clarify some FS comments

1 files changed, 12 insertions, 10 deletions

diff --git a/log.c b/log.c
index 832732c..5b827de 100644
--- a/log.c
+++ b/log.c
@@ -42,7 +42,7 @@ struct log {
   struct spinlock lock;
   int start;
   int size;
-  int intrans;
+  int busy; // a transaction is active
   int dev;
   struct logheader lh;
 };
@@ -75,7 +75,7 @@ install_trans(void)
     struct buf *lbuf = bread(log.dev, log.start+tail+1); // read log block
     struct buf *dbuf = bread(log.dev, log.lh.sector[tail]); // read dst
     memmove(dbuf->data, lbuf->data, BSIZE);  // copy block to dst
-    bwrite(dbuf);  // flush dst to disk
+    bwrite(dbuf);  // write dst to disk
     brelse(lbuf); 
     brelse(dbuf);
   }
@@ -95,7 +95,9 @@ read_head(void)
   brelse(buf);
 }
 
-// Write in-memory log header to disk, committing log entries till head
+// Write in-memory log header to disk.
+// This is the true point at which the
+// current transaction commits.
 static void
 write_head(void)
 {
@@ -123,10 +125,10 @@ void
 begin_trans(void)
 {
   acquire(&log.lock);
-  while (log.intrans) {
+  while (log.busy) {
     sleep(&log, &log.lock);
   }
-  log.intrans = 1;
+  log.busy = 1;
   release(&log.lock);
 }
 
@@ -134,14 +136,14 @@ void
 commit_trans(void)
 {
   if (log.lh.n > 0) {
-    write_head();    // Causes all blocks till log.head to be commited
-    install_trans(); // Install all the transactions till head
+    write_head();    // Write header to disk -- the real commit
+    install_trans(); // Now install writes to home locations
     log.lh.n = 0; 
-    write_head();    // Reclaim log
+    write_head();    // Erase the transaction from the log
   }
   
   acquire(&log.lock);
-  log.intrans = 0;
+  log.busy = 0;
   wakeup(&log);
   release(&log.lock);
 }
@@ -161,7 +163,7 @@ log_write(struct buf *b)
 
   if (log.lh.n >= LOGSIZE || log.lh.n >= log.size - 1)
     panic("too big a transaction");
-  if (!log.intrans)
+  if (!log.busy)
     panic("write outside of trans");
 
   for (i = 0; i < log.lh.n; i++) {