test6.c

最新的sqlite3.6.2源代码

/*
** 2004 May 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that modified the OS layer in order to simulate
** the effect on the database file of an OS crash or power failure.  This
** is used to test the ability of SQLite to recover from those situations.
**
** $Id: test6.c,v 1.39 2008/06/06 11:11:26 danielk1977 Exp $
*/
#if SQLITE_TEST          /* This file is used for testing only */
#include "sqliteInt.h"
#include "tcl.h"

#ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */

/* #define TRACE_CRASHTEST */

typedef struct CrashFile CrashFile;
typedef struct CrashGlobal CrashGlobal;
typedef struct WriteBuffer WriteBuffer;

/*
** Method:
**
**   This layer is implemented as a wrapper around the "real" 
**   sqlite3_file object for the host system. Each time data is 
**   written to the file object, instead of being written to the
**   underlying file, the write operation is stored in an in-memory 
**   structure (type WriteBuffer). This structure is placed at the
**   end of a global ordered list (the write-list).
**
**   When data is read from a file object, the requested region is
**   first retrieved from the real file. The write-list is then 
**   traversed and data copied from any overlapping WriteBuffer 
**   structures to the output buffer. i.e. a read() operation following
**   one or more write() operations works as expected, even if no
**   data has actually been written out to the real file.
**
**   When a fsync() operation is performed, an operating system crash 
**   may be simulated, in which case exit(-1) is called (the call to 
**   xSync() never returns). Whether or not a crash is simulated,
**   the data associated with a subset of the WriteBuffer structures 
**   stored in the write-list is written to the real underlying files 
**   and the entries removed from the write-list. If a crash is simulated,
**   a subset of the buffers may be corrupted before the data is written.
**
**   The exact subset of the write-list written and/or corrupted is
**   determined by the simulated device characteristics and sector-size.
**
** "Normal" mode:
**
**   Normal mode is used when the simulated device has none of the
**   SQLITE_IOCAP_XXX flags set.
**
**   In normal mode, if the fsync() is not a simulated crash, the 
**   write-list is traversed from beginning to end. Each WriteBuffer
**   structure associated with the file handle used to call xSync()
**   is written to the real file and removed from the write-list.
**
**   If a crash is simulated, one of the following takes place for 
**   each WriteBuffer in the write-list, regardless of which 
**   file-handle it is associated with:
**
**     1. The buffer is correctly written to the file, just as if
**        a crash were not being simulated.
**
**     2. Nothing is done.
**
**     3. Garbage data is written to all sectors of the file that 
**        overlap the region specified by the WriteBuffer. Or garbage
**        data is written to some contiguous section within the 
**        overlapped sectors.
**
** Device Characteristic flag handling:
**
**   If the IOCAP_ATOMIC flag is set, then option (3) above is 
**   never selected.
**
**   If the IOCAP_ATOMIC512 flag is set, and the WriteBuffer represents
**   an aligned write() of an integer number of 512 byte regions, then
**   option (3) above is never selected. Instead, each 512 byte region
**   is either correctly written or left completely untouched. Similar
**   logic governs the behaviour if any of the other ATOMICXXX flags
**   is set.
**
**   If either the IOCAP_SAFEAPPEND or IOCAP_SEQUENTIAL flags are set
**   and a crash is being simulated, then an entry of the write-list is
**   selected at random. Everything in the list after the selected entry 
**   is discarded before processing begins.
**
**   If IOCAP_SEQUENTIAL is set and a crash is being simulated, option 
**   (1) is selected for all write-list entries except the last. If a 
**   crash is not being simulated, then all entries in the write-list
**   that occur before at least one write() on the file-handle specified
**   as part of the xSync() are written to their associated real files.
**
**   If IOCAP_SAFEAPPEND is set and the first byte written by the write()
**   operation is one byte past the current end of the file, then option
**   (1) is always selected.
*/

/*
** Each write operation in the write-list is represented by an instance
** of the following structure.
**
** If zBuf is 0, then this structure represents a call to xTruncate(), 
** not xWrite(). In that case, iOffset is the size that the file is
** truncated to.
*/
struct WriteBuffer {
  i64 iOffset;                 /* Byte offset of the start of this write() */
  int nBuf;                    /* Number of bytes written */
  u8 *zBuf;                    /* Pointer to copy of written data */
  CrashFile *pFile;            /* File this write() applies to */

  WriteBuffer *pNext;          /* Next in CrashGlobal.pWriteList */
};

struct CrashFile {
  const sqlite3_io_methods *pMethod;   /* Must be first */
  sqlite3_file *pRealFile;             /* Underlying "real" file handle */
  char *zName;

