[RFC][PATCH 7/12]ext4: Add the EXT4_IOC_FREE_BLOCKS_INFO ioctl

[Akira Fujita <a-fujita@rs.jp.nec.com>]

ext4: online defrag -- Add the EXT4_IOC_FREE_BLOCKS_INFO ioctl.

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

The EXT4_IOC_FREE_BLOCKS_INFO ioctl gets free extents
information of the target block group.
This ioctl is used only in the force defrag (-f).

Defragger calculates the victim extents (which will be moved
into other block group in order to make contiguous free space for the target file)
based on used/unused extents information.

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: Takashi Sato <t-sato@yk.jp.nec.com>
---
 fs/ext4/balloc.c |    2 +-
 fs/ext4/defrag.c |  112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/ext4.h   |   27 +++++++++++++
 fs/ext4/ioctl.c  |    3 +-
 4 files changed, 142 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 02068fa..64ec04c 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -919,7 +919,7 @@ static int ext4_test_allocatable(ext4_grpblk_t nr, struct buffer_head *bh)
  * bitmap on disk and the last-committed copy in journal, until we find a
  * bit free in both bitmaps.
  */
-static ext4_grpblk_t
+ext4_grpblk_t
 bitmap_search_next_usable_block(ext4_grpblk_t start, struct buffer_head *bh,
 					ext4_grpblk_t maxblocks)
 {
diff --git a/fs/ext4/defrag.c b/fs/ext4/defrag.c
index cb7d237..941414b 100644
--- a/fs/ext4/defrag.c
+++ b/fs/ext4/defrag.c
@@ -90,6 +90,102 @@ err:
 	return -EIO;
 }

+/**
+ * ext4_defrag_fblocks_distribution - Search free blocks distribution
+ *
+ * @org_inode:	original inode
+ * @ext_info:	ext4_extents_info
+ *
+ * This function returns 0 if succeed, otherwise returns error value.
+ */
+static int
+ext4_defrag_fblocks_distribution(struct inode *org_inode,
+			struct ext4_extents_info *ext_info)
+{
+	struct buffer_head *bitmap_bh = NULL;
+	struct super_block *sb = org_inode->i_sb;
+	handle_t *handle;
+	ext4_group_t group_no;
+	ext4_grpblk_t start, end;
+	ext4_fsblk_t start_block = 0;
+	int i, err;
+	int num = 0;
+	int len = 0;
+	int block_set = 0;
+	int extra_block = 0;
+
+	if (!sb) {
+		printk(KERN_ERR "ext4 defrag: Non-existent device\n");
+		return -ENOSPC;
+	}
+
+	group_no = (org_inode->i_ino - 1) / EXT4_INODES_PER_GROUP(sb);
+	start = ext_info->g_offset;
+	end = EXT4_BLOCKS_PER_GROUP(sb) - 1;
+
+	/* We consider about the boot block if bs = 1k */
+	if (sb->s_blocksize == 1024)
+		extra_block = 1;
+
+	handle = ext4_journal_start(org_inode, 1);
+	if (IS_ERR(handle)) {
+		err = PTR_ERR(handle);
+		return err;
+	}
+
+	bitmap_bh = ext4_read_block_bitmap(sb, group_no);
+	if (!bitmap_bh) {
+		err = -EIO;
+		goto out;
+	}
+
+	BUFFER_TRACE(bitmap_bh, "get undo access for new block");
+	err = ext4_journal_get_undo_access(handle, bitmap_bh);
+	if (err)
+		goto out;
+
+	for (i = start; i <= end ; i++) {
+		if (bitmap_search_next_usable_block(i, bitmap_bh, i + 1) >= 0) {
+			len++;
+			/*
+			 * Reset start_block if the free block is
+			 * the head of region.
+			 */
+			if (!block_set) {
+				start_block =
+				 i + group_no * EXT4_BLOCKS_PER_GROUP(sb) +
+				 extra_block;
+				block_set = 1;
+			}
+		} else if (len) {
+			ext_info->ext[num].start = start_block;
+			ext_info->ext[num].len = len;
+			num++;
+			len = 0;
+			block_set = 0;
+			if (num == ext_info->max_entries) {
+				ext_info->g_offset = i + 1;
+				break;
+			}
+		}
+		if (i == end && len) {
+			ext_info->ext[num].start = start_block;
+			ext_info->ext[num].len = len;
+			num++;
+		}
+	}
+
+	ext_info->entries = num;
+out:
+	ext4_journal_release_buffer(handle, bitmap_bh);
+	brelse(bitmap_bh);
+
+	if (handle)
+		ext4_journal_stop(handle);
+
+	return err;
+}
+
 int ext4_defrag_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 			unsigned long arg)
 {
@@ -125,6 +221,22 @@ int ext4_defrag_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
 		if (copy_to_user((struct ext4_group_data_info __user *)arg,
 			&grp_data, sizeof(grp_data)))
 			return -EFAULT;
+	} else if (cmd == EXT4_IOC_FREE_BLOCKS_INFO) {
+		struct ext4_extents_info ext_info;
+
+		if (copy_from_user(&ext_info,
+			(struct ext4_extents_info __user *)arg,
+			sizeof(ext_info)))
+			return -EFAULT;
+
+		BUG_ON(ext_info.ino != inode->i_ino);
+
+		err = ext4_defrag_fblocks_distribution(inode, &ext_info);
+
+		if (!err)
+			err = copy_to_user(
+				(struct ext4_extents_info __user *)arg,
+				&ext_info, sizeof(ext_info));
 	} else if (cmd == EXT4_IOC_DEFRAG) {
 		struct ext4_ext_defrag_data defrag;
 		struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index a635a76..ffe687b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -305,6 +305,7 @@ struct ext4_new_group_data {
 #define EXT4_IOC_DEFRAG			_IOW('f', 15, struct ext4_ext_defrag_data)
 #define EXT4_IOC_FIBMAP			_IOW('f', 16, ext4_fsblk_t)
 #define EXT4_IOC_GROUP_INFO		_IOW('f', 17, struct ext4_group_data_info)
+#define EXT4_IOC_FREE_BLOCKS_INFO	_IOW('f', 18, struct ext4_extents_info)

