ovl: defer upper dir lock to tempfile link

On copy up of regular file using an O_TMPFILE, lock upper dir only
before linking the tempfile in place.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 5e8fd99557e101cfb4e83a32a5001bdcbb62aacb..28711af7f9db2cfd17316227a9349c9fa9c7e470 100644 (file)
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -316,6 +316,35 @@ static int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
        return err;
 }
 
+static int ovl_install_temp(struct dentry *workdir, struct dentry *upperdir,
+                           struct dentry *dentry,
+                           struct dentry *temp, struct kstat *pstat,
+                           bool tmpfile, struct dentry **newdentry)
+{
+       int err;
+       struct dentry *upper;
+       struct inode *udir = d_inode(upperdir);
+
+       upper = lookup_one_len(dentry->d_name.name, upperdir,
+                              dentry->d_name.len);
+       if (IS_ERR(upper))
+               return PTR_ERR(upper);
+
+       if (tmpfile)
+               err = ovl_do_link(temp, udir, upper, true);
+       else
+               err = ovl_do_rename(d_inode(workdir), temp, udir, upper, 0);
+
+       /* Restore timestamps on parent (best effort) */
+       if (!err) {
+               ovl_set_timestamps(upperdir, pstat);
+               *newdentry = dget(tmpfile ? upper : temp);
+       }
+       dput(upper);
+
+       return err;
+}
+
 static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
                              struct dentry *dentry, struct path *lowerpath,
                              struct kstat *stat, const char *link,
@@ -324,7 +353,6 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
        struct inode *wdir = workdir->d_inode;
        struct inode *udir = upperdir->d_inode;
        struct dentry *newdentry = NULL;
-       struct dentry *upper = NULL;
        struct dentry *temp = NULL;
        int err;
        const struct cred *old_creds = NULL;
@@ -371,16 +399,7 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
                BUG_ON(upperpath.dentry != NULL);
                upperpath.dentry = temp;
 
-               if (tmpfile) {
-                       inode_unlock(udir);
-                       err = ovl_copy_up_data(lowerpath, &upperpath,
-                                              stat->size);
-                       inode_lock_nested(udir, I_MUTEX_PARENT);
-               } else {
-                       err = ovl_copy_up_data(lowerpath, &upperpath,
-                                              stat->size);
-               }
-
+               err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
                if (err)
                        goto out_cleanup;
        }
@@ -408,29 +427,21 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
                        goto out_cleanup;
        }
 
-       upper = lookup_one_len(dentry->d_name.name, upperdir,
-                              dentry->d_name.len);
-       if (IS_ERR(upper)) {
-               err = PTR_ERR(upper);
-               upper = NULL;
-               goto out_cleanup;
+       if (tmpfile) {
+               inode_lock_nested(udir, I_MUTEX_PARENT);
+               err = ovl_install_temp(workdir, upperdir, dentry, temp, pstat,
+                                      tmpfile, &newdentry);
+               inode_unlock(udir);
+       } else {
+               err = ovl_install_temp(workdir, upperdir, dentry, temp, pstat,
+                                      tmpfile, &newdentry);
        }
-
-       if (tmpfile)
-               err = ovl_do_link(temp, udir, upper, true);
-       else
-               err = ovl_do_rename(wdir, temp, udir, upper, 0);
        if (err)
                goto out_cleanup;
 
-       newdentry = dget(tmpfile ? upper : temp);
        ovl_inode_update(d_inode(dentry), newdentry);
-
-       /* Restore timestamps on parent (best effort) */
-       ovl_set_timestamps(upperdir, pstat);
 out:
        dput(temp);
-       dput(upper);
        return err;
 
 out_cleanup:
@@ -496,10 +507,8 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
                        goto out_done;
                }
 
-               inode_lock_nested(upperdir->d_inode, I_MUTEX_PARENT);
                err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
                                         stat, link, &pstat, true);
-               inode_unlock(upperdir->d_inode);
                ovl_copy_up_end(dentry);
                goto out_done;
        }

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 22ed51f80e58937d955f326d1c278a89c080ce1f..c80b4bf1e64f1ce06244d98a0a8823cabdc7df8e 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -236,7 +236,6 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 {
        struct inode *upperinode = d_inode(upperdentry);
 
-       WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
        WARN_ON(OVL_I(inode)->__upperdentry);
 
        /*