Introduce a handy list_first_entry macro
There are many places in the kernel where the construction like
foo = list_entry(head->next, struct foo_struct, list);
are used.
The code might look more descriptive and neat if using the macro
list_first_entry(head, type, member) \
list_entry((head)->next, type, member)
Here is the macro itself and the examples of its usage in the generic code.
If it will turn out to be useful, I can prepare the set of patches to
inject in into arch-specific code, drivers, networking, etc.
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/dquot.c b/fs/dquot.c
index dcc5a58..3a99584 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -474,7 +474,7 @@
spin_lock(&dq_list_lock);
dirty = &dqopt->info[cnt].dqi_dirty_list;
while (!list_empty(dirty)) {
- dquot = list_entry(dirty->next, struct dquot, dq_dirty);
+ dquot = list_first_entry(dirty, struct dquot, dq_dirty);
/* Dirty and inactive can be only bad dquot... */
if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
clear_dquot_dirty(dquot);
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d0b8606..b5c7ca5 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -453,7 +453,7 @@
mutex_lock(&epmutex);
while (!list_empty(lsthead)) {
- epi = list_entry(lsthead->next, struct epitem, fllink);
+ epi = list_first_entry(lsthead, struct epitem, fllink);
ep = epi->ep;
list_del_init(&epi->fllink);
@@ -1143,7 +1143,7 @@
if (nwait) {
while (!list_empty(lsthead)) {
- pwq = list_entry(lsthead->next, struct eppoll_entry, llink);
+ pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
list_del_init(&pwq->llink);
remove_wait_queue(pwq->whead, &pwq->wait);
@@ -1359,7 +1359,7 @@
* read.
*/
for (eventcnt = 0; !list_empty(txlist) && eventcnt < maxevents;) {
- epi = list_entry(txlist->next, struct epitem, rdllink);
+ epi = list_first_entry(txlist, struct epitem, rdllink);
prefetch(epi->rdllink.next);
/*
diff --git a/fs/inode.c b/fs/inode.c
index 81508b0..410f235 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -275,7 +275,7 @@
while (!list_empty(head)) {
struct inode *inode;
- inode = list_entry(head->next, struct inode, i_list);
+ inode = list_first_entry(head, struct inode, i_list);
list_del(&inode->i_list);
if (inode->i_data.nrpages)
diff --git a/fs/inotify.c b/fs/inotify.c
index f5099d8..7457501 100644
--- a/fs/inotify.c
+++ b/fs/inotify.c
@@ -509,7 +509,7 @@
mutex_unlock(&ih->mutex);
break;
}
- watch = list_entry(watches->next, struct inotify_watch, h_list);
+ watch = list_first_entry(watches, struct inotify_watch, h_list);
get_inotify_watch(watch);
mutex_unlock(&ih->mutex);
diff --git a/fs/namespace.c b/fs/namespace.c
index c5b8810..72bb106 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -499,7 +499,7 @@
{
struct vfsmount *mnt;
while (!list_empty(head)) {
- mnt = list_entry(head->next, struct vfsmount, mnt_hash);
+ mnt = list_first_entry(head, struct vfsmount, mnt_hash);
list_del_init(&mnt->mnt_hash);
if (mnt->mnt_parent != mnt) {
struct dentry *dentry;
@@ -1177,7 +1177,7 @@
while (!list_empty(graveyard)) {
LIST_HEAD(umounts);
- mnt = list_entry(graveyard->next, struct vfsmount, mnt_expire);
+ mnt = list_first_entry(graveyard, struct vfsmount, mnt_expire);
list_del_init(&mnt->mnt_expire);
/* don't do anything if the namespace is dead - all the
diff --git a/fs/pnode.c b/fs/pnode.c
index 56aacea..89940f2 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -59,7 +59,7 @@
} else {
struct list_head *p = &mnt->mnt_slave_list;
while (!list_empty(p)) {
- slave_mnt = list_entry(p->next,
+ slave_mnt = list_first_entry(p,
struct vfsmount, mnt_slave);
list_del_init(&slave_mnt->mnt_slave);
slave_mnt->mnt_master = NULL;
diff --git a/include/linux/list.h b/include/linux/list.h
index f9d71ea..9202703 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -426,6 +426,17 @@
container_of(ptr, type, member)
/**
+ * list_first_entry - get the first element from a list
+ * @ptr: the list head to take the element from.
+ * @type: the type of the struct this is embedded in.
+ * @member: the name of the list_struct within the struct.
+ *
+ * Note, that list is expected to be not empty.
+ */
+#define list_first_entry(ptr, type, member) \
+ list_entry((ptr)->next, type, member)
+
+/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 657f776..1de710e 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -971,7 +971,7 @@
maxfire = 20;
tsk->it_prof_expires = cputime_zero;
while (!list_empty(timers)) {
- struct cpu_timer_list *t = list_entry(timers->next,
+ struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
@@ -986,7 +986,7 @@
maxfire = 20;
tsk->it_virt_expires = cputime_zero;
while (!list_empty(timers)) {
- struct cpu_timer_list *t = list_entry(timers->next,
+ struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
@@ -1001,7 +1001,7 @@
maxfire = 20;
tsk->it_sched_expires = 0;
while (!list_empty(timers)) {
- struct cpu_timer_list *t = list_entry(timers->next,
+ struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || tsk->sched_time < t->expires.sched) {
@@ -1057,7 +1057,7 @@
maxfire = 20;
prof_expires = cputime_zero;
while (!list_empty(timers)) {
- struct cpu_timer_list *t = list_entry(timers->next,
+ struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
@@ -1072,7 +1072,7 @@
maxfire = 20;
virt_expires = cputime_zero;
while (!list_empty(timers)) {
- struct cpu_timer_list *t = list_entry(timers->next,
+ struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
@@ -1087,7 +1087,7 @@
maxfire = 20;
sched_expires = 0;
while (!list_empty(timers)) {
- struct cpu_timer_list *t = list_entry(timers->next,
+ struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || sched_time < t->expires.sched) {
@@ -1400,7 +1400,7 @@
*/
head = &tsk->signal->cpu_timers[clock_idx];
if (list_empty(head) ||
- cputime_ge(list_entry(head->next,
+ cputime_ge(list_first_entry(head,
struct cpu_timer_list, entry)->expires.cpu,
*newval)) {
/*
diff --git a/kernel/timer.c b/kernel/timer.c
index ba41af2..7a64483 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -629,7 +629,7 @@
void (*fn)(unsigned long);
unsigned long data;
- timer = list_entry(head->next,struct timer_list,entry);
+ timer = list_first_entry(head, struct timer_list,entry);
fn = timer->function;
data = timer->data;
@@ -1248,7 +1248,7 @@
struct timer_list *timer;
while (!list_empty(head)) {
- timer = list_entry(head->next, struct timer_list, entry);
+ timer = list_first_entry(head, struct timer_list, entry);
detach_timer(timer, 0);
timer_set_base(timer, new_base);
internal_add_timer(new_base, timer);