  /* Cache of the entire file. This is used to speed up OsRead() and 
  ** OsFileSize() calls. Although both could be done by traversing the
  ** write-list, in practice this is impractically slow.
  */
  int iSize;                           /* Size of file in bytes */
  int nData;                           /* Size of buffer allocated at zData */
  u8 *zData;                           /* Buffer containing file contents */
};

struct CrashGlobal {
  WriteBuffer *pWriteList;     /* Head of write-list */
  WriteBuffer *pWriteListEnd;  /* End of write-list */

  int iSectorSize;             /* Value of simulated sector size */
  int iDeviceCharacteristics;  /* Value of simulated device characteristics */

  int iCrash;                  /* Crash on the iCrash'th call to xSync() */
  char zCrashFile[500];        /* Crash during an xSync() on this file */ 
};

static CrashGlobal g = {0, 0, SQLITE_DEFAULT_SECTOR_SIZE, 0, 0};

/*
** Set this global variable to 1 to enable crash testing.
*/
static int sqlite3CrashTestEnable = 0;

static void *crash_malloc(int nByte){
  return (void *)Tcl_Alloc((size_t)nByte);
}
static void crash_free(void *p){
  Tcl_Free(p);
}
static void *crash_realloc(void *p, int n){
  return (void *)Tcl_Realloc(p, (size_t)n);
}

/*
** Flush the write-list as if xSync() had been called on file handle
** pFile. If isCrash is true, simulate a crash.
*/
static int writeListSync(CrashFile *pFile, int isCrash){
  int rc = SQLITE_OK;
  int iDc = g.iDeviceCharacteristics;

  WriteBuffer *pWrite;
  WriteBuffer **ppPtr;

  /* If this is not a crash simulation, set pFinal to point to the 
  ** last element of the write-list that is associated with file handle
  ** pFile.
  **
  ** If this is a crash simulation, set pFinal to an arbitrarily selected
  ** element of the write-list.
  */
  WriteBuffer *pFinal = 0;
  if( !isCrash ){
    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext){
      if( pWrite->pFile==pFile ){
        pFinal = pWrite;
      }
    }
  }else if( iDc&(SQLITE_IOCAP_SEQUENTIAL|SQLITE_IOCAP_SAFE_APPEND) ){
    int nWrite = 0;
    int iFinal;
    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext) nWrite++;
    sqlite3_randomness(sizeof(int), &iFinal);
    iFinal = ((iFinal<0)?-1*iFinal:iFinal)%nWrite;
    for(pWrite=g.pWriteList; iFinal>0; pWrite=pWrite->pNext) iFinal--;
    pFinal = pWrite;
  }

#ifdef TRACE_CRASHTEST
  printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
#endif

  ppPtr = &g.pWriteList;
  for(pWrite=*ppPtr; rc==SQLITE_OK && pWrite; pWrite=*ppPtr){
    sqlite3_file *pRealFile = pWrite->pFile->pRealFile;

    /* (eAction==1)      -> write block out normally,
    ** (eAction==2)      -> do nothing,
    ** (eAction==3)      -> trash sectors.
    */
    int eAction = 0;
    if( !isCrash ){
      eAction = 2;
      if( (pWrite->pFile==pFile || iDc&SQLITE_IOCAP_SEQUENTIAL) ){
        eAction = 1;
      }
    }else{
      char random;
      sqlite3_randomness(1, &random);

      /* Do not select option 3 (sector trashing) if the IOCAP_ATOMIC flag 
      ** is set or this is an OsTruncate(), not an Oswrite().
      */
      if( (iDc&SQLITE_IOCAP_ATOMIC) || (pWrite->zBuf==0) ){
        random &= 0x01;
      }

      /* If IOCAP_SEQUENTIAL is set and this is not the final entry
      ** in the truncated write-list, always select option 1 (write
      ** out correctly).
      */
      if( (iDc&SQLITE_IOCAP_SEQUENTIAL && pWrite!=pFinal) ){
        random = 0;
      }

      /* If IOCAP_SAFE_APPEND is set and this OsWrite() operation is
      ** an append (first byte of the written region is 1 byte past the
      ** current EOF), always select option 1 (write out correctly).
      */
      if( iDc&SQLITE_IOCAP_SAFE_APPEND && pWrite->zBuf ){
        i64 iSize;
        sqlite3OsFileSize(pRealFile, &iSize);
        if( iSize==pWrite->iOffset ){
          random = 0;
        }
      }

      if( (random&0x06)==0x06 ){
        eAction = 3;
      }else{
        eAction = ((random&0x01)?2:1);
      }
    }

    switch( eAction ){
      case 1: {               /* Write out correctly */
        if( pWrite->zBuf ){
          rc = sqlite3OsWrite(
              pRealFile, pWrite->zBuf, pWrite->nBuf, pWrite->iOffset
          );
        }else{
          rc = sqlite3OsTruncate(pRealFile, pWrite->iOffset);
        }
        *ppPtr = pWrite->pNext;
#ifdef TRACE_CRASHTEST
        if( isCrash ){
          printf("Writing %d bytes @ %d (%s)\n", 
            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
          );
        }
#endif
        crash_free(pWrite);
        break;
      }
      case 2: {               /* Do nothing */
        ppPtr = &pWrite->pNext;
#ifdef TRACE_CRASHTEST
        if( isCrash ){
          printf("Omiting %d bytes @ %d (%s)\n", 
            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
          );
        }
#endif
        break;
      }
      case 3: {               /* Trash sectors */
        u8 *zGarbage;
        int iFirst = (pWrite->iOffset/g.iSectorSize);
        int iLast = (pWrite->iOffset+pWrite->nBuf-1)/g.iSectorSize;

        assert(pWrite->zBuf);

