Merge branch 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin

* 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin: (57 commits)
  fs: scale mntget/mntput
  fs: rename vfsmount counter helpers
  fs: implement faster dentry memcmp
  fs: prefetch inode data in dcache lookup
  fs: improve scalability of pseudo filesystems
  fs: dcache per-inode inode alias locking
  fs: dcache per-bucket dcache hash locking
  bit_spinlock: add required includes
  kernel: add bl_list
  xfs: provide simple rcu-walk ACL implementation
  btrfs: provide simple rcu-walk ACL implementation
  ext2,3,4: provide simple rcu-walk ACL implementation
  fs: provide simple rcu-walk generic_check_acl implementation
  fs: provide rcu-walk aware permission i_ops
  fs: rcu-walk aware d_revalidate method
  fs: cache optimise dentry and inode for rcu-walk
  fs: dcache reduce branches in lookup path
  fs: dcache remove d_mounted
  fs: fs_struct use seqlock
  fs: rcu-walk for path lookup
  ...

5 files changed, 164 insertions, 114 deletions

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 3d283abf67d7..0fffe1c24cec 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -16,6 +16,7 @@
 #include <linux/auto_fs4.h>
 #include <linux/auto_dev-ioctl.h>
 #include <linux/mutex.h>
+#include <linux/spinlock.h>
 #include <linux/list.h>
 
 /* This is the range of ioctl() numbers we claim as ours */
@@ -60,6 +61,8 @@ do {							\
                 current->pid, __func__, ##args);        \
 } while (0)
 
+extern spinlock_t autofs4_lock;
+
 /* Unified info structure.  This is pointed to by both the dentry and
    inode structures.  Each file in the filesystem has an instance of this
    structure.  It holds a reference to the dentry, so dentries are never
@@ -254,17 +257,15 @@ static inline int simple_positive(struct dentry *dentry)
         return dentry->d_inode && !d_unhashed(dentry);
 }
 
-static inline int __simple_empty(struct dentry *dentry)
+static inline void __autofs4_add_expiring(struct dentry *dentry)
 {
-        struct dentry *child;
-        int ret = 0;
-
-        list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
-                if (simple_positive(child))
-                        goto out;
-        ret = 1;
-out:
-        return ret;
+        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
+        struct autofs_info *ino = autofs4_dentry_ino(dentry);
+        if (ino) {
+                if (list_empty(&ino->expiring))
+                        list_add(&ino->expiring, &sbi->expiring_list);
+        }
+        return;
 }
 
 static inline void autofs4_add_expiring(struct dentry *dentry)
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index a796c9417fb1..cc1d01365905 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -91,24 +91,64 @@ done:
 }
 
 /*
- * Calculate next entry in top down tree traversal.
- * From next_mnt in namespace.c - elegant.
+ * Calculate and dget next entry in top down tree traversal.
  */
-static struct dentry *next_dentry(struct dentry *p, struct dentry *root)
+static struct dentry *get_next_positive_dentry(struct dentry *prev,
+                                                struct dentry *root)
 {
-        struct list_head *next = p->d_subdirs.next;
+        struct list_head *next;
+        struct dentry *p, *ret;
+
+        if (prev == NULL)
+                return dget(prev);
 
+        spin_lock(&autofs4_lock);
+relock:
+        p = prev;
+        spin_lock(&p->d_lock);
+again:
+        next = p->d_subdirs.next;
         if (next == &p->d_subdirs) {
                 while (1) {
-                        if (p == root)
+                        struct dentry *parent;
+
+                        if (p == root) {
+                                spin_unlock(&p->d_lock);
+                                spin_unlock(&autofs4_lock);
+                                dput(prev);
                                 return NULL;
+                        }
+
+                        parent = p->d_parent;
+                        if (!spin_trylock(&parent->d_lock)) {
+                                spin_unlock(&p->d_lock);
+                                cpu_relax();
+                                goto relock;
+                        }
+                        spin_unlock(&p->d_lock);
                         next = p->d_u.d_child.next;
-                        if (next != &p->d_parent->d_subdirs)
+                        p = parent;
+                        if (next != &parent->d_subdirs)
                                 break;
-                        p = p->d_parent;
                 }
         }
-        return list_entry(next, struct dentry, d_u.d_child);
+        ret = list_entry(next, struct dentry, d_u.d_child);
+
+        spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
+        /* Negative dentry - try next */
+        if (!simple_positive(ret)) {
+                spin_unlock(&ret->d_lock);
+                p = ret;
+                goto again;
+        }
+        dget_dlock(ret);
+        spin_unlock(&ret->d_lock);
+        spin_unlock(&p->d_lock);
+        spin_unlock(&autofs4_lock);
+
+        dput(prev);
+
+        return ret;
 }
 
