[PATCH 1 of 2] fsstack: Introduce fsstack_copy_{attr,inode}_*

[PATCH 1 of 2] fsstack: Introduce fsstack_copy_{attr,inode}_*

[Josef Jeff Sipek]

From: Josef "Jeff" Sipek <jsipek@cs.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@cs.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 */
+

Re: [PATCH 1 of 2] fsstack: Introduce fsstack_copy_{attr,inode}_*

[Jan Engelhardt]

>To: null@josefsipek.net

(Superb idea to prekill any Cc, re-adding them)

>+void __fsstack_copy_attr_all(struct inode *dest,
>+			     const struct inode *src,
>+			     int (*get_nlinks)(struct inode *))
>+{
>[big]
>+}
>+
>+/* externs for fs/stack.c */
>+extern void __fsstack_copy_attr_all(struct inode *dest,
>+				    const struct inode *src,
>+				    int (*get_nlinks)(struct inode *));
>+
>+static inline void fsstack_copy_attr_all(struct inode *dest,
>+					 const struct inode *src)
>+{
>+	__fsstack_copy_attr_all(dest, src, NULL);
>+}

Do we really need this indirection? Can't __fsstack_copy_attr_all be 
named fsstack_copy_attr_all instead?


	-`J'
-- 

Re: [PATCH 1 of 2] fsstack: Introduce fsstack_copy_{attr,inode}_*

[Josef Sipek]

On Tue, Oct 17, 2006 at 12:40:31PM +0200, Jan Engelhardt wrote:
> 
> >To: null@josefsipek.net
> 
> (Superb idea to prekill any Cc, re-adding them)
 
Yeah, I like to test the emails but I accidentally sent them. From now on,
no testing :)
 
> >+void __fsstack_copy_attr_all(struct inode *dest,
> >+			     const struct inode *src,
> >+			     int (*get_nlinks)(struct inode *))
> >+{
> >[big]
> >+}
> >+
> >+/* externs for fs/stack.c */
> >+extern void __fsstack_copy_attr_all(struct inode *dest,
> >+				    const struct inode *src,
> >+				    int (*get_nlinks)(struct inode *));
> >+
> >+static inline void fsstack_copy_attr_all(struct inode *dest,
> >+					 const struct inode *src)
> >+{
> >+	__fsstack_copy_attr_all(dest, src, NULL);
> >+}
> 
> Do we really need this indirection? Can't __fsstack_copy_attr_all be 
> named fsstack_copy_attr_all instead?

I suppose it could. There is no API-breakage to avoid.

Josef "Jeff" Sipek.

-- 
Computer Science is no more about computers than astronomy is about
telescopes.
		- Edsger Dijkstra