fs: rcu-walk aware d_revalidate method

Require filesystems be aware of .d_revalidate being called in rcu-walk
mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning
-ECHILD from all implementations.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

27 files changed, 215 insertions, 61 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index bdad6414dfa0..e90ffe61eb65 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -9,7 +9,7 @@ be able to use diff(1).
 
 --------------------------- dentry_operations --------------------------
 prototypes:
-        int (*d_revalidate)(struct dentry *, int);
+        int (*d_revalidate)(struct dentry *, struct nameidata *);
         int (*d_hash)(const struct dentry *, const struct inode *,
                         struct qstr *);
         int (*d_compare)(const struct dentry *, const struct inode *,
@@ -21,14 +21,14 @@ prototypes:
         char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
 
 locking rules:
-                rename_lock     ->d_lock        may block
-d_revalidate:   no              no              yes
-d_hash          no              no              no
-d_compare:      yes             no              no
-d_delete:       no              yes             no
-d_release:      no              no              yes
-d_iput:         no              no              yes
-d_dname:        no              no              no
+                rename_lock     ->d_lock        may block       rcu-walk
+d_revalidate:   no              no              yes (ref-walk)  maybe
+d_hash          no              no              no              maybe
+d_compare:      yes             no              no              maybe
+d_delete:       no              yes             no              no
+d_release:      no              no              yes             no
+d_iput:         no              no              yes             no
+d_dname:        no              no              no              no
 
 --------------------------- inode_operations --------------------------- 
 prototypes:
diff --git a/Documentation/filesystems/path-lookup.txt b/Documentation/filesystems/path-lookup.txt
index 09b2878724a1..8789d1810bed 100644
--- a/Documentation/filesystems/path-lookup.txt
+++ b/Documentation/filesystems/path-lookup.txt
@@ -317,11 +317,10 @@ The detailed design for rcu-walk is like this:
 The cases where rcu-walk cannot continue are:
 * NULL dentry (ie. any uncached path element)
 * parent with d_inode->i_op->permission or ACLs
-* dentries with d_revalidate
 * Following links
 
-In future patches, permission checks and d_revalidate become rcu-walk aware. It
-may be possible eventually to make following links rcu-walk aware.
+In future patches, permission checks become rcu-walk aware. It may be possible
+eventually to make following links rcu-walk aware.
 
 Uncached path elements will always require dropping to ref-walk mode, at the
 very least because i_mutex needs to be grabbed, and objects allocated.
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index ccf0ce7866b9..cd9756a2709d 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -360,3 +360,23 @@ i_dentry to be reinitialized before it is freed, so an:
   INIT_LIST_HEAD(&inode->i_dentry);
 
 must be done in the RCU callback.
+
+--
+[recommended]
+        vfs now tries to do path walking in "rcu-walk mode", which avoids
+atomic operations and scalability hazards on dentries and inodes (see
+Documentation/filesystems/path-walk.txt). d_hash and d_compare changes (above)
+are examples of the changes required to support this. For more complex
+filesystem callbacks, the vfs drops out of rcu-walk mode before the fs call, so
+no changes are required to the filesystem. However, this is costly and loses
+the benefits of rcu-walk mode. We will begin to add filesystem callbacks that
+are rcu-walk aware, shown below. Filesystems should take advantage of this
+where possible.
+
+--
+[mandatory]
+        d_revalidate is a callback that is made on every path element (if
+the filesystem provides it), which requires dropping out of rcu-walk mode. This
+may now be called in rcu-walk mode (nd->flags & LOOKUP_RCU). -ECHILD should be
+returned if the filesystem cannot handle rcu-walk. See
+Documentation/filesystems/vfs.txt for more details.
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 69b10ff5ec81..c936b4912383 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -863,6 +863,15 @@ struct dentry_operations {
         dcache. Most filesystems leave this as NULL, because all their
         dentries in the dcache are valid
 