 /*
@@ -158,18 +198,11 @@ static int autofs4_tree_busy(struct vfsmount *mnt,
         if (!simple_positive(top))
                 return 1;
 
-        spin_lock(&dcache_lock);
-        for (p = top; p; p = next_dentry(p, top)) {
-                /* Negative dentry - give up */
-                if (!simple_positive(p))
-                        continue;
-
+        p = NULL;
+        while ((p = get_next_positive_dentry(p, top))) {
                 DPRINTK("dentry %p %.*s",
                         p, (int) p->d_name.len, p->d_name.name);
 
-                p = dget(p);
-                spin_unlock(&dcache_lock);
-
                 /*
                  * Is someone visiting anywhere in the subtree ?
                  * If there's no mount we need to check the usage
@@ -198,16 +231,13 @@ static int autofs4_tree_busy(struct vfsmount *mnt,
                         else
                                 ino_count++;
 
-                        if (atomic_read(&p->d_count) > ino_count) {
+                        if (p->d_count > ino_count) {
                                 top_ino->last_used = jiffies;
                                 dput(p);
                                 return 1;
                         }
                 }
-                dput(p);
-                spin_lock(&dcache_lock);
         }
-        spin_unlock(&dcache_lock);
 
         /* Timeout of a tree mount is ultimately determined by its top dentry */
         if (!autofs4_can_expire(top, timeout, do_now))
@@ -226,32 +256,21 @@ static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
         DPRINTK("parent %p %.*s",
                 parent, (int)parent->d_name.len, parent->d_name.name);
 
-        spin_lock(&dcache_lock);
-        for (p = parent; p; p = next_dentry(p, parent)) {
-                /* Negative dentry - give up */
-                if (!simple_positive(p))
-                        continue;
-
+        p = NULL;
+        while ((p = get_next_positive_dentry(p, parent))) {
                 DPRINTK("dentry %p %.*s",
                         p, (int) p->d_name.len, p->d_name.name);
 
-                p = dget(p);
-                spin_unlock(&dcache_lock);
-
                 if (d_mountpoint(p)) {
                         /* Can we umount this guy */
                         if (autofs4_mount_busy(mnt, p))
-                                goto cont;
+                                continue;
 
                         /* Can we expire this guy */
                         if (autofs4_can_expire(p, timeout, do_now))
                                 return p;
                 }
-cont:
-                dput(p);
-                spin_lock(&dcache_lock);
         }
-        spin_unlock(&dcache_lock);
         return NULL;
 }
 
@@ -276,7 +295,9 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
                 struct autofs_info *ino = autofs4_dentry_ino(root);
                 if (d_mountpoint(root)) {
                         ino->flags |= AUTOFS_INF_MOUNTPOINT;
-                        root->d_mounted--;
+                        spin_lock(&root->d_lock);
+                        root->d_flags &= ~DCACHE_MOUNTED;
+                        spin_unlock(&root->d_lock);
                 }
                 ino->flags |= AUTOFS_INF_EXPIRING;
                 init_completion(&ino->expire_complete);
@@ -302,8 +323,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 {
         unsigned long timeout;
         struct dentry *root = sb->s_root;
+        struct dentry *dentry;
         struct dentry *expired = NULL;
-        struct list_head *next;
         int do_now = how & AUTOFS_EXP_IMMEDIATE;
         int exp_leaves = how & AUTOFS_EXP_LEAVES;
         struct autofs_info *ino;
@@ -315,23 +336,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
         now = jiffies;
         timeout = sbi->exp_timeout;
 
