Merge branch 'stable-6.10' into stable-7.0
* stable-6.10:
Do not always refresh packed-refs during ref updates
Change-Id: I4cdc1b80841481f83b64b800ef54da0b8ef8753a
diff --git a/Documentation/config-options.md b/Documentation/config-options.md
index 78930e6..b30b958 100644
--- a/Documentation/config-options.md
+++ b/Documentation/config-options.md
@@ -55,7 +55,7 @@
| `core.supportsAtomicFileCreation` | `true` | ⃞ | Whether the filesystem supports atomic file creation. |
| `core.symlinks` | Auto detect if filesystem supports symlinks| ✅ | If false, symbolic links are checked out as small plain files that contain the link text. |
| `core.trustFolderStat` | `true` | ⃞ | Whether to trust the pack folder's, packed-refs file's and loose-objects folder's file attributes (Java equivalent of stat command on *nix). When looking for pack files, if `false` JGit will always scan the `.git/objects/pack` folder and if set to `true` it assumes that pack files are unchanged if the file attributes of the pack folder are unchanged. When getting the list of packed refs, if `false` JGit will always read the packed-refs file and if set to `true` it uses the file attributes of the packed-refs file and will only read it if a file attribute has changed. When looking for loose objects, if `false` and if a loose object is not found, JGit will open and close a stream to `.git/objects` folder (which can refresh its directory listing, at least on some NFS clients) and retry looking for that loose object. Setting this option to `false` can help to workaround caching issues on NFS, but reduces performance. |
-| `core.trustPackedRefsStat` | `unset` | ⃞ | Whether to trust the file attributes (Java equivalent of stat command on *nix) of the packed-refs file. If `never` JGit will ignore the file attributes of the packed-refs file and always read it. If `always` JGit will trust the file attributes of the packed-refs file and will only read it if a file attribute has changed. `after_open` behaves the same as `always`, except that the packed-refs file is opened and closed before its file attributes are considered. An open/close of the packed-refs file is known to refresh its file attributes, at least on some NFS clients. If `unset`, JGit will use the behavior described in `trustFolderStat`. |
+| `core.trustPackedRefsStat` | `unset` | ⃞ | Whether to trust the file attributes (Java equivalent of stat command on *nix) of the packed-refs file. If `never` JGit will ignore the file attributes of the packed-refs file and always read it. If `always` JGit will trust the file attributes of the packed-refs file and will only read it if a file attribute has changed. `after_open` behaves the same as `always`, except that the packed-refs file is opened and closed before its file attributes are considered. An open/close of the packed-refs file is known to refresh its file attributes, at least on some NFS clients. If `unset`, JGit will use the behavior described in `trustFolderStat`. Note: since 6.10.2, this setting applies during both ref reads and ref updates, but previously only applied during reads.|
| `core.trustLooseRefStat` | `always` | ⃞ | Whether to trust the file attributes (Java equivalent of stat command on *nix) of the loose ref. If `always` JGit will trust the file attributes of the loose ref and its parent directories. `after_open` behaves similar to `always`, except that all parent directories of the loose ref up to the repository root are opened and closed before its file attributes are considered. An open/close of these parent directories is known to refresh the file attributes, at least on some NFS clients. |
| `core.worktree` | Root directory of the working tree if it is not the parent directory of the `.git` directory | ✅ | The path to the root of the working tree. |
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
index 5584f13..4b5566e 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackedBatchRefUpdate.java
@@ -172,7 +172,7 @@ public void execute(RevWalk walk, ProgressMonitor monitor,
}
packedRefsLock = refdb.lockPackedRefsOrThrow();
