[RFC][PATCH 6/9]ext4: Add the EXT4_IOC_FREE_BLOCKS_INFO ioctl

[RFC][PATCH 6/9]ext4: Add the EXT4_IOC_FREE_BLOCKS_INFO ioctl

[Akira Fujita]

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.

ext4_defrag_fblocks_distribution() was renamed as ext4_mb_search_free_extents()
and moved into mballoc.c.  Because it uses ext4_buddy structure.

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: Takashi Sato <t-sato@yk.jp.nec.com>
---
 fs/ext4/ext4.h    |   27 +++++++++++++++++
 fs/ext4/ioctl.c   |   20 +++++++++++++
 fs/ext4/mballoc.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 128 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 94c4186..f7b092d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -304,6 +304,7 @@ struct ext4_new_group_data {
  /* note ioctl 11 reserved for filesystem-independent FIEMAP ioctl */
 #define EXT4_IOC_DEFRAG			_IOW('f', 15, struct ext4_ext_defrag_data)
 #define EXT4_IOC_SUPER_INFO		_IOR('f', 16, struct ext4_super_block)
+#define EXT4_IOC_FREE_BLOCKS_INFO	_IOWR('f', 17, struct ext4_extents_info)

 /*
  * ioctl commands in 32 bit emulation
@@ -321,12 +322,36 @@ 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 */
 	ext4_fsblk_t goal;		/* block offset for allocation */
 };

+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 */

 /*
@@ -1069,6 +1094,8 @@ extern int ext4_mb_add_more_groupinfo(struct super_block *sb,
 		ext4_group_t i, struct ext4_group_desc *desc);
 extern void ext4_mb_update_group_info(struct ext4_group_info *grp,
 		ext4_grpblk_t add);
+extern int ext4_mb_search_free_extents(struct inode *inode,
+					struct ext4_extents_info *ext_info);


 /* inode.c */
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index f8ce89b..5709574 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -256,6 +256,26 @@ setversion_out:
 			return 0;
 	}

+	case EXT4_IOC_FREE_BLOCKS_INFO: {
+		struct ext4_extents_info ext_info;
+		int err;
+
+		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_mb_search_free_extents(inode, &ext_info);
+
+		if (!err)
+			err = copy_to_user(
+			(struct ext4_extents_info __user *)arg,
+				&ext_info, sizeof(ext_info));
+		return err;
+	}
+
 	case EXT4_IOC_GROUP_ADD: {
 		struct ext4_new_group_data input;
 		struct super_block *sb = inode->i_sb;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index dfe17a1..eebcf7c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4654,3 +4654,84 @@ error_return:
 		kmem_cache_free(ext4_ac_cachep, ac);
 	return;
 }
+
+/**
+ * ext4_mb_search_free_extents
+ *    - Search free extents in the block group where target inode is located
+ *
+ * @inode:	target inode
+ * @ext_info:	ext4_extents_info is used to store free extents
+ *
+ * This function returns 0 if succeed, otherwise returns error value.
+ */
+int
+ext4_mb_search_free_extents(struct inode *inode,
+			struct ext4_extents_info *ext_info)
+{
+	struct super_block *sb = inode->i_sb;
+	struct ext4_buddy e4b;
+	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 = (inode->i_ino - 1) / EXT4_INODES_PER_GROUP(sb);
+	start = ext_info->g_offset;
+	end = EXT4_BLOCKS_PER_GROUP(sb) - 1;
+
+	err = ext4_mb_load_buddy(sb, group_no, &e4b);
+	if (err)
+		return err;
+
+	/* We consider about the boot block if bs = 1k */
+	if (sb->s_blocksize == 1024)
+		extra_block = 1;
+
+	ext4_lock_group(sb, group_no);
+
+	for (i = start; i <= end ; i++) {
+		if (!mb_test_bit(i, e4b.bd_bitmap)) {
+			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;
+
+	ext4_unlock_group(sb, group_no);
+	ext4_mb_release_desc(&e4b);
+
+	return err;
+}