Patchwork [RFC,1/12] ext4: Add the EXT4_IOC_DEFRAG ioctl and defrag main function

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Submitter Akira Fujita
Date Sept. 27, 2008, 7:26 a.m.
Message ID <48DDE02A.4000703@rs.jp.nec.com>
Download mbox | patch
Permalink /patch/1757/
State Changes Requested
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Akira Fujita - Sept. 27, 2008, 7:26 a.m.
ext4: online defrag -- Add the EXT4_IOC_DEFRAG ioctl and defrag main function.

From: Akira Fujita <a-fujita@rs.jp.nec.com>

The EXT4_IOC_DEFRAG ioctl is the main ioctl of ext4 online defrag.
Create the temporary inode in memory and allocate contiguous blocks to it.
After that exchange data blocks between original inode and temporary inode.
Lastly, remove the temporary inode which has fragmented data blocks.
This method would be done between user space and kernel space per 64MB data size.

This patch is equivalent to creating/removing a temporary inode
and common defrag functions.

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: Takashi Sato <t-sato@yk.jp.nec.com>
---
 fs/ext4/Makefile       |    2 +-
 fs/ext4/defrag.c       |  467 ++++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/ext4.h         |   14 ++
 fs/ext4/ext4_extents.h |    2 +
 fs/ext4/extents.c      |    2 +-
 fs/ext4/inode.c        |    2 +-
 fs/ext4/ioctl.c        |    3 +
 7 files changed, 489 insertions(+), 3 deletions(-)


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Patch

diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index ac6fa8c..8028102 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -6,7 +6,7 @@  obj-$(CONFIG_EXT4DEV_FS) += ext4dev.o

 ext4dev-y	:= balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
 		   ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
-		   ext4_jbd2.o migrate.o mballoc.o
+		   ext4_jbd2.o migrate.o mballoc.o defrag.o

