[PATCH 0/3 ver. 7] Ext3/Ext4 Batched discard support

[PATCH 0/3 ver. 7] Ext3/Ext4 Batched discard support

[Lukas Czerner]

Hi all,

this is "hopefully" the final version of the patch set, since it looks like
everyone agree with this. Since the last version some simple fixes was done.

- As Jan noticed it should subtract the s_first_data_block before modulo when
computing the group starting block.
- As Dimitry proposed cond_reshed() is really useless in the ext4_trim_extent
and rescheduling should be done in the ext4_trim_all_free.

Also from previous version it supports "partial" fs discard see [PATCH 1/3].

The patch set consist of these three patches. Second and third patch are
independent on each other and dependent on the first patch.

[PATCH 1/3] Add ioctl FITRIM.
[PATCH 2/3] Add batched discard support for ext3
[PATCH 3/3] Add batched discard support for ext4

Regards
-Lukas

---
 fs/ext3/balloc.c        |  250 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/super.c         |    1 +
 fs/ext4/ext4.h          |    2 +
 fs/ext4/mballoc.c       |  200 +++++++++++++++++++++++++++++++++++++
 fs/ext4/super.c         |    1 +
 fs/ioctl.c              |   34 +++++++
 include/linux/ext3_fs.h |    1 +
 include/linux/fs.h      |    2 +
 8 files changed, 491 insertions(+), 0 deletions(-)

[PATCH 1/3] Add ioctl FITRIM.

[Lukas Czerner]

Adds an filesystem independent ioctl to allow implementation of file
system batched discard support. It takes an array of three uint64_t
as an argument, the meaning of each item is as follows:

array[0] - (start) first Byte to trim
array[1] - (len) number of Bytes to trim from start
array[2] - (minlen) minimum extent length to trim, free extents shorter
than this number of Bytes will be ignored. This number will be rounded
up to the block size.

It is also possible to specify NULL as an argument. In this case the
arguments will set itself as follows:

args[0] = 0;
args[1] = ULLONG_MAX;
args[2] = 0;

So it will trim the whole file system at one run.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ioctl.c         |   34 ++++++++++++++++++++++++++++++++++
 include/linux/fs.h |    2 ++
 2 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 2d140a7..a0e243c 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -540,6 +540,36 @@ static int ioctl_fsthaw(struct file *filp)
 	return thaw_super(sb);
 }
 
+static int ioctl_fstrim(struct file *filp, void __user *argp)
+{
+	struct super_block *sb = filp->f_path.dentry->d_inode->i_sb;
+	uint64_t args[3];
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	/* If filesystem doesn't support trim feature, return. */
+	if (sb->s_op->trim_fs == NULL)
+		return -EOPNOTSUPP;
+
+	/* If a blockdevice-backed filesystem isn't specified, return EINVAL. */
+	if (sb->s_bdev == NULL)
+		return -EINVAL;
+
+	if (argp == NULL) {
+		args[0] = 0;
+		args[1] = ULLONG_MAX;
+		args[2] = 0;
+	} else if (copy_from_user(args, argp, sizeof(args)))
+		return -EFAULT;
+
+	err = sb->s_op->trim_fs(sb, args[0], args[1], args[2]);
+	if (err)
+		return err;
+	return 0;
+}
+
 /*
  * When you add any new common ioctls to the switches above and below
  * please update compat_sys_ioctl() too.
@@ -590,6 +620,10 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 		error = ioctl_fsthaw(filp);
 		break;
 
+	case FITRIM:
+		error = ioctl_fstrim(filp, argp);
+		break;
+
 	case FS_IOC_FIEMAP:
 		return ioctl_fiemap(filp, arg);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e5106e4..0cc196f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -316,6 +316,7 @@ struct inodes_stat_t {
 #define FIGETBSZ   _IO(0x00,2)	/* get the block size used for bmap */
 #define FIFREEZE	_IOWR('X', 119, int)	/* Freeze */
 #define FITHAW		_IOWR('X', 120, int)	/* Thaw */
+#define FITRIM		_IOW('X', 121, uint64_t)/* Trim */
 
