From 9eee5a179133da5d46b2b69dca9e9f73e25f3eaf Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Fri, 29 Mar 2024 16:54:04 +0300
Subject: [PATCH] Prevent panic possible on parallel conflict & multipart
 complete

---
 internal/file.go | 79 ++++++++++++++++++++++++++----------------------
 1 file changed, 43 insertions(+), 36 deletions(-)

diff --git a/internal/file.go b/internal/file.go
index e456b5a..2f05c2d 100644
--- a/internal/file.go
+++ b/internal/file.go
@@ -1649,6 +1649,10 @@ func (inode *Inode) flushPart(part uint64) {
 // LOCKS_REQUIRED(inode.mu)
 func (inode *Inode) completeMultipart() {
 	// Server-side copy unmodified parts
+	if inode.mpu == nil {
+		// Multipart upload was canceled in the meantime (by a parallel conflict) => do not complete
+		return
+	}
 	finalSize := inode.Attributes.Size
 	numParts := inode.fs.partNum(finalSize)
 	numPartOffset, _ := inode.fs.partRange(numParts)
@@ -1668,47 +1672,50 @@ func (inode *Inode) completeMultipart() {
 		return
 	}
 	inode.recordFlushError(err)
-	if err == nil && (inode.CacheState == ST_CREATED || inode.CacheState == ST_MODIFIED) {
-		cloud, key := inode.cloud()
-		if inode.oldParent != nil {
-			// Always apply modifications before moving
-			_, key = inode.oldParent.cloud()
-			key = appendChildName(key, inode.oldName)
+	if err != nil || inode.CacheState != ST_CREATED && inode.CacheState != ST_MODIFIED ||
+		inode.mpu == nil {
+		// Error, or already flushed, or conflict => do not complete
+		return
+	}
+	cloud, key := inode.cloud()
+	if inode.oldParent != nil {
+		// Always apply modifications before moving
+		_, key = inode.oldParent.cloud()
+		key = appendChildName(key, inode.oldName)
+	}
+	// Finalize the upload
+	mpu := inode.mpu
+	mpu.NumParts = uint32(numParts)
+	inode.mu.Unlock()
+	inode.fs.addInflightChange(key)
+	resp, err := cloud.MultipartBlobCommit(mpu)
+	inode.fs.completeInflightChange(key)
+	inode.mu.Lock()
+	if inode.mpu != mpu || inode.CacheState != ST_CREATED && inode.CacheState != ST_MODIFIED {
+		// Already flushed or conflict => do not complete
+		return
+	}
+	inode.recordFlushError(err)
+	if err != nil {
+		log.Warnf("Failed to finalize multi-part upload of object %v: %v", key, err)
+		if inode.mpu.Metadata != nil {
+			inode.userMetadataDirty = 2
 		}
-		// Finalize the upload
-		inode.mpu.NumParts = uint32(numParts)
-		inode.mu.Unlock()
-		inode.fs.addInflightChange(key)
-		resp, err := cloud.MultipartBlobCommit(inode.mpu)
-		inode.fs.completeInflightChange(key)
-		inode.mu.Lock()
+	} else {
+		log.Debugf("Finalized multi-part upload of object %v: etag=%v, size=%v", key, NilStr(resp.ETag), finalSize)
+		if inode.userMetadataDirty == 1 {
+			inode.userMetadataDirty = 0
+		}
+		inode.mpu = nil
+		inode.buffers.SetFlushedClean()
+		inode.updateFromFlush(finalSize, resp.ETag, resp.LastModified, resp.StorageClass)
 		if inode.CacheState == ST_CREATED || inode.CacheState == ST_MODIFIED {
-			inode.recordFlushError(err)
-			if err != nil {
-				log.Warnf("Failed to finalize multi-part upload of object %v: %v", key, err)
-				if inode.mpu.Metadata != nil {
-					inode.userMetadataDirty = 2
-				}
+			if !inode.isStillDirty() {
+				inode.SetCacheState(ST_CACHED)
 			} else {
-				log.Debugf("Finalized multi-part upload of object %v: etag=%v, size=%v", key, NilStr(resp.ETag), finalSize)
-				if inode.userMetadataDirty == 1 {
-					inode.userMetadataDirty = 0
-				}
-				inode.mpu = nil
-				inode.buffers.SetFlushedClean()
-				inode.updateFromFlush(finalSize, resp.ETag, resp.LastModified, resp.StorageClass)
-				if inode.CacheState == ST_CREATED || inode.CacheState == ST_MODIFIED {
-					if !inode.isStillDirty() {
-						inode.SetCacheState(ST_CACHED)
-					} else {
-						inode.SetCacheState(ST_MODIFIED)
-					}
-				}
+				inode.SetCacheState(ST_MODIFIED)
 			}
 		}
-	} else {
-		// FIXME: Abort multipart upload, but not just here
-		// For example, we also should abort it if a partially flushed file is deleted
 	}
 }