Recently there was discussion about an "FIle Extent MAP"(FIEMAP) ioctl for efficiently mapping the extents and holes of a file. This will be many times more efficient than FIBMAP by cutting down the number of ioctls.
This patch adds the FIEMAP ioctl for ext4. The spec for the FIEMAP ioctl was posted earlier by Andreas Dilger and can be found at:

http://www.mail-archive.com/linux-ext4@vger.kernel.org/msg03944.html
Signed-off-by: Andreas Dilger <adilger@sun.com>

Signed-off-by: Kalpak Shah <kalpak.shah@sun.com> 
Index: linux-2.6.23.1/fs/ext4/ioctl.c

===================================================================

--- linux-2.6.23.1.orig/fs/ext4/ioctl.c

+++ linux-2.6.23.1/fs/ext4/ioctl.c

@@ -16,6 +16,7 @@

 #include <linux/compat.h>

 #include <linux/smp_lock.h>

 #include <asm/uaccess.h>

+#include <linux/fiemap.h>
 int ext4_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,

 		unsigned long arg)

@@ -248,6 +249,9 @@ flags_err:
 		return err;

 	}

+	case EXT4_IOC_FIEMAP: {

+		return ext4_fiemap(inode, filp, cmd, arg);

+	}
 	default:

 		return -ENOTTY;

Index: linux-2.6.23.1/include/linux/ext4_fs.h

===================================================================

--- linux-2.6.23.1.orig/include/linux/ext4_fs.h

+++ linux-2.6.23.1/include/linux/ext4_fs.h

@@ -228,15 +228,20 @@ struct ext4_new_group_data {

 #define	EXT4_IOC_SETFLAGS		FS_IOC_SETFLAGS

 #define	EXT4_IOC_GETVERSION		_IOR('f', 3, long)

 #define	EXT4_IOC_SETVERSION		_IOW('f', 4, long)

+#define EXT4_IOC_GETRSVSZ		_IOR('f', 5, long)

+#define EXT4_IOC_SETRSVSZ		_IOW('f', 6, long)

 #define EXT4_IOC_GROUP_EXTEND		_IOW('f', 7, unsigned long)

 #define EXT4_IOC_GROUP_ADD		_IOW('f', 8,struct ext4_new_group_input)

+#define EXT4_IOC_FIEMAP			_IOWR('f', 10, struct fiemap)

 #define	EXT4_IOC_GETVERSION_OLD		FS_IOC_GETVERSION

 #define	EXT4_IOC_SETVERSION_OLD		FS_IOC_SETVERSION

 #ifdef CONFIG_JBD2_DEBUG

 #define EXT4_IOC_WAIT_FOR_READONLY	_IOR('f', 99, long)

 #endif

-#de...
[ message continues ]

Please make this common - we dont want a new ioctl for every
Most of this function will be common to all IOC_FIEMAP
	struct address_space *mapping = filp->f_mapping;
	if (!mapping->a_ops->fiemap)
The common form is:
	if (fiemap_s->fm_flags & FIEMAP_FLAG_SYNC)
This becomes:
	error = mapping->a_ops->fiemap(inode, ....);
and the lock, extent walk, etc becomes ext4_fiemap() which is set up

in the a_ops for the filesystem. Any filesystems specific checks go
That's common, too.
I don't want to see this implemented over and over again with minute

variations and bugs. The common implementation should be called from

in do_file_ioctl() like FIBMAP....
Cheers,
Dave.

--

Dave Chinner

Principal Engineer

SGI Australian Software Group

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