[PATCH 0/3 v. 8] Ext3/Ext4 Batched discard support

[PATCH 0/3 v. 8] Ext3/Ext4 Batched discard support

[Lukas Czerner]

Hi,

since it has been a while from my last post, I have rebased patches to
cleanly apply to the newest kernel. Also there have been some changes
regarding blkdev_issue_discard() and its helpers, I have changed patches
to use the new helper (ext4_issue_discard() for ext4) and new format of
sb_issue_discard() (in ext3).

Also in order to give the user better control over the discard I have
changed FITRIM ioctl to return the exact amount of discarded Bytes, so
the user will know how much space has been reclaimed to wear-leveling.

SHORT DESCRIPTION:
==================

Batched discard adds ability to discard free space on mounded filesystem,
in order to avoid using current discard implementation which discards
recently freed blocks. This approach may on some devices (it depends on
how efficient is the device wear-leveling algorithm) result in huge
performance loss.

Batched discard can be invoked from user-space through FITRIM ioctl on
the whole, or just a part, of file system. With this approach we are
searching for continuous free blocks bigger than defined through ioctl
to discard them. So, since we are searching for big continuous extents
it is much more efficient than current approach and it gives user fine
grained control over how much disk space will be reclaimed for
wear-leveling and what impact will it have on performance.


I have attached source code for example application which uses FITRIM
to discard just a part or whole filesystem. Since FITRIM is filesystem
independent ioctl it can be used by any filesystem which supports it.

Usage: fstrim [-s start] [-l length] [-m minimum-extent] [-v] directory
        -s Starting Byte to discard from
        -l Number of Bytes to discard from the start
        -m Minimum extent length to discard
        -v Verbose - prints out number of really discarded Bytes

---
a1edaf3 ext3: Add batched discard support
4ed7168 ext4: Add batched discard support
88f8c20 Add ioctl FITRIM.

 fs/ext3/balloc.c        |  251 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/super.c         |    1 +
 fs/ext4/ext4.h          |    2 +
 fs/ext4/mballoc.c       |  191 +++++++++++++++++++++++++++++++++++
 fs/ext4/super.c         |    1 +
 fs/ioctl.c              |   39 +++++++
 include/linux/ext3_fs.h |    1 +
 include/linux/fs.h      |    2 +
 8 files changed, 488 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.

After the FITRIM is done, the number of actually discarded Bytes is stored
in args[1] (len) to give the user better insight on how much storage
space was really released for wear-leveling.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ioctl.c         |   39 +++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h |    2 ++
 2 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index f855ea4..3dd96b6 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -530,6 +530,41 @@ 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 ret = 0;
+
+	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;
+
+	ret = sb->s_op->trim_fs(sb, args);
+	if (ret < 0)
+		return ret;
+
+	if ((argp != NULL) &&
+	    (copy_to_user(argp, args, sizeof(args))))
+		return -EFAULT;
+
+	return 0;
+}
+
 /*
  * When you add any new common ioctls to the switches above and below
  * please update compat_sys_ioctl() too.
@@ -580,6 +615,10 @@ 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 76041b6..e1b8a4a 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		_IOWR('X', 121, uint64_t)	/* Trim */
 
 #define	FS_IOC_GETFLAGS			_IOR('f', 1, long)
 #define	FS_IOC_SETFLAGS			_IOW('f', 2, long)
@@ -1577,6 +1578,7 @@ 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 *);
 };
 
 /*
-- 
1.7.2.3

Re: [PATCH 1/3] Add ioctl FITRIM.

[Andreas Dilger]

On 2010-09-24, at 09:35, Lukas Czerner wrote:
> 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;

(minor) you use "array[]" in one place and "args[]" in another.

> +#define FITRIM		_IOWR('X', 121, uint64_t)	/* Trim */

This ioctl definition isn't strictly correct.  The "size" parameter is actually uint64_t[3], though I'm not sure whether you need to define a structure in order to specify this.