 ext4dev-$(CONFIG_EXT4DEV_FS_XATTR)	+= xattr.o xattr_user.o xattr_trusted.o
 ext4dev-$(CONFIG_EXT4DEV_FS_POSIX_ACL)	+= acl.o
diff --git a/fs/ext4/defrag.c b/fs/ext4/defrag.c
new file mode 100644
index 0000000..1750714
--- /dev/null
+++ b/fs/ext4/defrag.c
@@ -0,0 +1,467 @@ 
+/*
+ * Copyright (c) 2008, NEC Software Tohoku, Ltd.
+ * Written by Takashi Sato <t-sato@yk.jp.nec.com>
+ *            Akira Fujita <a-fujita@rs.jp.nec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+/* Online defragmentation for EXT4 */
+
+#include <linux/quotaops.h>
+#include "ext4_jbd2.h"
+#include "ext4_extents.h"
+#include "group.h"
+
+/**
+ * ext4_defrag_next_extent - Search for the next extent and set it to "extent"
+ *
+ * @inode:	inode which is searched
+ * @path:	this will obtain data for the next extent
+ * @extent:	pointer to the next extent we have just gotten
+ *
+ * This function returns 0 or 1(last entry) if succeed, otherwise
+ * returns -EIO.
+ */
+static int
+ext4_defrag_next_extent(struct inode *inode, struct ext4_ext_path *path,
+			struct ext4_extent **extent)
+{
+	return 0;
+}
+
+int ext4_defrag_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
+			unsigned long arg)
+{
+	int err = 0;
+
+	if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)) {
+		printk(KERN_ERR "ext4 defrag: ino[%lu] is not extents "
+					"based file\n", inode->i_ino);
+		return -EOPNOTSUPP;
+	}
+
+	if (cmd == EXT4_IOC_DEFRAG) {
+		struct ext4_ext_defrag_data defrag;
+
+		if (!capable(CAP_DAC_OVERRIDE)) {
+			if ((inode->i_mode & S_IRUSR) != S_IRUSR)
+				return -EACCES;
+			if (current->fsuid != inode->i_uid)
+				return -EACCES;
+		}
+
+		if (copy_from_user(&defrag,
+			(struct ext4_ext_defrag_data __user *)arg,
+						sizeof(defrag)))
+			return -EFAULT;
+
+		err = ext4_defrag(filp, defrag.start_offset,
+				defrag.defrag_size);
+	}
+
+	return err;
+}
+
+/**
+ * ext4_defrag_partial - Defrag a file per page
+ *
+ * @tmp_inode:			temporary inode
+ * @filp:			pointer to file
+ * @org_page_offset:		page index on original file
+ * @dest_blk_offset:		block index on temporary file
+ * @data_offset_in_page:	block index where data swapping starts
+ * @block_len_in_page:		the number of blocks to be swapped
+ *
+ * This function returns 0 if succeed, otherwise returns error value.
+ */
+static int
+ext4_defrag_partial(struct inode *tmp_inode, struct file *filp,
+			pgoff_t org_page_offset, ext4_lblk_t dest_blk_offset,
+			int data_offset_in_page, int block_len_in_page)
+{
+	return 0;
+}
+
+/**
+ * ext4_defrag_new_extent_tree - Get contiguous blocks and build an extent tree
+ *
+ * @org_inode:		original inode
+ * @tmp_inode:		temporary inode
+ * @org_path:		indicating the original inode's extent
+ * @req_start:		starting offset to allocate in blocks
+ * @req_blocks:		the number of blocks to allocate
+ * @iblock:		file related offset
+ *
+ * This function returns the value as below:
+ *	0 (succeed)
+ *	1 (not improved)
+ *	negative value (error case)
+ */
+static int
+ext4_defrag_new_extent_tree(struct inode *org_inode, struct inode *tmp_inode,
+			struct ext4_ext_path *org_path, ext4_lblk_t req_start,
+			ext4_lblk_t req_blocks, ext4_lblk_t iblock)
+{
+	return 0;
+}
+
+/**
+ * ext4_defrag_check - Check the environment whether a defrag can be done
+ *
+ * @org_inode:		original inode
+ * @defrag_size:	size of defrag in blocks
+ *
+ * This function returns 0 if succeed, otherwise returns error value.
+ */
+static int
+ext4_defrag_check(struct inode *org_inode, ext4_lblk_t defrag_size)
+{
+	/* ext4 online defrag needs mballoc mount option. */
+	if (!test_opt(org_inode->i_sb, MBALLOC)) {
+		printk(KERN_ERR "ext4 defrag: multiblock allocation "
+				"is disabled\n");
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+/**
+ * ext4_defrag_init_tmp_inode - Create a temporary inode
+ *
+ * @org_inode:		original inode
+ *
+ * This function returns pointer to the struct inode if succeed,
+ * otherwise returns error value.
+ */
+static struct inode *
+ext4_defrag_init_tmp_inode(struct inode *org_inode)
+{
+	handle_t *handle;
+	struct inode *tmp_inode;
+
+	handle = ext4_journal_start(org_inode,
+		EXT4_DATA_TRANS_BLOCKS(org_inode->i_sb) +
+		EXT4_INDEX_EXTRA_TRANS_BLOCKS + 4 +
+		2 * EXT4_QUOTA_INIT_BLOCKS(org_inode->i_sb));
+	if (IS_ERR(handle))
+		/* Return error code */
+		return (struct inode *)handle;
+
+	tmp_inode = ext4_new_inode(handle,
+		org_inode->i_sb->s_root->d_inode, S_IFREG);
+	if (IS_ERR(tmp_inode))
+		goto out;
+
+	i_size_write(tmp_inode, i_size_read(org_inode));
+	tmp_inode->i_nlink = 0;
+	ext4_ext_tree_init(handle, tmp_inode);
+	ext4_orphan_add(handle, tmp_inode);
+
+out:
+	ext4_journal_stop(handle);
+
+	return tmp_inode;
+}
+
+/**
+ * ext4_defrag - Defrag the specified range of a file
+ *
+ * If no-option is specified, ext4_defrag() proceeds the following order.
+ * 1.ext4_defrag() calculates the block number where defrag terminates
+ *   by the start block number(defrag_start) and the size of defraged data
+ *   (defrag_size) specified as arguments.
+ *   If the defrag_start points a hole, the extent's start offset pointed by
+ *   ext_cur(current extent), holecheck_path, org_path are set after
+ *   hole behind.
+ * 2.Continue step 3 to step 5, until the holecheck_path points to last_extent
+ *   or the ext_cur exceeds the block_end which is last logical block number.
+ * 3.To get a length of continues area, call ext4_defrag_next_extent()
+ *   specified with the ext_cur(initial value is holecheck_path) re-cursive,
+ *   until find un-continuous extent, the start logical block number exceeds
+ *   the block_end or the extent points to the last extent.
+ * 4.After determining the length of continuous block,
+ *   allocates continuous blocks to a temporary inode
+ *   by ext4_defrag_new_extent_tree().
+ * 5.Exchange the original inode data with temporary inode data
+ *   from org_page_offset to seq_end_page.
+ *   The start indexes of data are specified as arguments.
+ *   That of the original inode is org_page_offset,
+ *   and that of the temporary inode is dest_block_offset
+ *   (To easily handle blocksize != pagesize case, the offset for the
+ *    temporary inode is block unit).
+ * 6.Update holecheck_path and org_path to points a next proceeding extent,
+ *   and release the temporary inode holding the original fragmented data.
+ *   Then, returns to step 2.
+ * 7.Release holecheck_path, org_path and temporary inode,
+ *    and returns the defrag_size which is the size of defraged data.
+ *    The defrag_size is used for the command to calculate the file offset
+ *    where a next defrag processing start.
+ *    (Since the defrag command calls defrag_ioctl() by 64MB unit,
+ *     a file bigger than 64MB calls defrag_ioctl many times.)
+ *
+ * @filp:		pointer to file
+ * @block_start:	starting offset to defrag in blocks
+ * @defrag_size:	size of defrag in blocks
+ *
+ * This function returns the number of blocks if succeed, otherwise
+ * returns error value.
+ */
+int
+ext4_defrag(struct file *filp, ext4_lblk_t block_start,
+		ext4_lblk_t defrag_size)
+{
+	struct inode *org_inode = filp->f_dentry->d_inode, *tmp_inode = NULL;
+	struct ext4_ext_path *org_path = NULL, *holecheck_path = NULL;
+	struct ext4_extent *ext_prev, *ext_cur, *ext_dummy;
+	ext4_lblk_t block_end, seq_start, add_blocks, file_end, seq_blocks = 0;
+	ext4_lblk_t dest_block_offset;
+	ext4_lblk_t rest_blocks;
+	pgoff_t org_page_offset, seq_end_page;
+	int ret, depth, seq_extents, last_extent = 0;
+	int blocks_per_page;
+	int data_offset_in_page;
+	int block_len_in_page;
+
+	/* Check the filesystem environment whether defrag can be done */
+	ret = ext4_defrag_check(org_inode, defrag_size);
+	if (ret < 0)
+		return ret;
+
+	blocks_per_page = PAGE_CACHE_SIZE >> org_inode->i_blkbits;
+	file_end = (org_inode->i_size - 1) >> org_inode->i_blkbits;
+	block_end = block_start + defrag_size - 1;
+	if (file_end < block_end)
+		defrag_size -= block_end - file_end;
+
+	mutex_lock(&org_inode->i_mutex);
+	down_write(&EXT4_I(org_inode)->i_data_sem);
+
+	org_path = ext4_ext_find_extent(org_inode, block_start, NULL);
+	if (IS_ERR(org_path)) {
+		ret = PTR_ERR(org_path);
+		org_path = NULL;
+		goto out;
+	}
+
+	/* Get path structure to check the hole */
+	holecheck_path = ext4_ext_find_extent(org_inode, block_start, NULL);
+	if (IS_ERR(holecheck_path)) {
+		ret = PTR_ERR(holecheck_path);
+		holecheck_path = NULL;
+		goto out;
+	}
+
+	depth = ext_depth(org_inode);
+	ext_cur = holecheck_path[depth].p_ext;
+	if (ext_cur == NULL)
+		goto out;
+
+	/*
+	 * Get proper extent whose ee_block is beyond block_start
+	 * if block_start was within the hole.
+	 */
+	if (le32_to_cpu(ext_cur->ee_block) +
+		le16_to_cpu(ext_cur->ee_len) - 1 < block_start) {
+		last_extent = ext4_defrag_next_extent(org_inode,
+					holecheck_path, &ext_cur);
+		if (last_extent < 0) {
+			ret = last_extent;
+			goto out;
+		}
+		last_extent = ext4_defrag_next_extent(org_inode, org_path,
+							&ext_dummy);
+		if (last_extent < 0) {
+			ret = last_extent;
+			goto out;
+		}
+	}
+	seq_extents = 1;
+	seq_start = le32_to_cpu(ext_cur->ee_block);
+
+	/* No blocks within the specified range. */
+	if (le32_to_cpu(ext_cur->ee_block) > block_end) {
+		printk(KERN_INFO "ext4 defrag: The specified range of file"
+				" may be the hole\n");
+		goto out;
+	}
+
+	/* Adjust start blocks */
+	add_blocks = min(le32_to_cpu(ext_cur->ee_block) +
