VFS: Put a small type field into struct dentry::d_flags

Put a type field into struct dentry::d_flags to indicate if the dentry is one
of the following types that relate particularly to pathwalk:

	Miss (negative dentry)
	Directory
	"Automount" directory (defective - no i_op->lookup())
	Symlink
	Other (regular, socket, fifo, device)

The type field is set to one of the first five types on a dentry by calls to
__d_instantiate() and d_obtain_alias() from information in the inode (if one is
given).

The type is cleared by dentry_unlink_inode() when it reconstitutes an existing
dentry as a negative dentry.

Accessors provided are:

	d_set_type(dentry, type)
	d_is_directory(dentry)
	d_is_autodir(dentry)
	d_is_symlink(dentry)
	d_is_file(dentry)
	d_is_negative(dentry)
	d_is_positive(dentry)

A bunch of checks in pathname resolution switched to those.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 38 insertions, 57 deletions

diff --git a/fs/namei.c b/fs/namei.c
index e5c0118ba9f8..e1fa43346c61 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1501,18 +1501,9 @@ static void terminate_walk(struct nameidata *nd)
  * so we keep a cache of "no, this doesn't need follow_link"
  * for the common case.
  */
-static inline int should_follow_link(struct inode *inode, int follow)
+static inline int should_follow_link(struct dentry *dentry, int follow)
 {
-        if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
-                if (likely(inode->i_op->follow_link))
-                        return follow;
-
-                /* This gets set once for the inode lifetime */
-                spin_lock(&inode->i_lock);
-                inode->i_opflags |= IOP_NOFOLLOW;
-                spin_unlock(&inode->i_lock);
-        }
-        return 0;
+        return unlikely(d_is_symlink(dentry)) ? follow : 0;
 }
 
 static inline int walk_component(struct nameidata *nd, struct path *path,
@@ -1542,7 +1533,7 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
         if (!inode)
                 goto out_path_put;
 
-        if (should_follow_link(inode, follow)) {
+        if (should_follow_link(path->dentry, follow)) {
                 if (nd->flags & LOOKUP_RCU) {
                         if (unlikely(unlazy_walk(nd, path->dentry))) {
                                 err = -ECHILD;
@@ -1601,26 +1592,6 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
 }
 
 /*
- * We really don't want to look at inode->i_op->lookup
- * when we don't have to. So we keep a cache bit in
- * the inode ->i_opflags field that says "yes, we can
- * do lookup on this inode".
- */
-static inline int can_lookup(struct inode *inode)
-{
-        if (likely(inode->i_opflags & IOP_LOOKUP))
-                return 1;
-        if (likely(!inode->i_op->lookup))
-                return 0;
-
-        /* We do this once for the lifetime of the inode */
-        spin_lock(&inode->i_lock);
-        inode->i_opflags |= IOP_LOOKUP;
-        spin_unlock(&inode->i_lock);
-        return 1;
-}
-
-/*
  * We can do the critical dentry name comparison and hashing
  * operations one word at a time, but we are limited to:
  *
@@ -1823,7 +1794,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
                         if (err)
                                 return err;
                 }
-                if (!can_lookup(nd->inode)) {
+                if (!d_is_directory(nd->path.dentry)) {
                         err = -ENOTDIR; 
                         break;
                 }
@@ -1841,9 +1812,10 @@ static int path_init(int dfd, const char *name, unsigned int flags,
         nd->flags = flags | LOOKUP_JUMPED;
         nd->depth = 0;
         if (flags & LOOKUP_ROOT) {
-                struct inode *inode = nd->root.dentry->d_inode;
+                struct dentry *root = nd->root.dentry;
+                struct inode *inode = root->d_inode;
                 if (*name) {
-                        if (!can_lookup(inode))
+                        if (!d_is_directory(root))
                                 return -ENOTDIR;
                         retval = inode_permission(inode, MAY_EXEC);
                         if (retval)
@@ -1899,7 +1871,7 @@ static int path_init(int dfd, const char *name, unsigned int flags,
                 dentry = f.file->f_path.dentry;
 
                 if (*name) {
-                        if (!can_lookup(dentry->d_inode)) {
+                        if (!d_is_directory(dentry)) {
                                 fdput(f);
                                 return -ENOTDIR;
                         }
@@ -1981,7 +1953,7 @@ static int path_lookupat(int dfd, const char *name,
                 err = complete_walk(nd);
 
         if (!err && nd->flags & LOOKUP_DIRECTORY) {
-                if (!can_lookup(nd->inode)) {
+                if (!d_is_directory(nd->path.dentry)) {
                         path_put(&nd->path);
                         err = -ENOTDIR;
                 }
@@ -2273,7 +2245,7 @@ done:
         }
         path->dentry = dentry;
         path->mnt = mntget(nd->path.mnt);
-        if (should_follow_link(dentry->d_inode, nd->flags & LOOKUP_FOLLOW))
+        if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW))
                 return 1;
         follow_mount(path);
         error = 0;
@@ -2417,12 +2389,14 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)
  * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
  *     nfs_async_unlink().
  */
-static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
+static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
 {
+        struct inode *inode = victim->d_inode;
         int error;
 
