[PATCH for 4.9.x] Revert "btrfs: Honour FITRIM range constraints during free space trim"

[David Sterba <dsterba@suse.com>]

This reverts commit 038ec2c13e0d1f7b9d45a081786f18f75b65f11b.

There is currently no corresponding patch in master due to additional
changes that would be significantly different from plain revert in the
respective stable branch.

The range argument was not handled correctly and could cause trim to
overlap allocated areas or reach beyond the end of the device. The
address space that fitrim normally operates on is in logical
coordinates, while the discards are done on the physical device extents.
This distinction cannot be made with the current ioctl interface and
caused the confusion.

The bug depends on the layout of block groups and does not always
happen. The whole-fs trim (run by default by the fstrim tool) is not
affected.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/extent-tree.c | 25 ++++++-------------------
 1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 6b29165f766f..7938c48c72ff 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -11150,9 +11150,9 @@ int btrfs_error_unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
  * transaction.
  */
 static int btrfs_trim_free_extents(struct btrfs_device *device,
-				   struct fstrim_range *range, u64 *trimmed)
+				   u64 minlen, u64 *trimmed)
 {
-	u64 start = range->start, len = 0;
+	u64 start = 0, len = 0;
 	int ret;
 
 	*trimmed = 0;
@@ -11188,8 +11188,8 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
 			atomic_inc(&trans->use_count);
 		spin_unlock(&fs_info->trans_lock);
 
-		ret = find_free_dev_extent_start(trans, device, range->minlen,
-						 start, &start, &len);
+		ret = find_free_dev_extent_start(trans, device, minlen, start,
+						 &start, &len);
 		if (trans)
 			btrfs_put_transaction(trans);
 
@@ -11201,16 +11201,6 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
 			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);
 		up_read(&fs_info->commit_root_sem);
 		mutex_unlock(&fs_info->chunk_mutex);
@@ -11221,10 +11211,6 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
 		start += len;
 		*trimmed += bytes;
 
-		/* We've trimmed enough */
-		if (*trimmed >= range->len)
-			break;
-
 		if (fatal_signal_pending(current)) {
 			ret = -ERESTARTSYS;
 			break;
@@ -11309,7 +11295,8 @@ int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
 	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, &group_trimmed);
+		ret = btrfs_trim_free_extents(device, range->minlen,
+					      &group_trimmed);
 		if (ret) {
 			dev_failed++;
 			dev_ret = ret;
-- 
2.21.0