+			 le16_to_cpu(ext_cur->ee_len), block_end + 1) -
+		     max(le32_to_cpu(ext_cur->ee_block), block_start);
+
+	while (!last_extent && le32_to_cpu(ext_cur->ee_block) <= block_end) {
+		seq_blocks += add_blocks;
+
+		/* Create a temporary inode to be exchanged data block */
+		tmp_inode = ext4_defrag_init_tmp_inode(org_inode);
+		if (IS_ERR(tmp_inode)) {
+			ret = PTR_ERR(tmp_inode);
+			tmp_inode = NULL;
+			goto out;
+		}
+
+		/* Adjust tail blocks */
+		if (seq_start + seq_blocks - 1 > block_end)
+			seq_blocks = block_end - seq_start + 1;
+
+		ext_prev = ext_cur;
+		last_extent = ext4_defrag_next_extent(org_inode,
+					holecheck_path, &ext_cur);
+		if (last_extent < 0) {
+			ret = last_extent;
+			break;
+		}
+		if (!last_extent)
+			seq_extents++;
+		add_blocks = le16_to_cpu(ext_cur->ee_len);
+
+		/*
+		 * Extend the length of contiguous block (seq_blocks)
+		 * if extents are contiguous.
+		 */
+		if (le32_to_cpu(ext_prev->ee_block) +
+				le16_to_cpu(ext_prev->ee_len) ==
+				le32_to_cpu(ext_cur->ee_block) &&
+				block_end >= le32_to_cpu(ext_cur->ee_block) &&
+				!last_extent) {
+			if (tmp_inode) {
+				iput(tmp_inode);
+				tmp_inode = NULL;
+			}
+			continue;
+		}
+
+		/* Found an isolated block */
+		if (seq_extents == 1) {
+			seq_start = le32_to_cpu(ext_cur->ee_block);
+			goto CLEANUP;
+		}
+
+		ret = ext4_defrag_new_extent_tree(org_inode, tmp_inode,
+					org_path, seq_start, seq_blocks,
+					block_start);
+
+		if (ret < 0) {
+			break;
+		} else if (ret == 1) {
+			ret = 0;
+			seq_start = le32_to_cpu(ext_cur->ee_block);
+			goto CLEANUP;
+		}
+
+		data_offset_in_page = seq_start % blocks_per_page;
+
+		/*
+		 * Calculate data blocks count that should be swapped
+		 * at the first page.
+		 */
+		if (data_offset_in_page + seq_blocks > blocks_per_page) {
+			/* Swapped blocks are across pages */
+			block_len_in_page =
+					blocks_per_page - data_offset_in_page;
+		} else {
+			/* Swapped blocks are in a page */
+			block_len_in_page = seq_blocks;
+		}
+
+		org_page_offset = seq_start >>
+				(PAGE_CACHE_SHIFT - org_inode->i_blkbits);
+		seq_end_page = (seq_start + seq_blocks - 1) >>
+				(PAGE_CACHE_SHIFT - org_inode->i_blkbits);
+		seq_start = le32_to_cpu(ext_cur->ee_block);
+		rest_blocks = seq_blocks;
+		/* Offset for the tmp_inode */
+		dest_block_offset = 0;
+
+		/*
+		 * Discard all preallocations.
+		 * This is provisional solution.
+		 * When true ext4_mb_return_to_preallocation() is
+		 * implemented, this will be removed.
+		 */
+		ext4_mb_discard_inode_preallocations(org_inode);
+
+		while (org_page_offset <= seq_end_page) {
+
+			/* Swap original branches with new branches */
+			ret = ext4_defrag_partial(tmp_inode, filp,
+						org_page_offset,
+						dest_block_offset,
+						data_offset_in_page,
+						block_len_in_page);
+			if (ret < 0)
+				goto out;
+
+			org_page_offset++;
+			dest_block_offset += block_len_in_page;
+
+			data_offset_in_page = 0;
+			rest_blocks -= block_len_in_page;
+			if (rest_blocks > blocks_per_page)
+				block_len_in_page = blocks_per_page;
+			else
+				block_len_in_page = rest_blocks;
+		}
+
+		/* Decrease buffer counter */
+		if (holecheck_path)
+			ext4_ext_drop_refs(holecheck_path);
+		holecheck_path = ext4_ext_find_extent(org_inode,
+						seq_start, holecheck_path);
+		if (IS_ERR(holecheck_path)) {
+			ret = PTR_ERR(holecheck_path);
+			holecheck_path = NULL;
+			break;
+		}
+		depth = holecheck_path->p_depth;
+
+CLEANUP:
+		/* Decrease buffer counter */
+		if (org_path)
+			ext4_ext_drop_refs(org_path);
+		org_path = ext4_ext_find_extent(org_inode, seq_start, org_path);
+		if (IS_ERR(org_path)) {
+			ret = PTR_ERR(org_path);
+			org_path = NULL;
+			break;
+		}
+
+		ext_cur = holecheck_path[depth].p_ext;
+		add_blocks = le16_to_cpu(ext_cur->ee_len);
+		seq_blocks = 0;
+		seq_extents = 1;
+
+		if (tmp_inode) {
+			iput(tmp_inode);
+			tmp_inode = NULL;
+		}
+	}
+
+out:
+	if (org_path) {
+		ext4_ext_drop_refs(org_path);
+		kfree(org_path);
+	}
+	if (holecheck_path) {
+		ext4_ext_drop_refs(holecheck_path);
+		kfree(holecheck_path);
+	}
+
+	up_write(&EXT4_I(org_inode)->i_data_sem);
+	mutex_unlock(&org_inode->i_mutex);
+
+	if (tmp_inode)
+		iput(tmp_inode);
+
+	return ret ? ret : defrag_size;
+}
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index c8ab668..64c61ae 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -302,6 +302,7 @@  struct ext4_new_group_data {
 #define EXT4_IOC_GROUP_ADD		_IOW('f', 8, struct ext4_new_group_input)
 #define EXT4_IOC_MIGRATE		_IO('f', 9)
  /* note ioctl 11 reserved for filesystem-independent FIEMAP ioctl */
+#define EXT4_IOC_DEFRAG			_IOW('f', 15, struct ext4_ext_defrag_data)

