[PATCH 02/25] vfs: reorganize do_last()

[Miklos Szeredi]

From: Miklos Szeredi <mszeredi@xxxxxxx>

Make the slow lookup part of O_CREAT and non-O_CREAT opens common.

This allows atomic_open to be hooked into the slow lookup part.

The audit_inode() from after mutex_unlock() was moved down just before the "ok:"
label.  Is this correct?

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
 fs/namei.c |   93 +++++++++++++++++++++++++++++++++++------------------------
 1 files changed, 55 insertions(+), 38 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index f9639bf..ff8bc94 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2113,6 +2113,8 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 	int want_write = 0;
 	int acc_mode = op->acc_mode;
 	struct file *filp;
+	struct inode *inode;
+	int symlink_ok = 0;
 	int error;
 
 	nd->flags &= ~LOOKUP_PARENT;
@@ -2144,47 +2146,38 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 	}
 
 	if (!(open_flag & O_CREAT)) {
-		int symlink_ok = 0;
 		if (nd->last.name[nd->last.len])
 			nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 		if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
 			symlink_ok = 1;
 		/* we _can_ be in RCU mode here */
-		error = walk_component(nd, path, &nd->last, LAST_NORM,
-					!symlink_ok);
-		if (error < 0)
-			return ERR_PTR(error);
-		if (error) /* symlink */
-			return NULL;
-		/* sayonara */
+		error = lookup_fast(nd, &nd->last, path, &inode);
+		if (error <= 0) {
+			if (error)
+				goto terminate;
+
+			goto finish_lookup;
+		}
+		/* cached lookup failed, no longer in RCU mode */
+	} else {
+		/* create side of things */
+
+		/*
+		 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
+		 * has been cleared when we got to the last component we are
+		 * about to look up
+		 */
 		error = complete_walk(nd);
 		if (error)
 			return ERR_PTR(error);
 
-		error = -ENOTDIR;
-		if (nd->flags & LOOKUP_DIRECTORY) {
-			if (!nd->inode->i_op->lookup)
-				goto exit;
-		}
-		audit_inode(pathname, nd->path.dentry);
-		goto ok;
+		audit_inode(pathname, dir);
+		error = -EISDIR;
+		/* trailing slashes? */
+		if (nd->last.name[nd->last.len])
+			goto exit;
 	}
 
-	/* create side of things */
-	/*
-	 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
-	 * cleared when we got to the last component we are about to look up
-	 */
-	error = complete_walk(nd);
-	if (error)
-		return ERR_PTR(error);
-
-	audit_inode(pathname, dir);
-	error = -EISDIR;
-	/* trailing slashes? */
-	if (nd->last.name[nd->last.len])
-		goto exit;
-
 	mutex_lock(&dir->d_inode->i_mutex);
 
 	dentry = lookup_hash(nd);
@@ -2197,9 +2190,14 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 	path->dentry = dentry;
 	path->mnt = nd->path.mnt;
 
-	/* Negative dentry, just create the file */
+	/* Negative dentry, create the file if O_CREAT */
 	if (!dentry->d_inode) {
 		umode_t mode = op->mode;
+
+		error = -ENOENT;
+		if (!(open_flag & O_CREAT))
+			goto exit_mutex_unlock;
+
 		if (!IS_POSIXACL(dir->d_inode))
 			mode &= ~current_umask();
 		/*
@@ -2233,7 +2231,6 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 	 * It already exists.
 	 */
 	mutex_unlock(&dir->d_inode->i_mutex);
-	audit_inode(pathname, path->dentry);
 
 	error = -EEXIST;
 	if (open_flag & O_EXCL)
@@ -2243,22 +2240,38 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 	if (error)
 		goto exit_dput;
 
+	inode = path->dentry->d_inode;
+finish_lookup:
 	error = -ENOENT;
-	if (!path->dentry->d_inode)
-		goto exit_dput;
+	if (!inode) {
+		path_to_nameidata(path, nd);
+		goto terminate;
+	}
 
-	if (path->dentry->d_inode->i_op->follow_link)
+	if (should_follow_link(inode, !symlink_ok)) {
+		if (nd->flags & LOOKUP_RCU) {
+			if (unlikely(unlazy_walk(nd, path->dentry))) {
+				error = -ECHILD;
+				goto terminate;
+			}
+		}
 		return NULL;
+	}
 
 	path_to_nameidata(path, nd);
-	nd->inode = path->dentry->d_inode;
-	/* Why this, you ask?  _Now_ we might have grown LOOKUP_JUMPED... */
+	nd->inode = inode;
+
 	error = complete_walk(nd);
 	if (error)
 		return ERR_PTR(error);
 	error = -EISDIR;
-	if (S_ISDIR(nd->inode->i_mode))
+	if ((open_flag & O_CREAT) && S_ISDIR(inode->i_mode))
+		goto exit;
+	error = -ENOTDIR;
+	if (nd->flags & LOOKUP_DIRECTORY && !inode->i_op->lookup)
 		goto exit;
+
+	audit_inode(pathname, nd->path.dentry);
 ok:
 	if (!S_ISREG(nd->inode->i_mode))
 		will_truncate = 0;
@@ -2303,6 +2316,10 @@ exit_dput:
 exit:
 	filp = ERR_PTR(error);
 	goto out;
+
+terminate:
+	terminate_walk(nd);
+	return ERR_PTR(error);
 }
 
 static struct file *path_openat(int dfd, const char *pathname,
-- 
1.7.7

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