From d21466f595d8ae115780e7561780e5e14dec0d49 Mon Sep 17 00:00:00 2001
From: Poorna K <poornas@users.noreply.github.com>
Date: Tue, 30 Nov 2021 10:22:42 -0800
Subject: [PATCH] cache: in writeback mode skip etag verification (#13781)

if the commit is still in pending or failed status

This PR also does some minor code cleanup
---
 cmd/disk-cache-backend.go |  4 ----
 cmd/disk-cache-utils.go   | 11 +++++++++++
 cmd/disk-cache.go         | 10 ++++++++++
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/cmd/disk-cache-backend.go b/cmd/disk-cache-backend.go
index 2a202aa51..e3730866f 100644
--- a/cmd/disk-cache-backend.go
+++ b/cmd/disk-cache-backend.go
@@ -808,10 +808,6 @@ func (c *diskCache) GetLockContext(ctx context.Context, bucket, object string) (
 
 // Caches the object to disk
 func (c *diskCache) Put(ctx context.Context, bucket, object string, data io.Reader, size int64, rs *HTTPRangeSpec, opts ObjectOptions, incHitsOnly, writeback bool) (oi ObjectInfo, err error) {
-	if !c.diskSpaceAvailable(size) {
-		io.Copy(ioutil.Discard, data)
-		return oi, errDiskFull
-	}
 	cLock, lkctx, err := c.GetLockContext(ctx, bucket, object)
 	if err != nil {
 		return oi, err
diff --git a/cmd/disk-cache-utils.go b/cmd/disk-cache-utils.go
index eb28b5f74..d1f1f435e 100644
--- a/cmd/disk-cache-utils.go
+++ b/cmd/disk-cache-utils.go
@@ -581,3 +581,14 @@ func (t *multiWriter) Write(p []byte) (n int, err error) {
 func cacheMultiWriter(w1 io.Writer, w2 *io.PipeWriter) io.Writer {
 	return &multiWriter{backendWriter: w1, cacheWriter: w2}
 }
+
+// skipETagVerification returns true if writeback commit is not complete
+func skipETagVerification(m map[string]string) bool {
+	if v, ok := m[writeBackStatusHeader]; ok {
+		switch cacheCommitStatus(v) {
+		case CommitPending, CommitFailed:
+			return true
+		}
+	}
+	return false
+}
diff --git a/cmd/disk-cache.go b/cmd/disk-cache.go
index fa3856f8a..0064622f5 100644
--- a/cmd/disk-cache.go
+++ b/cmd/disk-cache.go
@@ -276,6 +276,10 @@ func (c *cacheObjects) GetObjectNInfo(ctx context.Context, bucket, object string
 			bReader.ObjInfo.CacheStatus = CacheMiss
 			return bReader, err
 		}
+		// serve cached content without ETag verification if writeback commit is not yet complete
+		if skipETagVerification(cacheReader.ObjInfo.UserDefined) {
+			return cacheReader, nil
+		}
 	}
 
 	objInfo, err := c.InnerGetObjectInfoFn(ctx, bucket, object, opts)
@@ -422,6 +426,10 @@ func (c *cacheObjects) GetObjectInfo(ctx context.Context, bucket, object string,
 			c.cacheStats.incHit()
 			return cachedObjInfo, nil
 		}
+		// serve cache metadata without ETag verification if writeback commit is not yet complete
+		if skipETagVerification(cachedObjInfo.UserDefined) {
+			return cachedObjInfo, nil
+		}
 	}
 
 	objInfo, err := getObjectInfoFn(ctx, bucket, object, opts)
@@ -811,6 +819,8 @@ func (c *cacheObjects) uploadObject(ctx context.Context, oi ObjectInfo) {
 
 func (c *cacheObjects) queueWritebackRetry(oi ObjectInfo) {
 	select {
+	case <-GlobalContext.Done():
+		return
 	case c.wbRetryCh <- oi:
 		c.uploadObject(GlobalContext, oi)
 	default: