Rename icache to itable

The inode cache isn't really a cache. The main purpose of it is to
allow for synchronization (locking individual inodes), providing
long-lived references to inodes, and ensuring that there is only inode
in memory.

kernel/fs.c

@@ -113,9 +113,9 @@ bfree(int dev, uint b)
 // sb.startinode. Each inode has a number, indicating its
 // position on the disk.
 //
-// The kernel keeps a cache of in-use inodes in memory
+// The kernel keeps a table of in-use inodes in memory
 // to provide a place for synchronizing access
-// to inodes used by multiple processes. The cached
+// to inodes used by multiple processes. The in-memory
 // inodes include book-keeping information that is
 // not stored on disk: ip->ref and ip->valid.
 //
@@ -127,15 +127,15 @@ bfree(int dev, uint b)
 //   is non-zero. ialloc() allocates, and iput() frees if
 //   the reference and link counts have fallen to zero.
 //
-// * Referencing in cache: an entry in the inode cache
+// * Referencing in table: an entry in the inode table
 //   is free if ip->ref is zero. Otherwise ip->ref tracks
 //   the number of in-memory pointers to the entry (open
 //   files and current directories). iget() finds or
-//   creates a cache entry and increments its ref; iput()
+//   creates a table entry and increments its ref; iput()
 //   decrements ref.
 //
 // * Valid: the information (type, size, &c) in an inode
-//   cache entry is only correct when ip->valid is 1.
+//   table entry is only correct when ip->valid is 1.
 //   ilock() reads the inode from
 //   the disk and sets ip->valid, while iput() clears
 //   ip->valid if ip->ref has fallen to zero.
@@ -156,16 +156,16 @@ bfree(int dev, uint b)
 // and only lock it for short periods (e.g., in read()).
 // The separation also helps avoid deadlock and races during
 // pathname lookup. iget() increments ip->ref so that the inode
-// stays cached and pointers to it remain valid.
+// stays in the table and pointers to it remain valid.
 //
 // Many internal file system functions expect the caller to
 // have locked the inodes involved; this lets callers create
 // multi-step atomic operations.
 //
-// The icache.lock spin-lock protects the allocation of icache
+// The itable.lock spin-lock protects the allocation of itable
 // entries. Since ip->ref indicates whether an entry is free,
 // and ip->dev and ip->inum indicate which i-node an entry
-// holds, one must hold icache.lock while using any of those fields.
+// holds, one must hold itable.lock while using any of those fields.
 //
 // An ip->lock sleep-lock protects all ip-> fields other than ref,
 // dev, and inum.  One must hold ip->lock in order to
@@ -174,16 +174,16 @@ bfree(int dev, uint b)
 struct {
   struct spinlock lock;
   struct inode inode[NINODE];
-} icache;
+} itable;
 
 void
 iinit()
 {
   int i = 0;
   
-  initlock(&icache.lock, "icache");
+  initlock(&itable.lock, "itable");
   for(i = 0; i < NINODE; i++) {
-    initsleeplock(&icache.inode[i].lock, "inode");
+    initsleeplock(&itable.inode[i].lock, "inode");
   }
 }
 
@@ -216,7 +216,7 @@ ialloc(uint dev, short type)
 
 // Copy a modified in-memory inode to disk.
 // Must be called after every change to an ip->xxx field
-// that lives on disk, since i-node cache is write-through.
+// that lives on disk.
 // Caller must hold ip->lock.
 void
 iupdate(struct inode *ip)
@@ -244,21 +244,21 @@ iget(uint dev, uint inum)
 {
   struct inode *ip, *empty;
 
-  acquire(&icache.lock);
+  acquire(&itable.lock);
 
-  // Is the inode already cached?
+  // Is the inode already in the table?
   empty = 0;
-  for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){
+  for(ip = &itable.inode[0]; ip < &itable.inode[NINODE]; ip++){
     if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){
       ip->ref++;
-      release(&icache.lock);
+      release(&itable.lock);
       return ip;
     }
     if(empty == 0 && ip->ref == 0)    // Remember empty slot.
       empty = ip;
   }
 
-  // Recycle an inode cache entry.
+  // Recycle an inode entry.
   if(empty == 0)
     panic("iget: no inodes");
 
@@ -267,7 +267,7 @@ iget(uint dev, uint inum)
   ip->inum = inum;
   ip->ref = 1;
   ip->valid = 0;
-  release(&icache.lock);
+  release(&itable.lock);
 
   return ip;
 }
@@ -277,9 +277,9 @@ iget(uint dev, uint inum)
 struct inode*
 idup(struct inode *ip)
 {
-  acquire(&icache.lock);
+  acquire(&itable.lock);
   ip->ref++;
-  release(&icache.lock);
+  release(&itable.lock);
   return ip;
 }
 
@@ -323,7 +323,7 @@ iunlock(struct inode *ip)
 }
 
 // Drop a reference to an in-memory inode.
-// If that was the last reference, the inode cache entry can
+// If that was the last reference, the inode table entry can
 // be recycled.
 // If that was the last reference and the inode has no links
 // to it, free the inode (and its content) on disk.
@@ -332,7 +332,7 @@ iunlock(struct inode *ip)
 void
 iput(struct inode *ip)
 {
-  acquire(&icache.lock);
+  acquire(&itable.lock);
 
   if(ip->ref == 1 && ip->valid && ip->nlink == 0){
     // inode has no links and no other references: truncate and free.
@@ -341,7 +341,7 @@ iput(struct inode *ip)
     // so this acquiresleep() won't block (or deadlock).
     acquiresleep(&ip->lock);
 
-    release(&icache.lock);
+    release(&itable.lock);
 
     itrunc(ip);
     ip->type = 0;
@@ -350,11 +350,11 @@ iput(struct inode *ip)
 
     releasesleep(&ip->lock);
 
-    acquire(&icache.lock);
+    acquire(&itable.lock);
   }
 
   ip->ref--;
-  release(&icache.lock);
+  release(&itable.lock);
 }
 
 // Common idiom: unlock, then put.