1 files changed, 93 insertions, 35 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index a88948b8bd1..89509b5a090 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -36,6 +36,7 @@
 #include <linux/bit_spinlock.h>
 #include <linux/rculist_bl.h>
 #include <linux/prefetch.h>
+#include <linux/ratelimit.h>
 #include "internal.h"
 
 /*
@@ -225,7 +226,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
 }
 
 /*
- * dentry_lru_(add|del|move_tail) must be called with d_lock held.
+ * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
  */
 static void dentry_lru_add(struct dentry *dentry)
 {
@@ -245,6 +246,9 @@ static void __dentry_lru_del(struct dentry *dentry)
 	dentry_stat.nr_unused--;
 }
 
+/*
+ * Remove a dentry with references from the LRU.
+ */
 static void dentry_lru_del(struct dentry *dentry)
 {
 	if (!list_empty(&dentry->d_lru)) {
@@ -254,6 +258,23 @@ static void dentry_lru_del(struct dentry *dentry)
 	}
 }
 
+/*
+ * Remove a dentry that is unreferenced and about to be pruned
+ * (unhashed and destroyed) from the LRU, and inform the file system.
+ * This wrapper should be called _prior_ to unhashing a victim dentry.
+ */
+static void dentry_lru_prune(struct dentry *dentry)
+{
+	if (!list_empty(&dentry->d_lru)) {
+		if (dentry->d_flags & DCACHE_OP_PRUNE)
+			dentry->d_op->d_prune(dentry);
+
+		spin_lock(&dcache_lru_lock);
+		__dentry_lru_del(dentry);
+		spin_unlock(&dcache_lru_lock);
+	}
+}
+
 static void dentry_lru_move_tail(struct dentry *dentry)
 {
 	spin_lock(&dcache_lru_lock);
@@ -403,8 +424,12 @@ relock:
 
 	if (ref)
 		dentry->d_count--;
-	/* if dentry was on the d_lru list delete it from there */
-	dentry_lru_del(dentry);
+	/*
+	 * if dentry was on the d_lru list delete it from there.
+	 * inform the fs via d_prune that this dentry is about to be
+	 * unhashed and destroyed.
+	 */
+	dentry_lru_prune(dentry);
 	/* if it was on the hash then remove it */
 	__d_drop(dentry);
 	return d_kill(dentry, parent);
@@ -522,9 +547,11 @@ int d_invalidate(struct dentry * dentry)
 	 * 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_count > 1) {
-		if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
+	if (dentry->d_count > 1 && dentry->d_inode) {
+		if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
 			spin_unlock(&dentry->d_lock);
 			return -EBUSY;
 		}
@@ -854,8 +881,12 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 		do {
 			struct inode *inode;
 
-			/* detach from the system */
-			dentry_lru_del(dentry);
+			/*
+			 * remove the dentry from the lru, and inform
+			 * the fs that this dentry is about to be
+			 * unhashed and destroyed.
+			 */
+			dentry_lru_prune(dentry);
 			__d_shrink(dentry);
 
 			if (dentry->d_count != 0) {
@@ -1283,6 +1314,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
 		dentry->d_flags |= DCACHE_OP_REVALIDATE;
 	if (op->d_delete)
 		dentry->d_flags |= DCACHE_OP_DELETE;
+	if (op->d_prune)
+		dentry->d_flags |= DCACHE_OP_PRUNE;
 
 }
 EXPORT_SYMBOL(d_set_d_op);
@@ -2351,8 +2384,16 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 				actual = __d_unalias(inode, dentry, alias);
 			}
 			write_sequnlock(&rename_lock);
-			if (IS_ERR(actual))
+			if (IS_ERR(actual)) {
+				if (PTR_ERR(actual) == -ELOOP)
+					pr_warn_ratelimited(
+						"VFS: Lookup of '%s' in %s %s"
+						" would have caused loop\n",
+						dentry->d_name.name,
+						inode->i_sb->s_type->name,
+						inode->i_sb->s_id);
 				dput(alias);
+			}
 			goto out_nolock;
 		}
 	}
@@ -2398,16 +2439,14 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
 /**
  * prepend_path - Prepend path string to a buffer
  * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry (may be modified by this function)
+ * @root: root vfsmnt/dentry
  * @buffer: pointer to the end of the buffer
  * @buflen: pointer to buffer length
  *
  * Caller holds the rename_lock.
- *
- * If path is not reachable from the supplied root, then the value of
- * root is changed (without modifying refcounts).
  */
-static int prepend_path(const struct path *path, struct path *root,
+static int prepend_path(const struct path *path,
+			const struct path *root,
 			char **buffer, int *buflen)
 {
 	struct dentry *dentry = path->dentry;
@@ -2442,10 +2481,10 @@ static int prepend_path(const struct path *path, struct path *root,
 		dentry = parent;
 	}
 
-out:
 	if (!error && !slash)
 		error = prepend(buffer, buflen, "/", 1);
 
