[PATCH v2 2/2] exfat: add support FITRIM ioctl

[Hyeongseok Kim <hyeongseok@gmail.com>]

add FITRIM ioctl to support trimming mounted filesystem

Signed-off-by: Hyeongseok Kim <hyeongseok@gmail.com>
---
 fs/exfat/balloc.c   | 81 +++++++++++++++++++++++++++++++++++++++++++++
 fs/exfat/exfat_fs.h |  1 +
 fs/exfat/file.c     | 33 ++++++++++++++++++
 3 files changed, 115 insertions(+)

diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c
index 761c79c3a4ba..d47beef66892 100644
--- a/fs/exfat/balloc.c
+++ b/fs/exfat/balloc.c
@@ -273,3 +273,84 @@ int exfat_count_used_clusters(struct super_block *sb, unsigned int *ret_count)
 	*ret_count = count;
 	return 0;
 }
+
+int exfat_trim_fs(struct inode *inode, struct fstrim_range *range)
+{
+	unsigned int trim_begin, trim_end, count, next_free_clu;
+	u64 clu_start, clu_end, trim_minlen, trimmed_total = 0;
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	int err = 0;
+
+	clu_start = max_t(u64, range->start >> sbi->cluster_size_bits,
+				EXFAT_FIRST_CLUSTER);
+	clu_end = clu_start + (range->len >> sbi->cluster_size_bits) - 1;
+	trim_minlen = range->minlen >> sbi->cluster_size_bits;
+
+	if (clu_start >= sbi->num_clusters || range->len < sbi->cluster_size)
+		return -EINVAL;
+
+	if (clu_end >= sbi->num_clusters)
+		clu_end = sbi->num_clusters - 1;
+
+	mutex_lock(&EXFAT_SB(inode->i_sb)->s_lock);
+
+	trim_begin = trim_end = exfat_find_free_bitmap(sb, clu_start);
+	if (trim_begin == EXFAT_EOF_CLUSTER)
+		goto unlock;
+
+	next_free_clu = exfat_find_free_bitmap(sb, trim_end + 1);
+	if (next_free_clu == EXFAT_EOF_CLUSTER)
+		goto unlock;
+
+	do {
+		if (next_free_clu == trim_end + 1)
+			/* extend trim range for continuous free cluster */
+			trim_end++;
+		else {
+			/* trim current range if it's larger than trim_minlen */
+			count = trim_end - trim_begin + 1;
+			if (count >= trim_minlen) {
+				err = sb_issue_discard(sb,
+					exfat_cluster_to_sector(sbi, trim_begin),
+					count * sbi->sect_per_clus, GFP_NOFS, 0);
+				if (err)
+					goto unlock;
+
+				trimmed_total += count;
+			}
+
+			/* set next start point of the free hole */
+			trim_begin = trim_end = next_free_clu;
+		}
+
+		if (next_free_clu >= clu_end)
+			break;
+
+		if (fatal_signal_pending(current)) {
+			err = -ERESTARTSYS;
+			goto unlock;
+		}
+
+		next_free_clu = exfat_find_free_bitmap(sb, next_free_clu + 1);
+
+	} while (next_free_clu != EXFAT_EOF_CLUSTER &&
+			next_free_clu > trim_end);
+
+	/* try to trim remainder */
+	count = trim_end - trim_begin + 1;
+	if (count >= trim_minlen) {
+		err = sb_issue_discard(sb, exfat_cluster_to_sector(sbi, trim_begin),
+			count * sbi->sect_per_clus, GFP_NOFS, 0);
+		if (err)
+			goto unlock;
+
+		trimmed_total += count;
+	}
+
+unlock:
+	mutex_unlock(&EXFAT_SB(inode->i_sb)->s_lock);
+	range->len = trimmed_total << sbi->cluster_size_bits;
+
+	return err;
+}
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index a183021ae31d..e050aea0b639 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -411,6 +411,7 @@ int exfat_set_bitmap(struct inode *inode, unsigned int clu);
 void exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync);
 unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu);
 int exfat_count_used_clusters(struct super_block *sb, unsigned int *ret_count);
+int exfat_trim_fs(struct inode *inode, struct fstrim_range *range);
 
 /* file.c */
 extern const struct file_operations exfat_file_operations;
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 679828e7be07..0cbad1577841 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -349,9 +349,42 @@ int exfat_setattr(struct dentry *dentry, struct iattr *attr)
 	return error;
 }
 
+static int exfat_ioctl_fitrim(struct inode *inode, unsigned long arg)
+{
+	struct super_block *sb = inode->i_sb;
+	struct request_queue *q = bdev_get_queue(sb->s_bdev);
+	struct fstrim_range range;
+	int ret = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (!blk_queue_discard(q))
+		return -EOPNOTSUPP;
+
+	if (copy_from_user(&range, (struct fstrim_range __user *)arg, sizeof(range)))
+		return -EFAULT;
+
+	range.minlen = max_t(unsigned int, range.minlen,
+				q->limits.discard_granularity);
+
+	ret = exfat_trim_fs(inode, &range);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user((struct fstrim_range __user *)arg, &range, sizeof(range)))
+		return -EFAULT;
+
+	return 0;
+}
+
 long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
+	struct inode *inode = file_inode(filp);
+
 	switch (cmd) {
+	case FITRIM:
+		return exfat_ioctl_fitrim(inode, arg);
 	default:
 		return -ENOTTY;
 	}
-- 
2.27.0.83.g0313f36