Attachment 297533 Details for Bug 435456 – Third attempt at a patch

[patch] Third attempt at a patch

435456.upstream3.patch (text/plain), 3.56 KB, created by Robert Peterson on 2008-03-10 23:05:47 UTC

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Creator: Robert Peterson

Created: 2008-03-10 23:05:47 UTC

Size: 3.56 KB

patch

obsolete

> fs/gfs2/rgrp.c |   93 ++++++++++++++++++++++++++++++++++++-------------------
> 1 files changed, 61 insertions(+), 32 deletions(-)
>
>diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
>index 4291375..7e8f0b1 100644
>--- a/fs/gfs2/rgrp.c
>+++ b/fs/gfs2/rgrp.c
>@@ -14,6 +14,7 @@
> #include <linux/fs.h>
> #include <linux/gfs2_ondisk.h>
> #include <linux/lm_interface.h>
>+#include <linux/prefetch.h>
> 
> #include "gfs2.h"
> #include "incore.h"
>@@ -33,6 +34,16 @@
> #define BFITNOENT ((u32)~0)
> #define NO_BLOCK ((u64)~0)
> 
>+#if BITS_PER_LONG == 32
>+#define LBITMASK   (0x55555555UL)
>+#define LBITSKIP55 (0x55555555UL)
>+#define LBITSKIP00 (0x00000000UL)
>+#else
>+#define LBITMASK   (0x5555555555555555UL)
>+#define LBITSKIP55 (0x5555555555555555UL)
>+#define LBITSKIP00 (0x0000000000000000UL)
>+#endif
>+
> /*
>  * These routines are used by the resource group routines (rgrp.c)
>  * to keep track of block allocation.  Each block is represented by two
>@@ -138,45 +149,63 @@ static inline unsigned char gfs2_testbit(struct gfs2_rgrpd *rgd,
> static u32 gfs2_bitfit(const u8 *buffer, unsigned int buflen, u32 goal,
> 		       u8 old_state)
> {
>-	const u8 *byte;
>-	u32 blk = goal;
>-	unsigned int bit, bitlong;
>-	const unsigned long *plong;
>-#if BITS_PER_LONG == 32
>-	const unsigned long plong55 = 0x55555555;
>-#else
>-	const unsigned long plong55 = 0x5555555555555555;
>-#endif
>-
>-	byte = buffer + (goal / GFS2_NBBY);
>-	plong = (const unsigned long *)(buffer + (goal / GFS2_NBBY));
>-	bit = (goal % GFS2_NBBY) * GFS2_BIT_SIZE;
>-	bitlong = bit;
>-
>-	while (byte < buffer + buflen) {
>-
>-		if (bitlong == 0 && old_state == 0 && *plong == plong55) {
>-			plong++;
>-			byte += sizeof(unsigned long);
>-			blk += sizeof(unsigned long) * GFS2_NBBY;
>-			continue;
>+	const u8 *byte, *start, *end;
>+	int bit, startbit;
>+	u32 g1, g2, misaligned;
>+	unsigned long *plong;
>+	unsigned long lskipval;
>+
>+	lskipval = (old_state & GFS2_BLKST_USED) ? LBITSKIP00 : LBITSKIP55;
>+	g1 = (goal / GFS2_NBBY);
>+	start = buffer + g1;
>+	byte = start;
>+        end = buffer + buflen;
>+	g2 = ALIGN(g1, sizeof(unsigned long));
>+	plong = (unsigned long *)(buffer + g2);
>+	startbit = bit = (goal % GFS2_NBBY) * GFS2_BIT_SIZE;
>+	misaligned = g2 - g1;
>+	if (!misaligned)
>+		goto ulong_aligned;
>+/* parse the bitmap a byte at a time */
>+misaligned:
>+	while (byte < end) {
>+		if (((*byte >> bit) & GFS2_BIT_MASK) == old_state) {
>+			return goal +
>+				(((byte - start) * GFS2_NBBY) +
>+				 ((bit - startbit) >> 1));
> 		}
>-		if (((*byte >> bit) & GFS2_BIT_MASK) == old_state)
>-			return blk;
> 		bit += GFS2_BIT_SIZE;
>-		if (bit >= 8) {
>+		if (bit >= GFS2_NBBY * GFS2_BIT_SIZE) {
> 			bit = 0;
> 			byte++;
>+			misaligned--;
>+			if (!misaligned) {
>+				plong = (unsigned long *)byte;
>+				goto ulong_aligned;
>+			}
> 		}
>-		bitlong += GFS2_BIT_SIZE;
>-		if (bitlong >= sizeof(unsigned long) * 8) {
>-			bitlong = 0;
>-			plong++;
>-		}
>-
>-		blk++;
> 	}
>+	return BFITNOENT;
> 
>+/* parse the bitmap a unsigned long at a time */
>+ulong_aligned:
>+	/* Stop at "end - 1" or else prefetch can go past the end and segfault.
>+	   We could "if" it but we'd lose some of the performance gained.
>+	   This way will only slow down searching the very last 4/8 bytes
>+	   depending on architecture.  I've experimented with several ways
>+	   of writing this section such as using an else before the goto
>+	   but this one seems to be the fastest. */
>+	while ((unsigned char *)plong < end - 1) {
>+		prefetch(plong + 1);
>+		if (((*plong) & LBITMASK) != lskipval)
>+			break;
>+		plong++;
>+	}
>+	if ((unsigned char *)plong < end) {
>+		byte = (const u8 *)plong;
>+		misaligned += sizeof(unsigned long) - 1;
>+		goto misaligned;
>+	}
> 	return BFITNOENT;
> }
>

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Attachments on bug 435456: 297261 | 297459 | 297460 | 297533 | 297654 | 297802