 #define	FS_IOC_GETFLAGS			_IOR('f', 1, long)
 #define	FS_IOC_SETFLAGS			_IOW('f', 2, long)
@@ -1582,6 +1583,7 @@ struct super_operations {
 	ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
 #endif
 	int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
+	int (*trim_fs) (struct super_block *, uint64_t, uint64_t, uint64_t);
 };
 
 /*
-- 
1.7.2.1

[PATCH 2/3] Add batched discard support for ext3

[Lukas Czerner]

Walk through allocation groups and trim all free extents. It can be
invoked through FITRIM ioctl on the file system. The main idea is to
provide a way to trim the whole file system if needed, since some SSD's
may suffer from performance loss after the whole device was filled (it
does not mean that fs is full!).

It search for free extents in allocation groups specified by Byte range
start -> start+len. When the free extent is within this range, blocks are
marked as used and then trimmed. Afterwards these blocks are marked as
free in per-group bitmap.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ext3/balloc.c        |  250 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/super.c         |    1 +
 include/linux/ext3_fs.h |    1 +
 3 files changed, 252 insertions(+), 0 deletions(-)

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 4a32511..2e3f291 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -20,6 +20,7 @@
 #include <linux/ext3_jbd.h>
 #include <linux/quotaops.h>
 #include <linux/buffer_head.h>
+#include <linux/blkdev.h>
 
 /*
  * balloc.c contains the blocks allocation and deallocation routines
@@ -1882,3 +1883,252 @@ unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
 	return ext3_bg_num_gdb_meta(sb,group);
 
