return sum < 0 ? 0 : sum;
}
-int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
+int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
size_t *lenp, loff_t *ppos)
{
dentry_stat.nr_dentry = get_nr_dentry();
kmem_cache_free(dentry_cache, dentry);
}
-/*
- * no locks, please.
- */
-static void d_free(struct dentry *dentry)
+static void dentry_free(struct dentry *dentry)
{
- BUG_ON((int)dentry->d_lockref.count > 0);
- this_cpu_dec(nr_dentry);
- if (dentry->d_op && dentry->d_op->d_release)
- dentry->d_op->d_release(dentry);
-
/* if dentry was never visible to RCU, immediate free is OK */
if (!(dentry->d_flags & DCACHE_RCUACCESS))
__d_free(&dentry->d_u.d_rcu);
d_lru_add(dentry);
}
-/*
- * Remove a dentry with references from the LRU.
- *
- * If we are on the shrink list, then we can get to try_prune_one_dentry() and
- * lose our last reference through the parent walk. In this case, we need to
- * remove ourselves from the shrink list, not the LRU.
- */
-static void dentry_lru_del(struct dentry *dentry)
-{
- if (dentry->d_flags & DCACHE_LRU_LIST) {
- if (dentry->d_flags & DCACHE_SHRINK_LIST)
- return d_shrink_del(dentry);
- d_lru_del(dentry);
- }
-}
-
-/**
- * d_kill - kill dentry and return parent
- * @dentry: dentry to kill
- * @parent: parent dentry
- *
- * The dentry must already be unhashed and removed from the LRU.
- *
- * If this is the root of the dentry tree, return NULL.
- *
- * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
- * d_kill.
- */
-static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
- __releases(dentry->d_lock)
- __releases(parent->d_lock)
- __releases(dentry->d_inode->i_lock)
-{
- list_del(&dentry->d_u.d_child);
- /*
- * Inform d_walk() that we are no longer attached to the
- * dentry tree
- */
- dentry->d_flags |= DCACHE_DENTRY_KILLED;
- if (parent)
- spin_unlock(&parent->d_lock);
- dentry_iput(dentry);
- /*
- * dentry_iput drops the locks, at which point nobody (except
- * transient RCU lookups) can reach this dentry.
- */
- d_free(dentry);
- return parent;
-}
-
/**
* d_drop - drop a dentry
* @dentry: dentry to drop
}
EXPORT_SYMBOL(d_drop);
-/*
- * Finish off a dentry we've decided to kill.
- * dentry->d_lock must be held, returns with it unlocked.
- * If ref is non-zero, then decrement the refcount too.
- * Returns dentry requiring refcount drop, or NULL if we're done.
- */
-static struct dentry *
-dentry_kill(struct dentry *dentry, int unlock_on_failure)
- __releases(dentry->d_lock)
+static void __dentry_kill(struct dentry *dentry)
{
- struct inode *inode;
- struct dentry *parent;
-
- inode = dentry->d_inode;
- if (inode && !spin_trylock(&inode->i_lock)) {
-relock:
- if (unlock_on_failure) {
- spin_unlock(&dentry->d_lock);
- cpu_relax();
- }
- return dentry; /* try again with same dentry */
- }
- if (IS_ROOT(dentry))
- parent = NULL;
- else
+ struct dentry *parent = NULL;
+ bool can_free = true;
+ if (!IS_ROOT(dentry))
parent = dentry->d_parent;
- if (parent && !spin_trylock(&parent->d_lock)) {
- if (inode)
- spin_unlock(&inode->i_lock);
- goto relock;
- }
/*
* The dentry is now unrecoverably dead to the world.
if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
dentry->d_op->d_prune(dentry);
- dentry_lru_del(dentry);
+ if (dentry->d_flags & DCACHE_LRU_LIST) {
+ if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
+ d_lru_del(dentry);
+ }
/* if it was on the hash then remove it */
__d_drop(dentry);
- return d_kill(dentry, parent);
+ list_del(&dentry->d_u.d_child);
+ /*
+ * Inform d_walk() that we are no longer attached to the
+ * dentry tree
+ */
+ dentry->d_flags |= DCACHE_DENTRY_KILLED;
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ dentry_iput(dentry);
+ /*
+ * dentry_iput drops the locks, at which point nobody (except
+ * transient RCU lookups) can reach this dentry.
