From b2e8044fbdb854fa58a9a8c8881b40b66b21a890 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Mon, 8 May 2023 21:40:23 +0200
Subject: [PATCH 1/3] Fix inverted condition for fsync warning

The warning should only be printed if fsync is _not_ supported and not
the other way around.
---
 repo/repo.go | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/repo/repo.go b/repo/repo.go
index 3162980..0cae450 100644
--- a/repo/repo.go
+++ b/repo/repo.go
@@ -638,15 +638,16 @@ func (h *Handler) saveBlob(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if !syncNotSup {
+	if syncNotSup {
+		h.fsyncWarning.Do(func() {
+			log.Print("WARNING: fsync is not supported by the data storage. This can lead to data loss, if the system crashes or the storage is unexpectedly disconnected.")
+		})
+	} else {
 		if err := syncDir(filepath.Dir(path)); err != nil {
 			// Don't call os.Remove(path) as this is prone to race conditions with parallel upload retries
 			h.internalServerError(w, err)
 			return
 		}
-		h.fsyncWarning.Do(func() {
-			log.Print("WARNING: fsync is not supported by the data storage. This can lead to data loss, if the system crashes or the storage is unexpectedly disconnected.")
-		})
 	}
 
 	h.sendMetric(objectType, BlobWrite, uint64(written))

From be14687a9c862065ffcbd88eae250d9adde0a1fd Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Sat, 13 May 2023 21:50:39 +0200
Subject: [PATCH 2/3] Print fsync warning only once

The repo.Handler is freshly instantiated for every request such that it
forget that the fsync warning was already printed. Use a single instance
in the Server instead.
---
 handlers.go  | 3 +++
 repo/repo.go | 5 ++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/handlers.go b/handlers.go
index f1f3954..8163ccf 100644
--- a/handlers.go
+++ b/handlers.go
@@ -7,6 +7,7 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/restic/rest-server/quota"
 	"github.com/restic/rest-server/repo"
@@ -34,6 +35,7 @@ type Server struct {
 
 	htpasswdFile *HtpasswdFile
 	quotaManager *quota.Manager
+	fsyncWarning sync.Once
 }
 
 // MaxFolderDepth is the maxDepth param passed to splitURLPath.
@@ -91,6 +93,7 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		QuotaManager:   s.quotaManager, // may be nil
 		PanicOnError:   s.PanicOnError,
 		NoVerifyUpload: s.NoVerifyUpload,
+		FsyncWarning:   &s.fsyncWarning,
 	}
 	if s.Prometheus {
 		opt.BlobMetricFunc = makeBlobMetricFunc(username, folderPath)
diff --git a/repo/repo.go b/repo/repo.go
index 0cae450..a1ad642 100644
--- a/repo/repo.go
+++ b/repo/repo.go
@@ -39,6 +39,7 @@ type Options struct {
 
 	BlobMetricFunc BlobMetricFunc
 	QuotaManager   *quota.Manager
+	FsyncWarning   *sync.Once
 }
 
 // DefaultDirMode is the file mode used for directory creation if not
@@ -74,8 +75,6 @@ func New(path string, opt Options) (*Handler, error) {
 type Handler struct {
 	path string // filesystem path of repo
 	opt  Options
-
-	fsyncWarning sync.Once
 }
 
 // httpDefaultError write a HTTP error with the default description
@@ -639,7 +638,7 @@ func (h *Handler) saveBlob(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if syncNotSup {
-		h.fsyncWarning.Do(func() {
+		h.opt.FsyncWarning.Do(func() {
 			log.Print("WARNING: fsync is not supported by the data storage. This can lead to data loss, if the system crashes or the storage is unexpectedly disconnected.")
 		})
 	} else {

From 420c4c6683ea1e2dfaddf2d17fa9d37098452fdc Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Sat, 13 May 2023 21:59:48 +0200
Subject: [PATCH 3/3] Add changelog for fsync warning

---
 changelog/unreleased/issue-230 | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 changelog/unreleased/issue-230

diff --git a/changelog/unreleased/issue-230 b/changelog/unreleased/issue-230
new file mode 100644
index 0000000..6f9704d
--- /dev/null
+++ b/changelog/unreleased/issue-230
@@ -0,0 +1,9 @@
+Bugfix: Fix erroneous warnings about unsupported fsync
+
+Due to a regression in rest-server 0.12.0, it continuously printed
+`WARNING: fsync is not supported by the data storage. This can lead to data loss,
+if the system crashes or the storage is unexpectedly disconnected.` for systems
+that support fsync. We have fixed the warning.
+
+https://github.com/restic/rest-server/issues/230
+https://github.com/restic/rest-server/pull/231