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 a70e26896c735777c343624da3d4433bd18c03e1..4589480afacf6fbb38ba307bba741781d7c3391a 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2630,11 +2630,11 @@ 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 0c8dd78bacd703adbe910bca86456dfcb992a71a..80f4fe05d305918fb98dc068dbc73a5860ecd6dc 100644 (file)
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -1194,6 +1194,13 @@ 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
@@ -1230,9 +1237,8 @@ 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;