From eb13531c0f1fe01f5324c5d98de1027f3e98d69f Mon Sep 17 00:00:00 2001
From: Sears Russell <sears@cs.berkeley.edu>
Date: Fri, 21 Jul 2006 01:06:35 +0000
Subject: [PATCH] Partial handling of incomplete log entries.  (It detects when
 the log file does not end at the right byte, but doesn't checksum, or
 otherwise look for sectors that didn't make it to disk.)

---
 src/lladd/logger/logWriter.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/lladd/logger/logWriter.c b/src/lladd/logger/logWriter.c
index e9f1cc4..f1d25a9 100644
--- a/src/lladd/logger/logWriter.c
+++ b/src/lladd/logger/logWriter.c
@@ -138,7 +138,8 @@ int openLogWriter() {
      synchronous disk writes.  Therefore, all read accesses (and
      therefore all seeks) run through the second descriptor.  */
 
-  int logFD = open (LOG_FILE, O_CREAT | O_WRONLY | O_APPEND | O_SYNC, S_IRWXU | S_IRWXG | S_IRWXO);
+  //  int logFD = open (LOG_FILE, O_CREAT | O_WRONLY | O_APPEND | O_SYNC, S_IRWXU | S_IRWXG | S_IRWXO);
+  int logFD = open (LOG_FILE, O_CREAT | O_WRONLY | O_SYNC, S_IRWXU | S_IRWXG | S_IRWXO);
   if(logFD == -1) {
     perror("Couldn't open log file for append.\n");
     abort();
@@ -224,6 +225,8 @@ int openLogWriter() {
     nextAvailableLSN = le->LSN + sizeofLogEntry(le) + sizeof(lsn_t);;
     FreeLogEntry(le);
   }
+  // If there was a short write at the end of the log, just reuse its lsn, and overwrite it. 
+  fseek(log, nextAvailableLSN, SEEK_SET);
 
   return 0;
 }
@@ -375,8 +378,17 @@ static LogEntry * readLogEntry() {
       abort();
       return (LogEntry*)LLADD_IO_ERROR;
     } else { 
+      lsn_t newSize = size - bytesRead;
+      lsn_t newBytesRead = read (roLogFD, ((byte*)ret)+bytesRead, newSize);
+
+      if(newBytesRead == 0) { 
+	return NULL;
+      }
       fprintf(stderr, "short read from log.  Expected %ld bytes, got %ld.\nFIXME: This is 'normal', but currently not handled", sizeof(lsn_t), bytesRead);
       fflush(stderr);
+      fprintf(stderr, "\nattempt to read again produced newBytesRead = %ld, newSize was %ld\n", newBytesRead, newSize);
+      fflush(stderr);
+
       abort();  // really abort here.  This code should attempt to piece together short log reads...
     }
   }
@@ -398,12 +410,18 @@ static LogEntry * readLogEntry() {
       abort();
       return (LogEntry*)LLADD_IO_ERROR;
     } else { 
-      fprintf(stderr, "short read from log w/ lsn %ld.  Expected %ld bytes, got %ld.\nFIXME: This is 'normal', but currently not handled", debug_lsn, size, bytesRead);
-      fflush(stderr);
       lsn_t newSize = size - bytesRead;
       lsn_t newBytesRead = read (roLogFD, ((byte*)ret)+bytesRead, newSize);
+
+      if(newBytesRead == 0) { 
+	return NULL;
+      }
+
+      fprintf(stderr, "short read from log w/ lsn %ld.  Expected %ld bytes, got %ld.\nFIXME: This is 'normal', but currently not handled", debug_lsn, size, bytesRead);
+      fflush(stderr);
       fprintf(stderr, "\nattempt to read again produced newBytesRead = %ld, newSize was %ld\n", newBytesRead, newSize);
       fflush(stderr);
+
       abort();
       return (LogEntry*)LLADD_IO_ERROR;
     }