list.h: improve hlist

Hi Linus,

Please consider pulling from:

bk://kernel.bkbits.net/acme/hlist-2.5

I discussed this with Andi and he gave me an ACK to submit, please
let me know if you don't like anything and I'll be happy to fix it. The hlist_for_each_entry is being used in my current work of converting net/ to use hlist_{head,node}.

Best Regards,

- Arnaldo

You can import this changeset into BK by piping this whole message to:
'| bk receive [path to repository]' or apply the patch as usual.

===================================================================

[email protected], 2003-06-07 14:22:10-03:00, [email protected]
o list.h: improve hlist

This changeset:

1. Implements hlist_add_after
2. uses prefetch in hlist_for_each, using a trick that ends up being equivalent to having the prefetch instruction in the first block of the hlist_for_each for block, the compiler optimizes the second "test" away, as its result is constant
3. implements hlist_for_each_entry and hlist_for_each_entry safe, using a struct hlist_node as iterator to avoid the extra branches a similar implementation to list_for_each_entry would have if used a typed iterator, but while avoiding having to have the explicit hlist_entry as in hlist_for_each.

4. Converts the hlist_for_each users that had explicit prefetches, i.e. removed the explicit prefetch

5. fix a harmless list_entry use in a hlist_for_each in inode.c

 fs/dcache.c          |    3 ---
 fs/inode.c           |    4 +---
 include/linux/list.h |   35 ++++++++++++++++++++++++++++++++++-
 3 files changed, 35 insertions(+), 7 deletions(-)

diff -Nru a/fs/dcache.c b/fs/dcache.c
@@ -983,8 +983,6 @@
 		struct dentry *dentry; 
 		unsigned long move_count;
 		struct qstr * qstr;
-		
-		prefetch(node->next);
 
 		smp_read_barrier_depends();
 		dentry = hlist_entry(node, struct dentry, d_hash);

@@ -1072,7 +1070,6 @@
 	spin_lock(&dcache_lock);
 	base = d_hash(dparent, dentry->d_name.hash);
 	hlist_for_each(lhp,base) { 
-		prefetch(lhp->next);
 		/* read_barrier_depends() not required for d_hash list
 		 * as it is parsed under dcache_lock
 		 */

diff -Nru a/fs/inode.c b/fs/inode.c
@@ -484,7 +484,6 @@
 
 repeat:
 	hlist_for_each (node, head) { 
-		prefetch(node->next);
 		inode = hlist_entry(node, struct inode, i_hash);
 		if (inode->i_sb != sb)
 			continue;

@@ -510,8 +509,7 @@
 
 repeat:
 	hlist_for_each (node, head) {
-		prefetch(node->next);
-		inode = list_entry(node, struct inode, i_hash);
+		inode = hlist_entry(node, struct inode, i_hash);
 		if (inode->i_ino != ino)
 			continue;
 		if (inode->i_sb != sb)

diff -Nru a/include/linux/list.h b/include/linux/list.h
@@ -443,17 +443,50 @@
 	*(n->pprev) = n;
 }
 
+static __inline__ void hlist_add_after(struct hlist_node *n,
+				       struct hlist_node *next)
+{
+	next->next	= n->next;
+	*(next->pprev)	= n;
+	n->next		= next;
+}
+
 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 
 /* Cannot easily do prefetch unfortunately */
 #define hlist_for_each(pos, head) \
-	for (pos = (head)->first; pos; \
+	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
 	     pos = pos->next) 
 
 #define hlist_for_each_safe(pos, n, head) \
 	for (pos = (head)->first; n = pos ? pos->next : 0, pos; \
 	     pos = n)
 
+/**
+ * hlist_for_each_entry	- iterate over list of given type
+ * @tpos:	the type * to use as a loop counter.
+ * @pos:	the &struct hlist_node to use as a loop counter.
+ * @head:	the head for your list.
+ * @member:	the name of the hlist_node within the struct.
+ */
+#define hlist_for_each_entry(tpos, pos, head, member)			 \
+	for (pos = (head)->first;					 \
+	     pos && ({ prefetch(pos->next); 1;}) &&			 \
+		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+	     pos = pos->next)
+/**
+ * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
+ * @tpos:	the type * to use as a loop counter.
+ * @pos:	the &struct hlist_node to use as a loop counter.
+ * @n:		another &struct hlist_node to use as temporary storage
+ * @head:	the head for your list.
+ * @member:	the name of the hlist_node within the struct.
+ */
+#define hlist_for_each_entry_safe(tpos, pos, n, head, member) 		 \
+	for (pos = (head)->first;					 \
+	     pos && ({ n = pos->next; 1; }) && 				 \
+		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+	     pos = n)
 #else
 #warning "don't include kernel headers in userspace"
 #endif /* __KERNEL__ */

===================================================================

This BitKeeper patch contains the following changesets:
1.1320
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