+        d_revalidate may be called in rcu-walk mode (nd->flags & LOOKUP_RCU).
+        If in rcu-walk mode, the filesystem must revalidate the dentry without
+        blocking or storing to the dentry, d_parent and d_inode should not be
+        used without care (because they can go NULL), instead nd->inode should
+        be used.
+
+        If a situation is encountered that rcu-walk cannot handle, return
+        -ECHILD and it will be called again in ref-walk mode.
+
   d_hash: called when the VFS adds a dentry to the hash table. The first
         dentry passed to d_hash is the parent directory that the name is
         to be hashed into. The inode is the dentry's inode.
diff --git a/drivers/staging/autofs/root.c b/drivers/staging/autofs/root.c
index b09adb57971f..bf0e9755da67 100644
--- a/drivers/staging/autofs/root.c
+++ b/drivers/staging/autofs/root.c
@@ -154,13 +154,16 @@ static int try_to_fill_dentry(struct dentry *dentry, struct super_block *sb, str
  * yet completely filled in, and revalidate has to delay such
  * lookups..
  */
-static int autofs_revalidate(struct dentry * dentry, struct nameidata *nd)
+static int autofs_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode * dir;
         struct autofs_sb_info *sbi;
         struct autofs_dir_ent *ent;
         int res;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         lock_kernel();
         dir = dentry->d_parent->d_inode;
         sbi = autofs_sbi(dir->i_sb);
diff --git a/drivers/staging/smbfs/dir.c b/drivers/staging/smbfs/dir.c
index 78f09412740c..dd612f50749f 100644
--- a/drivers/staging/smbfs/dir.c
+++ b/drivers/staging/smbfs/dir.c
@@ -14,6 +14,7 @@
 #include <linux/ctype.h>
 #include <linux/net.h>
 #include <linux/sched.h>
+#include <linux/namei.h>
 
 #include "smb_fs.h"
 #include "smb_mount.h"
@@ -301,13 +302,20 @@ static const struct dentry_operations smbfs_dentry_operations_case =
  * This is the callback when the dcache has a lookup hit.
  */
 static int
-smb_lookup_validate(struct dentry * dentry, struct nameidata *nd)
+smb_lookup_validate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct smb_sb_info *server = server_from_dentry(dentry);
-        struct inode * inode = dentry->d_inode;
-        unsigned long age = jiffies - dentry->d_time;
+        struct smb_sb_info *server;
+        struct inode *inode;
+        unsigned long age;
         int valid;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        server = server_from_dentry(dentry);
+        inode = dentry->d_inode;
+        age = jiffies - dentry->d_time;
+
         /*
          * The default validation is based on dentry age:
          * we believe in dentries for a few seconds.  (But each
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index b8bb7e7148d0..34a3263d60a4 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/fs.h>
+#include <linux/namei.h>
 #include <linux/pagemap.h>
 #include <linux/ctype.h>
 #include <linux/sched.h>
@@ -607,6 +608,9 @@ static int afs_d_revalidate(struct dentry *dentry, struct nameidata *nd)
         void *dir_version;
         int ret;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         vnode = AFS_FS_I(dentry->d_inode);
 
         if (dentry->d_inode)
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index bfe3f2eb684d..651e4ef563b1 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -315,12 +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)) {
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index cc01cf826769..fa7ca04ee816 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -990,7 +990,12 @@ static int dir_lease_is_valid(struct inode *dir, struct dentry *dentry)
  */
 static int ceph_d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *dir = dentry->d_parent->d_inode;
+        struct inode *dir;
+
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        dir = dentry->d_parent->d_inode;
 
         dout("d_revalidate %p '%.*s' inode %p offset %lld\n", dentry,
              dentry->d_name.len, dentry->d_name.name, dentry->d_inode,
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index e3b10ca6d453..db2a58c00f7b 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -656,6 +656,9 @@ lookup_out:
 static int
 cifs_d_revalidate(struct dentry *direntry, struct nameidata *nd)
 {
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         if (direntry->d_inode) {
                 if (cifs_revalidate_dentry(direntry))
                         return 0;
diff --git a/fs/coda/dir.c b/fs/coda/dir.c
index aa40c811f8d2..619a8303766e 100644
--- a/fs/coda/dir.c
+++ b/fs/coda/dir.c
@@ -18,6 +18,7 @@
 #include <linux/errno.h>
 #include <linux/string.h>
 #include <linux/spinlock.h>
+#include <linux/namei.h>
 
 #include <asm/uaccess.h>
 
@@ -541,9 +542,13 @@ out:
 /* called when a cache lookup succeeds */
 static int coda_dentry_revalidate(struct dentry *de, struct nameidata *nd)
 {
-        struct inode *inode = de->d_inode;
+        struct inode *inode;
         struct coda_inode_info *cii;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = de->d_inode;
         if (!inode || coda_isroot(inode))
                 goto out;
         if (is_bad_inode(inode))
diff --git a/fs/ecryptfs/dentry.c b/fs/ecryptfs/dentry.c
index 906e803f7f79..6fc4f319b550 100644
--- a/fs/ecryptfs/dentry.c
+++ b/fs/ecryptfs/dentry.c
@@ -44,12 +44,17 @@
  */
 static int ecryptfs_d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
-        struct vfsmount *lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
+        struct dentry *lower_dentry;
+        struct vfsmount *lower_mnt;
         struct dentry *dentry_save;
         struct vfsmount *vfsmount_save;
         int rc = 1;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        lower_dentry = ecryptfs_dentry_to_lower(dentry);
+        lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
         if (!lower_dentry->d_op || !lower_dentry->d_op->d_revalidate)
                 goto out;
         dentry_save = nd->path.dentry;
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 3be5ed7d859f..e3ffc5e12332 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -43,6 +43,9 @@ static int vfat_revalidate_shortname(struct dentry *dentry)
 
