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PackedBatchRefUpdate: Ensure updates are applied on latest packed refs 

In the window between refs being packed (via refDb.pack) and obtaining
updates (via applyUpdates), packed-refs may have been updated by another
actor and relying on the previously read contents may lead to losing the
updates done by the other actor. To help avoid this, read packed-refs
from disk to ensure we have the latest copy after it is locked and
before committing updates to it.

Bug: 581641
Change-Id: Iae71cb30830b307d0df929c9131911ee476c711c
Signed-off-by: Kaushik Lingarkar <quic_kaushikl@quicinc.com>
This commit is contained in:
Kaushik Lingarkar 2023-02-27 15:03:32 -08:00 committed by Matthias Sohn
parent bf9b704d19
commit 47f2f3613c
2 changed files with 29 additions and 16 deletions
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32
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
View File

@ -160,31 +160,35 @@ public void execute(RevWalk walk, ProgressMonitor monitor,
Map<String, LockFile> locks = null;
refdb.inProcessPackedRefsLock.lock();
try {
PackedRefList oldPackedList;
// During clone locking isn't needed since no refs exist yet.
// This also helps to avoid problems with refs only differing in
// case on a case insensitive filesystem (bug 528497)
if (!refdb.isInClone() && shouldLockLooseRefs) {
locks = lockLooseRefs(pending);
if (locks == null) {
return;
}
oldPackedList = refdb.pack(locks);
} else {
// During clone locking isn't needed since no refs exist yet.
// This also helps to avoid problems with refs only differing in
// case on a case insensitive filesystem (bug 528497)
oldPackedList = refdb.getPackedRefs();
}
RefList<Ref> newRefs = applyUpdates(walk, oldPackedList, pending);
if (newRefs == null) {
return;
refdb.pack(locks);
}
LockFile packedRefsLock = refdb.lockPackedRefs();
if (packedRefsLock == null) {
lockFailure(pending.get(0), pending);
return;
}
// commitPackedRefs removes lock file (by renaming over real file).
refdb.commitPackedRefs(packedRefsLock, newRefs, oldPackedList,
true);
try {
PackedRefList oldPackedList = refdb.refreshPackedRefs();
RefList<Ref> newRefs = applyUpdates(walk, oldPackedList, pending);
if (newRefs == null) {
return;
}
refdb.commitPackedRefs(packedRefsLock, newRefs, oldPackedList,
true);
} finally {
// This will be no-op if commitPackedRefs is successful as it
// will remove the lock file (by renaming over real file).
packedRefsLock.unlock();
}
} finally {
try {
unlockAll(locks);

13
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
View File

@ -924,9 +924,18 @@ PackedRefList getPackedRefs() throws IOException {
break;
}
return refreshPackedRefs(curList);
}
PackedRefList refreshPackedRefs() throws IOException {
return refreshPackedRefs(packedRefs.get());
}
private PackedRefList refreshPackedRefs(PackedRefList curList)
throws IOException {
final PackedRefList newList = readPackedRefs();
if (packedRefs.compareAndSet(curList, newList)
&& !curList.id.equals(newList.id)) {
if (packedRefs.compareAndSet(curList, newList) && !curList.id.equals(
newList.id)) {
modCnt.incrementAndGet();
}
return newList;