//+-------------------------------------------------------------------------
//
// Copyright (C) 1992, Microsoft Corporation.
//
// File: fcbsup.c
//
// Contents: Support routines for associating DFS_FCB records with
// file objects, and looking them up again.
//
// Functions: DfsInitFcbs - Initialize the hash table for DFS_FCB lookup
// DfsLookupFcb - Lookup an DFS_FCB associated with a file object
// DfsAttachFcb - Associate an DFS_FCB with a file object
// DfsDetachFcb - Remove the Association between an DFS_FCB and
// a file object
//
// History: 20 Feb 1993 Alanw Created
//
// TODO: the FcbHashTable and Fcbs are currently allocated
// out of non-paged pool; these should probably be
// paged. This would require using some other
// synchronization method on the hash bucket chains
//
//--------------------------------------------------------------------------
#include "dfsprocs.h"
#include "fcbsup.h"
#define Dbg 0x1000
#define HASH(k,m) (((ULONG)(k)>>12^(ULONG)(k)>>2) & m)
#define DEFAULT_HASH_SIZE 16 // default size of hash table
NTSTATUS
DfsInitFcbHashTable(
IN ULONG cHash,
OUT PFCB_HASH_TABLE *ppHashTable);
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE, DfsInitFcbs)
#pragma alloc_text(PAGE, DfsInitFcbHashTable)
//
// The following routines are not pageable because they acquire spinlocks.
//
// DfsLookupFcb
// DfsAttachFcb
// DfsDetachFcb
//
#endif
//+-------------------------------------------------------------------------
//
// Function: DfsInitFcbs - Initialize the DFS_FCB lookup hash table
//
// Synopsis: This function initializes data structures which are
// used for looking up an DFS_FCB associated with some open
// file object.
//
// Arguments: [cHash] -- Size of the hash table to be allocated. Must be
// a power of two. If zero, a default size is used.
//
// Returns: NTSTATUS -- STATUS_SUCCESS, unless memory allocation
// fails.
//
// Note: The hash buckets are initialized to zero, then later
// initialized to a list head when used. This is a debugging
// aid to determine if some hash buckets are never used.
//
//--------------------------------------------------------------------------
NTSTATUS
DfsInitFcbHashTable(
IN ULONG cHash,
OUT PFCB_HASH_TABLE *ppHashTable)
{
PFCB_HASH_TABLE pHashTable;
ULONG cbHashTable;
if (cHash == 0) {
cHash = DEFAULT_HASH_SIZE;
}
ASSERT ((cHash & (cHash-1)) == 0); // Assure cHash is a power of two
cbHashTable = sizeof (FCB_HASH_TABLE) + (cHash-1)*sizeof (LIST_ENTRY);
pHashTable = ExAllocatePool(NonPagedPool, cbHashTable);
if (pHashTable == NULL) {
return STATUS_NO_MEMORY;
}
pHashTable->NodeTypeCode = DSFS_NTC_FCB_HASH;
pHashTable->NodeByteSize = (NODE_BYTE_SIZE) cbHashTable;
pHashTable->HashMask = (cHash-1);
KeInitializeSpinLock( &pHashTable->HashListSpinLock );
RtlZeroMemory(&pHashTable->HashBuckets[0], cHash * sizeof (LIST_ENTRY));
*ppHashTable = pHashTable;
return(STATUS_SUCCESS);
}
NTSTATUS
DfsInitFcbs(
IN ULONG cHash
) {
NTSTATUS status;
status = DfsInitFcbHashTable( cHash, &DfsData.FcbHashTable );
return status;
}
//+-------------------------------------------------------------------------
//
// Function: DfsLookupFcb - Lookup an DFS_FCB in the hash table
//
// Synopsis: This function will lookup the DFS_FCB associated with
// a particular file object.
//
// Arguments: [pFile] -- Pointer to file object for which the DFS_FCB is
// being looked up.
//
// Returns: PVOID -- pointer to the DFS_FCB found, or NULL if none
//
// Algorithm: Knuth would call it hashing with conflict resoulution
// by chaining.