 /*
  * ioctl commands in 32 bit emulation
@@ -319,6 +320,12 @@  struct ext4_new_group_data {
 #define EXT4_IOC32_GETVERSION_OLD	FS_IOC32_GETVERSION
 #define EXT4_IOC32_SETVERSION_OLD	FS_IOC32_SETVERSION

+struct ext4_ext_defrag_data {
+	ext4_lblk_t start_offset;	/* start offset to defrag in blocks */
+	ext4_lblk_t defrag_size;	/* size of defrag in blocks */
+	ext4_fsblk_t goal;		/* block offset for allocation */
+};
+

 /*
  *  Mount options
@@ -1081,6 +1088,8 @@  extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
 extern int ext4_block_truncate_page(handle_t *handle,
 		struct address_space *mapping, loff_t from);
 extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct page *page);
+extern int ext4_get_block(struct inode *inode, sector_t iblock,
+		struct buffer_head *bh_result, int create);

 /* ioctl.c */
 extern long ext4_ioctl(struct file *, unsigned int, unsigned long);
@@ -1128,6 +1137,11 @@  extern void ext4_inode_bitmap_set(struct super_block *sb,
 				  struct ext4_group_desc *bg, ext4_fsblk_t blk);
 extern void ext4_inode_table_set(struct super_block *sb,
 				 struct ext4_group_desc *bg, ext4_fsblk_t blk);
+/* defrag.c */
+extern int ext4_defrag(struct file *filp, ext4_lblk_t block_start,
+			ext4_lblk_t defrag_size);
+extern int ext4_defrag_ioctl(struct inode *, struct file *, unsigned int,
+				unsigned long);

 static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es)
 {
diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index bec7ce5..0325158 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -246,5 +246,7 @@  extern int ext4_ext_search_left(struct inode *, struct ext4_ext_path *,
 extern int ext4_ext_search_right(struct inode *, struct ext4_ext_path *,
 						ext4_lblk_t *, ext4_fsblk_t *);
 extern void ext4_ext_drop_refs(struct ext4_ext_path *);
+extern ext4_fsblk_t ext_pblock(struct ext4_extent *ex);
+extern void ext4_ext_drop_refs(struct ext4_ext_path *path);
 #endif /* _EXT4_EXTENTS */

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 3094ed3..d05dfb7 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -49,7 +49,7 @@ 
  * ext_pblock:
  * combine low and high parts of physical block number into ext4_fsblk_t
  */
-static ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
+ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
 {
 	ext4_fsblk_t block;

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9764b79..9b0117c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1161,7 +1161,7 @@  int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
 /* Maximum number of blocks we map for direct IO at once. */
 #define DIO_MAX_BLOCKS 4096

-static int ext4_get_block(struct inode *inode, sector_t iblock,
+int ext4_get_block(struct inode *inode, sector_t iblock,
 			struct buffer_head *bh_result, int create)
 {
 	handle_t *handle = ext4_journal_current_handle();
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 3e14060..1c25e8e 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -256,6 +256,9 @@  setversion_out:

 		return err;
 	}
+	case EXT4_IOC_DEFRAG: {
+		return ext4_defrag_ioctl(inode, filp, cmd, arg);
+	}
 	case EXT4_IOC_GROUP_ADD: {
 		struct ext4_new_group_data input;
 		struct super_block *sb = inode->i_sb;