 }
+
+/**
+ * ext3_trim_all_free -- function to trim all free space in alloc. group
+ * @sb:			super block for file system
+ * @group:		allocation group to trim
+ * @start:		first group block to examine
+ * @max:		last group block to examine
+ * @gdp:		allocation group description structure
+ * @minblocks:		minimum extent block count
+ *
+ * ext3_trim_all_free walks through group's block bitmap searching for free
+ * blocks. When the free block is found, it tries to allocate this block and
+ * consequent free block to get the biggest free extent possible, until it
+ * reaches any used block. Then issue a TRIM command on this extent and free
+ * the extent in the block bitmap. This is done until whole group is scanned.
+ */
+ext3_grpblk_t ext3_trim_all_free(struct super_block *sb, unsigned int group,
+				ext3_grpblk_t start, ext3_grpblk_t max,
+				ext3_grpblk_t minblocks)
+{
+	handle_t *handle;
+	ext3_grpblk_t next, count = 0, bit;
+	struct ext3_sb_info *sbi;
+	ext3_fsblk_t discard_block;
+	struct buffer_head *bitmap_bh = NULL;
+	struct buffer_head *gdp_bh;
+	ext3_grpblk_t free_blocks;
+	struct ext3_group_desc *gdp;
+	int err = 0, ret = 0;
+	ext3_grpblk_t freed;
+
+	/*
+	 * We will update one block bitmap, and one group descriptor
+	 */
+	handle = ext3_journal_start_sb(sb, 2);
+	if (IS_ERR(handle)) {
+		err = PTR_ERR(handle);
+		return err;
+	}
+
+	bitmap_bh = read_block_bitmap(sb, group);
+	if (!bitmap_bh)
+		goto err_out;
+
+	BUFFER_TRACE(bitmap_bh, "getting undo access");
+	err = ext3_journal_get_undo_access(handle, bitmap_bh);
+	if (err)
+		goto err_out;
+
+	gdp = ext3_get_group_desc(sb, group, &gdp_bh);
+	if (!gdp)
+		goto err_out;
+
+	BUFFER_TRACE(gdp_bh, "get_write_access");
+	err = ext3_journal_get_write_access(handle, gdp_bh);
+	if (err)
+		goto err_out;
+
+	free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
+	sbi = EXT3_SB(sb);
+
+	 /* Walk through the whole group */
+	while (start < max) {
+
+		start = bitmap_search_next_usable_block(start, bitmap_bh, max);
+		if (start < 0)
+			break;
+		next = start;
+
+		/*
+		 * Allocate contiguous free extents by setting bits in the
+		 * block bitmap
+		 */
+		while (next < max
+			&& claim_block(sb_bgl_lock(sbi, group),
+					next, bitmap_bh)) {
+			next++;
+		}
+
+		 /* We did not claim any blocks */
+		if (next == start)
+			continue;
+
+		discard_block = (ext3_fsblk_t)start +
+				ext3_group_first_block_no(sb, group);
+
+		/* Update counters */
+		spin_lock(sb_bgl_lock(sbi, group));
+		le16_add_cpu(&gdp->bg_free_blocks_count, start - next);
+		spin_unlock(sb_bgl_lock(sbi, group));
+		percpu_counter_sub(&sbi->s_freeblocks_counter, next - start);
+
+		/* Do not issue a TRIM on extents smaller than minblocks */
+		if ((next - start) < minblocks)
+			goto free_extent;
+
+		 /* Send the TRIM command down to the device */
+		ret = sb_issue_discard(sb, discard_block, next - start);
+		count += (next - start);
+
+free_extent:
+		freed = 0;
+
+		/*
+		 * Clear bits in the bitmap
+		 */
+		for (bit = start; bit < next; bit++) {
+			BUFFER_TRACE(bitmap_bh, "clear bit");
+			if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, group),
+						bit, bitmap_bh->b_data)) {
+				ext3_error(sb, __func__,
+					"bit already cleared for block "E3FSBLK,
+					 (unsigned long)bit);
+				BUFFER_TRACE(bitmap_bh, "bit already cleared");
+			} else {
+				freed++;
+			}
+		}
+
+		/* Update couters */
+		spin_lock(sb_bgl_lock(sbi, group));
