Patchwork [2/8] bitmap: Introduce bitmap_set, bitmap_clear, bitmap_find_next_zero_area

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Submitter Akinobu Mita
Date Oct. 9, 2009, 8:29 a.m.
Message ID <1255076961-21325-2-git-send-email-akinobu.mita@gmail.com>
Download mbox | patch
Permalink /patch/35592/
State Not Applicable
Delegated to: David Miller
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Comments

Akinobu Mita - Oct. 9, 2009, 8:29 a.m.
This introduces new bitmap functions:

bitmap_set: Set specified bit area
bitmap_clear: Clear specified bit area
bitmap_find_next_zero_area: Find free bit area

These are stolen from iommu helper.

I changed the return value of bitmap_find_next_zero_area if there is
no zero area.

find_next_zero_area in iommu helper: returns -1
bitmap_find_next_zero_area: return >= bitmap size

Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@ozlabs.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Lothar Wassmann <LW@KARO-electronics.de>
Cc: linux-usb@vger.kernel.org
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Cc: netdev@vger.kernel.org
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Cc: linux-altix@sgi.com
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 include/linux/bitmap.h |   11 +++++++++++
 lib/bitmap.c           |   47 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 0 deletions(-)
Andrew Morton - Oct. 9, 2009, 11:41 p.m.
On Fri,  9 Oct 2009 17:29:15 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> This introduces new bitmap functions:
> 
> bitmap_set: Set specified bit area
> bitmap_clear: Clear specified bit area
> bitmap_find_next_zero_area: Find free bit area
> 
> These are stolen from iommu helper.
> 
> I changed the return value of bitmap_find_next_zero_area if there is
> no zero area.
> 
> find_next_zero_area in iommu helper: returns -1
> bitmap_find_next_zero_area: return >= bitmap size

I'll plan to merge this patch into 2.6.32 so we can trickle all the
other patches into subsystems in an orderly fashion.

> +void bitmap_set(unsigned long *map, int i, int len)
> +{
> +	int end = i + len;
> +
> +	while (i < end) {
> +		__set_bit(i, map);
> +		i++;
> +	}
> +}

This is really inefficient, isn't it?  It's a pretty trivial matter to
romp through memory 32 or 64 bits at a time.

> +EXPORT_SYMBOL(bitmap_set);
> +
> +void bitmap_clear(unsigned long *map, int start, int nr)
> +{
> +	int end = start + nr;
> +
> +	while (start < end) {
> +		__clear_bit(start, map);
> +		start++;
> +	}
> +}
> +EXPORT_SYMBOL(bitmap_clear);

Ditto.

> +unsigned long bitmap_find_next_zero_area(unsigned long *map,
> +					 unsigned long size,
> +					 unsigned long start,
> +					 unsigned int nr,
> +					 unsigned long align_mask)
> +{
> +	unsigned long index, end, i;
> +again:
> +	index = find_next_zero_bit(map, size, start);
> +
> +	/* Align allocation */
> +	index = (index + align_mask) & ~align_mask;
> +
> +	end = index + nr;
> +	if (end >= size)
> +		return end;
> +	i = find_next_bit(map, end, index);
> +	if (i < end) {
> +		start = i + 1;
> +		goto again;
> +	}
> +	return index;
> +}
> +EXPORT_SYMBOL(bitmap_find_next_zero_area);

This needs documentation, please.  It appears that `size' is the size
of the bitmap and `nr' is the number of zeroed bits we're looking for,
but an inattentive programmer could get those reversed.

Also the semantics of `align_mask' could benefit from spelling out.  Is
the alignment with respect to memory boundaries or with respect to
`map' or with respect to map+start or what?

And why does align_mask exist at all?  I was a bit surprised to see it
there.  In which scenarios will it be non-zero?

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Akinobu Mita - Oct. 13, 2009, 2:18 a.m.
On Fri, Oct 09, 2009 at 04:41:00PM -0700, Andrew Morton wrote:
> On Fri,  9 Oct 2009 17:29:15 +0900
> Akinobu Mita <akinobu.mita@gmail.com> wrote:
> 
> > This introduces new bitmap functions:
> > 
> > bitmap_set: Set specified bit area
> > bitmap_clear: Clear specified bit area
> > bitmap_find_next_zero_area: Find free bit area
> > 
> > These are stolen from iommu helper.
> > 
> > I changed the return value of bitmap_find_next_zero_area if there is
> > no zero area.
> > 
> > find_next_zero_area in iommu helper: returns -1
> > bitmap_find_next_zero_area: return >= bitmap size
> 
> I'll plan to merge this patch into 2.6.32 so we can trickle all the
> other patches into subsystems in an orderly fashion.

Sounds good.

> > +void bitmap_set(unsigned long *map, int i, int len)
> > +{
> > +	int end = i + len;
> > +
> > +	while (i < end) {
> > +		__set_bit(i, map);
> > +		i++;
> > +	}
> > +}
> 
> This is really inefficient, isn't it?  It's a pretty trivial matter to
> romp through memory 32 or 64 bits at a time.

