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Subject[PATCH V3] sort: Introduce generic list_sort function
On Tue, Jan 05, 2010 at 12:31:15PM +0100, Andi Kleen wrote:
> Dave Chinner <david@fromorbit.com> writes:
> > +
> > +/**
> > + * list_sort - sort a list.
> > + * @priv: private data, passed to @cmp
> > + * @head: the list to sort
> > + * @cmp: the elements comparison function
> > + *
> > + * This function has been implemented by Mark J Roberts <mjr@znex.org>. It
> > + * implements "merge sort" which has O(nlog(n)) complexity. The list is sorted
> > + * in ascending order.
> > + *
> > + * The comparison function @cmp is supposed to return a negative value if @a is
> > + * than @b, and a positive value if @a is greater than @b. If @a and @b are
> > + * equivalent, then it does not matter what this function returns.
> > + */
> > +void list_sort(void *priv, struct list_head *head,
> > + int (*cmp)(void *priv, struct list_head *a,
> > + struct list_head *b))
>
> No EXPORT_SYMBOL?

Bah, who uses modules? :P

Fixed. Updated patch below.

> Also it would seem cleaner to have it in a own file.

That might make sense if we had a large number of generic sort
functions and it was difficult to tell the code apart, but we've
only got 2 right now....
Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com

sort: Introduce generic list_sort function

There are two copies of list_sort() in the tree already, one in the DRM code,
another in ubifs. Now XFS needs this as well. Create a generic list_sort()
function from the ubifs version and convert existing users to it so we
don't end up with yet another copy in the tree.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Acked-by: Artem Bityutskiy <dedekind@infradead.org>
---
V3: Export list_sort()
V2: fix a typo
drivers/gpu/drm/drm_modes.c | 90 ++-------------------------------------
fs/ubifs/gc.c | 95 -----------------------------------------
include/linux/sort.h | 5 ++
lib/sort.c | 98 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 107 insertions(+), 181 deletions(-)
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 51f6772..3846ed4 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1,9 +1,4 @@
/*
- * The list_sort function is (presumably) licensed under the GPL (see the
- * top level "COPYING" file for details).
- *
- * The remainder of this file is:
- *
* Copyright © 1997-2003 by The XFree86 Project, Inc.
* Copyright © 2007 Dave Airlie
* Copyright © 2007-2008 Intel Corporation
@@ -36,6 +31,7 @@
*/

#include <linux/list.h>
+#include <linux/sort.h>
#include "drmP.h"
#include "drm.h"
#include "drm_crtc.h"
@@ -829,6 +825,7 @@ EXPORT_SYMBOL(drm_mode_prune_invalid);

/**
* drm_mode_compare - compare modes for favorability
+ * @priv: unused
* @lh_a: list_head for first mode
* @lh_b: list_head for second mode
*
@@ -842,7 +839,7 @@ EXPORT_SYMBOL(drm_mode_prune_invalid);
* Negative if @lh_a is better than @lh_b, zero if they're equivalent, or
* positive if @lh_b is better than @lh_a.
*/
-static int drm_mode_compare(struct list_head *lh_a, struct list_head *lh_b)
+static int drm_mode_compare(void *priv, struct list_head *lh_a, struct list_head *lh_b)
{
struct drm_display_mode *a = list_entry(lh_a, struct drm_display_mode, head);
struct drm_display_mode *b = list_entry(lh_b, struct drm_display_mode, head);
@@ -859,85 +856,6 @@ static int drm_mode_compare(struct list_head *lh_a, struct list_head *lh_b)
return diff;
}

