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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: a5ed918285 ("Btrfs: implement the free space B-tree")
Cc: stable@vger.kernel.org # 4.5+
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Omar Sandoval 2016-09-22 17:24:20 -07:00 committed by David Sterba
parent 08895a8b6b
commit 2fe1d55134
3 changed files with 76 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
fs/btrfs/extent_io.c
View File

@ -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];

22
fs/btrfs/extent_io.h
View File

@ -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;

17
fs/btrfs/free-space-tree.c
View File

@ -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) {