Fix two violations of the ResourceOwnerEnlarge/Remember protocol.

The point of having separate ResourceOwnerEnlargeFoo and
ResourceOwnerRememberFoo functions is so that resource allocation
can happen in between.  Doing it in some other order is just wrong.

OpenTemporaryFile() did open(), enlarge, remember, which would leak the
open file if the enlarge step ran out of memory.  Because fd.c has its own
layer of resource-remembering, the consequences look like they'd be limited
to an intratransaction FD leak, but it's still not good.

IncrBufferRefCount() did enlarge, remember, incr-refcount, which would blow
up if the incr-refcount step ever failed.  It was safe enough when written,
but since the introduction of PrivateRefCountHash, I think the assumption
that no error could happen there is pretty shaky.

The odds of real problems from either bug are probably small, but still,
back-patch to supported branches.

Thomas Munro and Tom Lane, per a comment from Andres Freund

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 2803159bc5879ee65c21f11061444e7a0642cc5d..d9adcf7fe6a57d8e95a4deea638ca2790f045ee6 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2629,11 +2629,11 @@ IncrBufferRefCount(Buffer buffer)
 {
    Assert(BufferIsPinned(buffer));
    ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
-   ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
    if (BufferIsLocal(buffer))
        LocalRefCount[-buffer - 1]++;
    else
        PrivateRefCount[buffer - 1]++;
+   ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
 }
 
 /*

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 845023590eab9e708ca82d342de6d0d8f5ddfa0f..53458cbbd6220b88bd8fac9323ecbecc8f20df36 100644 (file)
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -1193,6 +1193,13 @@ OpenTemporaryFile(bool interXact)
 {
    File        file = 0;
 
+   /*
+    * Make sure the current resource owner has space for this File before we
+    * open it, if we'll be registering it below.
+    */
+   if (!interXact)
+       ResourceOwnerEnlargeFiles(CurrentResourceOwner);
+
    /*
     * If some temp tablespace(s) have been given to us, try to use the next
     * one.  If a given tablespace can't be found, we silently fall back to
@@ -1229,9 +1236,8 @@ OpenTemporaryFile(bool interXact)
    {
        VfdCache[file].fdstate |= FD_XACT_TEMPORARY;
 
-       ResourceOwnerEnlargeFiles(CurrentResourceOwner);
-       ResourceOwnerRememberFile(CurrentResourceOwner, file);
        VfdCache[file].resowner = CurrentResourceOwner;
+       ResourceOwnerRememberFile(CurrentResourceOwner, file);
 
        /* ensure cleanup happens at eoxact */
        have_xact_temporary_files = true;