Merge branch 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs dcache updates from Al Viro:
 "Part of this is what the trylock loop elimination series has turned
  into, part making d_move() preserve the parent (and thus the path) of
  victim, plus some general cleanups"

* 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (22 commits)
  d_genocide: move export to definition
  fold dentry_lock_for_move() into its sole caller and clean it up
  make non-exchanging __d_move() copy ->d_parent rather than swap them
  oprofilefs: don't oops on allocation failure
  lustre: get rid of pointless casts to struct dentry *
  debugfs_lookup(): switch to lookup_one_len_unlocked()
  fold lookup_real() into __lookup_hash()
  take out orphan externs (empty_string/slash_string)
  split d_path() and friends into a separate file
  dcache.c: trim includes
  fs/dcache: Avoid a try_lock loop in shrink_dentry_list()
  get rid of trylock loop around dentry_kill()
  handle move to LRU in retain_dentry()
  dput(): consolidate the "do we need to retain it?" into an inlined helper
  split the slow part of lock_parent() off
  now lock_parent() can't run into killed dentry
  get rid of trylock loop in locking dentries on shrink list
  d_delete(): get rid of trylock loop
  fs/dcache: Move dentry_kill() below lock_parent()
  fs/dcache: Remove stale comment from dentry_kill()
  ...

8 files changed, 735 insertions, 764 deletions

diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c
index d77ebbfc67c9..4ea08979312c 100644
--- a/drivers/oprofile/oprofilefs.c
+++ b/drivers/oprofile/oprofilefs.c
@@ -138,6 +138,9 @@ static int __oprofilefs_create_file(struct dentry *root, char const *name,
         struct dentry *dentry;
         struct inode *inode;
 
+        if (!root)
+                return -ENOMEM;
+
         inode_lock(d_inode(root));
         dentry = d_alloc_name(root, name);
         if (!dentry) {
diff --git a/drivers/staging/lustre/lustre/llite/dcache.c b/drivers/staging/lustre/lustre/llite/dcache.c
index 549369739d80..6cd0318062e8 100644
--- a/drivers/staging/lustre/lustre/llite/dcache.c
+++ b/drivers/staging/lustre/lustre/llite/dcache.c
@@ -90,7 +90,7 @@ static int ll_dcompare(const struct dentry *dentry,
                d_count(dentry));
 
         /* mountpoint is always valid */
-        if (d_mountpoint((struct dentry *)dentry))
+        if (d_mountpoint(dentry))
                 return 0;
 
         if (d_lustre_invalid(dentry))
@@ -111,7 +111,7 @@ static int ll_ddelete(const struct dentry *de)
         LASSERT(de);
 
         CDEBUG(D_DENTRY, "%s dentry %pd (%p, parent %p, inode %p) %s%s\n",
-               d_lustre_invalid((struct dentry *)de) ? "deleting" : "keeping",
+               d_lustre_invalid(de) ? "deleting" : "keeping",
                de, de, de->d_parent, d_inode(de),
                d_unhashed(de) ? "" : "hashed,",
                list_empty(&de->d_subdirs) ? "" : "subdirs");
@@ -119,7 +119,7 @@ static int ll_ddelete(const struct dentry *de)
         /* kernel >= 2.6.38 last refcount is decreased after this function. */
         LASSERT(d_count(de) == 1);
 
-        if (d_lustre_invalid((struct dentry *)de))
+        if (d_lustre_invalid(de))
                 return 1;
         return 0;
 }
diff --git a/fs/Makefile b/fs/Makefile
index add789ea270a..c9375fd2c8c4 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -11,7 +11,7 @@ obj-y :=	open.o read_write.o file_table.o super.o \
                 ioctl.o readdir.o select.o dcache.o inode.o \
                 attr.o bad_inode.o file.o filesystems.o namespace.o \
                 seq_file.o xattr.o libfs.o fs-writeback.o \
-                pnode.o splice.o sync.o utimes.o \
+                pnode.o splice.o sync.o utimes.o d_path.o \
                 stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
 