+		le16_add_cpu(&gdp->bg_free_blocks_count, freed);
+		spin_unlock(sb_bgl_lock(sbi, group));
+		percpu_counter_add(&sbi->s_freeblocks_counter, next - start);
+
+		start = next;
+
+		if (ret < 0) {
+			if (ret == -EOPNOTSUPP) {
+				ext3_warning(sb, __func__,
+					"discard not supported!");
+				count = ret;
+				break;
+			}
+			err = ret;
+			break;
+		}
+
+		if (signal_pending(current)) {
+			count = -ERESTARTSYS;
+			break;
+		}
+
+		cond_resched();
+
+		/* No more suitable extents */
+		if ((free_blocks - count) < minblocks)
+			break;
+	}
+
+	/* We dirtied the bitmap block */
+	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
+	err = ext3_journal_dirty_metadata(handle, bitmap_bh);
+
+	/* And the group descriptor block */
+	BUFFER_TRACE(gdp_bh, "dirtied group descriptor block");
+	ret = ext3_journal_dirty_metadata(handle, gdp_bh);
+	if (!err)
+		err = ret;
+
+	ext3_debug("trimmed %d blocks in the group %d\n",
+		count, group);
+
+err_out:
+	if (err) {
+		ext3_std_error(sb, err);
+		count = err;
+	}
+
+	ext3_journal_stop(handle);
+	brelse(bitmap_bh);
+
+	return count;
+}
+
+/**
+ * ext3_trim_fs() -- trim ioctl handle function
+ * @sb:			superblock for filesystem
+ * @start:		First Byte to trim
+ * @len:		number of Bytes to trim from start
+ * @minlen:		minimum extent length in Bytes
+ *
+ * ext3_trim_fs goes through all allocation groups containing Bytes from
+ * start to start+len. For each such a group ext3_trim_all_free function
+ * is invoked to trim all free space.
+ */
+int ext3_trim_fs(struct super_block *sb, uint64_t start, uint64_t len,
+		uint64_t minlen)
+{
+	ext3_grpblk_t last_block, first_block, free_blocks;
+	unsigned long long first_group, last_group;
+	unsigned long group, ngroups;
+	struct ext3_group_desc *gdp;
+	struct ext3_super_block *es;
+	int ret = 0;
+
+	start >>= sb->s_blocksize_bits;
+	len >>= sb->s_blocksize_bits;
+	minlen >>= sb->s_blocksize_bits;
+
+	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
+		return -EINVAL;
+
+	es = EXT3_SB(sb)->s_es;
+	ngroups = EXT3_SB(sb)->s_groups_count;
+	smp_rmb();
+
+	/* Determine first and last group to examine based on start and len */
+	first_group = (start - le32_to_cpu(es->s_first_data_block)) /
+		      EXT3_BLOCKS_PER_GROUP(sb);
+	last_group = (start + len - le32_to_cpu(es->s_first_data_block)) /
+		     EXT3_BLOCKS_PER_GROUP(sb);
+	last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
+
+	if (first_group > last_group)
+		return -EINVAL;
+
+	first_block = (start - le32_to_cpu(es->s_first_data_block)) %
+			EXT3_BLOCKS_PER_GROUP(sb);
+	last_block = EXT3_BLOCKS_PER_GROUP(sb);
+
+	for (group = first_group; group <= last_group; group++) {
+
+		gdp = ext3_get_group_desc(sb, group, NULL);
+		if (!gdp)
+			break;
+
+		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
+		if (free_blocks < minlen)
+			continue;
+
+		if (len >= EXT3_BLOCKS_PER_GROUP(sb))
+			len -= (EXT3_BLOCKS_PER_GROUP(sb) - first_block);
+		else
+			last_block = len;
+
+		ret = ext3_trim_all_free(sb, group, first_block,
+					last_block, minlen);
+		if (ret < 0)
+			break;
+
+		first_block = 0;
+	}
+
+	if (ret >= 0)
+		ret = 0;
+
+	return ret;
+}
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 6c953bb..b172c88 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -797,6 +797,7 @@ static const struct super_operations ext3_sops = {
 	.quota_write	= ext3_quota_write,
 #endif
 	.bdev_try_to_free_page = bdev_try_to_free_page,
+	.trim_fs	= ext3_trim_fs,
 };
 
