split read_seqretry_or_unlock(), convert d_walk() to resulting primitives
Separate "check if we need to retry" from "unlock if we are done and
had seq_writelock"; that allows to use these guys in d_walk(), where
we need to recheck every time we ascend back to parent, but do *not*
want to unlock until the very end. Lift rcu_read_lock/rcu_read_unlock
out into callers.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index 38b1b09..b9caf47 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -100,30 +100,21 @@
*/
static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq)
{
- if (!(*seq & 1)) { /* Even */
+ if (!(*seq & 1)) /* Even */
*seq = read_seqbegin(lock);
- rcu_read_lock();
- } else /* Odd */
+ else /* Odd */
write_seqlock(lock);
}
-/**
- * read_seqretry_or_unlock - end a seqretry or lock block & return retry status
- * lock : sequence lock
- * seq : sequence number
- * Return: 1 to retry operation again, 0 to continue
- */
-static inline int read_seqretry_or_unlock(seqlock_t *lock, int *seq)
+static inline int need_seqretry(seqlock_t *lock, int seq)
{
- if (!(*seq & 1)) { /* Even */
- rcu_read_unlock();
- if (read_seqretry(lock, *seq)) {
- (*seq)++; /* Take writer lock */
- return 1;
- }
- } else /* Odd */
+ return !(seq & 1) && read_seqretry(lock, seq);
+}
+
+static inline void done_seqretry(seqlock_t *lock, int seq)
+{
+ if (seq & 1)
write_sequnlock(lock);
- return 0;
}
/*
@@ -1047,7 +1038,7 @@
* the parenthood after dropping the lock and check
* that the sequence number still matches.
*/
-static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
+static struct dentry *try_to_ascend(struct dentry *old, unsigned seq)
{
struct dentry *new = old->d_parent;
@@ -1061,7 +1052,7 @@
*/
if (new != old->d_parent ||
(old->d_flags & DCACHE_DENTRY_KILLED) ||
- (!locked && read_seqretry(&rename_lock, seq))) {
+ need_seqretry(&rename_lock, seq)) {
spin_unlock(&new->d_lock);
new = NULL;
}
@@ -1098,13 +1089,12 @@
{
struct dentry *this_parent;
struct list_head *next;
- unsigned seq;
- int locked = 0;
+ unsigned seq = 0;
enum d_walk_ret ret;
bool retry = true;
- seq = read_seqbegin(&rename_lock);
again:
+ read_seqbegin_or_lock(&rename_lock, &seq);
this_parent = parent;
spin_lock(&this_parent->d_lock);
@@ -1158,13 +1148,13 @@
*/
if (this_parent != parent) {
struct dentry *child = this_parent;
- this_parent = try_to_ascend(this_parent, locked, seq);
+ this_parent = try_to_ascend(this_parent, seq);
if (!this_parent)
goto rename_retry;
next = child->d_u.d_child.next;
goto resume;
}
- if (!locked && read_seqretry(&rename_lock, seq)) {
+ if (need_seqretry(&rename_lock, seq)) {
spin_unlock(&this_parent->d_lock);
goto rename_retry;
}
@@ -1173,17 +1163,13 @@
out_unlock:
spin_unlock(&this_parent->d_lock);
- if (locked)
- write_sequnlock(&rename_lock);
+ done_seqretry(&rename_lock, seq);
return;
rename_retry:
if (!retry)
return;
- if (locked)
- goto again;
- locked = 1;
- write_seqlock(&rename_lock);
+ seq = 1;
goto again;
}
@@ -2745,6 +2731,7 @@
char *bptr;
int blen;
+ rcu_read_lock();
restart:
bptr = *buffer;
blen = *buflen;
@@ -2783,8 +2770,13 @@
dentry = parent;
}
- if (read_seqretry_or_unlock(&rename_lock, &seq))
+ if (!(seq & 1))
+ rcu_read_unlock();
+ if (need_seqretry(&rename_lock, seq)) {
+ seq = 1;
goto restart;
+ }
+ done_seqretry(&rename_lock, seq);
if (error >= 0 && bptr == *buffer) {
if (--blen < 0)
@@ -2957,6 +2949,7 @@
int len, seq = 0;
int error = 0;
+ rcu_read_lock();
restart:
end = buf + buflen;
len = buflen;
@@ -2979,8 +2972,13 @@
retval = end;
dentry = parent;
}
- if (read_seqretry_or_unlock(&rename_lock, &seq))
+ if (!(seq & 1))
+ rcu_read_unlock();
+ if (need_seqretry(&rename_lock, seq)) {
+ seq = 1;
goto restart;
+ }
+ done_seqretry(&rename_lock, seq);
if (error)
goto Elong;
return retval;