Cheers, Andreas

Re: [PATCH 1/3] Add ioctl FITRIM.

[Lukas Czerner]

On Fri, 24 Sep 2010, Andreas Dilger wrote:

> On 2010-09-24, at 09:35, Lukas Czerner wrote:
> > 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;
> 
> (minor) you use "array[]" in one place and "args[]" in another.
> 
> > +#define FITRIM		_IOWR('X', 121, uint64_t)	/* Trim */
> 
> This ioctl definition isn't strictly correct.  The "size" parameter is actually uint64_t[3], though I'm not sure whether you need to define a structure in order to specify this.

You,re probably right. A structure would be better. But for example
BLKDISCARD takes takes uint64_t[2] and its definition looks like:

#define BLKDISCARD _IO(0x12,119)

which confuses me a bit.

> 
> Cheers, Andreas

[PATCH 2/3] ext4: Add batched discard support

[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 |  191 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/super.c   |    1 +
 3 files changed, 194 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 889ec9d..693ce4e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1630,6 +1630,8 @@ 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 *);
+
 /* 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 4b4ad4b..1328e50 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4689,3 +4689,194 @@ 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)
+{
+	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);
+
+	ret = ext4_issue_discard(sb, group, start, count);
+	if (ret)
+		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 (fatal_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
+ * @args:		Array of arguments (start, len, minlen)
+ *
+ * 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 *args)
+{
+	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 = 0, first_block, last_block;
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+	uint64_t start, len, minlen, trimmed;
+	int ret = 0;
+
+	start = args[0] >> sb->s_blocksize_bits;
+	len = args[1] >> sb->s_blocksize_bits;
+	minlen = args[2] >> sb->s_blocksize_bits;
+	trimmed = 0;
+
+	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);
+		trimmed += cnt;
+		first_block = 0;
+	}
+	args[1] = trimmed * sb->s_blocksize;
+
+	return ret;
+}
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2614774..686b849 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1173,6 +1173,7 @@ 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 = {
-- 
1.7.2.3

[PATCH 3/3] ext3: Add batched discard support

[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        |  251 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/super.c         |    1 +
 include/linux/ext3_fs.h |    1 +
 3 files changed, 253 insertions(+), 0 deletions(-)

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 4a32511..25fbc2f 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 +1883,253 @@ 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,
+				       GFP_NOFS, 0);
+		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 (fatal_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 5dbf4db..2e095db 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -782,6 +782,7 @@ 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 6ce1bca..07040dc 100644
--- a/include/linux/ext3_fs.h
+++ b/include/linux/ext3_fs.h
@@ -856,6 +856,7 @@ 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 *sb, uint64_t *args);
 
 /* dir.c */
 extern int ext3_check_dir_entry(const char *, struct inode *,
-- 
1.7.2.3

Re: [PATCH 0/3 v. 8] Ext3/Ext4 Batched discard support

[Lukas Czerner]

FSTRIM
=======

/*
 * e2trim.c - discard the part (or whole) mounted filesystem.
 *
 * Copyright (C) 2009 Red Hat, Inc., Lukas Czerner <lczerner@redhat.com>
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 *
 * Usage: e2trim [options] <mount point>
 */

#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <limits.h>

#ifdef HAVE_GETOPT_H
#include <getopt.h>
#else
extern char *optarg;
extern int optind;
#endif

#include <sys/ioctl.h>
#include <sys/stat.h>
#include <linux/fs.h>

#ifndef FITRIM
#define FITRIM		_IOWR('X', 121, uint64_t)
#endif

const char *program_name = "fstrim";

struct options {
	uint64_t *range;
	char mpoint[PATH_MAX];
	char verbose;
};

static void usage(void)
{
	fprintf(stderr, "Usage: %s [-s start] [-l length] [-m minimum-extent]"
	" [-v] directory\n\t-s Starting Byte to discard from\n"
	"\t-l Number of Bytes to discard from the start\n"
	"\t-m Minimum extent length to discard\n"
	"\t-v Verbose - prints out number of really discarded Bytes\n",
	program_name);
}