#ifdef TRACE_CRASHTEST
        printf("Trashing %d sectors @ sector %d (%s)\n", 
            1+iLast-iFirst, iFirst, pWrite->pFile->zName
        );
#endif

        zGarbage = crash_malloc(g.iSectorSize);
        if( zGarbage ){
          sqlite3_int64 i;
          for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
            sqlite3_randomness(g.iSectorSize, zGarbage); 
            rc = sqlite3OsWrite(
              pRealFile, zGarbage, g.iSectorSize, i*g.iSectorSize
            );
          }
          crash_free(zGarbage);
        }else{
          rc = SQLITE_NOMEM;
        }

        ppPtr = &pWrite->pNext;
        break;
      }

      default:
        assert(!"Cannot happen");
    }

    if( pWrite==pFinal ) break;
  }

  if( rc==SQLITE_OK && isCrash ){
    exit(-1);
  }

  for(pWrite=g.pWriteList; pWrite && pWrite->pNext; pWrite=pWrite->pNext);
  g.pWriteListEnd = pWrite;

  return rc;
}

/*
** Add an entry to the end of the write-list.
*/
static int writeListAppend(
  sqlite3_file *pFile,
  sqlite3_int64 iOffset,
  const u8 *zBuf,
  int nBuf
){
  WriteBuffer *pNew;

  assert((zBuf && nBuf) || (!nBuf && !zBuf));

  pNew = (WriteBuffer *)crash_malloc(sizeof(WriteBuffer) + nBuf);
  if( pNew==0 ){
    fprintf(stderr, "out of memory in the crash simulator\n");
  }
  memset(pNew, 0, sizeof(WriteBuffer)+nBuf);
  pNew->iOffset = iOffset;
  pNew->nBuf = nBuf;
  pNew->pFile = (CrashFile *)pFile;
  if( zBuf ){
    pNew->zBuf = (u8 *)&pNew[1];
    memcpy(pNew->zBuf, zBuf, nBuf);
  }

  if( g.pWriteList ){
    assert(g.pWriteListEnd);
    g.pWriteListEnd->pNext = pNew;
  }else{
    g.pWriteList = pNew;
  }
  g.pWriteListEnd = pNew;
  
  return SQLITE_OK;
}

/*
** Close a crash-file.
*/
static int cfClose(sqlite3_file *pFile){
  CrashFile *pCrash = (CrashFile *)pFile;
  writeListSync(pCrash, 0);
  sqlite3OsClose(pCrash->pRealFile);
  return SQLITE_OK;
}

/*
** Read data from a crash-file.
*/
static int cfRead(
  sqlite3_file *pFile, 
  void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  CrashFile *pCrash = (CrashFile *)pFile;

  /* Check the file-size to see if this is a short-read */
  if( pCrash->iSize<(iOfst+iAmt) ){
    return SQLITE_IOERR_SHORT_READ;
  }

  memcpy(zBuf, &pCrash->zData[iOfst], iAmt);
  return SQLITE_OK;
}

/*
** Write data to a crash-file.
*/
static int cfWrite(
  sqlite3_file *pFile, 
  const void *zBuf, 
  int iAmt, 
  sqlite_int64 iOfst
){
  CrashFile *pCrash = (CrashFile *)pFile;
  if( iAmt+iOfst>pCrash->iSize ){
    pCrash->iSize = iAmt+iOfst;
  }
  while( pCrash->iSize>pCrash->nData ){
    u8 *zNew;
    int nNew = (pCrash->nData*2) + 4096;
    zNew = crash_realloc(pCrash->zData, nNew);
    if( !zNew ){
      return SQLITE_NOMEM;
    }
    memset(&zNew[pCrash->nData], 0, nNew-pCrash->nData);
    pCrash->nData = nNew;
    pCrash->zData = zNew;
  }
  memcpy(&pCrash->zData[iOfst], zBuf, iAmt);
  return writeListAppend(pFile, iOfst, zBuf, iAmt);
}

/*
** Truncate a crash-file.
*/
static int cfTruncate(sqlite3_file *pFile, sqlite_int64 size){
  CrashFile *pCrash = (CrashFile *)pFile;
  assert(size>=0);
  if( pCrash->iSize>size ){