+out:
 	br_read_unlock(vfsmount_lock);
 	return error;
 
@@ -2459,15 +2498,17 @@ global_root:
 		WARN(1, "Root dentry has weird name <%.*s>\n",
 		     (int) dentry->d_name.len, dentry->d_name.name);
 	}
-	root->mnt = vfsmnt;
-	root->dentry = dentry;
+	if (!slash)
+		error = prepend(buffer, buflen, "/", 1);
+	if (!error)
+		error = vfsmnt->mnt_ns ? 1 : 2;
 	goto out;
 }
 
 /**
  * __d_path - return the path of a dentry
  * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry (may be modified by this function)
+ * @root: root vfsmnt/dentry
  * @buf: buffer to return value in
  * @buflen: buffer length
  *
@@ -2478,10 +2519,10 @@ global_root:
  *
  * "buflen" should be positive.
  *
- * If path is not reachable from the supplied root, then the value of
- * root is changed (without modifying refcounts).
+ * If the path is not reachable from the supplied root, return %NULL.
  */
-char *__d_path(const struct path *path, struct path *root,
+char *__d_path(const struct path *path,
+	       const struct path *root,
 	       char *buf, int buflen)
 {
 	char *res = buf + buflen;
@@ -2492,7 +2533,28 @@ char *__d_path(const struct path *path, struct path *root,
 	error = prepend_path(path, root, &res, &buflen);
 	write_sequnlock(&rename_lock);
 
-	if (error)
+	if (error < 0)
+		return ERR_PTR(error);
+	if (error > 0)
+		return NULL;
+	return res;
+}
+
+char *d_absolute_path(const struct path *path,
+	       char *buf, int buflen)
+{
+	struct path root = {};
+	char *res = buf + buflen;
+	int error;
+
+	prepend(&res, &buflen, "\0", 1);
+	write_seqlock(&rename_lock);
+	error = prepend_path(path, &root, &res, &buflen);
+	write_sequnlock(&rename_lock);
+
+	if (error > 1)
+		error = -EINVAL;
+	if (error < 0)
 		return ERR_PTR(error);
 	return res;
 }
@@ -2500,8 +2562,9 @@ char *__d_path(const struct path *path, struct path *root,
 /*
  * same as __d_path but appends "(deleted)" for unlinked files.
  */
-static int path_with_deleted(const struct path *path, struct path *root,
-				 char **buf, int *buflen)
+static int path_with_deleted(const struct path *path,
+			     const struct path *root,
+			     char **buf, int *buflen)
 {
 	prepend(buf, buflen, "\0", 1);
 	if (d_unlinked(path->dentry)) {
@@ -2538,7 +2601,6 @@ char *d_path(const struct path *path, char *buf, int buflen)
 {
 	char *res = buf + buflen;
 	struct path root;
-	struct path tmp;
 	int error;
 
 	/*
@@ -2553,9 +2615,8 @@ char *d_path(const struct path *path, char *buf, int buflen)
 
 	get_fs_root(current->fs, &root);
 	write_seqlock(&rename_lock);
-	tmp = root;
-	error = path_with_deleted(path, &tmp, &res, &buflen);
-	if (error)
+	error = path_with_deleted(path, &root, &res, &buflen);
+	if (error < 0)
 		res = ERR_PTR(error);
 	write_sequnlock(&rename_lock);
 	path_put(&root);
@@ -2576,7 +2637,6 @@ char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
 {
 	char *res = buf + buflen;
 	struct path root;
-	struct path tmp;
 	int error;
 
 	if (path->dentry->d_op && path->dentry->d_op->d_dname)
@@ -2584,9 +2644,8 @@ char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
 
 	get_fs_root(current->fs, &root);
 	write_seqlock(&rename_lock);
-	tmp = root;
-	error = path_with_deleted(path, &tmp, &res, &buflen);
-	if (!error && !path_equal(&tmp, &root))
+	error = path_with_deleted(path, &root, &res, &buflen);
+	if (error > 0)
 		error = prepend_unreachable(&res, &buflen);
 	write_sequnlock(&rename_lock);
 	path_put(&root);
@@ -2717,19 +2776,18 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 	write_seqlock(&rename_lock);
 	if (!d_unlinked(pwd.dentry)) {
 		unsigned long len;
-		struct path tmp = root;
 		char *cwd = page + PAGE_SIZE;
 		int buflen = PAGE_SIZE;
 
 		prepend(&cwd, &buflen, "\0", 1);
-		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
+		error = prepend_path(&pwd, &root, &cwd, &buflen);
 		write_sequnlock(&rename_lock);
 
-		if (error)
+		if (error < 0)
 			goto out;
 
 		/* Unreachable from current root */
-		if (!path_equal(&tmp, &root)) {
+		if (error > 0) {
 			error = prepend_unreachable(&cwd, &buflen);
 			if (error)
 				goto out;