FAILED: patch "[PATCH] btrfs: Honour FITRIM range constraints during free space trim" failed to apply to 4.4-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From c2d1b3aae33605a61cbab445d8ae1c708ccd2698 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov <nborisov@xxxxxxxx>
Date: Mon, 25 Mar 2019 14:31:21 +0200
Subject: [PATCH] btrfs: Honour FITRIM range constraints during free space trim

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>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index aa52b0995fba..c5f9e8359c6f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -11309,9 +11309,9 @@ int btrfs_error_unpin_extent_range(struct btrfs_fs_info *fs_info,
  * 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;
@@ -11354,8 +11354,8 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
 		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);
@@ -11368,6 +11368,16 @@ 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);
 		mutex_unlock(&fs_info->chunk_mutex);
 
@@ -11377,6 +11387,10 @@ 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;
@@ -11460,8 +11474,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, 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->minlen,
-					      &group_trimmed);
+		ret = btrfs_trim_free_extents(device, range, &group_trimmed);
 		if (ret) {
 			dev_failed++;
 			dev_ret = ret;