I agree. Your suggestion is more good.
Thanks for your review.
On 2013년 11월 15일 13:31, Jaegeuk Kim wrote:
Hi,
IMO, it would be better give names like __find_rev_next(_zero)_bit.
If there is no objection, I'll modify and apply them by myself.
Thanks, :)
2013-11-15 (금), 10:42 +0900, Changman Lee:
When f2fs_set_bit is used, in a byte MSB and LSB is reversed,
in that case we can use f2fs_find_next_bit or f2fs_find_next_zero_bit.
Signed-off-by: Changman Lee <cm224.lee@xxxxxxxxxxx>
---
fs/f2fs/segment.c | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 143 insertions(+)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fa284d3..b2de887 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -21,6 +21,149 @@
#include <trace/events/f2fs.h>
/*
+ * f2fs_ffs is copied from include/asm-generic/bitops/__ffs.h because
+ * MSB and LSB is reversed in a byte by f2fs_set_bit.
+ */
+static inline unsigned long f2fs_ffs(unsigned long word)
+{
+ int num = 0;
+
+#if BITS_PER_LONG == 64
+ if ((word & 0xffffffff) == 0) {
+ num += 32;
+ word >>= 32;
+ }
+#endif
+ if ((word & 0xffff) == 0) {
+ num += 16;
+ word >>= 16;
+ }
+ if ((word & 0xff) == 0) {
+ num += 8;
+ 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;
+}
+
+#define f2fs_ffz(x) f2fs_ffs(~(x))
+
+/*
+ * f2fs_find_next(_zero)_bit is copied from lib/find_next_bit.c becasue
+ * 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
+ */
+static unsigned long f2fs_find_next_bit(const unsigned long *addr,
+ unsigned long size, unsigned long offset)
+{
+ 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;
+ size -= result;
+ offset %= BITS_PER_LONG;
+ 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;
+ if (size < BITS_PER_LONG)
+ goto found_first;
+ if (tmp)
+ goto found_middle;
+ size -= BITS_PER_LONG;
+ result += BITS_PER_LONG;
+aligned:
+ while (size & ~(BITS_PER_LONG-1)) {
+ tmp = *(p++);
+ if (tmp)
+ goto found_middle;
+ result += BITS_PER_LONG;
+ size -= BITS_PER_LONG;
+ }
+ if (!size)
+ return result;
+ tmp = *p;
+
+found_first:
+ tmp &= (~0UL >> (BITS_PER_LONG - size));
+ if (tmp == 0UL) /* Are any bits set? */
+ return result + size; /* Nope. */
+found_middle:
+ return result + f2fs_ffs(tmp);
+}
+
+static unsigned long f2fs_find_next_zero_bit(const unsigned long *addr,
+ unsigned long size, unsigned long offset)
+{
+ 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;
+ size -= result;
+ offset %= BITS_PER_LONG;
+ 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;
+ if (size < BITS_PER_LONG)
+ goto found_first;
+ if (~tmp)
+ goto found_middle;
+ size -= BITS_PER_LONG;
+ result += BITS_PER_LONG;
+aligned:
+ while (size & ~(BITS_PER_LONG - 1)) {
+ tmp = *(p++);
+ if (~tmp)
+ goto found_middle;
+ result += BITS_PER_LONG;
+ size -= BITS_PER_LONG;
+ }
+ if (!size)
+ return result;
+ tmp = *p;
+
+found_first:
+ tmp |= ~0UL << size;
+ if (tmp == ~0UL) /* Are any bits zero? */
+ return result + size; /* Nope. */
+found_middle:
+ return result + f2fs_ffz(tmp);
+}
+
+/*
* This function balances dirty node and dentry pages.
* In addition, it controls garbage collection.
*/
--
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