[RESEND PATCH] Don't reinvent the wheel but use existing llilst API

[RESEND PATCH] Don't reinvent the wheel but use existing llilst API

[Byungchul Park]

Hello Linus,

Even though llist APIs exist, serveral code in kernel reinvent the
implementation again and again. Since I think it's *worth* making it use
existing APIs, I submit patches doing it.

Actually I've submitted them to maintainers and commiters about 10 times
for 4 months, but they seem to be too busy to review or take them. Of
course you might be even busier, but it would be appriciated if you do
that instead. It might not take your time much since they are simple.

Patches worked on scheduler, irq_work, vhost/scsi and raid are already
taken by proper maintainers. For now, only ones for bcache, mm, fput and
namespace remain.

Thank you,
Byungchul

[RESEND PATCH] bcache: Don't reinvent the wheel but use existing llist API

[Byungchul Park]

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 drivers/md/bcache/closure.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/md/bcache/closure.c b/drivers/md/bcache/closure.c
index 864e673..1841d03 100644
--- a/drivers/md/bcache/closure.c
+++ b/drivers/md/bcache/closure.c
@@ -64,27 +64,16 @@ void closure_put(struct closure *cl)
 void __closure_wake_up(struct closure_waitlist *wait_list)
 {
 	struct llist_node *list;
-	struct closure *cl;
+	struct closure *cl, *t;
 	struct llist_node *reverse = NULL;
 
 	list = llist_del_all(&wait_list->list);
 
 	/* We first reverse the list to preserve FIFO ordering and fairness */
-
-	while (list) {
-		struct llist_node *t = list;
-		list = llist_next(list);
-
-		t->next = reverse;
-		reverse = t;
-	}
+	reverse = llist_reverse_order(list);
 
 	/* Then do the wakeups */
-
-	while (reverse) {
-		cl = container_of(reverse, struct closure, list);
-		reverse = llist_next(reverse);
-
+	llist_for_each_entry_safe(cl, t, reverse, list) {
 		closure_set_waiting(cl, 0);
 		closure_sub(cl, CLOSURE_WAITING + 1);
 	}
-- 
1.9.1

[RESEND PATCH] fput: Don't reinvent the wheel but use existing llist API

[Byungchul Park]

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
---
 fs/file_table.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index 6d982b5..3209da2 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -231,12 +231,10 @@ static void __fput(struct file *file)
 static void delayed_fput(struct work_struct *unused)
 {
 	struct llist_node *node = llist_del_all(&delayed_fput_list);
-	struct llist_node *next;
+	struct file *f, *t;
 
-	for (; node; node = next) {
-		next = llist_next(node);
-		__fput(llist_entry(node, struct file, f_u.fu_llist));
-	}
+	llist_for_each_entry_safe(f, t, node, f_u.fu_llist)
+		__fput(f);
 }
 
 static void ____fput(struct callback_head *work)
@@ -310,7 +308,7 @@ void put_filp(struct file *file)
 }
 
 void __init files_init(void)
-{ 
+{
 	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
 			SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
 	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
@@ -329,4 +327,4 @@ void __init files_maxfiles_init(void)
 	n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
 
 	files_stat.max_files = max_t(unsigned long, n, NR_FILE);
-} 
+}
-- 
1.9.1

[RESEND PATCH] mm: Don't reinvent the wheel but use existing llist API

[Byungchul Park]

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 mm/vmalloc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3ca82d4..8c0eb45 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -49,12 +49,10 @@ struct vfree_deferred {
 static void free_work(struct work_struct *w)
 {
 	struct vfree_deferred *p = container_of(w, struct vfree_deferred, wq);
-	struct llist_node *llnode = llist_del_all(&p->list);
-	while (llnode) {
-		void *p = llnode;
-		llnode = llist_next(llnode);
-		__vunmap(p, 1);
-	}
+	struct llist_node *t, *llnode;
+
+	llist_for_each_safe(llnode, t, llist_del_all(&p->list))
+		__vunmap((void *)llnode, 1);
 }
 
 /*** Page table manipulation functions ***/
-- 
1.9.1

[RESEND PATCH] namespace.c: Don't reinvent the wheel but use existing llist API

[Byungchul Park]