 /*
  * ioctl commands in 32 bit emulation
@@ -322,6 +323,20 @@ struct ext4_new_group_data {
 #define EXT4_IOC32_GETVERSION_OLD	FS_IOC32_GETVERSION
 #define EXT4_IOC32_SETVERSION_OLD	FS_IOC32_SETVERSION

+/*
+ * The following four macros are used for the defrag force mode.
+ *
+ * DEFRAG_MAX_ENT:	the maximum number of extents for exchanging between
+ *			kernel-space and user-space per an ioctl
+ */
+#define DEFRAG_MAX_ENT		32
+
+struct ext4_extent_data {
+	ext4_lblk_t block;		/* start logical block number */
+	ext4_fsblk_t start;		/* start physical block number */
+	int len;			/* blocks count */
+};
+
 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 */
@@ -333,6 +348,16 @@ struct ext4_group_data_info {
 	int s_inodes_per_group;		/* inodes per group */
 };

+struct ext4_extents_info {
+	unsigned long long ino;		/* inode number */
+	int max_entries;		/* maximum extents count */
+	int entries;			/* extent number/count */
+	ext4_lblk_t f_offset;		/* file offset */
+	ext4_grpblk_t g_offset;		/* group offset */
+	ext4_fsblk_t goal;		/* block offset for allocation */
+	struct ext4_extent_data ext[DEFRAG_MAX_ENT];
+};
+
 #define EXT4_TRANS_META_BLOCKS 4 /* bitmap + group desc + sb + inode */

 /*
@@ -1015,6 +1040,8 @@ extern struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
 extern int ext4_should_retry_alloc(struct super_block *sb, int *retries);
 extern void ext4_init_block_alloc_info(struct inode *);
 extern void ext4_rsv_window_add(struct super_block *sb, struct ext4_reserve_window_node *rsv);
+extern ext4_grpblk_t bitmap_search_next_usable_block(ext4_grpblk_t,
+				struct buffer_head *, ext4_grpblk_t);

 /* dir.c */
 extern int ext4_check_dir_entry(const char *, struct inode *,
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index c05502f..40bc2e1 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -258,7 +258,8 @@ setversion_out:
 	}
 	case EXT4_IOC_FIBMAP:
 	case EXT4_IOC_DEFRAG:
-	case EXT4_IOC_GROUP_INFO: {
+	case EXT4_IOC_GROUP_INFO:
+	case EXT4_IOC_FREE_BLOCKS_INFO: {
 		return ext4_defrag_ioctl(inode, filp, cmd, arg);
 	}
 	case EXT4_IOC_GROUP_ADD: {