+ */
+ BUG_ON((int)dentry->d_lockref.count > 0);
+ this_cpu_dec(nr_dentry);
+ if (dentry->d_op && dentry->d_op->d_release)
+ dentry->d_op->d_release(dentry);
+
+ spin_lock(&dentry->d_lock);
+ if (dentry->d_flags & DCACHE_SHRINK_LIST) {
+ dentry->d_flags |= DCACHE_MAY_FREE;
+ can_free = false;
+ }
+ spin_unlock(&dentry->d_lock);
+ if (likely(can_free))
+ dentry_free(dentry);
+}
+
+/*
+ * Finish off a dentry we've decided to kill.
+ * dentry->d_lock must be held, returns with it unlocked.
+ * If ref is non-zero, then decrement the refcount too.
+ * Returns dentry requiring refcount drop, or NULL if we're done.
+ */
+static struct dentry *dentry_kill(struct dentry *dentry)
+ __releases(dentry->d_lock)
+{
+ struct inode *inode = dentry->d_inode;
+ struct dentry *parent = NULL;
+
+ if (inode && unlikely(!spin_trylock(&inode->i_lock)))
+ goto failed;
+
+ if (!IS_ROOT(dentry)) {
+ parent = dentry->d_parent;
+ if (unlikely(!spin_trylock(&parent->d_lock))) {
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ goto failed;
+ }
+ }
+
+ __dentry_kill(dentry);
+ return parent;
+
+failed:
+ spin_unlock(&dentry->d_lock);
+ cpu_relax();
+ return dentry; /* try again with same dentry */
+}
+
+static inline struct dentry *lock_parent(struct dentry *dentry)
+{
+ struct dentry *parent = dentry->d_parent;
+ if (IS_ROOT(dentry))
+ return NULL;
+ if (unlikely((int)dentry->d_lockref.count < 0))
+ return NULL;
+ if (likely(spin_trylock(&parent->d_lock)))
+ return parent;
+ rcu_read_lock();
+ spin_unlock(&dentry->d_lock);
+again:
+ parent = ACCESS_ONCE(dentry->d_parent);
+ spin_lock(&parent->d_lock);
+ /*
+ * We can't blindly lock dentry until we are sure
+ * that we won't violate the locking order.
+ * Any changes of dentry->d_parent must have
+ * been done with parent->d_lock held, so
+ * spin_lock() above is enough of a barrier
+ * for checking if it's still our child.
+ */
+ if (unlikely(parent != dentry->d_parent)) {
+ spin_unlock(&parent->d_lock);
+ goto again;
+ }
+ rcu_read_unlock();
+ if (parent != dentry)
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ else
+ parent = NULL;
+ return parent;
}
/*
return;
kill_it:
- dentry = dentry_kill(dentry, 1);
+ dentry = dentry_kill(dentry);
if (dentry)
goto repeat;
}
}
EXPORT_SYMBOL(d_prune_aliases);
-/*
- * Try to throw away a dentry - free the inode, dput the parent.
- * Requires dentry->d_lock is held, and dentry->d_count == 0.
- * Releases dentry->d_lock.
- *
- * This may fail if locks cannot be acquired no problem, just try again.
- */
-static struct dentry * try_prune_one_dentry(struct dentry *dentry)
- __releases(dentry->d_lock)
-{
- struct dentry *parent;
-
- parent = dentry_kill(dentry, 0);
- /*
- * If dentry_kill returns NULL, we have nothing more to do.
- * if it returns the same dentry, trylocks failed. In either
- * case, just loop again.