 ifeq ($(CONFIG_BLOCK),y)
diff --git a/fs/d_path.c b/fs/d_path.c
new file mode 100644
index 000000000000..e8fce6b1174f
--- /dev/null
+++ b/fs/d_path.c
@@ -0,0 +1,470 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/syscalls.h>
+#include <linux/export.h>
+#include <linux/uaccess.h>
+#include <linux/fs_struct.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/prefetch.h>
+#include "mount.h"
+
+static int prepend(char **buffer, int *buflen, const char *str, int namelen)
+{
+        *buflen -= namelen;
+        if (*buflen < 0)
+                return -ENAMETOOLONG;
+        *buffer -= namelen;
+        memcpy(*buffer, str, namelen);
+        return 0;
+}
+
+/**
+ * prepend_name - prepend a pathname in front of current buffer pointer
+ * @buffer: buffer pointer
+ * @buflen: allocated length of the buffer
+ * @name:   name string and length qstr structure
+ *
+ * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to
+ * make sure that either the old or the new name pointer and length are
+ * fetched. However, there may be mismatch between length and pointer.
+ * The length cannot be trusted, we need to copy it byte-by-byte until
+ * the length is reached or a null byte is found. It also prepends "/" at
+ * 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.
+ *
+ * Load acquire is needed to make sure that we see that terminating NUL.
+ */
+static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
+{
+        const char *dname = smp_load_acquire(&name->name); /* ^^^ */
+        u32 dlen = READ_ONCE(name->len);
+        char *p;
+
+        *buflen -= dlen + 1;
+        if (*buflen < 0)
+                return -ENAMETOOLONG;
+        p = *buffer -= dlen + 1;
+        *p++ = '/';
+        while (dlen--) {
+                char c = *dname++;
+                if (!c)
+                        break;
+                *p++ = c;
+        }
+        return 0;
+}
+
+/**
+ * prepend_path - Prepend path string to a buffer
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry
+ * @buffer: pointer to the end of the buffer
+ * @buflen: pointer to buffer length
+ *
+ * The function will first try to write out the pathname without taking any
+ * lock other than the RCU read lock to make sure that dentries won't go away.
+ * It only checks the sequence number of the global rename_lock as any change
+ * in the dentry's d_seq will be preceded by changes in the rename_lock
+ * sequence number. If the sequence number had been changed, it will restart
+ * the whole pathname back-tracing sequence again by taking the rename_lock.
+ * In this case, there is no need to take the RCU read lock as the recursive
+ * parent pointer references will keep the dentry chain alive as long as no
+ * rename operation is performed.
+ */
+static int prepend_path(const struct path *path,
+                        const struct path *root,
+                        char **buffer, int *buflen)
+{
+        struct dentry *dentry;
+        struct vfsmount *vfsmnt;
+        struct mount *mnt;
+        int error = 0;
+        unsigned seq, m_seq = 0;
+        char *bptr;
+        int blen;
+
+        rcu_read_lock();
+restart_mnt:
+        read_seqbegin_or_lock(&mount_lock, &m_seq);
+        seq = 0;
+        rcu_read_lock();
+restart:
+        bptr = *buffer;
+        blen = *buflen;
+        error = 0;
+        dentry = path->dentry;
+        vfsmnt = path->mnt;
+        mnt = real_mount(vfsmnt);
+        read_seqbegin_or_lock(&rename_lock, &seq);
+        while (dentry != root->dentry || vfsmnt != root->mnt) {
+                struct dentry * parent;
+
+                if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+                        struct mount *parent = READ_ONCE(mnt->mnt_parent);
+                        /* Escaped? */
+                        if (dentry != vfsmnt->mnt_root) {
+                                bptr = *buffer;
+                                blen = *buflen;
+                                error = 3;
+                                break;
+                        }
+                        /* Global root? */
+                        if (mnt != parent) {
+                                dentry = READ_ONCE(mnt->mnt_mountpoint);
+                                mnt = parent;
+                                vfsmnt = &mnt->mnt;
+                                continue;
+                        }
+                        if (!error)
+                                error = is_mounted(vfsmnt) ? 1 : 2;
+                        break;
+                }
+                parent = dentry->d_parent;
+                prefetch(parent);
+                error = prepend_name(&bptr, &blen, &dentry->d_name);
+                if (error)
+                        break;
+
+                dentry = parent;
+        }
+        if (!(seq & 1))
+                rcu_read_unlock();
+        if (need_seqretry(&rename_lock, seq)) {
+                seq = 1;
+                goto restart;
+        }
+        done_seqretry(&rename_lock, seq);
+
+        if (!(m_seq & 1))
+                rcu_read_unlock();
+        if (need_seqretry(&mount_lock, m_seq)) {
+                m_seq = 1;
+                goto restart_mnt;
+        }
+        done_seqretry(&mount_lock, m_seq);
+
+        if (error >= 0 && bptr == *buffer) {
+                if (--blen < 0)
+                        error = -ENAMETOOLONG;
+                else
+                        *--bptr = '/';
+        }
+        *buffer = bptr;
+        *buflen = blen;
+        return error;
+}
+
+/**
+ * __d_path - return the path of a dentry
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name.
+ *
+ * Returns a pointer into the buffer or an error code if the
+ * path was too long.
+ *
+ * "buflen" should be positive.
+ *
+ * If the path is not reachable from the supplied root, return %NULL.
+ */
+char *__d_path(const struct path *path,
+               const struct path *root,
+               char *buf, int buflen)
+{
+        char *res = buf + buflen;
+        int error;
+
+        prepend(&res, &buflen, "\0", 1);
+        error = prepend_path(path, root, &res, &buflen);
+
+        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);
+        error = prepend_path(path, &root, &res, &buflen);
+
+        if (error > 1)
+                error = -EINVAL;
+        if (error < 0)
+                return ERR_PTR(error);
+        return res;
+}
+
+/*
+ * same as __d_path but appends "(deleted)" for unlinked files.
+ */
+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)) {
+                int error = prepend(buf, buflen, " (deleted)", 10);
+                if (error)
+                        return error;
+        }
+
+        return prepend_path(path, root, buf, buflen);
+}
+
+static int prepend_unreachable(char **buffer, int *buflen)
+{
+        return prepend(buffer, buflen, "(unreachable)", 13);
+}
+
+static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
+{
+        unsigned seq;
+
+        do {
+                seq = read_seqcount_begin(&fs->seq);
+                *root = fs->root;
+        } while (read_seqcount_retry(&fs->seq, seq));
+}
+
+/**
+ * d_path - return the path of a dentry
+ * @path: path to report
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name. If the entry has been deleted
+ * the string " (deleted)" is appended. Note that this is ambiguous.
+ *
+ * Returns a pointer into the buffer or an error code if the path was
+ * too long. Note: Callers should use the returned pointer, not the passed
+ * in buffer, to use the name! The implementation often starts at an offset
+ * into the buffer, and may leave 0 bytes at the start.
+ *
+ * "buflen" should be positive.
+ */
+char *d_path(const struct path *path, char *buf, int buflen)
+{
+        char *res = buf + buflen;
+        struct path root;
+        int error;
+
+        /*
+         * We have various synthetic filesystems that never get mounted.  On
+         * these filesystems dentries are never used for lookup purposes, and
+         * thus don't need to be hashed.  They also don't need a name until a
+         * user wants to identify the object in /proc/pid/fd/.  The little hack
+         * below allows us to generate a name for these objects on demand:
+         *
+         * Some pseudo inodes are mountable.  When they are mounted
+         * path->dentry == path->mnt->mnt_root.  In that case don't call d_dname
+         * and instead have d_path return the mounted path.
+         */
+        if (path->dentry->d_op && path->dentry->d_op->d_dname &&
+            (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
+                return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
+
+        rcu_read_lock();
+        get_fs_root_rcu(current->fs, &root);
+        error = path_with_deleted(path, &root, &res, &buflen);
+        rcu_read_unlock();
+
+        if (error < 0)
+                res = ERR_PTR(error);
+        return res;
+}
+EXPORT_SYMBOL(d_path);
+
+/*
+ * Helper function for dentry_operations.d_dname() members
+ */
+char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
+                        const char *fmt, ...)
+{
+        va_list args;
+        char temp[64];
+        int sz;
+
+        va_start(args, fmt);
+        sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
+        va_end(args);
+
+        if (sz > sizeof(temp) || sz > buflen)
+                return ERR_PTR(-ENAMETOOLONG);
+
+        buffer += buflen - sz;
+        return memcpy(buffer, temp, sz);
+}
+
+char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+        char *end = buffer + buflen;
+        /* these dentries are never renamed, so d_lock is not needed */
+        if (prepend(&end, &buflen, " (deleted)", 11) ||
+            prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
+            prepend(&end, &buflen, "/", 1))  
+                end = ERR_PTR(-ENAMETOOLONG);
+        return end;
+}
+EXPORT_SYMBOL(simple_dname);
+
+/*
+ * Write full pathname from the root of the filesystem into the buffer.
+ */
+static char *__dentry_path(struct dentry *d, char *buf, int buflen)
+{
+        struct dentry *dentry;
+        char *end, *retval;
+        int len, seq = 0;
+        int error = 0;
+
+        if (buflen < 2)
+                goto Elong;
+
+        rcu_read_lock();
+restart:
+        dentry = d;
+        end = buf + buflen;
+        len = buflen;
+        prepend(&end, &len, "\0", 1);
+        /* Get '/' right */
+        retval = end-1;
+        *retval = '/';
+        read_seqbegin_or_lock(&rename_lock, &seq);
+        while (!IS_ROOT(dentry)) {
+                struct dentry *parent = dentry->d_parent;
+
+                prefetch(parent);
+                error = prepend_name(&end, &len, &dentry->d_name);
+                if (error)
+                        break;
+
+                retval = end;
+                dentry = parent;
+        }
+        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;
+Elong:
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
+{
+        return __dentry_path(dentry, buf, buflen);
+}
+EXPORT_SYMBOL(dentry_path_raw);
+
+char *dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+        char *p = NULL;
+        char *retval;
+
+        if (d_unlinked(dentry)) {
+                p = buf + buflen;
+                if (prepend(&p, &buflen, "//deleted", 10) != 0)
+                        goto Elong;
+                buflen++;
+        }
+        retval = __dentry_path(dentry, buf, buflen);
+        if (!IS_ERR(retval) && p)
+                *p = '/';       /* restore '/' overriden with '\0' */
+        return retval;
+Elong:
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
+                                    struct path *pwd)
+{
+        unsigned seq;
+
+        do {
+                seq = read_seqcount_begin(&fs->seq);
+                *root = fs->root;
+                *pwd = fs->pwd;
+        } while (read_seqcount_retry(&fs->seq, seq));
+}
+
+/*
+ * NOTE! The user-level library version returns a
+ * character pointer. The kernel system call just
+ * returns the length of the buffer filled (which
+ * includes the ending '\0' character), or a negative
+ * error value. So libc would do something like
+ *
+ *      char *getcwd(char * buf, size_t size)
+ *      {
+ *              int retval;
+ *
+ *              retval = sys_getcwd(buf, size);
+ *              if (retval >= 0)
+ *                      return buf;
+ *              errno = -retval;
+ *              return NULL;
+ *      }
+ */
+SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
+{
+        int error;
+        struct path pwd, root;
+        char *page = __getname();
+
+        if (!page)
+                return -ENOMEM;
+
+        rcu_read_lock();
+        get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
+
+        error = -ENOENT;
+        if (!d_unlinked(pwd.dentry)) {
+                unsigned long len;
+                char *cwd = page + PATH_MAX;
+                int buflen = PATH_MAX;
+
+                prepend(&cwd, &buflen, "\0", 1);
+                error = prepend_path(&pwd, &root, &cwd, &buflen);
+                rcu_read_unlock();
+
+                if (error < 0)
+                        goto out;
+
+                /* Unreachable from current root */
+                if (error > 0) {
+                        error = prepend_unreachable(&cwd, &buflen);
+                        if (error)
+                                goto out;
+                }
+
+                error = -ERANGE;
+                len = PATH_MAX + page - cwd;
+                if (len <= size) {
+                        error = len;
+                        if (copy_to_user(buf, cwd, len))
+                                error = -EFAULT;
+                }
+        } else {
+                rcu_read_unlock();
+        }
+
+out:
+        __putname(page);
+        return error;
+}
diff --git a/fs/dcache.c b/fs/dcache.c
index 8945e6cabd93..593079176123 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -14,7 +14,7 @@
  * the dcache entry is deleted or garbage collected.
  */
 
