X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=fs%2Fdcache.c;h=d5a23fd0da903848682c659085a6c560e48d8a8c;hb=e25b492741373542fb593477547fcf7a6b7d8b04;hp=cb25a1a5e3073748cbef154b6d3575da3f55982d;hpb=f86dc4b04dd5292cae3708c16ca6e46dbb5c95fa;p=firefly-linux-kernel-4.4.55.git

diff --git a/fs/dcache.c b/fs/dcache.c
index cb25a1a5e307..d5a23fd0da90 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -235,18 +235,49 @@ static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *c
 	return dentry_string_cmp(cs, ct, tcount);
 }
 
+struct external_name {
+	union {
+		atomic_t count;
+		struct rcu_head head;
+	} u;
+	unsigned char name[];
+};
+
+static inline struct external_name *external_name(struct dentry *dentry)
+{
+	return container_of(dentry->d_name.name, struct external_name, name[0]);
+}
+
 static void __d_free(struct rcu_head *head)
 {
 	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
 
 	WARN_ON(!hlist_unhashed(&dentry->d_alias));
-	if (dname_external(dentry))
-		kfree(dentry->d_name.name);
 	kmem_cache_free(dentry_cache, dentry); 
 }
 
+static void __d_free_external(struct rcu_head *head)
+{
+	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
+	WARN_ON(!hlist_unhashed(&dentry->d_alias));
+	kfree(external_name(dentry));
+	kmem_cache_free(dentry_cache, dentry); 
+}
+
+static inline int dname_external(const struct dentry *dentry)
+{
+	return dentry->d_name.name != dentry->d_iname;
+}
+
 static void dentry_free(struct dentry *dentry)
 {
+	if (unlikely(dname_external(dentry))) {
+		struct external_name *p = external_name(dentry);
+		if (likely(atomic_dec_and_test(&p->u.count))) {
+			call_rcu(&dentry->d_u.d_rcu, __d_free_external);
+			return;
+		}
+	}
 	/* if dentry was never visible to RCU, immediate free is OK */
 	if (!(dentry->d_flags & DCACHE_RCUACCESS))
 		__d_free(&dentry->d_u.d_rcu);
@@ -456,7 +487,7 @@ static void __dentry_kill(struct dentry *dentry)
 	 * inform the fs via d_prune that this dentry is about to be
 	 * unhashed and destroyed.
 	 */
-	if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
+	if (dentry->d_flags & DCACHE_OP_PRUNE)
 		dentry->d_op->d_prune(dentry);
 
 	if (dentry->d_flags & DCACHE_LRU_LIST) {
@@ -619,62 +650,6 @@ kill_it:
 }
 EXPORT_SYMBOL(dput);
 
-/**
- * d_invalidate - invalidate a dentry
- * @dentry: dentry to invalidate
- *
- * Try to invalidate the dentry if it turns out to be
- * possible. If there are other dentries that can be
- * reached through this one we can't delete it and we
- * return -EBUSY. On success we return 0.
- *
- * no dcache lock.
- */
- 
-int d_invalidate(struct dentry * dentry)
-{
-	/*
-	 * If it's already been dropped, return OK.
-	 */
-	spin_lock(&dentry->d_lock);
-	if (d_unhashed(dentry)) {
-		spin_unlock(&dentry->d_lock);
-		return 0;
-	}
-	/*
-	 * Check whether to do a partial shrink_dcache
-	 * to get rid of unused child entries.
-	 */
-	if (!list_empty(&dentry->d_subdirs)) {
-		spin_unlock(&dentry->d_lock);
-		shrink_dcache_parent(dentry);
-		spin_lock(&dentry->d_lock);
-	}
-
-	/*
-	 * Somebody else still using it?
-	 *
-	 * If it's a directory, we can't drop it
-	 * for fear of somebody re-populating it
-	 * with children (even though dropping it
-	 * would make it unreachable from the root,
-	 * we might still populate it if it was a
-	 * working directory or similar).
-	 * We also need to leave mountpoints alone,
-	 * directory or not.
-	 */
-	if (dentry->d_lockref.count > 1 && dentry->d_inode) {
-		if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
-			spin_unlock(&dentry->d_lock);
-			return -EBUSY;
-		}
-	}
-
-	__d_drop(dentry);
-	spin_unlock(&dentry->d_lock);
-	return 0;
-}
-EXPORT_SYMBOL(d_invalidate);
 