- *
- * Otherwise, we need to prune ancestors too. This is necessary
- * to prevent quadratic behavior of shrink_dcache_parent(), but
- * is also expected to be beneficial in reducing dentry cache
- * fragmentation.
- */
- if (!parent)
- return NULL;
- if (parent == dentry)
- return dentry;
-
- /* Prune ancestors. */
- dentry = parent;
- while (dentry) {
- if (lockref_put_or_lock(&dentry->d_lockref))
- return NULL;
- dentry = dentry_kill(dentry, 1);
- }
- return NULL;
-}
-
static void shrink_dentry_list(struct list_head *list)
{
- struct dentry *dentry;
-
- rcu_read_lock();
- for (;;) {
- dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
- if (&dentry->d_lru == list)
- break; /* empty */
+ struct dentry *dentry, *parent;
- /*
- * Get the dentry lock, and re-verify that the dentry is
- * this on the shrinking list. If it is, we know that
- * DCACHE_SHRINK_LIST and DCACHE_LRU_LIST are set.
- */
+ while (!list_empty(list)) {
+ struct inode *inode;
+ dentry = list_entry(list->prev, struct dentry, d_lru);
spin_lock(&dentry->d_lock);
- if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
- spin_unlock(&dentry->d_lock);
- continue;
- }
+ parent = lock_parent(dentry);
/*
* The dispose list is isolated and dentries are not accounted
* We found an inuse dentry which was not removed from
* the LRU because of laziness during lookup. Do not free it.
*/
- if (dentry->d_lockref.count) {
+ if ((int)dentry->d_lockref.count > 0) {
spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
continue;
}
- rcu_read_unlock();
- /*
- * If 'try_to_prune()' returns a dentry, it will
- * be the same one we passed in, and d_lock will
- * have been held the whole time, so it will not
- * have been added to any other lists. We failed
- * to get the inode lock.
- *
- * We just add it back to the shrink list.
- */
- dentry = try_prune_one_dentry(dentry);
- rcu_read_lock();
- if (dentry) {
+ if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
+ bool can_free = dentry->d_flags & DCACHE_MAY_FREE;
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ if (can_free)
+ dentry_free(dentry);
+ continue;
+ }
+
+ inode = dentry->d_inode;
+ if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
d_shrink_add(dentry, list);
spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ continue;
+ }
+
+ __dentry_kill(dentry);
+
+ /*
+ * We need to prune ancestors too. This is necessary to prevent
+ * quadratic behavior of shrink_dcache_parent(), but is also
+ * expected to be beneficial in reducing dentry cache
+ * fragmentation.
+ */
+ dentry = parent;
+ while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
+ parent = lock_parent(dentry);
+ if (dentry->d_lockref.count != 1) {
+ dentry->d_lockref.count--;
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ break;
+ }
+ inode = dentry->d_inode; /* can't be NULL */
+ if (unlikely(!spin_trylock(&inode->i_lock))) {
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ cpu_relax();
+ continue;
+ }
+ __dentry_kill(dentry);
+ dentry = parent;
}
}
- rcu_read_unlock();
}
static enum lru_status
if (data->start == dentry)
goto out;
- /*
- * move only zero ref count dentries to the dispose list.
- *
- * Those which are presently on the shrink list, being processed
- * by shrink_dentry_list(), shouldn't be moved. Otherwise the
- * loop in shrink_dcache_parent() might not make any progress
- * and loop forever.
- */
- if (dentry->d_lockref.count) {
- dentry_lru_del(dentry);
- } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
- /*
- * We can't use d_lru_shrink_move() because we
- * need to get the global LRU lock and do the
- * LRU accounting.