-#include <linux/syscalls.h>
+#include <linux/ratelimit.h>
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
@@ -24,18 +24,11 @@
 #include <linux/hash.h>
 #include <linux/cache.h>
 #include <linux/export.h>
-#include <linux/mount.h>
-#include <linux/file.h>
-#include <linux/uaccess.h>
 #include <linux/security.h>
 #include <linux/seqlock.h>
-#include <linux/swap.h>
 #include <linux/bootmem.h>
-#include <linux/fs_struct.h>
 #include <linux/bit_spinlock.h>
 #include <linux/rculist_bl.h>
-#include <linux/prefetch.h>
-#include <linux/ratelimit.h>
 #include <linux/list_lru.h>
 #include "internal.h"
 #include "mount.h"
@@ -74,9 +67,7 @@
  *       dentry->d_lock
  *
  * If no ancestor relationship:
- * if (dentry1 < dentry2)
- *   dentry1->d_lock
- *     dentry2->d_lock
+ * arbitrary, since it's serialized on rename_lock
  */
 int sysctl_vfs_cache_pressure __read_mostly = 100;
 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
@@ -440,17 +431,6 @@ static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
         list_lru_isolate_move(lru, &dentry->d_lru, list);
 }
 
-/*
- * dentry_lru_(add|del)_list) must be called with d_lock held.
- */
-static void dentry_lru_add(struct dentry *dentry)
-{
-        if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
-                d_lru_add(dentry);
-        else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
-                dentry->d_flags |= DCACHE_REFERENCED;
-}
-
 /**
  * d_drop - drop a dentry
  * @dentry: dentry to drop
@@ -470,30 +450,29 @@ static void dentry_lru_add(struct dentry *dentry)
  */
 static void ___d_drop(struct dentry *dentry)
 {
-        if (!d_unhashed(dentry)) {
-                struct hlist_bl_head *b;
-                /*
-                 * Hashed dentries are normally on the dentry hashtable,
-                 * with the exception of those newly allocated by
-                 * d_obtain_root, which are always IS_ROOT:
-                 */
-                if (unlikely(IS_ROOT(dentry)))
-                        b = &dentry->d_sb->s_roots;
-                else
-                        b = d_hash(dentry->d_name.hash);
+        struct hlist_bl_head *b;
+        /*
+         * Hashed dentries are normally on the dentry hashtable,
+         * with the exception of those newly allocated by
+         * d_obtain_root, which are always IS_ROOT:
+         */
+        if (unlikely(IS_ROOT(dentry)))
+                b = &dentry->d_sb->s_roots;
+        else
+                b = d_hash(dentry->d_name.hash);
 
-                hlist_bl_lock(b);
-                __hlist_bl_del(&dentry->d_hash);
-                hlist_bl_unlock(b);
-                /* After this call, in-progress rcu-walk path lookup will fail. */
-                write_seqcount_invalidate(&dentry->d_seq);
-        }
+        hlist_bl_lock(b);
+        __hlist_bl_del(&dentry->d_hash);
+        hlist_bl_unlock(b);
 }
 
 void __d_drop(struct dentry *dentry)
 {
-        ___d_drop(dentry);
-        dentry->d_hash.pprev = NULL;
+        if (!d_unhashed(dentry)) {
+                ___d_drop(dentry);
+                dentry->d_hash.pprev = NULL;
+                write_seqcount_invalidate(&dentry->d_seq);
+        }
 }
 EXPORT_SYMBOL(__d_drop);
 
