linux-kernel - Re: [PATCH] add gen_pool

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Message-ID: <20060928154849.GA10434@sgi.com>
Date:	Thu, 28 Sep 2006 10:48:49 -0500
From:	Dean Nelson <dcn@....com>
To:	torvalds@...l.org
Cc:	linux-kernel@...r.kernel.org, holt@....com,
	swise@...ngridcomputing.com, rdunlap@...otime.net,
	jes@...ined-monkey.org, avolkov@...ma-el.com, dcn@....com
Subject: Re: [PATCH] add gen_pool_destroy()

Modules using the genpool allocator need to be able to kfree() the memory
used for the genpool data structures when unloading.

Signed-off-by: Steve Wise <swise@...ngridcomputing.com>
Signed-off-by: Dean Nelson <dcn@....com>

---

On Thu, Sep 28, 2006 at 09:51:42AM -0500, Robin Holt wrote:
> Nack this.
> 
> Dean, you changed the list_for_each to list_for_each_safe where it was
> not needed.  I think you only needed to change that in the remove path.
> IIRC, list_for_each_safe is intended for walking a list where you unlink
> the entry as part of your operation.  Keep it for the gen_pool_destroy
> function since you are using kfree on those objects and somebody else
> could reuse them (sort of a list delete), but do not change them for
> the other case.  The list_for_each does an explicit prefetch which will
> improve performance in many cases.

Thanks Robin.

Linus, here's a new version of the patch which corrects the
issue that Robin Holt pointed out.

Again, there is an issue with the block comments not being up to
kernel-doc standards that plagues the entire file, which I will
remedy in a followup patch.

Thanks,
Dean


 include/linux/genalloc.h |    1 +
 lib/genalloc.c           |   30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)


Index: linux-2.6/lib/genalloc.c
===================================================================
--- linux-2.6.orig/lib/genalloc.c	2006-09-28 09:53:53.372104302 -0500
+++ linux-2.6/lib/genalloc.c	2006-09-28 10:42:47.627258805 -0500
@@ -71,6 +71,36 @@
 
 
 /*
+ * Destroy a memory pool. Verifies that there are no outstanding allocations.
+ *
+ * @pool: pool to destroy
+ */
+void gen_pool_destroy(struct gen_pool *pool)
+{
+	struct list_head *_chunk, *_next_chunk;
+	struct gen_pool_chunk *chunk;
+	int order = pool->min_alloc_order;
+	int bit, end_bit;
+
+
+	write_lock(&pool->lock);
+	list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
+		chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
+		list_del(&chunk->next_chunk);
+
+		end_bit = (chunk->end_addr - chunk->start_addr) >> order;
+		bit = find_next_bit(chunk->bits, end_bit, 0);
+		BUG_ON(bit < end_bit);
+
+		kfree(chunk);
+	}
+	kfree(pool);
+	return;
+}
+EXPORT_SYMBOL(gen_pool_destroy);
+
+
+/*
  * Allocate the requested number of bytes from the specified pool.
  * Uses a first-fit algorithm.
  *
Index: linux-2.6/include/linux/genalloc.h
===================================================================
--- linux-2.6.orig/include/linux/genalloc.h	2006-09-28 09:53:53.372104302 -0500
+++ linux-2.6/include/linux/genalloc.h	2006-09-28 09:53:55.200331504 -0500
@@ -31,5 +31,6 @@
 
 extern struct gen_pool *gen_pool_create(int, int);
 extern int gen_pool_add(struct gen_pool *, unsigned long, size_t, int);
+extern void gen_pool_destroy(struct gen_pool *);
 extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
 extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
-
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