From 16514290411b99b5887653043647429e8c6cba91 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Mon, 4 Apr 2022 09:55:05 +0100
Subject: [PATCH] union: add min_free_space option for lfs/eplfs policies -
 fixes #6071

---
 backend/union/common/options.go |  1 +
 backend/union/policy/eplfs.go   | 19 +++++++++++++------
 backend/union/union.go          |  8 ++++++++
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/backend/union/common/options.go b/backend/union/common/options.go
index cc275cc37..edc715203 100644
--- a/backend/union/common/options.go
+++ b/backend/union/common/options.go
@@ -13,4 +13,5 @@ type Options struct {
 	CreatePolicy string          `config:"create_policy"`
 	SearchPolicy string          `config:"search_policy"`
 	CacheTime    int             `config:"cache_time"`
+	MinFreeSpace fs.SizeSuffix   `config:"min_free_space"`
 }
diff --git a/backend/union/policy/eplfs.go b/backend/union/policy/eplfs.go
index a2788138c..28d84ff5c 100644
--- a/backend/union/policy/eplfs.go
+++ b/backend/union/policy/eplfs.go
@@ -2,6 +2,7 @@ package policy
 
 import (
 	"context"
+	"errors"
 	"math"
 
 	"github.com/rclone/rclone/backend/union/upstream"
@@ -18,6 +19,8 @@ type EpLfs struct {
 	EpAll
 }
 
+var errNoUpstreamsFound = errors.New("no upstreams found with more than min_free_space space spare")
+
 func (p *EpLfs) lfs(upstreams []*upstream.Fs) (*upstream.Fs, error) {
 	var minFreeSpace int64 = math.MaxInt64
 	var lfsupstream *upstream.Fs
@@ -27,31 +30,35 @@ func (p *EpLfs) lfs(upstreams []*upstream.Fs) (*upstream.Fs, error) {
 			fs.LogPrintf(fs.LogLevelNotice, nil,
 				"Free Space is not supported for upstream %s, treating as infinite", u.Name())
 		}
-		if space < minFreeSpace {
+		if space < minFreeSpace && space > int64(u.Opt.MinFreeSpace) {
 			minFreeSpace = space
 			lfsupstream = u
 		}
 	}
 	if lfsupstream == nil {
-		return nil, fs.ErrorObjectNotFound
+		return nil, errNoUpstreamsFound
 	}
 	return lfsupstream, nil
 }
 
 func (p *EpLfs) lfsEntries(entries []upstream.Entry) (upstream.Entry, error) {
-	var minFreeSpace int64
+	var minFreeSpace int64 = math.MaxInt64
 	var lfsEntry upstream.Entry
 	for _, e := range entries {
-		space, err := e.UpstreamFs().GetFreeSpace()
+		u := e.UpstreamFs()
+		space, err := u.GetFreeSpace()
 		if err != nil {
 			fs.LogPrintf(fs.LogLevelNotice, nil,
-				"Free Space is not supported for upstream %s, treating as infinite", e.UpstreamFs().Name())
+				"Free Space is not supported for upstream %s, treating as infinite", u.Name())
 		}
-		if space < minFreeSpace {
+		if space < minFreeSpace && space > int64(u.Opt.MinFreeSpace) {
 			minFreeSpace = space
 			lfsEntry = e
 		}
 	}
+	if lfsEntry == nil {
+		return nil, errNoUpstreamsFound
+	}
 	return lfsEntry, nil
 }
 
diff --git a/backend/union/union.go b/backend/union/union.go
index dc4e2c589..9776c55d2 100644
--- a/backend/union/union.go
+++ b/backend/union/union.go
@@ -50,6 +50,14 @@ func init() {
 			Name:    "cache_time",
 			Help:    "Cache time of usage and free space (in seconds).\n\nThis option is only useful when a path preserving policy is used.",
 			Default: 120,
+		}, {
+			Name: "min_free_space",
+			Help: `Minimum viable free space for lfs/eplfs policies.
+
+If a remote has less than this much free space then it won't be
+considered for use in lfs or eplfs policies.`,
+			Advanced: true,
+			Default:  fs.Gibi,
 		}},
 	}
 	fs.Register(fsi)