@@ -589,10 +568,71 @@ static void __dentry_kill(struct dentry *dentry)
                 dentry_free(dentry);
 }
 
+static struct dentry *__lock_parent(struct dentry *dentry)
+{
+        struct dentry *parent;
+        rcu_read_lock();
+        spin_unlock(&dentry->d_lock);
+again:
+        parent = READ_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;
+}
+
+static inline struct dentry *lock_parent(struct dentry *dentry)
+{
+        struct dentry *parent = dentry->d_parent;
+        if (IS_ROOT(dentry))
+                return NULL;
+        if (likely(spin_trylock(&parent->d_lock)))
+                return parent;
+        return __lock_parent(dentry);
+}
+
+static inline bool retain_dentry(struct dentry *dentry)
+{
+        WARN_ON(d_in_lookup(dentry));
+
+        /* Unreachable? Get rid of it */
+        if (unlikely(d_unhashed(dentry)))
+                return false;
+
+        if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
+                return false;
+
+        if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
+                if (dentry->d_op->d_delete(dentry))
+                        return false;
+        }
+        /* retain; LRU fodder */
+        dentry->d_lockref.count--;
+        if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
+                d_lru_add(dentry);
+        else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
+                dentry->d_flags |= DCACHE_REFERENCED;
+        return true;
+}
+
 /*
  * 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)
@@ -602,62 +642,43 @@ static struct dentry *dentry_kill(struct dentry *dentry)
         struct dentry *parent = NULL;
 
         if (inode && unlikely(!spin_trylock(&inode->i_lock)))
-                goto failed;
+                goto slow_positive;
 
         if (!IS_ROOT(dentry)) {
                 parent = dentry->d_parent;
                 if (unlikely(!spin_trylock(&parent->d_lock))) {
-                        if (inode)
-                                spin_unlock(&inode->i_lock);
-                        goto failed;
+                        parent = __lock_parent(dentry);
+                        if (likely(inode || !dentry->d_inode))
+                                goto got_locks;
+                        /* negative that became positive */
+                        if (parent)
+                                spin_unlock(&parent->d_lock);
+                        inode = dentry->d_inode;
+                        goto slow_positive;
                 }
         }
-
         __dentry_kill(dentry);
         return parent;
 
-failed:
+slow_positive:
         spin_unlock(&dentry->d_lock);
-        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(dentry->d_lockref.count < 0))
-                return NULL;
-        if (likely(spin_trylock(&parent->d_lock)))
+        spin_lock(&inode->i_lock);
+        spin_lock(&dentry->d_lock);
+        parent = lock_parent(dentry);
+got_locks:
+        if (unlikely(dentry->d_lockref.count != 1)) {
+                dentry->d_lockref.count--;
+        } else if (likely(!retain_dentry(dentry))) {
+                __dentry_kill(dentry);
                 return parent;
-        rcu_read_lock();
-        spin_unlock(&dentry->d_lock);
-again:
-        parent = READ_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;
         }
-        if (parent != dentry) {
-                spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-                if (unlikely(dentry->d_lockref.count < 0)) {
-                        spin_unlock(&parent->d_lock);
-                        parent = NULL;
-                }
-        } else {
-                parent = NULL;
-        }
-        rcu_read_unlock();
-        return parent;
+        /* we are keeping it, after all */
+        if (inode)
+                spin_unlock(&inode->i_lock);
+        if (parent)
+                spin_unlock(&parent->d_lock);
+        spin_unlock(&dentry->d_lock);
+        return NULL;
 }
 
 /*
@@ -807,27 +828,11 @@ repeat:
         /* Slow case: now with the dentry lock held */
         rcu_read_unlock();
 
-        WARN_ON(d_in_lookup(dentry));
-
-        /* Unreachable? Get rid of it */
-        if (unlikely(d_unhashed(dentry)))
-                goto kill_it;
-
-        if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
-                goto kill_it;
-
-        if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
-                if (dentry->d_op->d_delete(dentry))
-                        goto kill_it;
+        if (likely(retain_dentry(dentry))) {
+                spin_unlock(&dentry->d_lock);
+                return;
         }
 
-        dentry_lru_add(dentry);
-
-        dentry->d_lockref.count--;
-        spin_unlock(&dentry->d_lock);
-        return;
-
-kill_it:
         dentry = dentry_kill(dentry);
         if (dentry) {
                 cond_resched();
@@ -976,56 +981,83 @@ restart:
 }
 EXPORT_SYMBOL(d_prune_aliases);
 
-static void shrink_dentry_list(struct list_head *list)
+/*
+ * Lock a dentry from shrink list.
+ * Called under rcu_read_lock() and dentry->d_lock; the former
+ * guarantees that nothing we access will be freed under us.
+ * Note that dentry is *not* protected from concurrent dentry_kill(),
+ * d_delete(), etc.
+ *
+ * Return false if dentry has been disrupted or grabbed, leaving
+ * the caller to kick it off-list.  Otherwise, return true and have
+ * that dentry's inode and parent both locked.
+ */
+static bool shrink_lock_dentry(struct dentry *dentry)
 {
-        struct dentry *dentry, *parent;
+        struct inode *inode;
+        struct dentry *parent;
 
-        while (!list_empty(list)) {
-                struct inode *inode;
-                dentry = list_entry(list->prev, struct dentry, d_lru);
+        if (dentry->d_lockref.count)
+                return false;
+
+        inode = dentry->d_inode;
+        if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
+                spin_unlock(&dentry->d_lock);
+                spin_lock(&inode->i_lock);
                 spin_lock(&dentry->d_lock);
-                parent = lock_parent(dentry);
+                if (unlikely(dentry->d_lockref.count))
+                        goto out;
+                /* changed inode means that somebody had grabbed it */
+                if (unlikely(inode != dentry->d_inode))
+                        goto out;
+        }
 
-                /*
-                 * The dispose list is isolated and dentries are not accounted
-                 * to the LRU here, so we can simply remove it from the list
-                 * here regardless of whether it is referenced or not.
-                 */
-                d_shrink_del(dentry);
+        parent = dentry->d_parent;
+        if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
+                return true;
 
