untangle the "need_reval_dot" mess

instead of ad-hackery around need_reval_dot(), do the following:
set a flag (LOOKUP_JUMPED) in the beginning of path, on absolute
symlink traversal, on ".." and on procfs-style symlinks.  Clear on
normal components, leave unchanged on ".".  Non-nested callers of
link_path_walk() call handle_reval_path(), which checks that flag
is set and that fs does want the final revalidate thing, then does
->d_revalidate().  In link_path_walk() all the return_reval stuff
is gone.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namei.c b/fs/namei.c
index 4521b5f..450b686 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -613,19 +613,8 @@ do_revalidate_rcu(struct dentry *dentry, struct nameidata *nd)
        return dentry;
 }
 
-static inline int need_reval_dot(struct dentry *dentry)
-{
-       if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
-               return 0;
-
-       if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
-               return 0;
-
-       return 1;
-}
-
 /*
- * force_reval_path - force revalidation of a dentry
+ * handle_reval_path - force revalidation of a dentry
  *
  * In some situations the path walking code will trust dentries without
  * revalidating them. This causes problems for filesystems that depend on
@@ -639,27 +628,28 @@ static inline int need_reval_dot(struct dentry *dentry)
  * invalidate the dentry. It's up to the caller to handle putting references
  * to the path if necessary.
  */
-static int
-force_reval_path(struct path *path, struct nameidata *nd)
+static inline int handle_reval_path(struct nameidata *nd)
 {
+       struct dentry *dentry = nd->path.dentry;
        int status;
-       struct dentry *dentry = path->dentry;
 
-       /*
-        * only check on filesystems where it's possible for the dentry to
-        * become stale.
-        */
-       if (!need_reval_dot(dentry))
+       if (likely(!(nd->flags & LOOKUP_JUMPED)))
+               return 0;
+
+       if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
                return 0;
 
+       if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
+               return 0;
+
+       /* Note: we do not d_invalidate() */
        status = d_revalidate(dentry, nd);
        if (status > 0)
                return 0;
 
-       if (!status) {
-               d_invalidate(dentry);
+       if (!status)
                status = -ESTALE;
-       }
+
        return status;
 }
 
@@ -728,6 +718,7 @@ static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *l
                path_put(&nd->path);
                nd->path = nd->root;
                path_get(&nd->root);
+               nd->flags |= LOOKUP_JUMPED;
        }
        nd->inode = nd->path.dentry->d_inode;
 
@@ -779,11 +770,8 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
                error = 0;
                if (s)
                        error = __vfs_follow_link(nd, s);
-               else if (nd->last_type == LAST_BIND) {
-                       error = force_reval_path(&nd->path, nd);
-                       if (error)
-                               path_put(&nd->path);
-               }
+               else if (nd->last_type == LAST_BIND)
+                       nd->flags |= LOOKUP_JUMPED;
        }
        return error;
 }
@@ -1351,7 +1339,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
        while (*name=='/')
                name++;
        if (!*name)
-               goto return_reval;
+               goto return_base;
 
        if (nd->depth)
                lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
@@ -1385,12 +1373,16 @@ static int link_path_walk(const char *name, struct nameidata *nd)
                type = LAST_NORM;
                if (this.name[0] == '.') switch (this.len) {
                        case 2:
-                               if (this.name[1] == '.')
+                               if (this.name[1] == '.') {
                                        type = LAST_DOTDOT;
+                                       nd->flags |= LOOKUP_JUMPED;
+                               }
                                break;
                        case 1:
                                type = LAST_DOT;
                }
+               if (likely(type == LAST_NORM))
+                       nd->flags &= ~LOOKUP_JUMPED;
 