- PackedRefList oldPackedList = refdb.refreshPackedRefs();
+ PackedRefList oldPackedList = refdb.getLockedPackedRefs(packedRefsLock);
RefList<Ref> newRefs = applyUpdates(walk, oldPackedList, pending);
if (newRefs == null) {
return;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
index a9f0605..cc48176 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
@@ -702,7 +702,7 @@ void delete(RefDirectoryUpdate update) throws IOException {
PackedRefList packed = getPackedRefs();
if (packed.contains(name)) {
// Force update our packed-refs snapshot before writing
- packed = refreshPackedRefs();
+ packed = getLockedPackedRefs(lck);
int idx = packed.find(name);
if (0 <= idx) {
commitPackedRefs(lck, packed.remove(idx), packed, true);
@@ -770,7 +770,7 @@ private void pack(Collection<String> refs,
try {
LockFile lck = lockPackedRefsOrThrow();
try {
- PackedRefList oldPacked = refreshPackedRefs();
+ PackedRefList oldPacked = getLockedPackedRefs(lck);
RefList<Ref> newPacked = oldPacked;
// Iterate over all refs to be packed
@@ -953,6 +953,15 @@ else if (0 <= (idx = packed.find(dst.getName())))
}
PackedRefList getPackedRefs() throws IOException {
+ return refreshPackedRefsIfNeeded();
+ }
+
+ PackedRefList getLockedPackedRefs(LockFile packedRefsFileLock) throws IOException {
+ packedRefsFileLock.requireLock();
+ return refreshPackedRefsIfNeeded();
+ }
+
+ PackedRefList refreshPackedRefsIfNeeded() throws IOException {
PackedRefList curList = packedRefs.get();
if (!curList.shouldRefresh()) {
return curList;
@@ -967,23 +976,29 @@ private PackedRefsRefresher getPackedRefsRefresher(PackedRefList curList)
return refresher;
}
// This synchronized is NOT needed for correctness. Instead it is used
- // as a throttling mechanism to ensure that only one "read" thread does
- // the work to refresh the file. In order to avoid stalling writes which
- // must already be serialized and tend to be a bottleneck,
- // the refreshPackedRefs() need not be synchronized.
+ // as a mechanism to try to avoid parallel reads of the same file content
+ // since repeating work, even in parallel, hurts performance.
+ // Unfortunately, this approach can still lead to some unnecessary re-reads
+ // during the "racy" window of the snapshot timestamp.
synchronized (this) {
if (packedRefsRefresher.get() != refresher) {
refresher = packedRefsRefresher.get();
if (refresher != null) {
- // Refresher now guaranteed to have been created after the
- // current thread entered getPackedRefsRefresher(), even if
- // it's currently out of date.
+ // Refresher now guaranteed to have not started refreshing until
+ // after the current thread entered getPackedRefsRefresher(),
+ // even if it's currently out of date. And if the packed-refs
+ // lock is held before calling this method, then it is also
+ // guaranteed to not be out-of date even during the "racy"
+ // window of the snapshot timestamp.
return refresher;
}
}
- refresher = createPackedRefsRefresherAsLatest(curList);
+ refresher = new PackedRefsRefresher(curList);
+ packedRefsRefresher.set(refresher);
}
- return runAndClear(refresher);
+ refresher.run();
+ packedRefsRefresher.compareAndSet(refresher, null);
+ return refresher;
}
private boolean shouldRefreshPackedRefs(FileSnapshot snapshot) throws IOException {
@@ -1012,23 +1027,6 @@ private boolean shouldRefreshPackedRefs(FileSnapshot snapshot) throws IOExceptio
return true;
}
- PackedRefList refreshPackedRefs() throws IOException {
- return runAndClear(createPackedRefsRefresherAsLatest(packedRefs.get()))
- .getOrThrowIOException();
- }
-
- private PackedRefsRefresher createPackedRefsRefresherAsLatest(PackedRefList curList) {
- PackedRefsRefresher refresher = new PackedRefsRefresher(curList);
- packedRefsRefresher.set(refresher);
- return refresher;
- }
-
- private PackedRefsRefresher runAndClear(PackedRefsRefresher refresher) {
- refresher.run();
- packedRefsRefresher.compareAndSet(refresher, null);
- return refresher;
- }
-
private PackedRefList refreshPackedRefs(PackedRefList curList)
throws IOException {
final PackedRefList newList = readPackedRefs();