-        spin_lock(&dcache_lock);
-        next = root->d_subdirs.next;
-
-        /* On exit from the loop expire is set to a dgot dentry
-         * to expire or it's NULL */
-        while ( next != &root->d_subdirs ) {
-                struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
-
-                /* Negative dentry - give up */
-                if (!simple_positive(dentry)) {
-                        next = next->next;
-                        continue;
-                }
-
-                dentry = dget(dentry);
-                spin_unlock(&dcache_lock);
-
+        dentry = NULL;
+        while ((dentry = get_next_positive_dentry(dentry, root))) {
                 spin_lock(&sbi->fs_lock);
                 ino = autofs4_dentry_ino(dentry);
 
@@ -347,7 +353,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 
                         /* Path walk currently on this dentry? */
                         ino_count = atomic_read(&ino->count) + 2;
-                        if (atomic_read(&dentry->d_count) > ino_count)
+                        if (dentry->d_count > ino_count)
                                 goto next;
 
                         /* Can we umount this guy */
@@ -369,7 +375,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
                 if (!exp_leaves) {
                         /* Path walk currently on this dentry? */
                         ino_count = atomic_read(&ino->count) + 1;
-                        if (atomic_read(&dentry->d_count) > ino_count)
+                        if (dentry->d_count > ino_count)
                                 goto next;
 
                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
@@ -383,7 +389,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
                 } else {
                         /* Path walk currently on this dentry? */
                         ino_count = atomic_read(&ino->count) + 1;
-                        if (atomic_read(&dentry->d_count) > ino_count)
+                        if (dentry->d_count > ino_count)
                                 goto next;
 
                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
@@ -394,11 +400,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
                 }
 next:
                 spin_unlock(&sbi->fs_lock);
-                dput(dentry);
-                spin_lock(&dcache_lock);
-                next = next->next;
         }
-        spin_unlock(&dcache_lock);
         return NULL;
 
 found:
@@ -408,9 +410,13 @@ found:
         ino->flags |= AUTOFS_INF_EXPIRING;
         init_completion(&ino->expire_complete);
         spin_unlock(&sbi->fs_lock);
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
+        spin_lock(&expired->d_parent->d_lock);
+        spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
-        spin_unlock(&dcache_lock);
+        spin_unlock(&expired->d_lock);
+        spin_unlock(&expired->d_parent->d_lock);
+        spin_unlock(&autofs4_lock);
         return expired;
 }
 
@@ -499,7 +505,14 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 
                 spin_lock(&sbi->fs_lock);
                 if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
-                        sb->s_root->d_mounted++;
+                        spin_lock(&sb->s_root->d_lock);
+                        /*
+                         * If we haven't been expired away, then reset
+                         * mounted status.
+                         */
+                        if (mnt->mnt_parent != mnt)
+                                sb->s_root->d_flags |= DCACHE_MOUNTED;
+                        spin_unlock(&sb->s_root->d_lock);
                         ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
                 }
                 ino->flags &= ~AUTOFS_INF_EXPIRING;
diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index ac87e49fa706..a7bdb9dcac84 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -309,7 +309,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
                 goto fail_iput;
         pipe = NULL;
 
-        root->d_op = &autofs4_sb_dentry_operations;
+        d_set_d_op(root, &autofs4_sb_dentry_operations);
         root->d_fsdata = ino;
 
         /* Can this call block? */
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index d34896cfb19f..651e4ef563b1 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -23,6 +23,8 @@
 
 #include "autofs_i.h"
 
+DEFINE_SPINLOCK(autofs4_lock);
+
 static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
 static int autofs4_dir_unlink(struct inode *,struct dentry *);
 static int autofs4_dir_rmdir(struct inode *,struct dentry *);
@@ -142,12 +144,15 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
          * autofs file system so just let the libfs routines handle
          * it.
          */
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
+        spin_lock(&dentry->d_lock);
         if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
-                spin_unlock(&dcache_lock);
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&autofs4_lock);
                 return -ENOENT;
         }
-        spin_unlock(&dcache_lock);
+        spin_unlock(&dentry->d_lock);
+        spin_unlock(&autofs4_lock);
 