                /* remove trailing slashes? */
                if (!c)
@@ -1456,7 +1448,7 @@ last_component:
                                } else
                                        follow_dotdot(nd);
                        }
-                       goto return_reval;
+                       goto return_base;
                }
                err = do_lookup(nd, &this, &next, &inode);
                if (err)
@@ -1483,24 +1475,6 @@ last_component:
 lookup_parent:
                nd->last = this;
                nd->last_type = type;
-               if (type == LAST_NORM)
-                       goto return_base;
-return_reval:
-               /*
-                * We bypassed the ordinary revalidation routines.
-                * We may need to check the cached dentry for staleness.
-                */
-               if (need_reval_dot(nd->path.dentry)) {
-                       if (nameidata_drop_rcu_last_maybe(nd))
-                               return -ECHILD;
-                       /* Note: we do not d_invalidate() */
-                       err = d_revalidate(nd->path.dentry, nd);
-                       if (!err)
-                               err = -ESTALE;
-                       if (err < 0)
-                               break;
-                       return 0;
-               }
 return_base:
                if (nameidata_drop_rcu_last_maybe(nd))
                        return -ECHILD;
@@ -1523,7 +1497,7 @@ static int path_init(int dfd, const char *name, unsigned int flags, struct namei
        struct file *file;
 
        nd->last_type = LAST_ROOT; /* if there are only slashes... */
-       nd->flags = flags;
+       nd->flags = flags | LOOKUP_JUMPED;
        nd->depth = 0;
        nd->root.mnt = NULL;
        nd->file = NULL;
@@ -1630,6 +1604,9 @@ static int path_lookupat(int dfd, const char *name,
                br_read_unlock(vfsmount_lock);
        }
 
+       if (!retval)
+               retval = handle_reval_path(nd);
+
        if (nd->file) {
                fput(nd->file);
                nd->file = NULL;
@@ -1690,7 +1667,7 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
 
        /* same as do_path_lookup */
        nd->last_type = LAST_ROOT;
-       nd->flags = flags;
+       nd->flags = flags | LOOKUP_JUMPED;
        nd->depth = 0;
 
        nd->path.dentry = dentry;
@@ -1703,6 +1680,8 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
        current->total_link_count = 0;
 
        result = link_path_walk(name, nd);
+       if (!result)
+               result = handle_reval_path(nd);
        if (result == -ESTALE) {
                /* nd->path had been dropped */
                current->total_link_count = 0;
@@ -1710,8 +1689,11 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
                nd->path.mnt = mnt;
                nd->inode = dentry->d_inode;
                path_get(&nd->path);
-               nd->flags |= LOOKUP_REVAL;
+               nd->flags = flags | LOOKUP_JUMPED | LOOKUP_REVAL;
+
                result = link_path_walk(name, nd);
+               if (!result)
+                       result = handle_reval_path(nd);
        }
        if (unlikely(!result && !audit_dummy_context() && nd->path.dentry &&
                                nd->inode))
@@ -2198,30 +2180,29 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 {
        struct dentry *dir = nd->path.dentry;
        struct file *filp;
-       int error = -EISDIR;
+       int error;
 
        switch (nd->last_type) {
        case LAST_DOTDOT:
                follow_dotdot(nd);
                dir = nd->path.dentry;
        case LAST_DOT:
-               if (need_reval_dot(dir)) {
-                       int status = d_revalidate(nd->path.dentry, nd);
-                       if (!status)
-                               status = -ESTALE;
-                       if (status < 0) {
-                               error = status;
-                               goto exit;
-                       }
-               }
                /* fallthrough */
        case LAST_ROOT:
+               error = handle_reval_path(nd);
+               if (error)
+                       goto exit;
+               error = -EISDIR;
                goto exit;
        case LAST_BIND:
+               error = handle_reval_path(nd);
+               if (error)
+                       goto exit;
                audit_inode(pathname, dir);
                goto ok;
        }
 
+       error = -EISDIR;
        /* trailing slashes? */
        if (nd->last.name[nd->last.len])
                goto exit;
@@ -2422,7 +2403,7 @@ reval:
        /*
         * We have the parent and last component.
         */
-       nd.flags = flags;
+       nd.flags = (nd.flags & ~LOOKUP_PARENT) | flags;
        filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
        while (unlikely(!filp)) { /* trailing symlink */
                struct path link = path;

diff --git a/include/linux/namei.h b/include/linux/namei.h
index 58ce343..265378a 100644 (file)
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -63,6 +63,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
 #define LOOKUP_EXCL            0x0400
 #define LOOKUP_RENAME_TARGET   0x0800
 
+#define LOOKUP_JUMPED          0x1000
+
 extern int user_path_at(int, const char __user *, unsigned, struct path *);
 
 #define user_path(name, path) user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW, path)