 static const struct export_operations ext3_export_ops = {
diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
index 7fc62d4..9afacd4 100644
--- a/include/linux/ext3_fs.h
+++ b/include/linux/ext3_fs.h
@@ -857,6 +857,7 @@ extern struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
 extern int ext3_should_retry_alloc(struct super_block *sb, int *retries);
 extern void ext3_init_block_alloc_info(struct inode *);
 extern void ext3_rsv_window_add(struct super_block *sb, struct ext3_reserve_window_node *rsv);
+extern int ext3_trim_fs(struct super_block *, uint64_t, uint64_t, uint64_t);
 
 /* dir.c */
 extern int ext3_check_dir_entry(const char *, struct inode *,
-- 
1.7.2.1

[PATCH 3/3] Add batched discard support for ext4

[Lukas Czerner]

Walk through allocation groups and trim all free extents. It can be
invoked through FITRIM ioctl on the file system. The main idea is to
provide a way to trim the whole file system if needed, since some SSD's
may suffer from performance loss after the whole device was filled (it
does not mean that fs is full!).

It search for free extents in allocation groups specified by Byte range
start -> start+len. When the free extent is within this range, blocks
are marked as used and then trimmed. Afterwards these blocks are marked
as free in per-group bitmap.

Since fstrim is a long operation it is good to have an ability to
interrupt it by a signal. This was added by Dmitry Monakhov.
Thanks Dimitry.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ext4/ext4.h    |    2 +
 fs/ext4/mballoc.c |  200 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/super.c   |    1 +
 3 files changed, 203 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 19a4de5..2f96dc5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1558,6 +1558,8 @@ extern int ext4_mb_add_groupinfo(struct super_block *sb,
 extern int ext4_mb_get_buddy_cache_lock(struct super_block *, ext4_group_t);
 extern void ext4_mb_put_buddy_cache_lock(struct super_block *,
 						ext4_group_t, int);
+extern int ext4_trim_fs(struct super_block *, uint64_t, uint64_t, uint64_t);
+
 /* inode.c */
 struct buffer_head *ext4_getblk(handle_t *, struct inode *,
 						ext4_lblk_t, int, int *);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 0e83dfd..4c4132b 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4690,3 +4690,203 @@ error_return:
 		kmem_cache_free(ext4_ac_cachep, ac);
 	return;
 }
+
+/**
+ * ext4_trim_extent -- function to TRIM one single free extent in the group
+ * @sb:		super block for the file system
+ * @start:	starting block of the free extent in the alloc. group
+ * @count:	number of blocks to TRIM
+ * @group:	alloc. group we are working with
+ * @e4b:	ext4 buddy for the group
+ *
+ * Trim "count" blocks starting at "start" in the "group". To assure that no
+ * one will allocate those blocks, mark it as used in buddy bitmap. This must
+ * be called with under the group lock.
+ */
+static int ext4_trim_extent(struct super_block *sb, int start, int count,
+		ext4_group_t group, struct ext4_buddy *e4b)
+{
+	ext4_fsblk_t discard_block;
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+	struct ext4_free_extent ex;
+	int ret = 0;
+
+	assert_spin_locked(ext4_group_lock_ptr(sb, group));
+
+	ex.fe_start = start;
+	ex.fe_group = group;
+	ex.fe_len = count;
+
+	/*
+	 * Mark blocks used, so no one can reuse them while
+	 * being trimmed.
+	 */
+	mb_mark_used(e4b, &ex);
+	ext4_unlock_group(sb, group);
+
+	discard_block = (ext4_fsblk_t)group *
+			EXT4_BLOCKS_PER_GROUP(sb)
+			+ start
+			+ le32_to_cpu(es->s_first_data_block);
+	trace_ext4_discard_blocks(sb,
+			(unsigned long long)discard_block,
+			count);
+	ret = sb_issue_discard(sb, discard_block, count);
+	if (ret == -EOPNOTSUPP) {
+		ext4_warning(sb,
+			"discard not supported!");
+	} else if (ret < 0) {
+		ext4_std_error(sb, ret);
+	}
+
+	ext4_lock_group(sb, group);
+	mb_free_blocks(NULL, e4b, start, ex.fe_len);
+	return ret;
+}
+
+/**
+ * ext4_trim_all_free -- function to trim all free space in alloc. group
+ * @sb:			super block for file system
+ * @e4b:		ext4 buddy
+ * @start:		first group block to examine
+ * @max:		last group block to examine