/**
 * Get the number from argument. It can be number followed by
 * units: k|K,m|M,g|G
 */
static unsigned long long get_number(char **optarg)
{
	char *opt;
	unsigned long long number,max;

	/* get the max to avoid overflow */
	max = ULLONG_MAX / 10;
	number = 0;
	opt = *optarg;
	
	/* compute the number */
	while ((*opt >= '0') && (*opt <= '9') && (number < max)) {
		number = number * 10 + *opt++ - '0';
	}
	while (1) {
		/* determine if units are defined */
		switch(*opt++) {
			case 'K': /* kilobytes */
			case 'k': 
				number *= 1024;
				break;
			case 'M': /* megabytes */
			case 'm':
				number *= 1024 * 1024;
				break;
			case 'G': /* gigabytes */
			case 'g':
				number *= 1024 * 1024 * 1024;
				break;
			case ':': /* delimiter */
				if ((number > max) || (number == 0)) {
					fprintf(stderr,"Numeric argument out"
						" of range\n");
					return 0;
				}
				*optarg = opt;
				return number;
			case '\0': /* end of the string */
				if ((number > max) || (number == 0)) {
					fprintf(stderr,"Numeric argument out"
						" of range\n");
					return 0;
				}
				return number;
			default:
				fprintf(stderr,"Bad syntax of numeric"
					" argument\n");
				return 0;
		}
	}
	return number;
}


static int parse_opts(int argc, char **argv, struct options *opts)
{
	int c;

	while ((c = getopt(argc, argv, "s:l:m:v")) != EOF) {
		switch (c) {
			case 's': /* starting point */
				if ((opts->range[0] =
				     get_number(&optarg)) == 0) {
					return EXIT_FAILURE;
				}
				break;
			case 'l': /* length */
				if ((opts->range[1] =
				     get_number(&optarg)) == 0) {
					return EXIT_FAILURE;
				}
				break;
			case 'm': /* minlen */

				if ((opts->range[2] =
				     get_number(&optarg)) == 0) {
					return EXIT_FAILURE;
				}
				break;
			case 'v': /* verbose */
				opts->verbose = 1;
				break;
			default:
				return EXIT_FAILURE;
		}
	}

	return 0;
}

static void free_opts(struct options *opts)
{
	if (opts) {
		if (opts->range)
			free(opts->range);
		free(opts);
	}
}

static void free_opts_and_exit(struct options *opts)
{
	free_opts(opts);
	exit(EXIT_FAILURE);
}

static void print_usage_and_exit(struct options *opts)
{
	usage();
	free_opts_and_exit(opts);
}

int main (int argc, char **argv)
{
	struct options *opts;
	struct stat sb;
	int fd, ret = 0;

	opts = malloc(sizeof(struct options));
	if (!opts) {
		perror("malloc");
		return EXIT_FAILURE;
	}
	opts->range = NULL;
	opts->verbose = 0;

	if (argc > 1)
		strncpy(opts->mpoint, argv[argc - 1], sizeof(opts->mpoint));

	if (argc > 2) {
		opts->range = calloc(3, sizeof(uint64_t));
		if (!opts->range) {
			perror("calloc");
			free_opts_and_exit(opts);
		}
		opts->range[1] = ULLONG_MAX;
		ret = parse_opts(argc, argv, opts);
	}

	if (ret)
		print_usage_and_exit(opts);

	if (strnlen(opts->mpoint, 1) < 1) {
		fprintf(stderr,"You have to specify mount point.\n");
		print_usage_and_exit(opts);
	}

	if (stat(opts->mpoint, &sb) == -1) {
		fprintf(stderr,"%s is not a valid directory\n", opts->mpoint);
		print_usage_and_exit(opts);
	}

	if (!S_ISDIR(sb.st_mode)) {
		fprintf(stderr,"%s is not a valid directory\n", opts->mpoint);
		print_usage_and_exit(opts);
	}

