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lib: Introduce generic list_sort function

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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 <[email protected]>
Acked-by: Dave Airlie <[email protected]>
Acked-by: Artem Bityutskiy <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Dave Chinner 2010-01-12 17:39:16 +11:00 • committed by Linus Torvalds
commit 2c761270d5
5 changed files with 119 additions and 182 deletions
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96
fs/ubifs/gc.c
View file

@ -54,6 +54,7 @@
*/
#include <linux/pagemap.h>
#include <linux/list_sort.h>
#include "ubifs.h"
/*
@ -107,101 +108,6 @@ static int switch_gc_head(struct ubifs_info *c)
return err;
}
/**
* 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