 /* This must be called with d_lock held */
 static inline void __dget_dlock(struct dentry *dentry)
@@ -735,7 +710,8 @@ EXPORT_SYMBOL(dget_parent);
  * acquire the reference to alias and return it. Otherwise return NULL.
  * Notice that if inode is a directory there can be only one alias and
  * it can be unhashed only if it has no children, or if it is the root
- * of a filesystem.
+ * of a filesystem, or if the directory was renamed and d_revalidate
+ * was the first vfs operation to notice.
  *
  * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
  * any other hashed alias over that one.
@@ -799,20 +775,13 @@ restart:
 	hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
 		spin_lock(&dentry->d_lock);
 		if (!dentry->d_lockref.count) {
-			/*
-			 * inform the fs via d_prune that this dentry
-			 * is about to be unhashed and destroyed.
-			 */
-			if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
-			    !d_unhashed(dentry))
-				dentry->d_op->d_prune(dentry);
-
-			__dget_dlock(dentry);
-			__d_drop(dentry);
-			spin_unlock(&dentry->d_lock);
-			spin_unlock(&inode->i_lock);
-			dput(dentry);
-			goto restart;
+			struct dentry *parent = lock_parent(dentry);
+			if (likely(!dentry->d_lockref.count)) {
+				__dentry_kill(dentry);
+				goto restart;
+			}
+			if (parent)
+				spin_unlock(&parent->d_lock);
 		}
 		spin_unlock(&dentry->d_lock);
 	}
@@ -1193,7 +1162,7 @@ EXPORT_SYMBOL(have_submounts);
  * reachable (e.g. NFS can unhash a directory dentry and then the complete
  * subtree can become unreachable).
  *
- * Only one of check_submounts_and_drop() and d_set_mounted() must succeed.  For
+ * Only one of d_invalidate() and d_set_mounted() must succeed.  For
  * this reason take rename_lock and d_lock on dentry and ancestors.
  */
 int d_set_mounted(struct dentry *dentry)
@@ -1202,7 +1171,7 @@ int d_set_mounted(struct dentry *dentry)
 	int ret = -ENOENT;
 	write_seqlock(&rename_lock);
 	for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
-		/* Need exclusion wrt. check_submounts_and_drop() */
+		/* Need exclusion wrt. d_invalidate() */
 		spin_lock(&p->d_lock);
 		if (unlikely(d_unhashed(p))) {
 			spin_unlock(&p->d_lock);
@@ -1346,70 +1315,84 @@ void shrink_dcache_for_umount(struct super_block *sb)
 	}
 }
 
-static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry)
+struct detach_data {
+	struct select_data select;
+	struct dentry *mountpoint;
+};
+static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
 {
-	struct select_data *data = _data;
+	struct detach_data *data = _data;
 
 	if (d_mountpoint(dentry)) {
-		data->found = -EBUSY;
+		__dget_dlock(dentry);
+		data->mountpoint = dentry;
 		return D_WALK_QUIT;
 	}
 
-	return select_collect(_data, dentry);
+	return select_collect(&data->select, dentry);
 }
 
 static void check_and_drop(void *_data)
 {
-	struct select_data *data = _data;
+	struct detach_data *data = _data;
 
-	if (d_mountpoint(data->start))
-		data->found = -EBUSY;
-	if (!data->found)
-		__d_drop(data->start);
+	if (!data->mountpoint && !data->select.found)
+		__d_drop(data->select.start);
 }
 
 /**
- * check_submounts_and_drop - prune dcache, check for submounts and drop
+ * d_invalidate - detach submounts, prune dcache, and drop
+ * @dentry: dentry to invalidate (aka detach, prune and drop)
  *
- * All done as a single atomic operation relative to has_unlinked_ancestor().
- * Returns 0 if successfully unhashed @parent.  If there were submounts then
- * return -EBUSY.
+ * no dcache lock.
  *
- * @dentry: dentry to prune and drop
+ * The final d_drop is done as an atomic operation relative to
+ * rename_lock ensuring there are no races with d_set_mounted.  This
+ * ensures there are no unhashed dentries on the path to a mountpoint.
  */
-int check_submounts_and_drop(struct dentry *dentry)
+void d_invalidate(struct dentry *dentry)
 {
-	int ret = 0;
+	/*
+	 * If it's already been dropped, return OK.
+	 */
+	spin_lock(&dentry->d_lock);
+	if (d_unhashed(dentry)) {
+		spin_unlock(&dentry->d_lock);
+		return;
+	}
+	spin_unlock(&dentry->d_lock);
 
 	/* Negative dentries can be dropped without further checks */
 	if (!dentry->d_inode) {
 		d_drop(dentry);
-		goto out;
+		return;
 	}
 
 	for (;;) {
-		struct select_data data;
+		struct detach_data data;
 
-		INIT_LIST_HEAD(&data.dispose);
-		data.start = dentry;
-		data.found = 0;
+		data.mountpoint = NULL;
+		INIT_LIST_HEAD(&data.select.dispose);
+		data.select.start = dentry;
+		data.select.found = 0;
+
+		d_walk(dentry, &data, detach_and_collect, check_and_drop);
 
-		d_walk(dentry, &data, check_and_collect, check_and_drop);
-		ret = data.found;
+		if (data.select.found)
+			shrink_dentry_list(&data.select.dispose);
 
-		if (!list_empty(&data.dispose))
-			shrink_dentry_list(&data.dispose);
+		if (data.mountpoint) {
+			detach_mounts(data.mountpoint);
+			dput(data.mountpoint);
+		}
 
-		if (ret <= 0)
+		if (!data.mountpoint && !data.select.found)
 			break;
 
 		cond_resched();
 	}
-
-out:
-	return ret;
 }
-EXPORT_SYMBOL(check_submounts_and_drop);
+EXPORT_SYMBOL(d_invalidate);
 