-                /*
-                 * 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 > 0) {
-                        spin_unlock(&dentry->d_lock);
-                        if (parent)
-                                spin_unlock(&parent->d_lock);
-                        continue;
-                }
+        spin_unlock(&dentry->d_lock);
+        spin_lock(&parent->d_lock);
+        if (unlikely(parent != dentry->d_parent)) {
+                spin_unlock(&parent->d_lock);
+                spin_lock(&dentry->d_lock);
+                goto out;
+        }
+        spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+        if (likely(!dentry->d_lockref.count))
+                return true;
+        spin_unlock(&parent->d_lock);
+out:
+        if (inode)
+                spin_unlock(&inode->i_lock);
+        return false;
+}
 
+static void shrink_dentry_list(struct list_head *list)
+{
+        while (!list_empty(list)) {
+                struct dentry *dentry, *parent;
 
-                if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
-                        bool can_free = dentry->d_flags & DCACHE_MAY_FREE;
+                dentry = list_entry(list->prev, struct dentry, d_lru);
+                spin_lock(&dentry->d_lock);
+                rcu_read_lock();
+                if (!shrink_lock_dentry(dentry)) {
+                        bool can_free = false;
+                        rcu_read_unlock();
+                        d_shrink_del(dentry);
+                        if (dentry->d_lockref.count < 0)
+                                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;
-                }
-
+                rcu_read_unlock();
+                d_shrink_del(dentry);
+                parent = dentry->d_parent;
                 __dentry_kill(dentry);
-
+                if (parent == dentry)
+                        continue;
                 /*
                  * We need to prune ancestors too. This is necessary to prevent
                  * quadratic behavior of shrink_dcache_parent(), but is also
@@ -1033,26 +1065,8 @@ static void shrink_dentry_list(struct list_head *list)
                  * 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;
-                }
+                while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
+                        dentry = dentry_kill(dentry);
         }
 }
 
@@ -2379,32 +2393,22 @@ EXPORT_SYMBOL(d_hash_and_lookup);
  
 void d_delete(struct dentry * dentry)
 {
-        struct inode *inode;
-        int isdir = 0;
+        struct inode *inode = dentry->d_inode;
+        int isdir = d_is_dir(dentry);
+
+        spin_lock(&inode->i_lock);
+        spin_lock(&dentry->d_lock);
         /*
          * Are we the only user?
          */
-again:
-        spin_lock(&dentry->d_lock);
-        inode = dentry->d_inode;
-        isdir = S_ISDIR(inode->i_mode);
         if (dentry->d_lockref.count == 1) {
-                if (!spin_trylock(&inode->i_lock)) {
-                        spin_unlock(&dentry->d_lock);
-                        cpu_relax();
-                        goto again;
-                }
                 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
                 dentry_unlink_inode(dentry);
-                fsnotify_nameremove(dentry, isdir);
-                return;
-        }
-
-        if (!d_unhashed(dentry))
+        } else {
                 __d_drop(dentry);
-
-        spin_unlock(&dentry->d_lock);
-
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&inode->i_lock);
+        }
         fsnotify_nameremove(dentry, isdir);
 }
 EXPORT_SYMBOL(d_delete);
@@ -2769,57 +2773,6 @@ static void copy_name(struct dentry *dentry, struct dentry *target)
                 kfree_rcu(old_name, u.head);
 }
 
-static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
-{
-        /*
-         * XXXX: do we really need to take target->d_lock?
-         */
-        if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
-                spin_lock(&target->d_parent->d_lock);
-        else {
-                if (d_ancestor(dentry->d_parent, target->d_parent)) {
-                        spin_lock(&dentry->d_parent->d_lock);
-                        spin_lock_nested(&target->d_parent->d_lock,
-                                                DENTRY_D_LOCK_NESTED);
-                } else {
-                        spin_lock(&target->d_parent->d_lock);
-                        spin_lock_nested(&dentry->d_parent->d_lock,
-                                                DENTRY_D_LOCK_NESTED);
-                }
-        }
-        if (target < dentry) {
-                spin_lock_nested(&target->d_lock, 2);
-                spin_lock_nested(&dentry->d_lock, 3);
-        } else {
-                spin_lock_nested(&dentry->d_lock, 2);
-                spin_lock_nested(&target->d_lock, 3);
-        }
-}
-
-static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
-{
-        if (target->d_parent != dentry->d_parent)
-                spin_unlock(&dentry->d_parent->d_lock);
-        if (target->d_parent != target)
-                spin_unlock(&target->d_parent->d_lock);
-        spin_unlock(&target->d_lock);
-        spin_unlock(&dentry->d_lock);
-}
-
-/*
- * When switching names, the actual string doesn't strictly have to
- * be preserved in the target - because we're dropping the target
- * anyway. As such, we can just do a simple memcpy() to copy over
- * the new name before we switch, unless we are going to rehash
- * it.  Note that if we *do* unhash the target, we are not allowed
- * to rehash it without giving it a new name/hash key - whether
- * we swap or overwrite the names here, resulting name won't match
- * the reality in filesystem; it's only there for d_path() purposes.
- * Note that all of this is happening under rename_lock, so the
- * any hash lookup seeing it in the middle of manipulations will
- * be discarded anyway.  So we do not care what happens to the hash
- * key in that case.
- */
 /*
  * __d_move - move a dentry
  * @dentry: entry to move
@@ -2834,15 +2787,34 @@ static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
 static void __d_move(struct dentry *dentry, struct dentry *target,
                      bool exchange)
 {
+        struct dentry *old_parent, *p;
         struct inode *dir = NULL;
         unsigned n;
-        if (!dentry->d_inode)
-                printk(KERN_WARNING "VFS: moving negative dcache entry\n");
 
-        BUG_ON(d_ancestor(dentry, target));
+        WARN_ON(!dentry->d_inode);
+        if (WARN_ON(dentry == target))
+                return;
+
         BUG_ON(d_ancestor(target, dentry));
+        old_parent = dentry->d_parent;
+        p = d_ancestor(old_parent, target);
+        if (IS_ROOT(dentry)) {
+                BUG_ON(p);
+                spin_lock(&target->d_parent->d_lock);
+        } else if (!p) {
+                /* target is not a descendent of dentry->d_parent */
+                spin_lock(&target->d_parent->d_lock);
+                spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
+        } else {
+                BUG_ON(p == dentry);
+                spin_lock(&old_parent->d_lock);
+                if (p != target)
+                        spin_lock_nested(&target->d_parent->d_lock,
+                                        DENTRY_D_LOCK_NESTED);
+        }
+        spin_lock_nested(&dentry->d_lock, 2);
+        spin_lock_nested(&target->d_lock, 3);
 