OK. I'll do

> > +unsigned long bitmap_find_next_zero_area(unsigned long *map,
> > +					 unsigned long size,
> > +					 unsigned long start,
> > +					 unsigned int nr,
> > +					 unsigned long align_mask)
> > +{
> > +	unsigned long index, end, i;
> > +again:
> > +	index = find_next_zero_bit(map, size, start);
> > +
> > +	/* Align allocation */
> > +	index = (index + align_mask) & ~align_mask;
> > +
> > +	end = index + nr;
> > +	if (end >= size)
> > +		return end;
> > +	i = find_next_bit(map, end, index);
> > +	if (i < end) {
> > +		start = i + 1;
> > +		goto again;
> > +	}
> > +	return index;
> > +}
> > +EXPORT_SYMBOL(bitmap_find_next_zero_area);
> 
> This needs documentation, please.  It appears that `size' is the size
> of the bitmap and `nr' is the number of zeroed bits we're looking for,
> but an inattentive programmer could get those reversed.
> 
> Also the semantics of `align_mask' could benefit from spelling out.  Is
> the alignment with respect to memory boundaries or with respect to
> `map' or with respect to map+start or what?

OK. I will document it.

And I plan to change bitmap_find_next_zero_area() to take the alignment
instead of an align_mask as Roland said.

> And why does align_mask exist at all?  I was a bit surprised to see it
> there.  In which scenarios will it be non-zero?

Because the users of iommu-helper and mlx4 need the alignment requirement
for the zero area.

arch/powerpc/kernel/iommu.c
arch/x86/kernel/amd_iommu.c
arch/x86/kernel/pci-gart_64.c
drivers/net/mlx4/alloc.c

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Patch

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 756d78b..daf8c48 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -42,6 +42,9 @@ 
  * bitmap_empty(src, nbits)			Are all bits zero in *src?
  * bitmap_full(src, nbits)			Are all bits set in *src?
  * bitmap_weight(src, nbits)			Hamming Weight: number set bits
+ * bitmap_set(dst, pos, nbits)			Set specified bit area
+ * bitmap_clear(dst, pos, nbits)		Clear specified bit area
+ * bitmap_find_next_zero_area(buf, len, pos, n, mask)	Find bit free area
  * bitmap_shift_right(dst, src, n, nbits)	*dst = *src >> n
  * bitmap_shift_left(dst, src, n, nbits)	*dst = *src << n
  * bitmap_remap(dst, src, old, new, nbits)	*dst = map(old, new)(src)
@@ -108,6 +111,14 @@  extern int __bitmap_subset(const unsigned long *bitmap1,
 			const unsigned long *bitmap2, int bits);
 extern int __bitmap_weight(const unsigned long *bitmap, int bits);
 
+extern void bitmap_set(unsigned long *map, int i, int len);
+extern void bitmap_clear(unsigned long *map, int start, int nr);
+extern unsigned long bitmap_find_next_zero_area(unsigned long *map,
+					 unsigned long size,
+					 unsigned long start,
+					 unsigned int nr,
+					 unsigned long align_mask);
+
 extern int bitmap_scnprintf(char *buf, unsigned int len,
 			const unsigned long *src, int nbits);
 extern int __bitmap_parse(const char *buf, unsigned int buflen, int is_user,
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 7025658..95070fa 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -271,6 +271,53 @@  int __bitmap_weight(const unsigned long *bitmap, int bits)
 }
 EXPORT_SYMBOL(__bitmap_weight);
 
+void bitmap_set(unsigned long *map, int i, int len)
+{
+	int end = i + len;
+
+	while (i < end) {
+		__set_bit(i, map);
+		i++;
+	}
+}
+EXPORT_SYMBOL(bitmap_set);
+
+void bitmap_clear(unsigned long *map, int start, int nr)
+{
+	int end = start + nr;
+
+	while (start < end) {
+		__clear_bit(start, map);
+		start++;
+	}
+}
+EXPORT_SYMBOL(bitmap_clear);
+
+unsigned long bitmap_find_next_zero_area(unsigned long *map,
+					 unsigned long size,
+					 unsigned long start,
+					 unsigned int nr,
+					 unsigned long align_mask)
+{
+	unsigned long index, end, i;
+again:
+	index = find_next_zero_bit(map, size, start);
+
+	/* Align allocation */
+	index = (index + align_mask) & ~align_mask;
+
+	end = index + nr;
+	if (end >= size)
+		return end;
+	i = find_next_bit(map, end, index);
+	if (i < end) {
+		start = i + 1;
+		goto again;
+	}
+	return index;
+}
+EXPORT_SYMBOL(bitmap_find_next_zero_area);
+
 /*
  * Bitmap printing & parsing functions: first version by Bill Irwin,
  * second version by Paul Jackson, third by Joe Korty.