 static int vfat_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         /* This is not negative dentry. Always valid. */
         if (dentry->d_inode)
                 return 1;
@@ -51,6 +54,9 @@ static int vfat_revalidate(struct dentry *dentry, struct nameidata *nd)
 
 static int vfat_revalidate_ci(struct dentry *dentry, struct nameidata *nd)
 {
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         /*
          * This is not negative dentry. Always valid.
          *
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index c9a8a426a395..07f4b5e675fc 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -156,8 +156,12 @@ u64 fuse_get_attr_version(struct fuse_conn *fc)
  */
 static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
 {
-        struct inode *inode = entry->d_inode;
+        struct inode *inode;
+
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
 
+        inode = entry->d_inode;
         if (inode && is_bad_inode(inode))
                 return 0;
         else if (fuse_dentry_time(entry) < get_jiffies_64()) {
diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
index 50497f65763b..4a456338b873 100644
--- a/fs/gfs2/dentry.c
+++ b/fs/gfs2/dentry.c
@@ -11,6 +11,7 @@
 #include <linux/completion.h>
 #include <linux/buffer_head.h>
 #include <linux/gfs2_ondisk.h>
+#include <linux/namei.h>
 #include <linux/crc32.h>
 
 #include "gfs2.h"
@@ -34,15 +35,23 @@
 
 static int gfs2_drevalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct dentry *parent = dget_parent(dentry);
-        struct gfs2_sbd *sdp = GFS2_SB(parent->d_inode);
-        struct gfs2_inode *dip = GFS2_I(parent->d_inode);
-        struct inode *inode = dentry->d_inode;
+        struct dentry *parent;
+        struct gfs2_sbd *sdp;
+        struct gfs2_inode *dip;
+        struct inode *inode;
         struct gfs2_holder d_gh;
         struct gfs2_inode *ip = NULL;
         int error;
         int had_lock = 0;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        parent = dget_parent(dentry);
+        sdp = GFS2_SB(parent->d_inode);
+        dip = GFS2_I(parent->d_inode);
+        inode = dentry->d_inode;
+
         if (inode) {
                 if (is_bad_inode(inode))
                         goto invalid;
diff --git a/fs/hfs/sysdep.c b/fs/hfs/sysdep.c
index 7478f5c219aa..19cf291eb91f 100644
--- a/fs/hfs/sysdep.c
+++ b/fs/hfs/sysdep.c
@@ -8,15 +8,20 @@
  * This file contains the code to do various system dependent things.
  */
 
+#include <linux/namei.h>
 #include "hfs_fs.h"
 
 /* dentry case-handling: just lowercase everything */
 
 static int hfs_revalidate_dentry(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *inode = dentry->d_inode;
+        struct inode *inode;
         int diff;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = dentry->d_inode;
         if(!inode)
                 return 1;
 
diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index a151cbdec626..4414e3a42264 100644
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -1608,6 +1608,8 @@ out:
 
 static int jfs_ci_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
         /*
          * This is not negative dentry. Always valid.
          *
diff --git a/fs/namei.c b/fs/namei.c
index 90bd2873e117..6e275363e89d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -563,10 +563,26 @@ void release_open_intent(struct nameidata *nd)
                 fput(nd->intent.open.file);
 }
 
