Make use of new error context stack mechanism to allow random errors

detected during buffer dump to be labeled with the buffer location.
For example, if a page LSN is clobbered, we now produce something like
ERROR:  XLogFlush: request 2C000000/8468EC8 is not satisfied --- flushed only
to 0/8468EF0
CONTEXT:  writing block 0 of relation 428946/566240
whereas before there was no convenient way to find out which page had
been trashed.

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 119cfe92b0dafa1de23109fbda6cf671a56eec8e..89087f0fb877d8c31ab777c98f1dc3fbd4c6060d 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.135 2003/03/28 20:17:13 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.136 2003/05/10 19:04:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -68,6 +68,7 @@ static void WaitIO(BufferDesc *buf);
 static void StartBufferIO(BufferDesc *buf, bool forInput);
 static void TerminateBufferIO(BufferDesc *buf);
 static void ContinueBufferIO(BufferDesc *buf, bool forInput);
+static void buffer_write_error_callback(void *arg);
 
 /*
  * Macro : BUFFER_IS_BROKEN
@@ -699,14 +700,24 @@ BufferSync(void)
 {
    int         i;
    BufferDesc *bufHdr;
-   Buffer      buffer;
-   int         status;
-   RelFileNode rnode;
-   XLogRecPtr  recptr;
-   Relation    reln = NULL;
+   ErrorContextCallback errcontext;
+
+   /* Setup error traceback support for ereport() */
+   errcontext.callback = buffer_write_error_callback;
+   errcontext.arg = NULL;
+   errcontext.previous = error_context_stack;
+   error_context_stack = &errcontext;
 
    for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
    {
+       Buffer      buffer;
+       int         status;
+       RelFileNode rnode;
+       XLogRecPtr  recptr;
+       Relation    reln;
+
+       errcontext.arg = bufHdr;
+
        LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
 
        if (!(bufHdr->flags & BM_VALID))
@@ -834,6 +845,8 @@ BufferSync(void)
            RelationDecrementReferenceCount(reln);
    }
 
+   /* Pop the error context stack */
+   error_context_stack = errcontext.previous;
 }
 
 /*
@@ -1011,12 +1024,19 @@ BufferReplace(BufferDesc *bufHdr)
    Relation    reln;
    XLogRecPtr  recptr;
    int         status;
+   ErrorContextCallback errcontext;
 
    /* To check if block content changed while flushing. - vadim 01/17/97 */
    bufHdr->flags &= ~BM_JUST_DIRTIED;
 
    LWLockRelease(BufMgrLock);
 
+   /* Setup error traceback support for ereport() */
+   errcontext.callback = buffer_write_error_callback;
+   errcontext.arg = bufHdr;
+   errcontext.previous = error_context_stack;
+   error_context_stack = &errcontext;
+
    /*
     * No need to lock buffer context - no one should be able to end
     * ReadBuffer
@@ -1043,6 +1063,9 @@ BufferReplace(BufferDesc *bufHdr)
    if (reln != (Relation) NULL)
        RelationDecrementReferenceCount(reln);
 
+   /* Pop the error context stack */
+   error_context_stack = errcontext.previous;
+
    LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
 
    if (status == SM_FAIL)
@@ -1380,12 +1403,20 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
    BufferDesc *bufHdr;
    XLogRecPtr  recptr;
    int         status;
+   ErrorContextCallback errcontext;
+
+   /* Setup error traceback support for ereport() */
+   errcontext.callback = buffer_write_error_callback;
+   errcontext.arg = NULL;
+   errcontext.previous = error_context_stack;
+   error_context_stack = &errcontext;
 
    if (rel->rd_istemp)
    {
        for (i = 0; i < NLocBuffer; i++)
        {
            bufHdr = &LocalBufferDescriptors[i];
+           errcontext.arg = bufHdr;
            if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
            {
                if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
@@ -1395,6 +1426,7 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
                                       (char *) MAKE_PTR(bufHdr->data));
                    if (status == SM_FAIL)
                    {
+                       error_context_stack = errcontext.previous;
                        elog(WARNING, "FlushRelationBuffers(%s (local), %u): block %u is dirty, could not flush it",
                             RelationGetRelationName(rel), firstDelBlock,
                             bufHdr->tag.blockNum);
@@ -1405,6 +1437,7 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
                }
                if (LocalRefCount[i] > 0)
                {
+                   error_context_stack = errcontext.previous;
                    elog(WARNING, "FlushRelationBuffers(%s (local), %u): block %u is referenced (%ld)",
                         RelationGetRelationName(rel), firstDelBlock,
                         bufHdr->tag.blockNum, LocalRefCount[i]);
@@ -1414,6 +1447,10 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
                    bufHdr->tag.rnode.relNode = InvalidOid;
            }
        }
+
+       /* Pop the error context stack */
+       error_context_stack = errcontext.previous;
+
        return 0;
    }
 
@@ -1422,6 +1459,7 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
    for (i = 0; i < NBuffers; i++)
    {
        bufHdr = &BufferDescriptors[i];
+       errcontext.arg = bufHdr;
        if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
        {
            if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
@@ -1483,6 +1521,7 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
            if (!(bufHdr->flags & BM_FREE))
            {
                LWLockRelease(BufMgrLock);
+               error_context_stack = errcontext.previous;
                elog(WARNING, "FlushRelationBuffers(%s, %u): block %u is referenced (private %ld, global %d)",
                     RelationGetRelationName(rel), firstDelBlock,
                     bufHdr->tag.blockNum,
@@ -1493,7 +1532,12 @@ FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
                BufTableDelete(bufHdr);
        }
    }
+
    LWLockRelease(BufMgrLock);
+
+   /* Pop the error context stack */
+   error_context_stack = errcontext.previous;
+
    return 0;
 }
 
@@ -2083,3 +2127,17 @@ BufferGetFileNode(Buffer buffer)
 
    return (bufHdr->tag.rnode);
 }
+
+/*
+ * Error context callback for errors occurring during buffer writes.
+ */
+static void
+buffer_write_error_callback(void *arg)
+{
+   BufferDesc *bufHdr = (BufferDesc *) arg;
+
+   if (bufHdr != NULL)
+       errcontext("writing block %u of relation %u/%u",
+                  bufHdr->tag.blockNum,
+                  bufHdr->tag.rnode.tblNode, bufHdr->tag.rnode.relNode);
+}