	fd = open(opts->mpoint, O_RDONLY);
	if (fd < 0) {
		perror("open");
		free_opts_and_exit(opts);
	}

	if (ioctl(fd, FITRIM, opts->range)) {
		if (errno == EOPNOTSUPP)
			fprintf(stderr, "Filesystem at %s does not "
				"support FITRIM\n", opts->mpoint);
		else
			perror("FITRIM");
		free_opts_and_exit(opts);
	}

	if ((opts->verbose) && (opts->range))
		fprintf(stdout,"%lu Bytes was trimmed\n", opts->range[1]);

	free_opts(opts);
	return ret;
}

Re: [PATCH 0/3 v. 8] Ext3/Ext4 Batched discard support

[Andreas Dilger]

On 2010-09-24, at 09:38, Lukas Czerner wrote:
> /*
> * e2trim.c - discard the part (or whole) mounted filesystem.
> *
> * Usage: e2trim [options] <mount point>
> */

This tool isn't extN specific at all, and should probably go into util-linux or similar.  That said, it might make sense to add an option to e2fsck to have it trim the free space at the end, since it will just have verified the bitmaps are correct (which is the safest time to do this).

> const char *program_name = "fstrim";

Ah, your comment block has an inconsistent name for the program.

> static void usage(void)
> {
> 	fprintf(stderr, "Usage: %s [-s start] [-l length] [-m minimum-extent]"
> 	" [-v] directory\n\t-s Starting Byte to discard from\n"

This formatting, while saving a line, makes it hard to read.  Better is:

	fprintf(stderr,
                "Usage: %s [-s start] [-l length] [-m minimum-extent]"
	        " [-v] {mountpoint}\n\t"
		"-s Starting Byte to discard from\n\t"
		"-l Number of Bytes to discard from the start\n\t"
		"-m Minimum extent length to discard\n\t"
		"-v Verbose - number of discarded bytes\n",
		program_name);

> static unsigned long long get_number(char **optarg)
> {
> 	/* compute the number */
> 	while ((*opt >= '0') && (*opt <= '9') && (number < max)) {
> 		number = number * 10 + *opt++ - '0';
> 	}

Umm, strtoul(opt, &end, 0) is a much nicer way to parse this, and it also allows hex-formatted input.

> 	while (1) {
> 		/* determine if units are defined */
> 		switch(*opt++) {
> 			case 'K': /* kilobytes */
> 			case 'k': 
> 				number *= 1024;
> 				break;
> 			case 'M': /* megabytes */
> 			case 'm':
> 				number *= 1024 * 1024;
> 				break;
> 			case 'G': /* gigabytes */
> 			case 'g':
> 				number *= 1024 * 1024 * 1024;
> 				break;

I usually implement this by descending TGMK, multiply by 1024 at each step, and then skip the "break" in between.  Definitely you want to have "T" as a suffix these days.

> 			case ':': /* delimiter */

It isn't clear from the usage message what this delimiter is used for?

> 	if (argc > 2) {
> 		opts->range = calloc(3, sizeof(uint64_t));

Thinking about this more, it might make more sense to have a structure with named fields here.  This simplifies the ioctl definition, but also makes it much more clear from the caller which field is which.  Otherwise, there will be callers that get the order of parameters wrong, etc.

> 	if (stat(opts->mpoint, &sb) == -1) {
> 		fprintf(stderr,"%s is not a valid directory\n", opts->mpoint);

Using strerror() here to print the actual error is better.  It might be e.g. a permission problem, etc.  Also, using perror() will localize the message.

