[PATCH 1/2] nilfs2: add nilfs_sufile_trim_fs to trim clean segs

[Andreas Rohner <andreas.rohner@xxxxxxx>]

This patch adds the nilfs_sufile_trim_fs function, which takes a
fstrim_range structure and calls blkdev_issue_discard for every
clean segment in the specified range.

Signed-off-by: Andreas Rohner <andreas.rohner@xxxxxxx>
---
 fs/nilfs2/sufile.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/nilfs2/sufile.h |   1 +
 2 files changed, 115 insertions(+)

diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
index 3127e9f..022b17f 100644
--- a/fs/nilfs2/sufile.c
+++ b/fs/nilfs2/sufile.c
@@ -870,6 +870,120 @@ ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
 }
 
 /**
+ * nilfs_sufile_trim_fs() - trim ioctl handle function
+ * @sufile: inode of segment usage file
+ * @range: fstrim_range structure
+ *
+ * start:	First Byte to trim
+ * len:		number of Bytes to trim from start
+ * minlen:	minimum extent length in Bytes
+ *
+ * Decription: nilfs_sufile_trim_fs goes through all segments containing bytes
+ * from start to start+len. For each clean segment blkdev_issue_discard
+ * function is invoked to trim it.
+ *
+ * Return Value: On success, 0 is returned or negative error code, otherwise.
+ */
+int nilfs_sufile_trim_fs(struct inode *sufile, struct fstrim_range *range)
+{
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	struct buffer_head *su_bh;
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
+	ssize_t n;
+	sector_t seg_start, seg_end, start = 0, nblocks = 0;
+	u64 segnum, end, minlen, trimmed = 0;
+	int i, ret = 0;
+	unsigned long segusages_per_block;
+	unsigned int sects_per_block;
+
+	segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
+	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
+		bdev_logical_block_size(nilfs->ns_bdev);
+	segnum = nilfs_get_segnum_of_block(nilfs, range->start >>
+			nilfs->ns_blocksize_bits);
+	end = nilfs_get_segnum_of_block(nilfs, (range->start + range->len)
+			>> nilfs->ns_blocksize_bits);
+	minlen = range->minlen >> nilfs->ns_blocksize_bits;
+
+	if (minlen > nilfs->ns_blocks_per_segment ||
+	    segnum >= nilfs->ns_nsegments ||
+	    range->len < nilfs->ns_blocksize)
+		return -EINVAL;
+	if (end > nilfs->ns_nsegments)
+		end = nilfs->ns_nsegments;
+	if (end == segnum)
+		goto out;
+
+	down_read(&NILFS_MDT(sufile)->mi_sem);
+
+	while (segnum < end) {
+		n = min_t(unsigned long,
+			  segusages_per_block -
+				  nilfs_sufile_get_offset(sufile, segnum),
+			  end - segnum);
+		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
+							   &su_bh);
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				goto out_sem;
+			/* hole */
+			segnum += n;
+			continue;
+		}
+
+		kaddr = kmap(su_bh->b_page);
+		su = nilfs_sufile_block_get_segment_usage(
+			sufile, segnum, su_bh, kaddr);
+		for (i = 0; i < n; ++i, ++segnum, su = (void *)su + susz) {
+			if (!nilfs_segment_usage_clean(su))
+				continue;
+
+			nilfs_get_segment_range(nilfs, segnum, &seg_start,
+						&seg_end);
+
+			if (!nblocks) {
+				start = seg_start;
+				nblocks = seg_end - seg_start + 1;
+			} else if (start + nblocks == seg_start) {
+				nblocks += seg_end - seg_start + 1;
+			} else {
+				ret = blkdev_issue_discard(nilfs->ns_bdev,
+						start * sects_per_block,
+						nblocks * sects_per_block,
+						GFP_NOFS, 0);
+				if (ret < 0) {
+					kunmap(kaddr);
+					put_bh(su_bh);
+					goto out_sem;
+				}
+
+				trimmed += nblocks;
+				nblocks = 0;
+			}
+		}
+		kunmap(kaddr);
+		put_bh(su_bh);
+	}
+
+	if (nblocks) {
+		ret = blkdev_issue_discard(nilfs->ns_bdev,
+					   start * sects_per_block,
+					   nblocks * sects_per_block,
+					   GFP_NOFS, 0);
+		if (!ret)
+			trimmed += nblocks;
+	}
+
+out_sem:
+	up_read(&NILFS_MDT(sufile)->mi_sem);
+out:
+	range->len = trimmed << nilfs->ns_blocksize_bits;
+	return ret;
+}
+
+/**
  * nilfs_sufile_read - read or get sufile inode
  * @sb: super block instance
  * @susize: size of a segment usage entry
diff --git a/fs/nilfs2/sufile.h b/fs/nilfs2/sufile.h
index e84bc5b..2434abd 100644
--- a/fs/nilfs2/sufile.h
+++ b/fs/nilfs2/sufile.h
@@ -65,6 +65,7 @@ void nilfs_sufile_do_set_error(struct inode *, __u64, struct buffer_head *,
 int nilfs_sufile_resize(struct inode *sufile, __u64 newnsegs);
 int nilfs_sufile_read(struct super_block *sb, size_t susize,
 		      struct nilfs_inode *raw_inode, struct inode **inodep);
+int nilfs_sufile_trim_fs(struct inode *sufile, struct fstrim_range *range);
 
 /**
  * nilfs_sufile_scrap - make a segment garbage
-- 
1.8.5.4

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