Commit 74373c6a authored by Paul Mundt's avatar Paul Mundt Committed by Linus Torvalds
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[PATCH] bitmap: region multiword spanning support 



Add support to the lib/bitmap.c bitmap_*_region() routines

For bitmap regions larger than one word (nbits > BITS_PER_LONG).  This removes
a BUG_ON() in lib bitmap.

I have an updated store queue API for SH that is currently using this with
relative success, and at first glance, it seems like this could be useful for
x86 (arch/i386/kernel/pci-dma.c) as well.  Particularly for anything using
dma_declare_coherent_memory() on large areas and that attempts to allocate
large buffers from that space.

Paul Jackson also did some cleanup to this patch.

Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
Signed-off-by: default avatarPaul Jackson <pj@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 87e24802

lib/bitmap.c

+76 −34
Original line number Diff line number Diff line
@@ -692,27 +692,45 @@ EXPORT_SYMBOL(bitmap_bitremap); 
 */

int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)

{

	unsigned long mask;

	int nbits = 1 << order;

	int i;



	if (nbits > BITS_PER_LONG)

		return -EINVAL;

	int nbits;		/* number of bits in region */

	int nlongs;		/* num longs spanned by region in bitmap */

	int nbitsinlong;	/* num bits of region in each spanned long */

	unsigned long mask;	/* bitmask of bits [0 .. nbitsinlong-1] */

	int i;			/* scans bitmap by longs */



	nbits = 1 << order;

	nlongs = (nbits + (BITS_PER_LONG - 1)) / BITS_PER_LONG;

	nbitsinlong = nbits;

	if (nbitsinlong > BITS_PER_LONG)

		nbitsinlong = BITS_PER_LONG;



	/* make a mask of the order */

	mask = (1UL << (nbits - 1));

	mask = (1UL << (nbitsinlong - 1));

	mask += mask - 1;



	/* run up the bitmap nbits at a time */

	for (i = 0; i < bits; i += nbits) {

	/* run up the bitmap nbitsinlong at a time */

	for (i = 0; i < bits; i += nbitsinlong) {

		int index = i / BITS_PER_LONG;

		int offset = i - (index * BITS_PER_LONG);

		if ((bitmap[index] & (mask << offset)) == 0) {

		int j, space = 1;



		/* find space in the bitmap */

		for (j = 0; j < nlongs; j++)

			if ((bitmap[index + j] & (mask << offset))) {

				space = 0;

				break;

			}



		/* keep looking */

		if (unlikely(!space))

			continue;



		for (j = 0; j < nlongs; j++)

			/* set region in bitmap */

			bitmap[index] |= (mask << offset);

			bitmap[index + j] |= (mask << offset);



		return i;

	}

	}

	return -ENOMEM;

}

EXPORT_SYMBOL(bitmap_find_free_region);
@@ -728,13 +746,28 @@ EXPORT_SYMBOL(bitmap_find_free_region); 
 */

void bitmap_release_region(unsigned long *bitmap, int pos, int order)

{

	int nbits = 1 << order;

	unsigned long mask = (1UL << (nbits - 1));

	int index = pos / BITS_PER_LONG;

	int offset = pos - (index * BITS_PER_LONG);



	int nbits;		/* number of bits in region */

	int nlongs;		/* num longs spanned by region in bitmap */

	int index;		/* index first long of region in bitmap */

	int offset;		/* bit offset region in bitmap[index] */

	int nbitsinlong;	/* num bits of region in each spanned long */

	unsigned long mask;	/* bitmask of bits [0 .. nbitsinlong-1] */

	int i;			/* scans bitmap by longs */



	nbits = 1 << order;

	nlongs = (nbits + (BITS_PER_LONG - 1)) / BITS_PER_LONG;

	index = pos / BITS_PER_LONG;

	offset = pos - (index * BITS_PER_LONG);



	nbitsinlong = nbits;

	if (nbitsinlong > BITS_PER_LONG)

		nbitsinlong = BITS_PER_LONG;



	mask = (1UL << (nbitsinlong - 1));

	mask += mask - 1;

	bitmap[index] &= ~(mask << offset);



	for (i = 0; i < nlongs; i++)

		bitmap[index + i] &= ~(mask << offset);

}

EXPORT_SYMBOL(bitmap_release_region);
@@ -750,22 +783,31 @@ EXPORT_SYMBOL(bitmap_release_region); 
 */

int bitmap_allocate_region(unsigned long *bitmap, int pos, int order)

{

	int nbits = 1 << order;

	unsigned long mask = (1UL << (nbits - 1));

	int index = pos / BITS_PER_LONG;

	int offset = pos - (index * BITS_PER_LONG);



	/*

	 * We don't do regions of nbits > BITS_PER_LONG.  The

	 * algorithm would be a simple look for multiple zeros in the

	 * array, but there's no driver today that needs this.  If you

	 * trip this BUG(), you get to code it...

	 */

	BUG_ON(nbits > BITS_PER_LONG);

	int nbits;		/* number of bits in region */

	int nlongs;		/* num longs spanned by region in bitmap */

	int index;		/* index first long of region in bitmap */

	int offset;		/* bit offset region in bitmap[index] */

	int nbitsinlong;	/* num bits of region in each spanned long */

	unsigned long mask;	/* bitmask of bits [0 .. nbitsinlong-1] */

	int i;			/* scans bitmap by longs */



	nbits = 1 << order;

	nlongs = (nbits + (BITS_PER_LONG - 1)) / BITS_PER_LONG;

	index = pos / BITS_PER_LONG;

	offset = pos - (index * BITS_PER_LONG);



	nbitsinlong = nbits;

	if (nbitsinlong > BITS_PER_LONG)

		nbitsinlong = BITS_PER_LONG;



	mask = (1UL << (nbitsinlong - 1));

	mask += mask - 1;

	if (bitmap[index] & (mask << offset))



	for (i = 0; i < nlongs; i++)

		if (bitmap[index + i] & (mask << offset))

			return -EBUSY;

	bitmap[index] |= (mask << offset);

	for (i = 0; i < nlongs; i++)

		bitmap[index + i] |= (mask << offset);

	return 0;

}

EXPORT_SYMBOL(bitmap_allocate_region);

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