f2fs: refactor __find_rev_next_{zero}_bit

This patch refactors __find_rev_next_{zero}_bit which was disabled previously
due to bugs.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index f37c21233b5c8dc17a2783458c0a1060220355e0..7835e41868f0c14ecd14fb9c56b907c5436f814b 100644 (file)
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -29,6 +29,21 @@ static struct kmem_cache *discard_entry_slab;
 static struct kmem_cache *sit_entry_set_slab;
 static struct kmem_cache *inmem_entry_slab;
 
+static unsigned long __reverse_ulong(unsigned char *str)
+{
+       unsigned long tmp = 0;
+       int shift = 24, idx = 0;
+
+#if BITS_PER_LONG == 64
+       shift = 56;
+#endif
+       while (shift >= 0) {
+               tmp |= (unsigned long)str[idx++] << shift;
+               shift -= BITS_PER_BYTE;
+       }
+       return tmp;
+}
+
 /*
  * __reverse_ffs is copied from include/asm-generic/bitops/__ffs.h since
  * MSB and LSB are reversed in a byte by f2fs_set_bit.
@@ -38,27 +53,31 @@ static inline unsigned long __reverse_ffs(unsigned long word)
        int num = 0;
 
 #if BITS_PER_LONG == 64
-       if ((word & 0xffffffff) == 0) {
+       if ((word & 0xffffffff00000000UL) == 0)
                num += 32;
+       else
                word >>= 32;
-       }
 #endif
-       if ((word & 0xffff) == 0) {
+       if ((word & 0xffff0000) == 0)
                num += 16;
+       else
                word >>= 16;
-       }
-       if ((word & 0xff) == 0) {
+
+       if ((word & 0xff00) == 0)
                num += 8;
+       else
                word >>= 8;
-       }
+
        if ((word & 0xf0) == 0)
                num += 4;
        else
                word >>= 4;
+
        if ((word & 0xc) == 0)
                num += 2;
        else
                word >>= 2;
+
        if ((word & 0x2) == 0)
                num += 1;
        return num;
@@ -68,26 +87,16 @@ static inline unsigned long __reverse_ffs(unsigned long word)
  * __find_rev_next(_zero)_bit is copied from lib/find_next_bit.c because
  * f2fs_set_bit makes MSB and LSB reversed in a byte.
  * Example:
- *                             LSB <--> MSB
- *   f2fs_set_bit(0, bitmap) => 0000 0001
- *   f2fs_set_bit(7, bitmap) => 1000 0000
+ *                             MSB <--> LSB
+ *   f2fs_set_bit(0, bitmap) => 1000 0000
+ *   f2fs_set_bit(7, bitmap) => 0000 0001
  */
 static unsigned long __find_rev_next_bit(const unsigned long *addr,
                        unsigned long size, unsigned long offset)
 {
-       while (!f2fs_test_bit(offset, (unsigned char *)addr))
-               offset++;
-
-       if (offset > size)
-               offset = size;
-
-       return offset;
-#if 0
        const unsigned long *p = addr + BIT_WORD(offset);
        unsigned long result = offset & ~(BITS_PER_LONG - 1);
        unsigned long tmp;
-       unsigned long mask, submask;
-       unsigned long quot, rest;
 
        if (offset >= size)
                return size;
@@ -97,14 +106,9 @@ static unsigned long __find_rev_next_bit(const unsigned long *addr,
        if (!offset)
                goto aligned;
 
-       tmp = *(p++);
-       quot = (offset >> 3) << 3;
-       rest = offset & 0x7;
-       mask = ~0UL << quot;
-       submask = (unsigned char)(0xff << rest) >> rest;
-       submask <<= quot;
-       mask &= submask;
-       tmp &= mask;
+       tmp = __reverse_ulong((unsigned char *)p);
+       tmp &= ~0UL >> offset;
+
        if (size < BITS_PER_LONG)
                goto found_first;
        if (tmp)
@@ -112,42 +116,34 @@ static unsigned long __find_rev_next_bit(const unsigned long *addr,
 
        size -= BITS_PER_LONG;
        result += BITS_PER_LONG;
+       p++;
 aligned:
        while (size & ~(BITS_PER_LONG-1)) {
-               tmp = *(p++);
+               tmp = __reverse_ulong((unsigned char *)p);
                if (tmp)
                        goto found_middle;
                result += BITS_PER_LONG;
                size -= BITS_PER_LONG;
+               p++;
        }
        if (!size)
                return result;
-       tmp = *p;
+
+       tmp = __reverse_ulong((unsigned char *)p);
 found_first:
-       tmp &= (~0UL >> (BITS_PER_LONG - size));
-       if (tmp == 0UL)         /* Are any bits set? */
+       tmp &= (~0UL << (BITS_PER_LONG - size));
+       if (!tmp)               /* Are any bits set? */
                return result + size;   /* Nope. */
 found_middle:
        return result + __reverse_ffs(tmp);
-#endif
 }
 
 static unsigned long __find_rev_next_zero_bit(const unsigned long *addr,
                        unsigned long size, unsigned long offset)
 {
-       while (f2fs_test_bit(offset, (unsigned char *)addr))
-               offset++;
-
-       if (offset > size)
-               offset = size;
-
-       return offset;
-#if 0
        const unsigned long *p = addr + BIT_WORD(offset);
        unsigned long result = offset & ~(BITS_PER_LONG - 1);
        unsigned long tmp;
-       unsigned long mask, submask;
-       unsigned long quot, rest;
 
        if (offset >= size)
                return size;
@@ -157,40 +153,36 @@ static unsigned long __find_rev_next_zero_bit(const unsigned long *addr,
        if (!offset)
                goto aligned;
 
-       tmp = *(p++);
-       quot = (offset >> 3) << 3;
-       rest = offset & 0x7;
-       mask = ~(~0UL << quot);
-       submask = (unsigned char)~((unsigned char)(0xff << rest) >> rest);
-       submask <<= quot;
-       mask += submask;
-       tmp |= mask;
+       tmp = __reverse_ulong((unsigned char *)p);
+       tmp |= ~((~0UL << offset) >> offset);
+
        if (size < BITS_PER_LONG)
                goto found_first;
-       if (~tmp)
+       if (tmp != ~0UL)
                goto found_middle;
 
        size -= BITS_PER_LONG;
        result += BITS_PER_LONG;
+       p++;
 aligned:
        while (size & ~(BITS_PER_LONG - 1)) {
-               tmp = *(p++);
-               if (~tmp)
+               tmp = __reverse_ulong((unsigned char *)p);
+               if (tmp != ~0UL)
                        goto found_middle;
                result += BITS_PER_LONG;
                size -= BITS_PER_LONG;
+               p++;
        }
        if (!size)
                return result;
-       tmp = *p;
 
+       tmp = __reverse_ulong((unsigned char *)p);
 found_first:
-       tmp |= ~0UL << size;
-       if (tmp == ~0UL)        /* Are any bits zero? */
+       tmp |= ~(~0UL << (BITS_PER_LONG - size));
+       if (tmp == ~0UL)        /* Are any bits zero? */
                return result + size;   /* Nope. */
 found_middle:
        return result + __reverse_ffz(tmp);
-#endif
 }
 
 void register_inmem_page(struct inode *inode, struct page *page)