-/* FIXME: what we don't have a list sort function? */
-/* list sort from Mark J Roberts (mjr@znex.org) */
-void list_sort(struct list_head *head,
- int (*cmp)(struct list_head *a, struct list_head *b))
-{
- struct list_head *p, *q, *e, *list, *tail, *oldhead;
- int insize, nmerges, psize, qsize, i;
-
- list = head->next;
- list_del(head);
- insize = 1;
- for (;;) {
- p = oldhead = list;
- list = tail = NULL;
- nmerges = 0;
-
- while (p) {
- nmerges++;
- q = p;
- psize = 0;
- for (i = 0; i < insize; i++) {
- psize++;
- q = q->next == oldhead ? NULL : q->next;
- if (!q)
- break;
- }
-
- qsize = insize;
- while (psize > 0 || (qsize > 0 && q)) {
- if (!psize) {
- e = q;
- q = q->next;
- qsize--;
- if (q == oldhead)
- q = NULL;
- } else if (!qsize || !q) {
- e = p;
- p = p->next;
- psize--;
- if (p == oldhead)
- p = NULL;
- } else if (cmp(p, q) <= 0) {
- e = p;
- p = p->next;
- psize--;
- if (p == oldhead)
- p = NULL;
- } else {
- e = q;
- q = q->next;
- qsize--;
- if (q == oldhead)
- q = NULL;
- }
- if (tail)
- tail->next = e;
- else
- list = e;
- e->prev = tail;
- tail = e;
- }
- p = q;
- }
-
- tail->next = list;
- list->prev = tail;
-
- if (nmerges <= 1)
- break;
-
- insize *= 2;
- }
-
- head->next = list;
- head->prev = list->prev;
- list->prev->next = head;
- list->prev = head;
-}
-
/**
* drm_mode_sort - sort mode list
* @mode_list: list to sort
@@ -949,7 +867,7 @@ void list_sort(struct list_head *head,
*/
void drm_mode_sort(struct list_head *mode_list)
{
- list_sort(mode_list, drm_mode_compare);
+ list_sort(NULL, mode_list, drm_mode_compare);
}
EXPORT_SYMBOL(drm_mode_sort);

diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c
index 618c270..4976e07 100644
--- a/fs/ubifs/gc.c
+++ b/fs/ubifs/gc.c
@@ -108,101 +108,6 @@ static int switch_gc_head(struct ubifs_info *c)
}

/**
- * list_sort - sort a list.
- * @priv: private data, passed to @cmp
- * @head: the list to sort
- * @cmp: the elements comparison function
- *
- * This function has been implemented by Mark J Roberts <mjr@znex.org>. It
- * implements "merge sort" which has O(nlog(n)) complexity. The list is sorted
- * in ascending order.
- *
- * The comparison function @cmp is supposed to return a negative value if @a is
- * than @b, and a positive value if @a is greater than @b. If @a and @b are
- * equivalent, then it does not matter what this function returns.
- */
-static void list_sort(void *priv, struct list_head *head,
- int (*cmp)(void *priv, struct list_head *a,
- struct list_head *b))
-{
- struct list_head *p, *q, *e, *list, *tail, *oldhead;
- int insize, nmerges, psize, qsize, i;
-
- if (list_empty(head))
- return;
-
- list = head->next;
- list_del(head);
- insize = 1;
- for (;;) {
- p = oldhead = list;
- list = tail = NULL;
- nmerges = 0;
-
- while (p) {
- nmerges++;
- q = p;
- psize = 0;
- for (i = 0; i < insize; i++) {
- psize++;
- q = q->next == oldhead ? NULL : q->next;
- if (!q)
- break;
- }
-
- qsize = insize;
- while (psize > 0 || (qsize > 0 && q)) {
- if (!psize) {
- e = q;
- q = q->next;
- qsize--;
- if (q == oldhead)
- q = NULL;
- } else if (!qsize || !q) {
- e = p;
- p = p->next;
- psize--;
- if (p == oldhead)
- p = NULL;
- } else if (cmp(priv, p, q) <= 0) {
- e = p;
- p = p->next;
- psize--;
- if (p == oldhead)
- p = NULL;
- } else {
- e = q;
- q = q->next;
- qsize--;
- if (q == oldhead)
- q = NULL;
- }
- if (tail)
- tail->next = e;
- else
- list = e;
- e->prev = tail;
- tail = e;
- }
- p = q;
- }
-
- tail->next = list;
- list->prev = tail;
-
- if (nmerges <= 1)
- break;
-
- insize *= 2;
- }
-
- head->next = list;
- head->prev = list->prev;
- list->prev->next = head;
- list->prev = head;
-}
-
-/**
* data_nodes_cmp - compare 2 data nodes.
* @priv: UBIFS file-system description object
* @a: first data node
diff --git a/include/linux/sort.h b/include/linux/sort.h
index d534da2..99a2ed5 100644
--- a/include/linux/sort.h
+++ b/include/linux/sort.h
@@ -3,8 +3,13 @@