-        if (!victim->d_inode)
+        if (d_is_negative(victim))
                 return -ENOENT;
+        BUG_ON(!inode);
 
         BUG_ON(victim->d_parent->d_inode != dir);
         audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
@@ -2432,15 +2406,16 @@ static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
                 return error;
         if (IS_APPEND(dir))
                 return -EPERM;
-        if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
-            IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
+
+        if (check_sticky(dir, inode) || IS_APPEND(inode) ||
+            IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
                 return -EPERM;
         if (isdir) {
-                if (!S_ISDIR(victim->d_inode->i_mode))
+                if (!d_is_directory(victim) && !d_is_autodir(victim))
                         return -ENOTDIR;
                 if (IS_ROOT(victim))
                         return -EBUSY;
-        } else if (S_ISDIR(victim->d_inode->i_mode))
+        } else if (d_is_directory(victim) || d_is_autodir(victim))
                 return -EISDIR;
         if (IS_DEADDIR(dir))
                 return -ENOENT;
@@ -2974,7 +2949,7 @@ retry_lookup:
         /*
          * create/update audit record if it already exists.
          */
-        if (path->dentry->d_inode)
+        if (d_is_positive(path->dentry))
                 audit_inode(name, path->dentry, 0);
 
         /*
@@ -3003,12 +2978,12 @@ retry_lookup:
 finish_lookup:
         /* we _can_ be in RCU mode here */
         error = -ENOENT;
-        if (!inode) {
+        if (d_is_negative(path->dentry)) {
                 path_to_nameidata(path, nd);
                 goto out;
         }
 
-        if (should_follow_link(inode, !symlink_ok)) {
+        if (should_follow_link(path->dentry, !symlink_ok)) {
                 if (nd->flags & LOOKUP_RCU) {
                         if (unlikely(unlazy_walk(nd, path->dentry))) {
                                 error = -ECHILD;
@@ -3037,10 +3012,11 @@ finish_open:
         }
         audit_inode(name, nd->path.dentry, 0);
         error = -EISDIR;
-        if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
+        if ((open_flag & O_CREAT) &&
+            (d_is_directory(nd->path.dentry) || d_is_autodir(nd->path.dentry)))
                 goto out;
         error = -ENOTDIR;
-        if ((nd->flags & LOOKUP_DIRECTORY) && !can_lookup(nd->inode))
+        if ((nd->flags & LOOKUP_DIRECTORY) && !d_is_directory(nd->path.dentry))
                 goto out;
         if (!S_ISREG(nd->inode->i_mode))
                 will_truncate = false;
@@ -3266,7 +3242,7 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
         nd.root.mnt = mnt;
         nd.root.dentry = dentry;
 
-        if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
+        if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
                 return ERR_PTR(-ELOOP);
 
         file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
@@ -3316,8 +3292,9 @@ struct dentry *kern_path_create(int dfd, const char *pathname,
                 goto unlock;
 
         error = -EEXIST;
-        if (dentry->d_inode)
+        if (d_is_positive(dentry))
                 goto fail;
+
         /*
          * Special case - lookup gave negative, but... we had foo/bar/
          * From the vfs_mknod() POV we just have a negative dentry -
@@ -3706,7 +3683,7 @@ retry:
                 if (nd.last.name[nd.last.len])
                         goto slashes;
                 inode = dentry->d_inode;
-                if (!inode)
+                if (d_is_negative(dentry))
                         goto slashes;
                 ihold(inode);
                 error = security_path_unlink(&nd.path, dentry);
@@ -3731,8 +3708,12 @@ exit1:
         return error;
 
 slashes:
-        error = !dentry->d_inode ? -ENOENT :
-                S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
+        if (d_is_negative(dentry))
+                error = -ENOENT;
+        else if (d_is_directory(dentry) || d_is_autodir(dentry))
+                error = -EISDIR;
+        else
+                error = -ENOTDIR;
         goto exit2;
 }
 
@@ -4046,7 +4027,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                struct inode *new_dir, struct dentry *new_dentry)
 {
         int error;
-        int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
+        int is_dir = d_is_directory(old_dentry) || d_is_autodir(old_dentry);
         const unsigned char *old_name;
 
         if (old_dentry->d_inode == new_dentry->d_inode)
@@ -4134,10 +4115,10 @@ retry:
                 goto exit3;
         /* source must exist */
         error = -ENOENT;
-        if (!old_dentry->d_inode)
+        if (d_is_negative(old_dentry))
                 goto exit4;
         /* unless the source is a directory trailing slashes give -ENOTDIR */
-        if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
+        if (!d_is_directory(old_dentry) && !d_is_autodir(old_dentry)) {
                 error = -ENOTDIR;
                 if (oldnd.last.name[oldnd.last.len])
                         goto exit4;