 out:
         return dcache_dir_open(inode, file);
@@ -252,9 +257,11 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
         /* We trigger a mount for almost all flags */
         lookup_type = autofs4_need_mount(nd->flags);
         spin_lock(&sbi->fs_lock);
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
+        spin_lock(&dentry->d_lock);
         if (!(lookup_type || ino->flags & AUTOFS_INF_PENDING)) {
-                spin_unlock(&dcache_lock);
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&autofs4_lock);
                 spin_unlock(&sbi->fs_lock);
                 goto follow;
         }
@@ -266,7 +273,8 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
          */
         if (ino->flags & AUTOFS_INF_PENDING ||
             (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
-                spin_unlock(&dcache_lock);
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&autofs4_lock);
                 spin_unlock(&sbi->fs_lock);
 
                 status = try_to_fill_dentry(dentry, nd->flags);
@@ -275,7 +283,8 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 
                 goto follow;
         }
-        spin_unlock(&dcache_lock);
+        spin_unlock(&dentry->d_lock);
+        spin_unlock(&autofs4_lock);
         spin_unlock(&sbi->fs_lock);
 follow:
         /*
@@ -306,12 +315,19 @@ out_error:
  */
 static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *dir = dentry->d_parent->d_inode;
-        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
-        int oz_mode = autofs4_oz_mode(sbi);
+        struct inode *dir;
+        struct autofs_sb_info *sbi;
+        int oz_mode;
         int flags = nd ? nd->flags : 0;
         int status = 1;
 
+        if (flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        dir = dentry->d_parent->d_inode;
+        sbi = autofs4_sbi(dir->i_sb);
+        oz_mode = autofs4_oz_mode(sbi);
+
         /* Pending dentry */
         spin_lock(&sbi->fs_lock);
         if (autofs4_ispending(dentry)) {
@@ -346,12 +362,14 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
                 return 0;
 
         /* Check for a non-mountpoint directory with no contents */
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
+        spin_lock(&dentry->d_lock);
         if (S_ISDIR(dentry->d_inode->i_mode) &&
             !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
                 DPRINTK("dentry=%p %.*s, emptydir",
                          dentry, dentry->d_name.len, dentry->d_name.name);
-                spin_unlock(&dcache_lock);
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&autofs4_lock);
 
                 /* The daemon never causes a mount to trigger */
                 if (oz_mode)
@@ -367,7 +385,8 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 
                 return status;
         }
-        spin_unlock(&dcache_lock);
+        spin_unlock(&dentry->d_lock);
+        spin_unlock(&autofs4_lock);
 
         return 1;
 }
@@ -422,7 +441,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
         const unsigned char *str = name->name;
         struct list_head *p, *head;
 
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
         spin_lock(&sbi->lookup_lock);
         head = &sbi->active_list;
         list_for_each(p, head) {
@@ -436,7 +455,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
                 spin_lock(&active->d_lock);
 
                 /* Already gone? */
-                if (atomic_read(&active->d_count) == 0)
+                if (active->d_count == 0)
                         goto next;
 
                 qstr = &active->d_name;
@@ -452,17 +471,17 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
                         goto next;
 
                 if (d_unhashed(active)) {
-                        dget(active);
+                        dget_dlock(active);
                         spin_unlock(&active->d_lock);
                         spin_unlock(&sbi->lookup_lock);
-                        spin_unlock(&dcache_lock);
+                        spin_unlock(&autofs4_lock);
                         return active;
                 }
 next:
                 spin_unlock(&active->d_lock);
         }
         spin_unlock(&sbi->lookup_lock);
-        spin_unlock(&dcache_lock);
+        spin_unlock(&autofs4_lock);
 
         return NULL;
 }
@@ -477,7 +496,7 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
         const unsigned char *str = name->name;
         struct list_head *p, *head;
 
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
         spin_lock(&sbi->lookup_lock);
         head = &sbi->expiring_list;
         list_for_each(p, head) {
@@ -507,17 +526,17 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
                         goto next;
 
                 if (d_unhashed(expiring)) {
-                        dget(expiring);
+                        dget_dlock(expiring);
                         spin_unlock(&expiring->d_lock);
                         spin_unlock(&sbi->lookup_lock);
-                        spin_unlock(&dcache_lock);
+                        spin_unlock(&autofs4_lock);
                         return expiring;
                 }
 next:
                 spin_unlock(&expiring->d_lock);
         }
         spin_unlock(&sbi->lookup_lock);
-        spin_unlock(&dcache_lock);
+        spin_unlock(&autofs4_lock);
 
         return NULL;
 }
@@ -559,7 +578,7 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
                  * we check for the hashed dentry and return the newly
                  * hashed dentry.
                  */
-                dentry->d_op = &autofs4_root_dentry_operations;
+                d_set_d_op(dentry, &autofs4_root_dentry_operations);
 
