overlayfs copy_up recursive

overlayfs copy_up recursive

[Jordi Pujol]

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Hello,

this patch recodes ovl_copy_up and ovl_copy_up_truncate as a recursive 
routine,
there is less code and less number of instructions to execute, therefore maybe 
faster and easy to mantain,

I have tested it, that works,

Thanks,

Jordi Pujol

Live never ending Tale
GNU/Linux Live forever!
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[-- Attachment #2: 08-copy-up-recursive.patch --]
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--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -315,69 +315,46 @@ out_free_link:
 	return err;
 }
 
-int ovl_copy_up(struct dentry *dentry)
+/* Optimize by not copying up the file first and truncating later */
+int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
 {
 	int err;
+	struct dentry *actual;
+	struct dentry *parent;
+	struct path lowerpath;
+	struct kstat stat;
+	enum ovl_path_type type;
 
 	err = 0;
-	while (!err) {
-		struct dentry *next;
-		struct dentry *parent;
-		struct path lowerpath;
-		struct kstat stat;
-		enum ovl_path_type type = ovl_path_type(dentry);
-
-		if (type != OVL_PATH_LOWER)
-			break;
-
-		next = dget(dentry);
-		/* find the topmost dentry not yet copied up */
-		for (;;) {
-			parent = dget_parent(next);
-
-			type = ovl_path_type(parent);
-			if (type != OVL_PATH_LOWER)
-				break;
 
-			dput(next);
-			next = parent;
-		}
+	actual = dget(dentry);
+	type = ovl_path_type(actual);
+	if (type != OVL_PATH_LOWER)
+		goto out;
+
+	/* if the parent is not yet copied up, copy it now recursively */
+	err = ovl_copy_up_truncate(actual->d_parent, -1LL);
+	if (!err) {
+		parent = dget_parent(actual);
 
-		ovl_path_lower(next, &lowerpath);
+		ovl_path_lower(actual, &lowerpath);
 		err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
-		if (!err)
-			err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
+		if (!err) {
+			if (size >= 0 && size < stat.size)
+				stat.size = size;
+			err = ovl_copy_up_one(parent, actual, &lowerpath, &stat);
+		}
 
 		dput(parent);
-		dput(next);
 	}
 
+out:
+	dput(actual);
+
 	return err;
 }
 
-/* Optimize by not copying up the file first and truncating later */
-int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
+int ovl_copy_up(struct dentry *dentry)
 {
-	int err;
-	struct kstat stat;
-	struct path lowerpath;
-	struct dentry *parent = dget_parent(dentry);
-
-	err = ovl_copy_up(parent);
-	if (err)
-		goto out_dput_parent;
-
-	ovl_path_lower(dentry, &lowerpath);
-	err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
-	if (err)
-		goto out_dput_parent;
-
-	if (size < stat.size)
-		stat.size = size;
-
-	err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
-
-out_dput_parent:
-	dput(parent);
-	return err;
+	return ovl_copy_up_truncate(dentry, -1LL);
 }

Re: overlayfs copy_up recursive

[Miklos Szeredi]

Jordi Pujol <jordipujolp@gmail.com> writes:

> Hello,
>
> this patch recodes ovl_copy_up and ovl_copy_up_truncate as a recursive
> routine, there is less code and less number of instructions to
> execute, therefore maybe faster and easy to mantain,

Recursion depth in the kernel must be limited because of a very small
stack compared to userspace.  So unfortunately it's not an option here.

Thanks,
Miklos