Index: src/os_unix.c
==================================================================
--- src/os_unix.c
+++ src/os_unix.c
@@ -1348,10 +1348,11 @@
   unixFile *pFile = (unixFile*)id;
 
   SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
 
   assert( pFile );
+  assert( pFile->eFileLock<=SHARED_LOCK );
   unixEnterMutex(); /* Because pFile->pInode is shared across threads */
 
   /* Check if a thread in this process holds such a lock */
   if( pFile->pInode->eFileLock>SHARED_LOCK ){
     reserved = 1;
@@ -1758,13 +1759,11 @@
         lock.l_start = SHARED_FIRST;
         lock.l_len = divSize;
         if( unixFileLock(pFile, &lock)==(-1) ){
           tErrno = errno;
           rc = SQLITE_IOERR_UNLOCK;
-          if( IS_LOCK_ERROR(rc) ){
-            storeLastErrno(pFile, tErrno);
-          }
+          storeLastErrno(pFile, tErrno);
           goto end_unlock;
         }
         lock.l_type = F_RDLCK;
         lock.l_whence = SEEK_SET;
         lock.l_start = SHARED_FIRST;
@@ -1782,13 +1781,11 @@
         lock.l_start = SHARED_FIRST+divSize;
         lock.l_len = SHARED_SIZE-divSize;
         if( unixFileLock(pFile, &lock)==(-1) ){
           tErrno = errno;
           rc = SQLITE_IOERR_UNLOCK;
-          if( IS_LOCK_ERROR(rc) ){
-            storeLastErrno(pFile, tErrno);
-          }
+          storeLastErrno(pFile, tErrno);
           goto end_unlock;
         }
       }else
 #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
       {
@@ -2035,21 +2032,11 @@
   unixFile *pFile = (unixFile*)id;
 
   SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
   
   assert( pFile );
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    /* Either this connection or some other connection in the same process
-    ** holds a lock on the file.  No need to check further. */
-    reserved = 1;
-  }else{
-    /* The lock is held if and only if the lockfile exists */
-    const char *zLockFile = (const char*)pFile->lockingContext;
-    reserved = osAccess(zLockFile, 0)==0;
-  }
+  reserved = osAccess((const char*)pFile->lockingContext, 0)==0;
   OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
   *pResOut = reserved;
   return rc;
 }
 
@@ -2107,11 +2094,11 @@
     int tErrno = errno;
     if( EEXIST == tErrno ){
       rc = SQLITE_BUSY;
     } else {
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( IS_LOCK_ERROR(rc) ){
+      if( rc!=SQLITE_BUSY ){
         storeLastErrno(pFile, tErrno);
       }
     }
     return rc;
   } 
@@ -2154,18 +2141,16 @@
   }
   
   /* To fully unlock the database, delete the lock file */
   assert( eFileLock==NO_LOCK );
   rc = osRmdir(zLockFile);
-  if( rc<0 && errno==ENOTDIR ) rc = osUnlink(zLockFile);
   if( rc<0 ){
     int tErrno = errno;
-    rc = 0;
-    if( ENOENT != tErrno ){
+    if( tErrno==ENOENT ){
+      rc = SQLITE_OK;
+    }else{
       rc = SQLITE_IOERR_UNLOCK;
-    }
-    if( IS_LOCK_ERROR(rc) ){
       storeLastErrno(pFile, tErrno);
     }
     return rc; 
   }
   pFile->eFileLock = NO_LOCK;
@@ -2174,18 +2159,15 @@
 
 /*
 ** Close a file.  Make sure the lock has been released before closing.
 */
 static int dotlockClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    dotlockUnlock(id, NO_LOCK);
-    sqlite3_free(pFile->lockingContext);
-    rc = closeUnixFile(id);
-  }
-  return rc;
+  unixFile *pFile = (unixFile*)id;
+  assert( id!=0 );
+  dotlockUnlock(id, NO_LOCK);
+  sqlite3_free(pFile->lockingContext);
+  return closeUnixFile(id);
 }
 /****************** End of the dot-file lock implementation *******************
 ******************************************************************************/
 
 /******************************************************************************
@@ -2247,14 +2229,12 @@
       lrc = robust_flock(pFile->h, LOCK_UN);
       if ( lrc ) {
         int tErrno = errno;
         /* unlock failed with an error */
         lrc = SQLITE_IOERR_UNLOCK; 
-        if( IS_LOCK_ERROR(lrc) ){
-          storeLastErrno(pFile, tErrno);
-          rc = lrc;
-        }
+        storeLastErrno(pFile, tErrno);
+        rc = lrc;
       }
     } else {
       int tErrno = errno;
       reserved = 1;
       /* someone else might have it reserved */
@@ -2383,16 +2363,13 @@
 
 /*
 ** Close a file.
 */
 static int flockClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    flockUnlock(id, NO_LOCK);
-    rc = closeUnixFile(id);
-  }
-  return rc;
+  assert( id!=0 );
+  flockUnlock(id, NO_LOCK);
+  return closeUnixFile(id);
 }
 
 #endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */
 
 /******************* End of the flock lock implementation *********************
@@ -3013,27 +2990,26 @@
 /*
 ** Close a file & cleanup AFP specific locking context 
 */
 static int afpClose(sqlite3_file *id) {
   int rc = SQLITE_OK;
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    afpUnlock(id, NO_LOCK);
-    unixEnterMutex();
-    if( pFile->pInode && pFile->pInode->nLock ){
-      /* If there are outstanding locks, do not actually close the file just
-      ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pInode->aPending.  It will be automatically closed when
-      ** the last lock is cleared.
-      */
-      setPendingFd(pFile);
-    }
-    releaseInodeInfo(pFile);
-    sqlite3_free(pFile->lockingContext);
-    rc = closeUnixFile(id);
-    unixLeaveMutex();
-  }
+  unixFile *pFile = (unixFile*)id;
+  assert( id!=0 );
+  afpUnlock(id, NO_LOCK);
+  unixEnterMutex();
+  if( pFile->pInode && pFile->pInode->nLock ){
+    /* If there are outstanding locks, do not actually close the file just
+    ** yet because that would clear those locks.  Instead, add the file
+    ** descriptor to pInode->aPending.  It will be automatically closed when
+    ** the last lock is cleared.
+    */
+    setPendingFd(pFile);
+  }
+  releaseInodeInfo(pFile);
+  sqlite3_free(pFile->lockingContext);
+  rc = closeUnixFile(id);
+  unixLeaveMutex();
   return rc;
 }
 
 #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
 /*
@@ -7372,11 +7348,11 @@
 
 /*
 ** Close a file that uses proxy locks.
 */
 static int proxyClose(sqlite3_file *id) {
-  if( id ){
+  if( ALWAYS(id) ){
     unixFile *pFile = (unixFile*)id;
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
     unixFile *lockProxy = pCtx->lockProxy;
     unixFile *conchFile = pCtx->conchFile;
     int rc = SQLITE_OK;