[Ocfs2-devel] [PATCH 1/3] ocfs2: Add ocfs2_trim_fs for SSD trim support.

[Tristan Ye <tristan.ye@oracle.com>]

Hi Tao,

    Most of codes looks pretty neat to me, few comments inlined below:

Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
>
> Add ocfs2_trim_fs to support trimming freed clusters in the
> volume. A range will be given and all the freed clusters greater
> than minlen will be discarded to the block layer.
>
> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
> ---
>  fs/ocfs2/alloc.c |  154 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/ocfs2/alloc.h |    1 +
>  2 files changed, 155 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
> index b27a0d8..6e1b3b5 100644
> --- a/fs/ocfs2/alloc.c
> +++ b/fs/ocfs2/alloc.c
> @@ -29,6 +29,7 @@
>  #include <linux/highmem.h>
>  #include <linux/swap.h>
>  #include <linux/quotaops.h>
> +#include <linux/blkdev.h>
>  
>  #include <cluster/masklog.h>
>  
> @@ -7184,3 +7185,156 @@ out_commit:
>  out:
>  	return ret;
>  }
> +
> +static int ocfs2_trim_extent(struct super_block *sb,
> +			     struct ocfs2_group_desc *gd,
> +			     int start, int count)
> +{
> +	u64 discard;
> +
> +	count = ocfs2_clusters_to_blocks(sb, count);
> +	discard = le64_to_cpu(gd->bg_blkno) +
> +			ocfs2_clusters_to_blocks(sb, start);
> +
> +	return sb_issue_discard(sb, discard, count, GFP_NOFS, 0);
> +}
> +
> +static int ocfs2_trim_group(struct super_block *sb,
> +			    struct ocfs2_group_desc *gd,
> +			    int start, int max, int minbits)
> +{
> +	int ret = 0, count = 0, next;
> +	void *bitmap = gd->bg_bitmap;
> +
> +	while (start < max) {
> +		start = ocfs2_find_next_zero_bit(bitmap, max, start);
> +		if (start >= max)
> +			break;

    /* What if the 'start' stands within a hole */

    if (ocfs2_test_bit(...)) {
       start = ocfs2_find_next_zero_bit(...);
       if ((start == -1) || (start >= max))
          break;
    }

> +		next = ocfs2_find_next_bit(bitmap, max, start);
   
    next = ocfs2_find_next_bit(...);
    if (next == -1)
       break;

    if (next > max)
       next = max;
   
> +
> +		if ((next - start) >= minbits) {
> +			ret = ocfs2_trim_extent(sb, gd,
> +						start, next - start);
> +			if (ret < 0) {
> +				mlog_errno(ret);
> +				break;
> +			}
> +			count += next - start;
> +		}
> +		start = next + 1;
> +
> +		if (fatal_signal_pending(current)) {
> +			count = -ERESTARTSYS;
> +			break;
> +		}
> +
> +		if ((le16_to_cpu(gd->bg_free_bits_count) - count) < minbits)
> +			break;
> +	}
> +
> +	if (ret < 0)
> +		count = ret;
> +
> +	return count;
> +}
> +
> +int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
> +{
> +	struct ocfs2_super *osb = OCFS2_SB(sb);
> +	u64 start, len, minlen, trimmed, first_group, last_group, group;
    why not using u32 start, len, minlen, trimmed;
> +	int ret, cnt, first_bit, last_bit;
> +	struct buffer_head *main_bm_bh = NULL;
> +	struct inode *main_bm_inode = NULL;
> +	struct buffer_head *gd_bh = NULL;
> +	struct ocfs2_dinode *main_bm;
> +	struct ocfs2_group_desc *gd = NULL;
> +
> +	if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
> +		return -EROFS;
> +
> +	start = range->start >> osb->s_clustersize_bits;
> +	len = range->len >> osb->s_clustersize_bits;
> +	minlen = range->minlen >> osb->s_clustersize_bits;

    I guess you may want to count two corner clusters which cover the 
'start' and 'end' bytes,
so the appropriate way might be:

    start = range->start >> osb->s_clustersize_bits;
    len = ocfs2_clusters_for_bytes(osb->sb, range->start  + range->len);
    len -= start;
   
> +	trimmed = 0;
> +
> +	if (!len || !minlen || minlen >= osb->bitmap_cpg)
    'minlen == 0' looks acceptable, which means we allowing discarding 
for all size of extents.
and what's more, 'len == 0' may not be harmful enough to issue a 
'EINVAL', returning a legal '0'
to userspace immediately is fine.