+ * @minblocks:		minimum extent block count
+ *
+ * ext4_trim_all_free walks through group's buddy bitmap searching for free
+ * extents. When the free block is found, ext4_trim_extent is called to TRIM
+ * the extent.
+ *
+ *
+ * ext4_trim_all_free walks through group's block bitmap searching for free
+ * extents. When the free extent is found, mark it as used in group buddy
+ * bitmap. Then issue a TRIM command on this extent and free the extent in
+ * the group buddy bitmap. This is done until whole group is scanned.
+ */
+ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
+		ext4_grpblk_t start, ext4_grpblk_t max, ext4_grpblk_t minblocks)
+{
+	void *bitmap;
+	ext4_grpblk_t next, count = 0;
+	ext4_group_t group;
+	int ret = 0;
+
+	BUG_ON(e4b == NULL);
+
+	bitmap = e4b->bd_bitmap;
+	group = e4b->bd_group;
+	start = (e4b->bd_info->bb_first_free > start) ?
+		e4b->bd_info->bb_first_free : start;
+	ext4_lock_group(sb, group);
+
+	while (start < max) {
+
+		start = mb_find_next_zero_bit(bitmap, max, start);
+		if (start >= max)
+			break;
+		next = mb_find_next_bit(bitmap, max, start);
+
+		if ((next - start) >= minblocks) {
+			ret = ext4_trim_extent(sb, start,
+				next - start, group, e4b);
+			if (ret < 0)
+				break;
+			count += next - start;
+		}
+		start = next + 1;
+
+		if (signal_pending(current)) {
+			count = -ERESTARTSYS;
+			break;
+		}
+
+		if (need_resched()) {
+			ext4_unlock_group(sb, group);
+			cond_resched();
+			ext4_lock_group(sb, group);
+		}
+
+		if ((e4b->bd_info->bb_free - count) < minblocks)
+			break;
+	}
+	ext4_unlock_group(sb, group);
+
+	ext4_debug("trimmed %d blocks in the group %d\n",
+		count, group);
+
+	if (ret < 0)
+		count = ret;
+
+	return count;
+}
+
+/**
+ * ext4_trim_fs() -- trim ioctl handle function
+ * @sb:			superblock for filesystem
+ * @start:		First Byte to trim
+ * @len:		number of Bytes to trim from start
+ * @minlen:		minimum extent length in Bytes
+ *
+ * ext4_trim_fs goes through all allocation groups containing Bytes from
+ * start to start+len. For each such a group ext4_trim_all_free function
+ * is invoked to trim all free space.
+ */
+int ext4_trim_fs(struct super_block *sb, uint64_t start, uint64_t len,
+		uint64_t minlen)
+{
+	struct ext4_buddy e4b;
+	ext4_fsblk_t first_group, last_group;
+	ext4_group_t group, ngroups = ext4_get_groups_count(sb);
+	ext4_grpblk_t cnt, first_block, last_block;
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+	int ret = 0;
+
+	start >>= sb->s_blocksize_bits;
+	len >>= sb->s_blocksize_bits;
+	minlen >>= sb->s_blocksize_bits;
+
+	if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
+		return -EINVAL;
+
+	/* Determine first and last group to examine based on start and len */
+	first_group = (start - le32_to_cpu(es->s_first_data_block)) /
+		      EXT4_BLOCKS_PER_GROUP(sb);
+	last_group = (start + len - le32_to_cpu(es->s_first_data_block)) /
+		     EXT4_BLOCKS_PER_GROUP(sb);
+	last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
+
+	if (first_group > last_group)
+		return -EINVAL;
+
+	first_block = (start - le32_to_cpu(es->s_first_data_block)) %
+			EXT4_BLOCKS_PER_GROUP(sb);
+	last_block = EXT4_BLOCKS_PER_GROUP(sb);
+
+	for (group = first_group; group <= last_group; group++) {
+
+		ret = ext4_mb_load_buddy(sb, group, &e4b);
+		if (ret) {
+			ext4_error(sb, "Error in loading buddy "
+					"information for %u", group);
+			break;
+		}
+
+		if (len >= EXT4_BLOCKS_PER_GROUP(sb))
+			len -= (EXT4_BLOCKS_PER_GROUP(sb) - first_block);
+		else
+			last_block = len;
+
+		if (e4b.bd_info->bb_free >= minlen) {
+			cnt = ext4_trim_all_free(sb, &e4b, first_block,
+						last_block, minlen);
+			if (cnt < 0) {
+				ret = cnt;
+				ext4_mb_unload_buddy(&e4b);
+				break;
+			}
+		}
+		ext4_mb_unload_buddy(&e4b);
+
+		first_block = 0;
+	}
+	return ret;
+}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e72d323..3b05b3a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1114,6 +1114,7 @@ static const struct super_operations ext4_sops = {
 	.quota_write	= ext4_quota_write,
 #endif
 	.bdev_try_to_free_page = bdev_try_to_free_page,
+	.trim_fs	= ext4_trim_fs
 };
 
 static const struct super_operations ext4_nojournal_sops = {
-- 
1.7.2.1