17 +5524,45 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src, 
	}

}



/*

 * The extent buffer bitmap operations are done with byte granularity because

 * 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)))

void le_bitmap_set(u8 *map, unsigned int start, int len)

{

	u8 *p = map + BIT_BYTE(start);

	const unsigned int size = start + len;

	int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);

	u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);



	while (len - bits_to_set >= 0) {

		*p |= mask_to_set;

		len -= bits_to_set;

		bits_to_set = BITS_PER_BYTE;

		mask_to_set = ~(u8)0;

		p++;

	}

	if (len) {

		mask_to_set &= BITMAP_LAST_BYTE_MASK(size);

		*p |= mask_to_set;

	}

}



void le_bitmap_clear(u8 *map, unsigned int start, int len)

{

	u8 *p = map + BIT_BYTE(start);

	const unsigned int size = start + len;

	int bits_to_clear = BITS_PER_BYTE - (start % BITS_PER_BYTE);

	u8 mask_to_clear = BITMAP_FIRST_BYTE_MASK(start);



	while (len - bits_to_clear >= 0) {

		*p &= ~mask_to_clear;

		len -= bits_to_clear;

		bits_to_clear = BITS_PER_BYTE;

		mask_to_clear = ~(u8)0;

		p++;

	}

	if (len) {

		mask_to_clear &= BITMAP_LAST_BYTE_MASK(size);

		*p &= ~mask_to_clear;

	}

}



/*

 * eb_bitmap_offset() - calculate the page and offset of the byte containing the
@@ -5578,7 +5606,7 @@ static inline void eb_bitmap_offset(struct extent_buffer *eb, 
int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,

			   unsigned long nr)

{

	char *kaddr;

	u8 *kaddr;

	struct page *page;

	unsigned long i;

	size_t offset;
@@ -5600,13 +5628,13 @@ int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start, 
void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,

			      unsigned long pos, unsigned long len)

{

	char *kaddr;

	u8 *kaddr;

	struct page *page;

	unsigned long i;

	size_t offset;

	const unsigned int size = pos + len;

	int bits_to_set = BITS_PER_BYTE - (pos % BITS_PER_BYTE);

	unsigned int mask_to_set = BITMAP_FIRST_BYTE_MASK(pos);

	u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(pos);



	eb_bitmap_offset(eb, start, pos, &i, &offset);

	page = eb->pages[i];
@@ -5617,7 +5645,7 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start, 
		kaddr[offset] |= mask_to_set;

		len -= bits_to_set;

		bits_to_set = BITS_PER_BYTE;

		mask_to_set = ~0U;

		mask_to_set = ~(u8)0;

		if (++offset >= PAGE_SIZE && len > 0) {

			offset = 0;

			page = eb->pages[++i];
@@ -5642,13 +5670,13 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start, 
void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,

				unsigned long pos, unsigned long len)

{

	char *kaddr;

	u8 *kaddr;

	struct page *page;

	unsigned long i;

	size_t offset;

	const unsigned int size = pos + len;

	int bits_to_clear = BITS_PER_BYTE - (pos % BITS_PER_BYTE);

	unsigned int mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos);

	u8 mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos);



	eb_bitmap_offset(eb, start, pos, &i, &offset);

	page = eb->pages[i];
@@ -5659,7 +5687,7 @@ void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start, 
		kaddr[offset] &= ~mask_to_clear;

		len -= bits_to_clear;

		bits_to_clear = BITS_PER_BYTE;

		mask_to_clear = ~0U;

		mask_to_clear = ~(u8)0;

		if (++offset >= PAGE_SIZE && len > 0) {

			offset = 0;

			page = eb->pages[++i];

fs/btrfs/extent_io.h

+22 −0
Original line number Diff line number Diff line
@@ -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;

fs/btrfs/free-space-tree.c

+8 −9
Original line number Diff line number Diff line
@@ -151,7 +151,7 @@ static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize) 
	return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);

}



static unsigned long *alloc_bitmap(u32 bitmap_size)

static u8 *alloc_bitmap(u32 bitmap_size)

{

	void *mem;
@@ -180,8 +180,7 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans, 
	struct btrfs_free_space_info *info;

	struct btrfs_key key, found_key;

	struct extent_buffer *leaf;

	unsigned long *bitmap;

	char *bitmap_cursor;

	u8 *bitmap, *bitmap_cursor;

	u64 start, end;

	u64 bitmap_range, i;

	u32 bitmap_size, flags, expected_extent_count;
@@ -231,7 +230,7 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans, 
						block_group->sectorsize);

				last = div_u64(found_key.objectid + found_key.offset - start,

					       block_group->sectorsize);

				bitmap_set(bitmap, first, last - first);

				le_bitmap_set(bitmap, first, last - first);



				extent_count++;

				nr++;
@@ -269,7 +268,7 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans, 
		goto out;

	}



	bitmap_cursor = (char *)bitmap;

	bitmap_cursor = bitmap;

	bitmap_range = block_group->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;

	i = start;

	while (i < end) {
@@ -318,7 +317,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans, 
	struct btrfs_free_space_info *info;

	struct btrfs_key key, found_key;

	struct extent_buffer *leaf;

	unsigned long *bitmap;

	u8 *bitmap;

	u64 start, end;

	/* Initialize to silence GCC. */

	u64 extent_start = 0;
@@ -362,7 +361,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans, 
				break;

			} else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {

				unsigned long ptr;

				char *bitmap_cursor;

				u8 *bitmap_cursor;

				u32 bitmap_pos, data_size;



				ASSERT(found_key.objectid >= start);
@@ -372,7 +371,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans, 
				bitmap_pos = div_u64(found_key.objectid - start,

						     block_group->sectorsize *

						     BITS_PER_BYTE);

				bitmap_cursor = ((char *)bitmap) + bitmap_pos;

				bitmap_cursor = bitmap + bitmap_pos;

				data_size = free_space_bitmap_size(found_key.offset,

								   block_group->sectorsize);
@@ -409,7 +408,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans, 
	offset = start;

	bitnr = 0;

	while (offset < end) {

		bit = !!test_bit(bitnr, bitmap);

		bit = !!le_test_bit(bitnr, bitmap);

		if (prev_bit == 0 && bit == 1) {

			extent_start = offset;

		} else if (prev_bit == 1 && bit == 0) {

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