#include <linux/types.h>

+struct list_head;
+
void sort(void *base, size_t num, size_t size,
int (*cmp)(const void *, const void *),
void (*swap)(void *, void *, int));

+void list_sort(void *priv, struct list_head *head,
+ int (*cmp)(void *priv, struct list_head *a,
+ struct list_head *b));
#endif
diff --git a/lib/sort.c b/lib/sort.c
index 926d004..a9ce544 100644
--- a/lib/sort.c
+++ b/lib/sort.c
@@ -8,6 +8,7 @@
#include <linux/module.h>
#include <linux/sort.h>
#include <linux/slab.h>
+#include <linux/list.h>

static void u32_swap(void *a, void *b, int size)
{
@@ -121,3 +122,100 @@ static int sort_test(void)

module_init(sort_test);
#endif
+
+/**
+ * list_sort - sort a list.
+ * @priv: private data, passed to @cmp
+ * @head: the list to sort
+ * @cmp: the elements comparison function
+ *
+ * This function has been implemented by Mark J Roberts <mjr@znex.org>. It
+ * implements "merge sort" which has O(nlog(n)) complexity. The list is sorted
+ * in ascending order.
+ *
+ * The comparison function @cmp is supposed to return a negative value if @a is
+ * less than @b, and a positive value if @a is greater than @b. If @a and @b
+ * are equivalent, then it does not matter what this function returns.
+ */
+void list_sort(void *priv, struct list_head *head,
+ int (*cmp)(void *priv, struct list_head *a,
+ struct list_head *b))
+{
+ struct list_head *p, *q, *e, *list, *tail, *oldhead;
+ int insize, nmerges, psize, qsize, i;
+
+ if (list_empty(head))
+ return;
+
+ list = head->next;
+ list_del(head);
+ insize = 1;
+ for (;;) {
+ p = oldhead = list;
+ list = tail = NULL;
+ nmerges = 0;
+
+ while (p) {
+ nmerges++;
+ q = p;
+ psize = 0;
+ for (i = 0; i < insize; i++) {
+ psize++;
+ q = q->next == oldhead ? NULL : q->next;
+ if (!q)
+ break;
+ }
+
+ qsize = insize;
+ while (psize > 0 || (qsize > 0 && q)) {
+ if (!psize) {
+ e = q;
+ q = q->next;
+ qsize--;
+ if (q == oldhead)
+ q = NULL;
+ } else if (!qsize || !q) {
+ e = p;
+ p = p->next;
+ psize--;
+ if (p == oldhead)
+ p = NULL;
+ } else if (cmp(priv, p, q) <= 0) {
+ e = p;
+ p = p->next;
+ psize--;
+ if (p == oldhead)
+ p = NULL;
+ } else {
+ e = q;
+ q = q->next;
+ qsize--;
+ if (q == oldhead)
+ q = NULL;
+ }
+ if (tail)
+ tail->next = e;
+ else
+ list = e;
+ e->prev = tail;
+ tail = e;
+ }
+ p = q;
+ }
+
+ tail->next = list;
+ list->prev = tail;
+
+ if (nmerges <= 1)
+ break;
+
+ insize *= 2;
+ }
+
+ head->next = list;
+ head->prev = list->prev;
+ list->prev->next = head;
+ list->prev = head;
+}
+
+EXPORT_SYMBOL(list_sort);
--
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