> +		return -EINVAL;
> +
> +	main_bm_inode = ocfs2_get_system_file_inode(osb,
> +						    GLOBAL_BITMAP_SYSTEM_INODE,
> +						    OCFS2_INVALID_SLOT);
> +	if (!main_bm_inode) {
> +		ret = -EIO;
> +		mlog_errno(ret);
> +		goto out;
> +	}
> +
> +	mutex_lock(&main_bm_inode->i_mutex);
> +
> +	ret = ocfs2_inode_lock(main_bm_inode, &main_bm_bh, 0);
> +	if (ret < 0) {
> +		mlog_errno(ret);
> +		goto out_mutex;
> +	}
> +	main_bm = (struct ocfs2_dinode *)main_bm_bh->b_data;
> +
> +	if (start >= le32_to_cpu(main_bm->i_clusters)) {
> +		ret = -EINVAL;
> +		mlog_errno(ret);
> +		goto out_unlock;
> +	}
> +
> +	if (start + len > le32_to_cpu(main_bm->i_clusters))
> +		len = le32_to_cpu(main_bm->i_clusters) - start;
> +
> +	/* Determine first and last group to examine based on start and len */
> +	first_group = ocfs2_which_cluster_group(main_bm_inode, start);
> +	if (first_group == osb->first_cluster_group_blkno)
> +		first_bit = start;
> +	else
> +		first_bit = start - ocfs2_blocks_to_clusters(sb, first_group);
> +	last_group = ocfs2_which_cluster_group(main_bm_inode, start + len - 1);
> +	last_bit = osb->bitmap_cpg;
> +
> +	for (group = first_group; group <= last_group;) {
> +		if (first_bit + len >= osb->bitmap_cpg)
> +			last_bit = osb->bitmap_cpg - first_bit;

    is 'first_bit' and 'last_bit' both represent a local offset within a 
cluster group?
just wondering why last_bit wasn't equal to 'osb->bitmap_cpg' in above 
case(I meant the case
of 'first_bit + len >= osb->bitmap_cpg'

> +		else
> +			last_bit = start + len;

    why above case is not 'last_bit = first_bit + len';

> +
> +		ret = ocfs2_read_group_descriptor(main_bm_inode,
> +						  main_bm, group,
> +						  &gd_bh);
> +		if (ret < 0) {
> +			mlog_errno(ret);
> +			break;
> +		}
> +
> +		gd = (struct ocfs2_group_desc *)gd_bh->b_data;
> +		cnt = ocfs2_trim_group(sb, gd, first_bit, last_bit, minlen);
> +		brelse(gd_bh);
> +		gd_bh = NULL;
> +		if (cnt < 0) {
> +			ret = cnt;
> +			mlog_errno(ret);
> +			break;
> +		}
> +
> +		trimmed += cnt;
> +		len -= osb->bitmap_cpg - first_bit;
> +		first_bit = 0;
> +		if (group == osb->first_cluster_group_blkno)
> +			group = ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
> +		else
> +			group += ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
> +	}
> +	range->len = trimmed * sb->s_blocksize;
> +out_unlock:
> +	ocfs2_inode_unlock(main_bm_inode, 0);
> +	brelse(main_bm_bh);
> +out_mutex:
> +	mutex_unlock(&main_bm_inode->i_mutex);
> +	iput(main_bm_inode);
> +out:
> +	return ret;
> +}
> diff --git a/fs/ocfs2/alloc.h b/fs/ocfs2/alloc.h
> index 3bd08a0..ca381c5 100644
> --- a/fs/ocfs2/alloc.h
> +++ b/fs/ocfs2/alloc.h
> @@ -239,6 +239,7 @@ int ocfs2_find_leaf(struct ocfs2_caching_info *ci,
>  		    struct buffer_head **leaf_bh);
>  int ocfs2_search_extent_list(struct ocfs2_extent_list *el, u32 v_cluster);
>  
> +int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range);
>  /*
>   * Helper function to look at the # of clusters in an extent record.
>   */