[PATCH 7/9] staging: lustre: ldlm: tidy list walking in ldlm_flock()

From: NeilBrown
Date: Sun Oct 22 2017 - 20:55:53 EST


Use list_for_each_entry variants to
avoid the explicit list_entry() calls.
This allows us to use list_for_each_entry_safe_from()
instread of adding a local list-walking macro.

Also improve some comments so that it is more obvious
that the locks are sorted per-owner and that we need
to find the insertion point.

Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
drivers/staging/lustre/lustre/ldlm/ldlm_flock.c | 45 ++++++++++-------------
1 file changed, 19 insertions(+), 26 deletions(-)

diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c b/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
index 1bf56892fcf5..0bf6dce1c5b1 100644
--- a/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
+++ b/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
@@ -59,17 +59,6 @@
#include <linux/list.h>
#include "ldlm_internal.h"

-/**
- * list_for_remaining_safe - iterate over the remaining entries in a list
- * and safeguard against removal of a list entry.
- * \param pos the &struct list_head to use as a loop counter. pos MUST
- * have been initialized prior to using it in this macro.
- * \param n another &struct list_head to use as temporary storage
- * \param head the head for your list.
- */
-#define list_for_remaining_safe(pos, n, head) \
- for (n = pos->next; pos != (head); pos = n, n = pos->next)
-
static inline int
ldlm_same_flock_owner(struct ldlm_lock *lock, struct ldlm_lock *new)
{
@@ -125,8 +114,8 @@ static int ldlm_process_flock_lock(struct ldlm_lock *req)
{
struct ldlm_resource *res = req->l_resource;
struct ldlm_namespace *ns = ldlm_res_to_ns(res);
- struct list_head *tmp;
- struct list_head *ownlocks = NULL;
+ struct ldlm_lock *tmp;
+ struct ldlm_lock *ownlocks = NULL;
struct ldlm_lock *lock = NULL;
struct ldlm_lock *new = req;
struct ldlm_lock *new2 = NULL;
@@ -151,23 +140,23 @@ static int ldlm_process_flock_lock(struct ldlm_lock *req)
/* This loop determines where this processes locks start
* in the resource lr_granted list.
*/
- list_for_each(tmp, &res->lr_granted) {
- lock = list_entry(tmp, struct ldlm_lock,
- l_res_link);
+ list_for_each_entry(lock, &res->lr_granted, l_res_link) {
if (ldlm_same_flock_owner(lock, req)) {
- ownlocks = tmp;
+ ownlocks = lock;
break;
}
}

- /* Scan the locks owned by this process that overlap this request.
+ /* Scan the locks owned by this process to find the insertion point
+ * (as locks are ordered), and to handle overlaps.
* We may have to merge or split existing locks.
*/
- if (!ownlocks)
- ownlocks = &res->lr_granted;
-
- list_for_remaining_safe(ownlocks, tmp, &res->lr_granted) {
- lock = list_entry(ownlocks, struct ldlm_lock, l_res_link);
+ if (ownlocks)
+ lock = ownlocks;
+ else
+ lock = list_entry(&res->lr_granted,
+ struct ldlm_lock, l_res_link);
+ list_for_each_entry_safe_from(lock, tmp, &res->lr_granted, l_res_link) {

if (!ldlm_same_flock_owner(lock, new))
break;
@@ -295,7 +284,7 @@ static int ldlm_process_flock_lock(struct ldlm_lock *req)
lock->l_granted_mode);

/* insert new2 at lock */
- ldlm_resource_add_lock(res, ownlocks, new2);
+ ldlm_resource_add_lock(res, &lock->l_res_link, new2);
LDLM_LOCK_RELEASE(new2);
break;
}
@@ -309,8 +298,12 @@ static int ldlm_process_flock_lock(struct ldlm_lock *req)

if (!added) {
list_del_init(&req->l_res_link);
- /* insert new lock before ownlocks in list. */
- ldlm_resource_add_lock(res, ownlocks, req);
+ /* insert new lock before "lock", which might be the
+ * next lock for this owner, or might be the first
+ * lock for the next owner, or might not be a lock at
+ * all, but instead points at the head of the list
+ */
+ ldlm_resource_add_lock(res, &lock->l_res_link, req);
}

/* In case we're reprocessing the requested lock we can't destroy