fs: dcache scale d_unhashed
Protect d_unhashed(dentry) condition with d_lock. This means keeping
DCACHE_UNHASHED bit in synch with hash manipulations.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/fs/dcache.c b/fs/dcache.c
index 81e9150..ee127f9 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -46,6 +46,7 @@
* - d_name
* - d_lru
* - d_count
+ * - d_unhashed()
*
* Ordering:
* dcache_lock
@@ -53,6 +54,13 @@
* dcache_lru_lock
* dcache_hash_lock
*
+ * If there is an ancestor relationship:
+ * dentry->d_parent->...->d_parent->d_lock
+ * ...
+ * dentry->d_parent->d_lock
+ * dentry->d_lock
+ *
+ * If no ancestor relationship:
* if (dentry1 < dentry2)
* dentry1->d_lock
* dentry2->d_lock
@@ -379,7 +387,9 @@
* If it's already been dropped, return OK.
*/
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return 0;
}
@@ -388,9 +398,11 @@
* to get rid of unused child entries.
*/
if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
shrink_dcache_parent(dentry);
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
}
/*
@@ -403,7 +415,6 @@
* we might still populate it if it was a
* working directory or similar).
*/
- spin_lock(&dentry->d_lock);
if (dentry->d_count > 1) {
if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
spin_unlock(&dentry->d_lock);
@@ -490,35 +501,44 @@
* any other hashed alias over that one unless @want_discon is set,
* in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
*/
-
-static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
+static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
{
- struct list_head *head, *next, *tmp;
- struct dentry *alias, *discon_alias=NULL;
+ struct dentry *alias, *discon_alias;
- head = &inode->i_dentry;
- next = inode->i_dentry.next;
- while (next != head) {
- tmp = next;
- next = tmp->next;
- prefetch(next);
- alias = list_entry(tmp, struct dentry, d_alias);
+again:
+ discon_alias = NULL;
+ list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+ spin_lock(&alias->d_lock);
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
if (IS_ROOT(alias) &&
- (alias->d_flags & DCACHE_DISCONNECTED))
+ (alias->d_flags & DCACHE_DISCONNECTED)) {
discon_alias = alias;
- else if (!want_discon) {
- __dget_locked(alias);
+ } else if (!want_discon) {
+ __dget_locked_dlock(alias);
+ spin_unlock(&alias->d_lock);
return alias;
}
}
+ spin_unlock(&alias->d_lock);
}
- if (discon_alias)
- __dget_locked(discon_alias);
- return discon_alias;
+ if (discon_alias) {
+ alias = discon_alias;
+ spin_lock(&alias->d_lock);
+ if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
+ if (IS_ROOT(alias) &&
+ (alias->d_flags & DCACHE_DISCONNECTED)) {
+ __dget_locked_dlock(alias);
+ spin_unlock(&alias->d_lock);
+ return alias;
+ }
+ }
+ spin_unlock(&alias->d_lock);
+ goto again;
+ }
+ return NULL;
}
-struct dentry * d_find_alias(struct inode *inode)
+struct dentry *d_find_alias(struct inode *inode)
{
struct dentry *de = NULL;
@@ -801,8 +821,8 @@
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
dentry_lru_del(dentry);
- spin_unlock(&dentry->d_lock);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
for (;;) {
@@ -817,8 +837,8 @@
d_u.d_child) {
spin_lock(&loop->d_lock);
dentry_lru_del(loop);
- spin_unlock(&loop->d_lock);
__d_drop(loop);
+ spin_unlock(&loop->d_lock);
cond_resched_lock(&dcache_lock);
}
spin_unlock(&dcache_lock);
@@ -1863,7 +1883,10 @@
/*
* XXXX: do we really need to take target->d_lock?
*/
- if (target < dentry) {
+ if (d_ancestor(dentry, target)) {
+ spin_lock(&dentry->d_lock);
+ spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
+ } else if (d_ancestor(target, dentry) || target < dentry) {
spin_lock(&target->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
} else {
@@ -2542,13 +2565,16 @@
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
- if (d_unhashed(dentry)||!dentry->d_inode)
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ if (d_unhashed(dentry) || !dentry->d_inode) {
+ spin_unlock(&dentry->d_lock);
continue;
+ }
if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&dentry->d_lock);
this_parent = dentry;
goto repeat;
}
- spin_lock(&dentry->d_lock);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
}