Pick up where i left off in april:

- move log into metadata part of disk, so that marking
that the log's blocks are in use falls out for free
- superblock describes the whole disk (sizes and offets)
- sizes and offsets are computed in one place (mkfs) and
the rest of the code refers to the superblock for these values,
instead of recomputing them.

defs.h

@@ -39,7 +39,7 @@ int             dirlink(struct inode*, char*, uint);
 struct inode*   dirlookup(struct inode*, char*, uint*);
 struct inode*   ialloc(uint, short);
 struct inode*   idup(struct inode*);
-void            iinit(void);
+void            iinit(int dev);
 void            ilock(struct inode*);
 void            iput(struct inode*);
 void            iunlock(struct inode*);
@@ -81,7 +81,7 @@ void            lapicstartap(uchar, uint);
 void            microdelay(int);
 
 // log.c
-void            initlog(void);
+void            initlog(int dev);
 void            log_write(struct buf*);
 void            begin_op();
 void            end_op();

fs.c

@@ -22,6 +22,7 @@
 
 #define min(a, b) ((a) < (b) ? (a) : (b))
 static void itrunc(struct inode*);
+struct superblock sb;   // there should be one per dev, but we run with one dev
 
 // Read the super block.
 void
@@ -54,12 +55,10 @@ balloc(uint dev)
 {
   int b, bi, m;
   struct buf *bp;
-  struct superblock sb;
 
   bp = 0;
-  readsb(dev, &sb);
   for(b = 0; b < sb.size; b += BPB){
-    bp = bread(dev, BBLOCK(b, sb.ninodes));
+    bp = bread(dev, BBLOCK(b, sb));
     for(bi = 0; bi < BPB && b + bi < sb.size; bi++){
       m = 1 << (bi % 8);
       if((bp->data[bi/8] & m) == 0){  // Is block free?
@@ -80,11 +79,10 @@ static void
 bfree(int dev, uint b)
 {
   struct buf *bp;
-  struct superblock sb;
   int bi, m;
 
   readsb(dev, &sb);
-  bp = bread(dev, BBLOCK(b, sb.ninodes));
+  bp = bread(dev, BBLOCK(b, sb));
   bi = b % BPB;
   m = 1 << (bi % 8);
   if((bp->data[bi/8] & m) == 0)
@@ -101,8 +99,8 @@ bfree(int dev, uint b)
 // its size, the number of links referring to it, and the
 // list of blocks holding the file's content.
 //
-// The inodes are laid out sequentially on disk immediately after
+// The inodes are laid out sequentially on disk at
-// the superblock. Each inode has a number, indicating its
+// sb.startinode. Each inode has a number, indicating its
 // position on the disk.
 //
 // The kernel keeps a cache of in-use inodes in memory
@@ -162,9 +160,12 @@ struct {
 } icache;
 
 void
-iinit(void)
+iinit(int dev)
 {
   initlock(&icache.lock, "icache");
+  readsb(dev, &sb);
+  cprintf("sb: size %d nblocks %d ninodes %d nlog %d logstart %d inodestart %d bmap start %d\n", sb.size,
+          sb.nblocks, sb.ninodes, sb.nlog, sb.logstart, sb.inodestart, sb.bmapstart);
 }
 
 static struct inode* iget(uint dev, uint inum);
@@ -178,12 +179,9 @@ ialloc(uint dev, short type)
   int inum;
   struct buf *bp;
   struct dinode *dip;
-  struct superblock sb;
-
-  readsb(dev, &sb);
 
   for(inum = 1; inum < sb.ninodes; inum++){
-    bp = bread(dev, IBLOCK(inum));
+    bp = bread(dev, IBLOCK(inum, sb));
     dip = (struct dinode*)bp->data + inum%IPB;
     if(dip->type == 0){  // a free inode
       memset(dip, 0, sizeof(*dip));
@@ -204,7 +202,7 @@ iupdate(struct inode *ip)
   struct buf *bp;
   struct dinode *dip;
 