-        dentry_lock_for_move(dentry, target);
         if (unlikely(d_in_lookup(target))) {
                 dir = target->d_parent->d_inode;
                 n = start_dir_add(dir);
@@ -2853,47 +2825,44 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
         write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
 
         /* unhash both */
-        /* ___d_drop does write_seqcount_barrier, but they're OK to nest. */
-        ___d_drop(dentry);
-        ___d_drop(target);
+        if (!d_unhashed(dentry))
+                ___d_drop(dentry);
+        if (!d_unhashed(target))
+                ___d_drop(target);
 
-        /* Switch the names.. */
-        if (exchange)
-                swap_names(dentry, target);
-        else
+        /* ... and switch them in the tree */
+        dentry->d_parent = target->d_parent;
+        if (!exchange) {
                 copy_name(dentry, target);
-
-        /* rehash in new place(s) */
-        __d_rehash(dentry);
-        if (exchange)
-                __d_rehash(target);
-        else
                 target->d_hash.pprev = NULL;
-
-        /* ... and switch them in the tree */
-        if (IS_ROOT(dentry)) {
-                /* splicing a tree */
-                dentry->d_flags |= DCACHE_RCUACCESS;
-                dentry->d_parent = target->d_parent;
-                target->d_parent = target;
-                list_del_init(&target->d_child);
-                list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
+                dentry->d_parent->d_lockref.count++;
+                if (dentry == old_parent)
+                        dentry->d_flags |= DCACHE_RCUACCESS;
+                else
+                        WARN_ON(!--old_parent->d_lockref.count);
         } else {
-                /* swapping two dentries */
-                swap(dentry->d_parent, target->d_parent);
+                target->d_parent = old_parent;
+                swap_names(dentry, target);
                 list_move(&target->d_child, &target->d_parent->d_subdirs);
-                list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
-                if (exchange)
-                        fsnotify_update_flags(target);
-                fsnotify_update_flags(dentry);
+                __d_rehash(target);
+                fsnotify_update_flags(target);
         }
+        list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
+        __d_rehash(dentry);
+        fsnotify_update_flags(dentry);
 
         write_seqcount_end(&target->d_seq);
         write_seqcount_end(&dentry->d_seq);
 
         if (dir)
                 end_dir_add(dir, n);
-        dentry_unlock_for_move(dentry, target);
+
+        if (dentry->d_parent != old_parent)
+                spin_unlock(&dentry->d_parent->d_lock);
+        if (dentry != old_parent)
+                spin_unlock(&old_parent->d_lock);
+        spin_unlock(&target->d_lock);
+        spin_unlock(&dentry->d_lock);
 }
 
 /*
@@ -3041,12 +3010,14 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
                                         inode->i_sb->s_type->name,
                                         inode->i_sb->s_id);
                         } else if (!IS_ROOT(new)) {
+                                struct dentry *old_parent = dget(new->d_parent);
                                 int err = __d_unalias(inode, dentry, new);
                                 write_sequnlock(&rename_lock);
                                 if (err) {
                                         dput(new);
                                         new = ERR_PTR(err);
                                 }
+                                dput(old_parent);
                         } else {
                                 __d_move(new, dentry, false);
                                 write_sequnlock(&rename_lock);
@@ -3061,467 +3032,6 @@ out:
 }
 EXPORT_SYMBOL(d_splice_alias);
 