//
// History: 20 Feb 1993 Alanw Created
//
//--------------------------------------------------------------------------
PDFS_FCB
DfsLookupFcb(
IN PFILE_OBJECT pFile
) {
PLIST_ENTRY pListHead, pLink;
PDFS_FCB pFCB;
KIRQL SavedIrql;
PFCB_HASH_TABLE pHashTable = DfsData.FcbHashTable;
KeAcquireSpinLock( &pHashTable->HashListSpinLock, &SavedIrql );
pListHead = &pHashTable->HashBuckets[ HASH(pFile, pHashTable->HashMask) ];
if ((pListHead->Flink == NULL) || // list not initialized
(pListHead->Flink == pListHead)) { // list empty
KeReleaseSpinLock( &pHashTable->HashListSpinLock, SavedIrql );
return NULL;
}
for (pLink = pListHead->Flink; pLink != pListHead; pLink = pLink->Flink) {
pFCB = CONTAINING_RECORD(pLink, DFS_FCB, HashChain);
if (pFCB->FileObject == pFile) {
KeReleaseSpinLock( &pHashTable->HashListSpinLock, SavedIrql );
return pFCB;
}
}
KeReleaseSpinLock( &pHashTable->HashListSpinLock, SavedIrql );
return NULL;
}
//+-------------------------------------------------------------------------
//
// Function: DfsAttachFcb - Inserts an DFS_FCB into the hash table
//
// Synopsis: This function associates an DFS_FCB to a file object. This
// involves inserting it into the hash table.
//
// Arguments: [pFCB] -- Pointer to the DFS_FCB to be inserted.
// [pFileObj] -- Pointer to the corresponding file object, used
// as the hash key.
//
// Returns: -nothing-
//
//--------------------------------------------------------------------------
VOID
DfsAttachFcb(
IN PFILE_OBJECT pFileObj,
IN PDFS_FCB pFCB
) {
PFCB_HASH_TABLE pHashTable = (PFCB_HASH_TABLE) DfsData.FcbHashTable;
PLIST_ENTRY pListHead;
KIRQL SavedIrql;
KeAcquireSpinLock( &pHashTable->HashListSpinLock, &SavedIrql );
pListHead = &pHashTable->HashBuckets[ HASH(pFileObj, pHashTable->HashMask) ];
if (pListHead->Flink == NULL) {
InitializeListHead(pListHead);
}
InsertHeadList(pListHead, &pFCB->HashChain);
KeReleaseSpinLock( &pHashTable->HashListSpinLock, SavedIrql );
DfsDbgTrace(0, Dbg, "Attached Fcb %08lx ", pFCB);
DfsDbgTrace(0, Dbg, "For Fileobject %08lx ", pFileObj);
}
//+-------------------------------------------------------------------------
//
// Function: DfsDetachFcb - Detach an DFS_FCB from the lookup hash table
//
// Synopsis: This function detaches an DFS_FCB from the hash table. This
// involves just deleting it from the hash bucket chain.
//
// Arguments: [pFCB] -- Pointer to the DFS_FCB to be detached.
// [pFileObj] -- Pointer to the corresponding file object, used
// for debugging only.
//
// Returns: -nothing-
//
//--------------------------------------------------------------------------
VOID
DfsDetachFcb(
IN PFILE_OBJECT pFileObj,
IN PDFS_FCB pFCB
) {
PFCB_HASH_TABLE pHashTable = (PFCB_HASH_TABLE) DfsData.FcbHashTable;
KIRQL SavedIrql;
ASSERT(pFCB->FileObject == pFileObj);
ASSERT(DfsLookupFcb(pFCB->FileObject) == pFCB);
KeAcquireSpinLock( &pHashTable->HashListSpinLock, &SavedIrql );
RemoveEntryList(&pFCB->HashChain);
pFCB->FileObject = NULL;
KeReleaseSpinLock( &pHashTable->HashListSpinLock, SavedIrql );
DfsDbgTrace(0, Dbg, "Detached Fcb %08lx ", pFCB);
DfsDbgTrace(0, Dbg, "For Fileobject %08lx ", pFileObj);
}