-  bp = bread(ip->dev, IBLOCK(ip->inum));
+  bp = bread(ip->dev, IBLOCK(ip->inum, sb));
   dip = (struct dinode*)bp->data + ip->inum%IPB;
   dip->type = ip->type;
   dip->major = ip->major;
@@ -281,7 +279,7 @@ ilock(struct inode *ip)
   release(&icache.lock);
 
   if(!(ip->flags & I_VALID)){
-    bp = bread(ip->dev, IBLOCK(ip->inum));
+    bp = bread(ip->dev, IBLOCK(ip->inum, sb));
     dip = (struct dinode*)bp->data + ip->inum%IPB;
     ip->type = dip->type;
     ip->major = dip->major;

fs.h

@@ -1,22 +1,23 @@
 // On-disk file system format. 
 // Both the kernel and user programs use this header file.
 
-// Block 0 is unused.
-// Block 1 is super block.
-// Blocks 2 through sb.ninodes/IPB hold inodes.
-// Then free bitmap blocks holding sb.size bits.
-// Then sb.nblocks data blocks.
-// Then sb.nlog log blocks.
 
 #define ROOTINO 1  // root i-number
 #define BSIZE 512  // block size
 
-// File system super block
+// Disk layout:
+// [ boot block | super block | log | inode blocks | free bit map | data blocks ]
+//
+// mkfs computes the super block and builds an initial file system. The super describes
+// the disk layout:
 struct superblock {
   uint size;         // Size of file system image (blocks)
   uint nblocks;      // Number of data blocks
   uint ninodes;      // Number of inodes.
   uint nlog;         // Number of log blocks
+  uint logstart;     // Block number of first log block
+  uint inodestart;   // Block number of first inode block
+  uint bmapstart;    // Block number of first free map block
 };
 
 #define NDIRECT 12
@@ -37,13 +38,13 @@ struct dinode {
 #define IPB           (BSIZE / sizeof(struct dinode))
 
 // Block containing inode i
-#define IBLOCK(i)     ((i) / IPB + 2)
+#define IBLOCK(i, sb)     ((i) / IPB + sb.inodestart)
 
 // Bitmap bits per block
 #define BPB           (BSIZE*8)
 
-// Block containing bit for block b
+// Block of free map containing bit for block b
-#define BBLOCK(b, ninodes) (b/BPB + (ninodes)/IPB + 3)
+#define BBLOCK(b, sb) (b/BPB + sb.bmapstart)
 
 // Directory is a file containing a sequence of dirent structures.
 #define DIRSIZ 14

log.c

@@ -50,17 +50,17 @@ static void recover_from_log(void);
 static void commit();
 
 void
-initlog(void)
+initlog(int dev)
 {
   if (sizeof(struct logheader) >= BSIZE)
     panic("initlog: too big logheader");
 
   struct superblock sb;
   initlock(&log.lock, "log");
-  readsb(ROOTDEV, &sb);
+  readsb(dev, &sb);
-  log.start = sb.size - sb.nlog;
+  log.start = sb.logstart;
   log.size = sb.nlog;
-  log.dev = ROOTDEV;
+  log.dev = dev;
   recover_from_log();
 }
 

main.c

@@ -31,7 +31,6 @@ main(void)
   tvinit();        // trap vectors
   binit();         // buffer cache
   fileinit();      // file table
-  iinit();         // inode cache
   ideinit();       // disk
   if(!ismp)
     timerinit();   // uniprocessor timer

mkfs.c

@@ -16,12 +16,12 @@
 #define NINODES 200
 
 // Disk layout:
-// [ boot block | sb block | inode blocks | bit map | data blocks | log ]
+// [ boot block | sb block | log | inode blocks | free bit map | data blocks ]
 
 int nbitmap = FSSIZE/(BSIZE*8) + 1;
 int ninodeblocks = NINODES / IPB + 1;
 int nlog = LOGSIZE;  
-int nmeta;    // Number of meta blocks (inode, bitmap, and 2 extra)
+int nmeta;    // Number of meta blocks (boot, sb, nlog, inode, bitmap)
 int nblocks;  // Number of data blocks
 
