[PATCH 5.1 094/128] btrfs: Honour FITRIM range constraints during free space trim

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Nikolay Borisov <nborisov@xxxxxxxx>

commit c2d1b3aae33605a61cbab445d8ae1c708ccd2698 upstream.

Up until now trimming the freespace was done irrespective of what the
arguments of the FITRIM ioctl were. For example fstrim's -o/-l arguments
will be entirely ignored. Fix it by correctly handling those paramter.
This requires breaking if the found freespace extent is after the end of
the passed range as well as completing trim after trimming
fstrim_range::len bytes.

Fixes: 499f377f49f0 ("btrfs: iterate over unused chunk space in FITRIM")
CC: stable@xxxxxxxxxxxxxxx # 4.4+
Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/extent-tree.c |   25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -11315,9 +11315,9 @@ int btrfs_error_unpin_extent_range(struc
  * held back allocations.
  */
 static int btrfs_trim_free_extents(struct btrfs_device *device,
-				   u64 minlen, u64 *trimmed)
+				   struct fstrim_range *range, u64 *trimmed)
 {
-	u64 start = 0, len = 0;
+	u64 start = range->start, len = 0;
 	int ret;
 
 	*trimmed = 0;
@@ -11360,8 +11360,8 @@ static int btrfs_trim_free_extents(struc
 		if (!trans)
 			up_read(&fs_info->commit_root_sem);
 
-		ret = find_free_dev_extent_start(trans, device, minlen, start,
-						 &start, &len);
+		ret = find_free_dev_extent_start(trans, device, range->minlen,
+						 start, &start, &len);
 		if (trans) {
 			up_read(&fs_info->commit_root_sem);
 			btrfs_put_transaction(trans);
@@ -11374,6 +11374,16 @@ static int btrfs_trim_free_extents(struc
 			break;
 		}
 
+		/* If we are out of the passed range break */
+		if (start > range->start + range->len - 1) {
+			mutex_unlock(&fs_info->chunk_mutex);
+			ret = 0;
+			break;
+		}
+
+		start = max(range->start, start);
+		len = min(range->len, len);
+
 		ret = btrfs_issue_discard(device->bdev, start, len, &bytes);
 		mutex_unlock(&fs_info->chunk_mutex);
 
@@ -11383,6 +11393,10 @@ static int btrfs_trim_free_extents(struc
 		start += len;
 		*trimmed += bytes;
 
+		/* We've trimmed enough */
+		if (*trimmed >= range->len)
+			break;
+
 		if (fatal_signal_pending(current)) {
 			ret = -ERESTARTSYS;
 			break;
@@ -11466,8 +11480,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 	devices = &fs_info->fs_devices->devices;
 	list_for_each_entry(device, devices, dev_list) {
-		ret = btrfs_trim_free_extents(device, range->minlen,
-					      &group_trimmed);
+		ret = btrfs_trim_free_extents(device, range, &group_trimmed);
 		if (ret) {
 			dev_failed++;
 			dev_ret = ret;