+static int d_revalidate(struct dentry *dentry, struct nameidata *nd)
+{
+        int status;
+
+        status = dentry->d_op->d_revalidate(dentry, nd);
+        if (status == -ECHILD) {
+                if (nameidata_dentry_drop_rcu(nd, dentry))
+                        return status;
+                status = dentry->d_op->d_revalidate(dentry, nd);
+        }
+
+        return status;
+}
+
 static inline struct dentry *
 do_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        int status = dentry->d_op->d_revalidate(dentry, nd);
+        int status;
+
+        status = d_revalidate(dentry, nd);
         if (unlikely(status <= 0)) {
                 /*
                  * The dentry failed validation.
@@ -574,14 +590,20 @@ do_revalidate(struct dentry *dentry, struct nameidata *nd)
                  * the dentry otherwise d_revalidate is asking us
                  * to return a fail status.
                  */
-                if (!status) {
+                if (status < 0) {
+                        /* If we're in rcu-walk, we don't have a ref */
+                        if (!(nd->flags & LOOKUP_RCU))
+                                dput(dentry);
+                        dentry = ERR_PTR(status);
+
+                } else {
+                        /* Don't d_invalidate in rcu-walk mode */
+                        if (nameidata_dentry_drop_rcu_maybe(nd, dentry))
+                                return ERR_PTR(-ECHILD);
                         if (!d_invalidate(dentry)) {
                                 dput(dentry);
                                 dentry = NULL;
                         }
-                } else {
-                        dput(dentry);
-                        dentry = ERR_PTR(status);
                 }
         }
         return dentry;
@@ -626,7 +648,7 @@ force_reval_path(struct path *path, struct nameidata *nd)
         if (!need_reval_dot(dentry))
                 return 0;
 
-        status = dentry->d_op->d_revalidate(dentry, nd);
+        status = d_revalidate(dentry, nd);
         if (status > 0)
                 return 0;
 
@@ -1039,12 +1061,8 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
                         return -ECHILD;
 
                 nd->seq = seq;
-                if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
-                        /* We commonly drop rcu-walk here */
-                        if (nameidata_dentry_drop_rcu(nd, dentry))
-                                return -ECHILD;
+                if (dentry->d_flags & DCACHE_OP_REVALIDATE)
                         goto need_revalidate;
-                }
                 path->mnt = mnt;
                 path->dentry = dentry;
                 __follow_mount_rcu(nd, path, inode);
@@ -1292,12 +1310,11 @@ return_reval:
                  * We may need to check the cached dentry for staleness.
                  */
                 if (need_reval_dot(nd->path.dentry)) {
-                        if (nameidata_drop_rcu_maybe(nd))
-                                return -ECHILD;
-                        err = -ESTALE;
                         /* Note: we do not d_invalidate() */
-                        if (!nd->path.dentry->d_op->d_revalidate(
-                                        nd->path.dentry, nd))
+                        err = d_revalidate(nd->path.dentry, nd);
+                        if (!err)
+                                err = -ESTALE;
+                        if (err < 0)
                                 break;
                 }
 return_base:
@@ -2080,10 +2097,11 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                 dir = nd->path.dentry;
         case LAST_DOT:
                 if (need_reval_dot(dir)) {
-                        if (!dir->d_op->d_revalidate(dir, nd)) {
+                        error = d_revalidate(nd->path.dentry, nd);
+                        if (!error)
                                 error = -ESTALE;
+                        if (error < 0)
                                 goto exit;
-                        }
                 }
                 /* fallthrough */
         case LAST_ROOT:
diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c
index 4b9cbb28d7fa..28f136d4aaec 100644
--- a/fs/ncpfs/dir.c
+++ b/fs/ncpfs/dir.c
@@ -17,6 +17,7 @@
 #include <linux/kernel.h>
 #include <linux/vmalloc.h>
 #include <linux/mm.h>
+#include <linux/namei.h>
 #include <asm/uaccess.h>
 #include <asm/byteorder.h>
 
@@ -308,6 +309,9 @@ ncp_lookup_validate(struct dentry *dentry, struct nameidata *nd)
         int res, val = 0, len;
         __u8 __name[NCP_MAXPATHLEN + 1];
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         parent = dget_parent(dentry);
         dir = parent->d_inode;
 
diff --git a/fs/ncpfs/inode.c b/fs/ncpfs/inode.c
index 0c75a5f3cafd..9531c052d7a4 100644
--- a/fs/ncpfs/inode.c
+++ b/fs/ncpfs/inode.c
@@ -29,6 +29,7 @@
 #include <linux/vfs.h>
 #include <linux/mount.h>
 #include <linux/seq_file.h>
+#include <linux/namei.h>
 