 int fsfd;
@@ -88,15 +88,20 @@ main(int argc, char *argv[])
     exit(1);
   }
 
-  nmeta = 2 + ninodeblocks + nbitmap;
+  // 1 fs block = 1 disk sector
-  nblocks = FSSIZE - nlog - nmeta;
+  nmeta = 2 + nlog + ninodeblocks + nbitmap;
+  nblocks = FSSIZE - nmeta;
 
   sb.size = xint(FSSIZE);
-  sb.nblocks = xint(nblocks); // so whole disk is size sectors
+  sb.nblocks = xint(nblocks);
   sb.ninodes = xint(NINODES);
   sb.nlog = xint(nlog);
+  sb.logstart = xint(2);
+  sb.inodestart = xint(2+nlog);
+  sb.bmapstart = xint(2+nlog+ninodeblocks);
 
-  printf("nmeta %d (boot, super, inode blocks %u, bitmap blocks %u) blocks %d log %u total %d\n", nmeta, ninodeblocks, nbitmap, nblocks, nlog, FSSIZE);
+  printf("nmeta %d (boot, super, log blocks %u inode blocks %u, bitmap blocks %u) blocks %d total %d\n",
+         nmeta, nlog, ninodeblocks, nbitmap, nblocks, FSSIZE);
 
   freeblock = nmeta;     // the first free block that we can allocate
 
@@ -180,7 +185,7 @@ winode(uint inum, struct dinode *ip)
   uint bn;
   struct dinode *dip;
 
-  bn = IBLOCK(inum);
+  bn = IBLOCK(inum, sb);
   rsect(bn, buf);
   dip = ((struct dinode*)buf) + (inum % IPB);
   *dip = *ip;
@@ -194,7 +199,7 @@ rinode(uint inum, struct dinode *ip)
   uint bn;
   struct dinode *dip;
 
-  bn = IBLOCK(inum);
+  bn = IBLOCK(inum, sb);
   rsect(bn, buf);
   dip = ((struct dinode*)buf) + (inum % IPB);
   *ip = *dip;
@@ -239,8 +244,8 @@ balloc(int used)
   for(i = 0; i < used; i++){
     buf[i/8] = buf[i/8] | (0x1 << (i%8));
   }
-  printf("balloc: write bitmap block at sector %d\n", ninodeblocks+2);
+  printf("balloc: write bitmap block at sector %d\n", sb.bmapstart);
-  wsect(ninodeblocks+2, buf);
+  wsect(sb.bmapstart, buf);
 }
 
 #define min(a, b) ((a) < (b) ? (a) : (b))
@@ -256,8 +261,8 @@ iappend(uint inum, void *xp, int n)
   uint x;
 
   rinode(inum, &din);
-
   off = xint(din.size);
+  // printf("append inum %d at off %d sz %d\n", inum, off, n);
   while(n > 0){
     fbn = off / BSIZE;
     assert(fbn < MAXFILE);
@@ -268,10 +273,8 @@ iappend(uint inum, void *xp, int n)
       x = xint(din.addrs[fbn]);
     } else {
       if(xint(din.addrs[NDIRECT]) == 0){
-        // printf("allocate indirect block\n");
         din.addrs[NDIRECT] = xint(freeblock++);
       }
-      // printf("read indirect block\n");
       rsect(xint(din.addrs[NDIRECT]), (char*)indirect);
       if(indirect[fbn - NDIRECT] == 0){
         indirect[fbn - NDIRECT] = xint(freeblock++);

proc.c

@@ -339,7 +339,8 @@ forkret(void)
     // of a regular process (e.g., they call sleep), and thus cannot 
     // be run from main().
     first = 0;
-    initlog();
+    iinit(ROOTDEV);
+    initlog(ROOTDEV);
   }
   
   // Return to "caller", actually trapret (see allocproc).