-static int prepend(char **buffer, int *buflen, const char *str, int namelen)
-{
-        *buflen -= namelen;
-        if (*buflen < 0)
-                return -ENAMETOOLONG;
-        *buffer -= namelen;
-        memcpy(*buffer, str, namelen);
-        return 0;
-}
-
-/**
- * prepend_name - prepend a pathname in front of current buffer pointer
- * @buffer: buffer pointer
- * @buflen: allocated length of the buffer
- * @name:   name string and length qstr structure
- *
- * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to
- * make sure that either the old or the new name pointer and length are
- * fetched. However, there may be mismatch between length and pointer.
- * The length cannot be trusted, we need to copy it byte-by-byte until
- * the length is reached or a null byte is found. It also prepends "/" at
- * 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.
- *
- * Load acquire is needed to make sure that we see that terminating NUL.
- */
-static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
-{
-        const char *dname = smp_load_acquire(&name->name); /* ^^^ */
-        u32 dlen = READ_ONCE(name->len);
-        char *p;
-
-        *buflen -= dlen + 1;
-        if (*buflen < 0)
-                return -ENAMETOOLONG;
-        p = *buffer -= dlen + 1;
-        *p++ = '/';
-        while (dlen--) {
-                char c = *dname++;
-                if (!c)
-                        break;
-                *p++ = c;
-        }
-        return 0;
-}
-
-/**
- * prepend_path - Prepend path string to a buffer
- * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry
- * @buffer: pointer to the end of the buffer
- * @buflen: pointer to buffer length
- *
- * The function will first try to write out the pathname without taking any
- * lock other than the RCU read lock to make sure that dentries won't go away.
- * It only checks the sequence number of the global rename_lock as any change
- * in the dentry's d_seq will be preceded by changes in the rename_lock
- * sequence number. If the sequence number had been changed, it will restart
- * the whole pathname back-tracing sequence again by taking the rename_lock.
- * In this case, there is no need to take the RCU read lock as the recursive
- * parent pointer references will keep the dentry chain alive as long as no
- * rename operation is performed.
- */
-static int prepend_path(const struct path *path,
-                        const struct path *root,
-                        char **buffer, int *buflen)
-{
-        struct dentry *dentry;
-        struct vfsmount *vfsmnt;
-        struct mount *mnt;
-        int error = 0;
-        unsigned seq, m_seq = 0;
-        char *bptr;
-        int blen;
-
-        rcu_read_lock();
-restart_mnt:
-        read_seqbegin_or_lock(&mount_lock, &m_seq);
-        seq = 0;
-        rcu_read_lock();
-restart:
-        bptr = *buffer;
-        blen = *buflen;
-        error = 0;
-        dentry = path->dentry;
-        vfsmnt = path->mnt;
-        mnt = real_mount(vfsmnt);
-        read_seqbegin_or_lock(&rename_lock, &seq);
-        while (dentry != root->dentry || vfsmnt != root->mnt) {
-                struct dentry * parent;
-
-                if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
-                        struct mount *parent = READ_ONCE(mnt->mnt_parent);
-                        /* Escaped? */
-                        if (dentry != vfsmnt->mnt_root) {
-                                bptr = *buffer;
-                                blen = *buflen;
-                                error = 3;
-                                break;
-                        }
-                        /* Global root? */
-                        if (mnt != parent) {
-                                dentry = READ_ONCE(mnt->mnt_mountpoint);
-                                mnt = parent;
-                                vfsmnt = &mnt->mnt;
-                                continue;
-                        }
-                        if (!error)
-                                error = is_mounted(vfsmnt) ? 1 : 2;
-                        break;
-                }
-                parent = dentry->d_parent;
-                prefetch(parent);
-                error = prepend_name(&bptr, &blen, &dentry->d_name);
-                if (error)
-                        break;
-
-                dentry = parent;
-        }
-        if (!(seq & 1))
-                rcu_read_unlock();
-        if (need_seqretry(&rename_lock, seq)) {
-                seq = 1;
-                goto restart;
-        }
-        done_seqretry(&rename_lock, seq);
-
-        if (!(m_seq & 1))
-                rcu_read_unlock();
-        if (need_seqretry(&mount_lock, m_seq)) {
-                m_seq = 1;
-                goto restart_mnt;
-        }
-        done_seqretry(&mount_lock, m_seq);
-
-        if (error >= 0 && bptr == *buffer) {
-                if (--blen < 0)
-                        error = -ENAMETOOLONG;
-                else
-                        *--bptr = '/';
-        }
-        *buffer = bptr;
-        *buflen = blen;
-        return error;
-}
-
-/**
- * __d_path - return the path of a dentry
- * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry
- * @buf: buffer to return value in
- * @buflen: buffer length
- *
- * Convert a dentry into an ASCII path name.
- *
- * Returns a pointer into the buffer or an error code if the
- * path was too long.
- *
- * "buflen" should be positive.
- *
- * If the path is not reachable from the supplied root, return %NULL.
- */
-char *__d_path(const struct path *path,
-               const struct path *root,
-               char *buf, int buflen)
-{
-        char *res = buf + buflen;
-        int error;
-
-        prepend(&res, &buflen, "\0", 1);
-        error = prepend_path(path, root, &res, &buflen);
-
-        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);
-        error = prepend_path(path, &root, &res, &buflen);
-
-        if (error > 1)
-                error = -EINVAL;
-        if (error < 0)
-                return ERR_PTR(error);
-        return res;
-}
-
-/*
- * same as __d_path but appends "(deleted)" for unlinked files.
- */
-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)) {
-                int error = prepend(buf, buflen, " (deleted)", 10);
-                if (error)
-                        return error;
-        }
-
-        return prepend_path(path, root, buf, buflen);
-}
-
-static int prepend_unreachable(char **buffer, int *buflen)
-{
-        return prepend(buffer, buflen, "(unreachable)", 13);
-}
-
-static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
-{
-        unsigned seq;
-
-        do {
-                seq = read_seqcount_begin(&fs->seq);
-                *root = fs->root;
-        } while (read_seqcount_retry(&fs->seq, seq));
-}
-
-/**
- * d_path - return the path of a dentry
- * @path: path to report
- * @buf: buffer to return value in
- * @buflen: buffer length
- *
- * Convert a dentry into an ASCII path name. If the entry has been deleted
- * the string " (deleted)" is appended. Note that this is ambiguous.
- *
- * Returns a pointer into the buffer or an error code if the path was
- * too long. Note: Callers should use the returned pointer, not the passed
- * in buffer, to use the name! The implementation often starts at an offset
- * into the buffer, and may leave 0 bytes at the start.
- *
- * "buflen" should be positive.
- */
-char *d_path(const struct path *path, char *buf, int buflen)
-{
-        char *res = buf + buflen;
-        struct path root;
-        int error;
-
-        /*
-         * We have various synthetic filesystems that never get mounted.  On
-         * these filesystems dentries are never used for lookup purposes, and
-         * thus don't need to be hashed.  They also don't need a name until a
-         * user wants to identify the object in /proc/pid/fd/.  The little hack
-         * below allows us to generate a name for these objects on demand:
-         *
-         * Some pseudo inodes are mountable.  When they are mounted
-         * path->dentry == path->mnt->mnt_root.  In that case don't call d_dname
-         * and instead have d_path return the mounted path.
-         */
-        if (path->dentry->d_op && path->dentry->d_op->d_dname &&
-            (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
-                return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
-
-        rcu_read_lock();
-        get_fs_root_rcu(current->fs, &root);
-        error = path_with_deleted(path, &root, &res, &buflen);
-        rcu_read_unlock();
-
-        if (error < 0)
-                res = ERR_PTR(error);
-        return res;
-}
-EXPORT_SYMBOL(d_path);
-
-/*
- * Helper function for dentry_operations.d_dname() members
- */
-char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
-                        const char *fmt, ...)
-{
-        va_list args;
-        char temp[64];
-        int sz;
-
-        va_start(args, fmt);
-        sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
-        va_end(args);
-
-        if (sz > sizeof(temp) || sz > buflen)
-                return ERR_PTR(-ENAMETOOLONG);
-
-        buffer += buflen - sz;
-        return memcpy(buffer, temp, sz);
-}
-
-char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
-{
-        char *end = buffer + buflen;
-        /* these dentries are never renamed, so d_lock is not needed */
-        if (prepend(&end, &buflen, " (deleted)", 11) ||
-            prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
-            prepend(&end, &buflen, "/", 1))  
-                end = ERR_PTR(-ENAMETOOLONG);
-        return end;
-}
-EXPORT_SYMBOL(simple_dname);
-
-/*
- * Write full pathname from the root of the filesystem into the buffer.
- */
-static char *__dentry_path(struct dentry *d, char *buf, int buflen)
-{
-        struct dentry *dentry;
-        char *end, *retval;
-        int len, seq = 0;
-        int error = 0;
-
-        if (buflen < 2)
-                goto Elong;
-
-        rcu_read_lock();
-restart:
-        dentry = d;
-        end = buf + buflen;
-        len = buflen;
-        prepend(&end, &len, "\0", 1);
-        /* Get '/' right */
-        retval = end-1;
-        *retval = '/';
-        read_seqbegin_or_lock(&rename_lock, &seq);
-        while (!IS_ROOT(dentry)) {
-                struct dentry *parent = dentry->d_parent;
-
-                prefetch(parent);
-                error = prepend_name(&end, &len, &dentry->d_name);
-                if (error)
-                        break;
-
-                retval = end;
-                dentry = parent;
-        }
-        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;
-Elong:
-        return ERR_PTR(-ENAMETOOLONG);
-}
-
-char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
-{
-        return __dentry_path(dentry, buf, buflen);
-}
-EXPORT_SYMBOL(dentry_path_raw);
-
-char *dentry_path(struct dentry *dentry, char *buf, int buflen)
-{
-        char *p = NULL;
-        char *retval;
-
-        if (d_unlinked(dentry)) {
-                p = buf + buflen;
-                if (prepend(&p, &buflen, "//deleted", 10) != 0)
-                        goto Elong;
-                buflen++;
-        }
-        retval = __dentry_path(dentry, buf, buflen);
-        if (!IS_ERR(retval) && p)
-                *p = '/';       /* restore '/' overriden with '\0' */
-        return retval;
-Elong:
-        return ERR_PTR(-ENAMETOOLONG);
-}
-
-static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
-                                    struct path *pwd)
-{
-        unsigned seq;
-
-        do {
-                seq = read_seqcount_begin(&fs->seq);
-                *root = fs->root;
-                *pwd = fs->pwd;
-        } while (read_seqcount_retry(&fs->seq, seq));
-}
-
-/*
- * NOTE! The user-level library version returns a
- * character pointer. The kernel system call just
- * returns the length of the buffer filled (which
- * includes the ending '\0' character), or a negative
- * error value. So libc would do something like
- *
- *      char *getcwd(char * buf, size_t size)
- *      {
- *              int retval;
- *
- *              retval = sys_getcwd(buf, size);
- *              if (retval >= 0)
- *                      return buf;
- *              errno = -retval;
- *              return NULL;
- *      }
- */
-SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
-{
-        int error;
-        struct path pwd, root;
-        char *page = __getname();
-
-        if (!page)
-                return -ENOMEM;
-
-        rcu_read_lock();
-        get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
-
-        error = -ENOENT;
-        if (!d_unlinked(pwd.dentry)) {
-                unsigned long len;
-                char *cwd = page + PATH_MAX;
-                int buflen = PATH_MAX;
-
-                prepend(&cwd, &buflen, "\0", 1);
-                error = prepend_path(&pwd, &root, &cwd, &buflen);
-                rcu_read_unlock();
-
-                if (error < 0)
-                        goto out;
-
-                /* Unreachable from current root */
-                if (error > 0) {
-                        error = prepend_unreachable(&cwd, &buflen);
-                        if (error)
-                                goto out;
-                }
-
-                error = -ERANGE;
-                len = PATH_MAX + page - cwd;
-                if (len <= size) {
-                        error = len;
-                        if (copy_to_user(buf, cwd, len))
-                                error = -EFAULT;
-                }
-        } else {
-                rcu_read_unlock();
-        }
-
-out:
-        __putname(page);
-        return error;
-}
-
 /*
  * Test whether new_dentry is a subdirectory of old_dentry.
  *
@@ -3585,6 +3095,8 @@ void d_genocide(struct dentry *parent)
         d_walk(parent, parent, d_genocide_kill, NULL);
 }
 