- */
- d_lru_del(dentry);
- d_shrink_add(dentry, &data->dispose);
+ if (dentry->d_flags & DCACHE_SHRINK_LIST) {
data->found++;
- ret = D_WALK_NORETRY;
+ } else {
+ if (dentry->d_flags & DCACHE_LRU_LIST)
+ d_lru_del(dentry);
+ if (!dentry->d_lockref.count) {
+ d_shrink_add(dentry, &data->dispose);
+ data->found++;
+ }
}
/*
* We can return to the caller if we have found some (this
* ensures forward progress). We'll be coming back to find
* the rest.
*/
- if (data->found && need_resched())
- ret = D_WALK_QUIT;
+ if (!list_empty(&data->dispose))
+ ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
out:
return ret;
}
}
EXPORT_SYMBOL(shrink_dcache_parent);
-static enum d_walk_ret umount_collect(void *_data, struct dentry *dentry)
+static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
{
- struct select_data *data = _data;
- enum d_walk_ret ret = D_WALK_CONTINUE;
+ /* it has busy descendents; complain about those instead */
+ if (!list_empty(&dentry->d_subdirs))
+ return D_WALK_CONTINUE;
- if (dentry->d_lockref.count) {
- dentry_lru_del(dentry);
- if (likely(!list_empty(&dentry->d_subdirs)))
- goto out;
- if (dentry == data->start && dentry->d_lockref.count == 1)
- goto out;
- printk(KERN_ERR
- "BUG: Dentry %p{i=%lx,n=%s}"
- " still in use (%d)"
- " [unmount of %s %s]\n",
+ /* root with refcount 1 is fine */
+ if (dentry == _data && dentry->d_lockref.count == 1)
+ return D_WALK_CONTINUE;
+
+ printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
+ " still in use (%d) [unmount of %s %s]\n",
dentry,
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
- dentry->d_name.name,
+ dentry,
dentry->d_lockref.count,
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
- BUG();
- } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
- /*
- * We can't use d_lru_shrink_move() because we
- * need to get the global LRU lock and do the
- * LRU accounting.
- */
- if (dentry->d_flags & DCACHE_LRU_LIST)
- d_lru_del(dentry);
- d_shrink_add(dentry, &data->dispose);
- data->found++;
- ret = D_WALK_NORETRY;
- }
-out:
- if (data->found && need_resched())
- ret = D_WALK_QUIT;
- return ret;
+ WARN_ON(1);
+ return D_WALK_CONTINUE;
+}
+
+static void do_one_tree(struct dentry *dentry)
+{
+ shrink_dcache_parent(dentry);
+ d_walk(dentry, dentry, umount_check, NULL);
+ d_drop(dentry);
+ dput(dentry);
}
/*
{
struct dentry *dentry;
- if (down_read_trylock(&sb->s_umount))
- BUG();
+ WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
dentry = sb->s_root;
sb->s_root = NULL;
- for (;;) {
- struct select_data data;
-
- INIT_LIST_HEAD(&data.dispose);
- data.start = dentry;
- data.found = 0;
-
- d_walk(dentry, &data, umount_collect, NULL);
- if (!data.found)
- break;
-
- shrink_dentry_list(&data.dispose);
- cond_resched();
- }
- d_drop(dentry);
- dput(dentry);
+ do_one_tree(dentry);
while (!hlist_bl_empty(&sb->s_anon)) {
- struct select_data data;
- dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
-
- INIT_LIST_HEAD(&data.dispose);
- data.start = NULL;
- data.found = 0;
-
- d_walk(dentry, &data, umount_collect, NULL);
- if (data.found)
- shrink_dentry_list(&data.dispose);
- cond_resched();
+ dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash));
+ do_one_tree(dentry);
}
}
unsigned add_flags = d_flags_for_inode(inode);
spin_lock(&dentry->d_lock);
- dentry->d_flags &= ~DCACHE_ENTRY_TYPE;
- dentry->d_flags |= add_flags;
+ __d_set_type(dentry, add_flags);
if (inode)
hlist_add_head(&dentry->d_alias, &inode->i_dentry);
dentry->d_inode = inode;
projects / karo-tx-linux.git / blobdiff