                 /*
                  * And we need to ensure that the same dentry is used for
@@ -698,9 +717,9 @@ static int autofs4_dir_symlink(struct inode *dir,
         d_add(dentry, inode);
 
         if (dir == dir->i_sb->s_root->d_inode)
-                dentry->d_op = &autofs4_root_dentry_operations;
+                d_set_d_op(dentry, &autofs4_root_dentry_operations);
         else
-                dentry->d_op = &autofs4_dentry_operations;
+                d_set_d_op(dentry, &autofs4_dentry_operations);
 
         dentry->d_fsdata = ino;
         ino->dentry = dget(dentry);
@@ -753,12 +772,12 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 
         dir->i_mtime = CURRENT_TIME;
 
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
         autofs4_add_expiring(dentry);
         spin_lock(&dentry->d_lock);
         __d_drop(dentry);
         spin_unlock(&dentry->d_lock);
-        spin_unlock(&dcache_lock);
+        spin_unlock(&autofs4_lock);
 
         return 0;
 }
@@ -775,16 +794,20 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
         if (!autofs4_oz_mode(sbi))
                 return -EACCES;
 
-        spin_lock(&dcache_lock);
+        spin_lock(&autofs4_lock);
+        spin_lock(&sbi->lookup_lock);
+        spin_lock(&dentry->d_lock);
         if (!list_empty(&dentry->d_subdirs)) {
-                spin_unlock(&dcache_lock);
+                spin_unlock(&dentry->d_lock);
+                spin_unlock(&sbi->lookup_lock);
+                spin_unlock(&autofs4_lock);
                 return -ENOTEMPTY;
         }
-        autofs4_add_expiring(dentry);
-        spin_lock(&dentry->d_lock);
+        __autofs4_add_expiring(dentry);
+        spin_unlock(&sbi->lookup_lock);
         __d_drop(dentry);
         spin_unlock(&dentry->d_lock);
-        spin_unlock(&dcache_lock);
+        spin_unlock(&autofs4_lock);
 
         if (atomic_dec_and_test(&ino->count)) {
                 p_ino = autofs4_dentry_ino(dentry->d_parent);
@@ -829,9 +852,9 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
         d_add(dentry, inode);
 
         if (dir == dir->i_sb->s_root->d_inode)
-                dentry->d_op = &autofs4_root_dentry_operations;
+                d_set_d_op(dentry, &autofs4_root_dentry_operations);
         else
-                dentry->d_op = &autofs4_dentry_operations;
+                d_set_d_op(dentry, &autofs4_dentry_operations);
 
         dentry->d_fsdata = ino;
         ino->dentry = dget(dentry);
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index 2341375386f8..c5f8459c905e 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -186,16 +186,26 @@ static int autofs4_getpath(struct autofs_sb_info *sbi,
 {
         struct dentry *root = sbi->sb->s_root;
         struct dentry *tmp;
-        char *buf = *name;
+        char *buf;
         char *p;
-        int len = 0;
+        int len;
+        unsigned seq;
 
-        spin_lock(&dcache_lock);
+rename_retry:
+        buf = *name;
+        len = 0;
+
+        seq = read_seqbegin(&rename_lock);
+        rcu_read_lock();
+        spin_lock(&autofs4_lock);
         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
                 len += tmp->d_name.len + 1;
 
         if (!len || --len > NAME_MAX) {
-                spin_unlock(&dcache_lock);
+                spin_unlock(&autofs4_lock);
+                rcu_read_unlock();
+                if (read_seqretry(&rename_lock, seq))
+                        goto rename_retry;
                 return 0;
         }
 
@@ -208,7 +218,10 @@ static int autofs4_getpath(struct autofs_sb_info *sbi,
                 p -= tmp->d_name.len;
                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
         }
-        spin_unlock(&dcache_lock);
+        spin_unlock(&autofs4_lock);
+        rcu_read_unlock();
+        if (read_seqretry(&rename_lock, seq))
+                goto rename_retry;
 
         return len;
 }