[Cluster-devel] [GFS2] [Patch 3/10] Run through full bitmaps quicker in gfs2_bitfit

[Bob Peterson <rpeterso@redhat.com>]

On Wed, 2007-12-12 at 11:07 +0000, Steven Whitehouse wrote:
> Hi,
> 
> fs/gfs2/rgrp.c: In function ?gfs2_bitfit?:
> fs/gfs2/rgrp.c:139: warning: assignment from incompatible pointer type
> 
> Please can you send me a fix for the above. Thanks,
> 
> Steve.

Hi,

Sorry about that.  Here is a replacement for patch3 for the compile
error.

Note that the previous patch3 I sent also had some leftover useless
debug code in it (regarding static int c) which needed to be taken out.

Regards,

Bob Peterson
--
Signed-off-by: Bob Peterson <rpeterso@redhat.com> 
--
 .../fs/gfs2/rgrp.c                                 |   49 ++++++++++----------
  1 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index e0ee195..7a28339 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -126,41 +126,43 @@ static unsigned char gfs2_testbit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
  * Return: the block number (bitmap buffer scope) that was found
  */
 
-static u32 gfs2_bitfit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
-			    unsigned int buflen, u32 goal,
-			    unsigned char old_state)
+static u32 gfs2_bitfit(unsigned char *buffer, unsigned int buflen, u32 goal,
+		       unsigned char old_state)
 {
-	unsigned char *byte, *end, alloc;
+	unsigned char *byte;
 	u32 blk = goal;
-	unsigned int bit;
+	unsigned int bit, bitlong;
+	unsigned long *plong, plong55;
 
 	byte = buffer + (goal / GFS2_NBBY);
+	plong = (unsigned long *)buffer + (goal / GFS2_NBBY);
 	bit = (goal % GFS2_NBBY) * GFS2_BIT_SIZE;
-	end = buffer + buflen;
-	alloc = (old_state == GFS2_BLKST_FREE) ? 0x55 : 0;
-
-	while (byte < end) {
-		/* If we're looking for a free block we can eliminate all
-		   bitmap settings with 0x55, which represents four data
-		   blocks in a row.  If we're looking for a data block, we can
-		   eliminate 0x00 which corresponds to four free blocks. */
-		if ((*byte & 0x55) == alloc) {
-			blk += (8 - bit) >> 1;
-
-			bit = 0;
-			byte++;
-
+	bitlong = bit;
+#if BITS_PER_LONG == 32
+	plong55 = 0x55555555;
+#else
+	plong55 = 0x5555555555555555;
+#endif
+	while (byte < buffer + buflen) {
+
+		if (bitlong == 0 && old_state == 0 && *plong == plong55) {
+			plong++;
+			byte += sizeof(unsigned long);
+			blk += sizeof(unsigned long) * GFS2_NBBY;
 			continue;
 		}
-
 		if (((*byte >> bit) & GFS2_BIT_MASK) == old_state)
 			return blk;
-
 		bit += GFS2_BIT_SIZE;
 		if (bit >= 8) {
 			bit = 0;
 			byte++;
 		}
+		bitlong += GFS2_BIT_SIZE;
+		if (bitlong >= sizeof(unsigned long) * 8) {
+			bitlong = 0;
+			plong++;
+		}
 
 		blk++;
 	}
@@ -1318,11 +1320,10 @@ static u32 rgblk_search(struct gfs2_rgrpd *rgd, u32 goal,
 		/* The GFS2_BLKST_UNLINKED state doesn't apply to the clone
 		   bitmaps, so we must search the originals for that. */
 		if (old_state != GFS2_BLKST_UNLINKED && bi->bi_clone)
-			blk = gfs2_bitfit(rgd, bi->bi_clone + bi->bi_offset,
+			blk = gfs2_bitfit(bi->bi_clone + bi->bi_offset,
 					  bi->bi_len, goal, old_state);
 		else
-			blk = gfs2_bitfit(rgd,
-					  bi->bi_bh->b_data + bi->bi_offset,
+			blk = gfs2_bitfit(bi->bi_bh->b_data + bi->bi_offset,
 					  bi->bi_len, goal, old_state);
 		if (blk != BFITNOENT)
 			break;