+EXPORT_SYMBOL(d_genocide);
+
 void d_tmpfile(struct dentry *dentry, struct inode *inode)
 {
         inode_dec_link_count(inode);
@@ -3664,8 +3176,6 @@ static void __init dcache_init(void)
 struct kmem_cache *names_cachep __read_mostly;
 EXPORT_SYMBOL(names_cachep);
 
-EXPORT_SYMBOL(d_genocide);
-
 void __init vfs_caches_init_early(void)
 {
         int i;
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 63a998c3f252..13b01351dd1c 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -270,10 +270,7 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
         if (!parent)
                 parent = debugfs_mount->mnt_root;
 
-        inode_lock(d_inode(parent));
-        dentry = lookup_one_len(name, parent, strlen(name));
-        inode_unlock(d_inode(parent));
-
+        dentry = lookup_one_len_unlocked(name, parent, strlen(name));
         if (IS_ERR(dentry))
                 return NULL;
         if (!d_really_is_positive(dentry)) {
diff --git a/fs/namei.c b/fs/namei.c
index 5c2b953c352d..a09419379f5d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1474,43 +1474,36 @@ static struct dentry *lookup_dcache(const struct qstr *name,
 }
 
 /*
- * Call i_op->lookup on the dentry.  The dentry must be negative and
- * unhashed.
- *
- * dir->d_inode->i_mutex must be held
+ * Parent directory has inode locked exclusive.  This is one
+ * and only case when ->lookup() gets called on non in-lookup
+ * dentries - as the matter of fact, this only gets called
+ * when directory is guaranteed to have no in-lookup children
+ * at all.
  */
-static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
-                                  unsigned int flags)
-{
-        struct dentry *old;
-
-        /* Don't create child dentry for a dead directory. */
-        if (unlikely(IS_DEADDIR(dir))) {
-                dput(dentry);
-                return ERR_PTR(-ENOENT);
-        }
-
-        old = dir->i_op->lookup(dir, dentry, flags);
-        if (unlikely(old)) {
-                dput(dentry);
-                dentry = old;
-        }
-        return dentry;
-}
-
 static struct dentry *__lookup_hash(const struct qstr *name,
                 struct dentry *base, unsigned int flags)
 {
         struct dentry *dentry = lookup_dcache(name, base, flags);
+        struct dentry *old;
+        struct inode *dir = base->d_inode;
 
         if (dentry)
                 return dentry;
 
+        /* Don't create child dentry for a dead directory. */
+        if (unlikely(IS_DEADDIR(dir)))
+                return ERR_PTR(-ENOENT);
+
         dentry = d_alloc(base, name);
         if (unlikely(!dentry))
                 return ERR_PTR(-ENOMEM);
 
-        return lookup_real(base->d_inode, dentry, flags);
+        old = dir->i_op->lookup(dir, dentry, flags);
+        if (unlikely(old)) {
+                dput(dentry);
+                dentry = old;
+        }
+        return dentry;
 }
 
 static int lookup_fast(struct nameidata *nd,
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 82a99d366aec..94acbde17bb1 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -56,9 +56,7 @@ struct qstr {
 
 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
 
-extern const char empty_string[];
 extern const struct qstr empty_name;
-extern const char slash_string[];
 extern const struct qstr slash_name;
 
 struct dentry_stat_t {
@@ -361,7 +359,7 @@ static inline void dont_mount(struct dentry *dentry)
 
 extern void __d_lookup_done(struct dentry *);
 
-static inline int d_in_lookup(struct dentry *dentry)
+static inline int d_in_lookup(const struct dentry *dentry)
 {
         return dentry->d_flags & DCACHE_PAR_LOOKUP;
 }
@@ -489,7 +487,7 @@ static inline bool d_really_is_positive(const struct dentry *dentry)
         return dentry->d_inode != NULL;
 }
 
-static inline int simple_positive(struct dentry *dentry)
+static inline int simple_positive(const struct dentry *dentry)
 {
         return d_really_is_positive(dentry) && !d_unhashed(dentry);
 }