linux-kernel - [PATCH 1 of 2] fsstack: Introduce fsstack_copy_{attr,inode}

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Message-Id: <fe7c146c6457a4b288ab.1161060147@thor.fsl.cs.sunysb.edu>
Date:	Tue, 17 Oct 2006 00:42:27 -0400
From:	Josef "Jeff" Sipek <jsipek@...sunysb.edu>
To:	linux-kernel@...r.kernel.org
Cc:	linux-fsdevel@...r.kernel.org, akpm@...l.org, torvalds@...l.org,
	hch@...radead.org, viro@....linux.org.uk, penberg@...helsinki.fi,
	mhalcrow@...ibm.com, ezk@...sunysb.edu, jengelh@...ux01.gwdg.de
Subject: [PATCH 1 of 2] fsstack: Introduce fsstack_copy_{attr,inode}_*

From: Josef "Jeff" Sipek <jsipek@...sunysb.edu>

The following patch introduces several fsstack_copy_* functions which allow
stackable filesystems (such as eCryptfs and Unionfs) to easily copy over
(currently only) inode attributes. This prevents code duplication and allows
for code reuse.

Signed-off-by: Josef "Jeff" Sipek <jsipek@...sunysb.edu>

---

3 files changed, 80 insertions(+), 1 deletion(-)
fs/Makefile              |    3 ++-
fs/stack.c               |   39 +++++++++++++++++++++++++++++++++++++++
include/linux/fs_stack.h |   39 +++++++++++++++++++++++++++++++++++++++

diff --git a/fs/Makefile b/fs/Makefile
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -10,7 +10,8 @@ obj-y :=	open.o read_write.o file_table.
 		ioctl.o readdir.o select.o fifo.o locks.o dcache.o inode.o \
 		attr.o bad_inode.o file.o filesystems.o namespace.o aio.o \
 		seq_file.o xattr.o libfs.o fs-writeback.o \
-		pnode.o drop_caches.o splice.o sync.o utimes.o
+		pnode.o drop_caches.o splice.o sync.o utimes.o \
+		stack.o
 
 ifeq ($(CONFIG_BLOCK),y)
 obj-y +=	buffer.o bio.o block_dev.o direct-io.o mpage.o ioprio.o
diff --git a/fs/stack.c b/fs/stack.c
new file mode 100644
--- /dev/null
+++ b/fs/stack.c
@@ -0,0 +1,39 @@
+#include <linux/module.h>
+#include <linux/fs.h>
+
+/* does _NOT_ require i_mutex to be held.
+ *
+ * This function cannot be inlined since i_size_{read,write} is rather
+ * heavy-weight on 32-bit systems
+ */
+void fsstack_copy_inode_size(struct inode *dst, const struct inode *src)
+{
+	i_size_write(dst, i_size_read((struct inode *)src));
+	dst->i_blocks = src->i_blocks;
+}
+
+/* copy all attributes; get_nlinks is optional way to override the i_nlink
+ * copying
+ */
+void __fsstack_copy_attr_all(struct inode *dest,
+			     const struct inode *src,
+			     int (*get_nlinks)(struct inode *))
+{
+	if (!get_nlinks)
+		dest->i_nlink = src->i_nlink;
+	else
+		dest->i_nlink = (*get_nlinks)(dest);
+
+	dest->i_mode = src->i_mode;
+	dest->i_uid = src->i_uid;
+	dest->i_gid = src->i_gid;
+	dest->i_rdev = src->i_rdev;
+	dest->i_atime = src->i_atime;
+	dest->i_mtime = src->i_mtime;
+	dest->i_ctime = src->i_ctime;
+	dest->i_blkbits = src->i_blkbits;
+	dest->i_flags = src->i_flags;
+}
+
+EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
+EXPORT_SYMBOL_GPL(__fsstack_copy_attr_all);
diff --git a/include/linux/fs_stack.h b/include/linux/fs_stack.h
new file mode 100644
--- /dev/null
+++ b/include/linux/fs_stack.h
@@ -0,0 +1,39 @@
+#ifndef _LINUX_FS_STACK_H
+#define _LINUX_FS_STACK_H
+
+/* This file defines generic functions used primarily by stackable
+ * filesystems; none of these functions require i_mutex to be held.
+ */
+
+#include <linux/fs.h>
+
+/* externs for fs/stack.c */
+extern void __fsstack_copy_attr_all(struct inode *dest,
+				    const struct inode *src,
+				    int (*get_nlinks)(struct inode *));
+
+extern void fsstack_copy_inode_size(struct inode *dst, const struct inode *src);
+
+/* inlines */
+static inline void fsstack_copy_attr_atime(struct inode *dest,
+					   const struct inode *src)
+{
+	dest->i_atime = src->i_atime;
+}
+
+static inline void fsstack_copy_attr_times(struct inode *dest,
+					   const struct inode *src)
+{
+	dest->i_atime = src->i_atime;
+	dest->i_mtime = src->i_mtime;
+	dest->i_ctime = src->i_ctime;
+}
+
+static inline void fsstack_copy_attr_all(struct inode *dest,
+					 const struct inode *src)
+{
+	__fsstack_copy_attr_all(dest, src, NULL);
+}
+
+#endif /* _LINUX_FS_STACK_H */
+


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