> 	fd = open(opts->mpoint, O_RDONLY);
> 	if (fd < 0) {
> 		perror("open");

I prefer strerror() over perror(), since it allows creating a better error:

                  fprintf(stderr, "%s: open(%s): %s\n",
                           program_name, opts->mpoint, strerror(errno));


Cheers, Andreas

Re: [PATCH 0/3 v. 8] Ext3/Ext4 Batched discard support

[Lukas Czerner]

On Fri, 24 Sep 2010, Andreas Dilger wrote:

> On 2010-09-24, at 09:38, Lukas Czerner wrote:
> > /*
> > * e2trim.c - discard the part (or whole) mounted filesystem.
> > *
> > * Usage: e2trim [options] <mount point>
> > */
> 
> This tool isn't extN specific at all, and should probably go into util-linux or similar.  That said, it might make sense to add an option to e2fsck to have it trim the free space at the end, since it will just have verified the bitmaps are correct (which is the safest time to do this).
> 
> > const char *program_name = "fstrim";
> 
> Ah, your comment block has an inconsistent name for the program.

Right, I have changed it from e2trim to fstrim because of the same reason
you've just pointed out. Looks like I had missed some old comments.
> 
> > static void usage(void)
> > {
> > 	fprintf(stderr, "Usage: %s [-s start] [-l length] [-m minimum-extent]"
> > 	" [-v] directory\n\t-s Starting Byte to discard from\n"
> 
> This formatting, while saving a line, makes it hard to read.  Better is:
> 
> 	fprintf(stderr,
>                 "Usage: %s [-s start] [-l length] [-m minimum-extent]"
> 	        " [-v] {mountpoint}\n\t"
> 		"-s Starting Byte to discard from\n\t"
> 		"-l Number of Bytes to discard from the start\n\t"
> 		"-m Minimum extent length to discard\n\t"
> 		"-v Verbose - number of discarded bytes\n",
> 		program_name);
> 
> > static unsigned long long get_number(char **optarg)
> > {
> > 	/* compute the number */
> > 	while ((*opt >= '0') && (*opt <= '9') && (number < max)) {
> > 		number = number * 10 + *opt++ - '0';
> > 	}
> 
> Umm, strtoul(opt, &end, 0) is a much nicer way to parse this, and it also allows hex-formatted input.

That's right, but my original idea was to let the user write parameters
like 10kk etc. But when I think of it now, it is not exactly useful :)
> 
> > 	while (1) {
> > 		/* determine if units are defined */
> > 		switch(*opt++) {
> > 			case 'K': /* kilobytes */
> > 			case 'k': 
> > 				number *= 1024;
> > 				break;
> > 			case 'M': /* megabytes */
> > 			case 'm':
> > 				number *= 1024 * 1024;
> > 				break;
> > 			case 'G': /* gigabytes */
> > 			case 'g':
> > 				number *= 1024 * 1024 * 1024;
> > 				break;
> 
> I usually implement this by descending TGMK, multiply by 1024 at each step, and then skip the "break" in between.  Definitely you want to have "T" as a suffix these days.
> 
> > 			case ':': /* delimiter */
> 
> It isn't clear from the usage message what this delimiter is used for?

Oh, I have just reused this part from another project of mine, so I have
probably missed that out. Thanks.

> 
> > 	if (argc > 2) {
> > 		opts->range = calloc(3, sizeof(uint64_t));
> 
> Thinking about this more, it might make more sense to have a structure with named fields here.  This simplifies the ioctl definition, but also makes it much more clear from the caller which field is which.  Otherwise, there will be callers that get the order of parameters wrong, etc.

Definitely, looks like I am going to use a structure for this ioctl.

> 
> > 	if (stat(opts->mpoint, &sb) == -1) {
> > 		fprintf(stderr,"%s is not a valid directory\n", opts->mpoint);
> 
> Using strerror() here to print the actual error is better.  It might be e.g. a permission problem, etc.  Also, using perror() will localize the message.
> 
> > 	fd = open(opts->mpoint, O_RDONLY);
> > 	if (fd < 0) {
> > 		perror("open");
> 
> I prefer strerror() over perror(), since it allows creating a better error:
> 
>                   fprintf(stderr, "%s: open(%s): %s\n",
>                            program_name, opts->mpoint, strerror(errno));
> 
> 
> Cheers, Andreas
> 

Andreas, thanks a lot for reviewing this.

-Lukas