 #include <linux/ncp_fs.h>
 
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 37e0a8bb077e..58beace14b19 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -938,7 +938,8 @@ static int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
  * component of the path.
  * We check for this using LOOKUP_CONTINUE and LOOKUP_PARENT.
  */
-static inline unsigned int nfs_lookup_check_intent(struct nameidata *nd, unsigned int mask)
+static inline unsigned int nfs_lookup_check_intent(struct nameidata *nd,
+                                                unsigned int mask)
 {
         if (nd->flags & (LOOKUP_CONTINUE|LOOKUP_PARENT))
                 return 0;
@@ -1018,7 +1019,7 @@ int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,
  * If the parent directory is seen to have changed, we throw out the
  * cached dentry and do a new lookup.
  */
-static int nfs_lookup_revalidate(struct dentry * dentry, struct nameidata *nd)
+static int nfs_lookup_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode *dir;
         struct inode *inode;
@@ -1027,6 +1028,9 @@ static int nfs_lookup_revalidate(struct dentry * dentry, struct nameidata *nd)
         struct nfs_fattr *fattr = NULL;
         int error;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
         parent = dget_parent(dentry);
         dir = parent->d_inode;
         nfs_inc_stats(dir, NFSIOS_DENTRYREVALIDATE);
diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
index 4d54c60ceee4..0310b16a7238 100644
--- a/fs/ocfs2/dcache.c
+++ b/fs/ocfs2/dcache.c
@@ -52,9 +52,15 @@ void ocfs2_dentry_attach_gen(struct dentry *dentry)
 static int ocfs2_dentry_revalidate(struct dentry *dentry,
                                    struct nameidata *nd)
 {
-        struct inode *inode = dentry->d_inode;
+        struct inode *inode;
         int ret = 0;    /* if all else fails, just return false */
-        struct ocfs2_super *osb = OCFS2_SB(dentry->d_sb);
+        struct ocfs2_super *osb;
+
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = dentry->d_inode;
+        osb = OCFS2_SB(dentry->d_sb);
 
         mlog_entry("(0x%p, '%.*s')\n", dentry,
                    dentry->d_name.len, dentry->d_name.name);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 85f0a80912aa..dc5b2fcadc3b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1719,10 +1719,16 @@ static int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat
  */
 static int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *inode = dentry->d_inode;
-        struct task_struct *task = get_proc_task(inode);
+        struct inode *inode;
+        struct task_struct *task;
         const struct cred *cred;
 
+        if (nd && nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = dentry->d_inode;
+        task = get_proc_task(inode);
+
         if (task) {
                 if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
                     task_dumpable(task)) {
@@ -1888,12 +1894,19 @@ static int proc_fd_link(struct inode *inode, struct path *path)
 
 static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *inode = dentry->d_inode;
-        struct task_struct *task = get_proc_task(inode);
-        int fd = proc_fd(inode);
+        struct inode *inode;
+        struct task_struct *task;
+        int fd;
         struct files_struct *files;
         const struct cred *cred;
 
+        if (nd && nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = dentry->d_inode;
+        task = get_proc_task(inode);
+        fd = proc_fd(inode);
+
         if (task) {
                 files = get_files_struct(task);
                 if (files) {
@@ -2563,8 +2576,14 @@ static const struct pid_entry proc_base_stuff[] = {
  */
 static int proc_base_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct inode *inode = dentry->d_inode;
-        struct task_struct *task = get_proc_task(inode);
+        struct inode *inode;
+        struct task_struct *task;
+
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = dentry->d_inode;
+        task = get_proc_task(inode);
         if (task) {
                 put_task_struct(task);
                 return 1;
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 35efd85a4d32..c9097f43b425 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -5,6 +5,7 @@
 #include <linux/sysctl.h>
 #include <linux/proc_fs.h>
 #include <linux/security.h>
+#include <linux/namei.h>
 #include "internal.h"
 
 static const struct dentry_operations proc_sys_dentry_operations;
@@ -389,6 +390,8 @@ static const struct inode_operations proc_sys_dir_operations = {
 
 static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
         return !PROC_I(dentry->d_inode)->sysctl->unregistering;
 }
 
diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index e0f0d7ea10a1..9ea22a56cdf1 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -972,6 +972,8 @@ int reiserfs_permission(struct inode *inode, int mask)
 
 static int xattr_hide_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
         return -EPERM;
 }
 
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 3e076caa8daf..ea9120a830d8 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -239,9 +239,13 @@ static int sysfs_dentry_delete(const struct dentry *dentry)
 
 static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        struct sysfs_dirent *sd = dentry->d_fsdata;
+        struct sysfs_dirent *sd;
         int is_dir;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        sd = dentry->d_fsdata;
         mutex_lock(&sysfs_mutex);
 
         /* The sysfs dirent has been deleted */
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index b1aeda077258..8b2064d02928 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -190,7 +190,6 @@ struct dentry_operations {
 #define DCACHE_OP_REVALIDATE    0x4000
 #define DCACHE_OP_DELETE        0x8000
 
-
 extern spinlock_t dcache_inode_lock;
 extern seqlock_t rename_lock;