 /**
  * __d_alloc	-	allocate a dcache entry
@@ -1438,11 +1421,14 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	 */
 	dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
 	if (name->len > DNAME_INLINE_LEN-1) {
-		dname = kmalloc(name->len + 1, GFP_KERNEL);
-		if (!dname) {
+		size_t size = offsetof(struct external_name, name[1]);
+		struct external_name *p = kmalloc(size + name->len, GFP_KERNEL);
+		if (!p) {
 			kmem_cache_free(dentry_cache, dentry); 
 			return NULL;
 		}
+		atomic_set(&p->u.count, 1);
+		dname = p->name;
 	} else  {
 		dname = dentry->d_iname;
 	}	
@@ -2112,10 +2098,10 @@ struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
 	struct dentry *dentry;
 	unsigned seq;
 
-        do {
-                seq = read_seqbegin(&rename_lock);
-                dentry = __d_lookup(parent, name);
-                if (dentry)
+	do {
+		seq = read_seqbegin(&rename_lock);
+		dentry = __d_lookup(parent, name);
+		if (dentry)
 			break;
 	} while (read_seqretry(&rename_lock, seq));
 	return dentry;
@@ -2372,11 +2358,10 @@ void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
 }
 EXPORT_SYMBOL(dentry_update_name_case);
 
-static void switch_names(struct dentry *dentry, struct dentry *target,
-			 bool exchange)
+static void swap_names(struct dentry *dentry, struct dentry *target)
 {
-	if (dname_external(target)) {
-		if (dname_external(dentry)) {
+	if (unlikely(dname_external(target))) {
+		if (unlikely(dname_external(dentry))) {
 			/*
 			 * Both external: swap the pointers
 			 */
@@ -2392,7 +2377,7 @@ static void switch_names(struct dentry *dentry, struct dentry *target,
 			target->d_name.name = target->d_iname;
 		}
 	} else {
-		if (dname_external(dentry)) {
+		if (unlikely(dname_external(dentry))) {
 			/*
 			 * dentry:external, target:internal.  Give dentry's
 			 * storage to target and make dentry internal
@@ -2407,12 +2392,6 @@ static void switch_names(struct dentry *dentry, struct dentry *target,
 			 */
 			unsigned int i;
 			BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
-			if (!exchange) {
-				memcpy(dentry->d_iname, target->d_name.name,
-						target->d_name.len + 1);
-				dentry->d_name.hash_len = target->d_name.hash_len;
-				return;
-			}
 			for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
 				swap(((long *) &dentry->d_iname)[i],
 				     ((long *) &target->d_iname)[i]);
@@ -2422,6 +2401,24 @@ static void switch_names(struct dentry *dentry, struct dentry *target,
 	swap(dentry->d_name.hash_len, target->d_name.hash_len);
 }
 
+static void copy_name(struct dentry *dentry, struct dentry *target)
+{
+	struct external_name *old_name = NULL;
+	if (unlikely(dname_external(dentry)))
+		old_name = external_name(dentry);
+	if (unlikely(dname_external(target))) {
+		atomic_inc(&external_name(target)->u.count);
+		dentry->d_name = target->d_name;
+	} else {
+		memcpy(dentry->d_iname, target->d_name.name,
+				target->d_name.len + 1);
+		dentry->d_name.name = dentry->d_iname;
+		dentry->d_name.hash_len = target->d_name.hash_len;
+	}
+	if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
+		kfree_rcu(old_name, u.head);
+}
+
 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
 {
 	/*
@@ -2518,7 +2515,10 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	}
 
 	/* Switch the names.. */
-	switch_names(dentry, target, exchange);
+	if (exchange)
+		swap_names(dentry, target);
+	else
+		copy_name(dentry, target);
 
 	/* ... and switch them in the tree */
 	if (IS_ROOT(dentry)) {
@@ -2625,10 +2625,8 @@ static struct dentry *__d_unalias(struct inode *inode,
 		goto out_err;
 	m2 = &alias->d_parent->d_inode->i_mutex;
 out_unalias:
-	if (likely(!d_mountpoint(alias))) {
-		__d_move(alias, dentry, false);
-		ret = alias;
-	}
+	__d_move(alias, dentry, false);
+	ret = alias;
 out_err:
 	spin_unlock(&inode->i_lock);
 	if (m2)
@@ -2810,6 +2808,9 @@ static int prepend(char **buffer, int *buflen, const char *str, int namelen)
  * the beginning of the name. The sequence number check at the caller will
  * retry it again when a d_move() does happen. So any garbage in the buffer
  * due to mismatched pointer and length will be discarded.
+ *
+ * Data dependency barrier is needed to make sure that we see that terminating
+ * NUL.  Alpha strikes again, film at 11...
  */
 static int prepend_name(char **buffer, int *buflen, struct qstr *name)
 {
@@ -2817,6 +2818,8 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
 	u32 dlen = ACCESS_ONCE(name->len);
 	char *p;
 
+	smp_read_barrier_depends();
+
 	*buflen -= dlen + 1;
 	if (*buflen < 0)
 		return -ENAMETOOLONG;