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 fs/namespace.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index b5b1259..5cb2229 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1082,12 +1082,10 @@ static void __cleanup_mnt(struct rcu_head *head)
 static void delayed_mntput(struct work_struct *unused)
 {
 	struct llist_node *node = llist_del_all(&delayed_mntput_list);
-	struct llist_node *next;
+	struct mount *m, *t;
 
-	for (; node; node = next) {
-		next = llist_next(node);
-		cleanup_mnt(llist_entry(node, struct mount, mnt_llist));
-	}
+	llist_for_each_entry_safe(m, t, node, mnt_llist)
+		cleanup_mnt(m);
 }
 static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
 
@@ -1615,7 +1613,7 @@ void __detach_mounts(struct dentry *dentry)
 	namespace_unlock();
 }
 
-/* 
+/*
  * Is the caller allowed to modify his namespace?
  */
 static inline bool may_mount(void)
@@ -2159,7 +2157,7 @@ static int do_loopback(struct path *path, const char *old_name,
 
 	err = -EINVAL;
 	if (mnt_ns_loop(old_path.dentry))
-		goto out; 
+		goto out;
 
 	mp = lock_mount(path);
 	err = PTR_ERR(mp);
-- 
1.9.1

[RESEND PATCH] mm: Don't reinvent the wheel but use existing llist API

[Byungchul Park]

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 mm/vmalloc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3ca82d4..8c0eb45 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -49,12 +49,10 @@ struct vfree_deferred {
 static void free_work(struct work_struct *w)
 {
 	struct vfree_deferred *p = container_of(w, struct vfree_deferred, wq);
-	struct llist_node *llnode = llist_del_all(&p->list);
-	while (llnode) {
-		void *p = llnode;
-		llnode = llist_next(llnode);
-		__vunmap(p, 1);
-	}
+	struct llist_node *t, *llnode;
+
+	llist_for_each_safe(llnode, t, llist_del_all(&p->list))
+		__vunmap((void *)llnode, 1);
 }
 
 /*** Page table manipulation functions ***/
-- 
1.9.1

[RESEND PATCH] llist: Provide a safe version for llist_for_each

[Byungchul Park]

Sometimes we have to dereference next field of llist node before entering
loop becasue the node might be deleted or the next field might be
modified within the loop. So this adds the safe version of llist_for_each,
that is, llist_for_each_safe.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
---
 include/linux/llist.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/llist.h b/include/linux/llist.h
index fd4ca0b..b90c9f2 100644
--- a/include/linux/llist.h
+++ b/include/linux/llist.h
@@ -105,6 +105,25 @@ static inline void init_llist_head(struct llist_head *list)
 	for ((pos) = (node); pos; (pos) = (pos)->next)
 
 /**
+ * llist_for_each_safe - iterate over some deleted entries of a lock-less list
+ *			 safe against removal of list entry
+ * @pos:	the &struct llist_node to use as a loop cursor
+ * @n:		another &struct llist_node to use as temporary storage
+ * @node:	the first entry of deleted list entries
+ *
+ * In general, some entries of the lock-less list can be traversed
+ * safely only after being deleted from list, so start with an entry
+ * instead of list head.
+ *
+ * If being used on entries deleted from lock-less list directly, the
+ * traverse order is from the newest to the oldest added entry.  If
+ * you want to traverse from the oldest to the newest, you must
+ * reverse the order by yourself before traversing.
+ */
+#define llist_for_each_safe(pos, n, node)			\
+	for ((pos) = (node); (pos) && ((n) = (pos)->next, true); (pos) = (n))
+
+/**
  * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
  * @pos:	the type * to use as a loop cursor.
  * @node:	the fist entry of deleted list entries.
-- 
1.9.1

[RESEND PATCH] mm: Don't reinvent the wheel but use existing llist API

[Byungchul Park]

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 mm/vmalloc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3ca82d4..8c0eb45 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -49,12 +49,10 @@ struct vfree_deferred {
 static void free_work(struct work_struct *w)
 {
 	struct vfree_deferred *p = container_of(w, struct vfree_deferred, wq);
-	struct llist_node *llnode = llist_del_all(&p->list);
-	while (llnode) {
-		void *p = llnode;
-		llnode = llist_next(llnode);
-		__vunmap(p, 1);
-	}
+	struct llist_node *t, *llnode;
+
+	llist_for_each_safe(llnode, t, llist_del_all(&p->list))
+		__vunmap((void *)llnode, 1);
 }
 
 /*** Page table manipulation functions ***/
-- 
1.9.1