fix various comments

fs.c

@@ -26,9 +26,6 @@
 // so we don't use spin locks.  Instead, if a process wants to use
 // a particular inode, it must sleep(ip) to wait for it to be not busy.
 // See iget below.
-//
-// XXX Inodes with dev == 0 exist only in memory.  They have no on-disk
-// representation.  This functionality is used to implement pipes.
 struct inode inode[NINODE];
 struct spinlock inode_table_lock;
 
@@ -362,7 +359,6 @@ iincref(struct inode *ip)
 }
 
 // Copy stat information from inode.
-// XXX Assumes inode is from disk file system.
 void
 stati(struct inode *ip, struct stat *st)
 {
@@ -376,7 +372,6 @@ stati(struct inode *ip, struct stat *st)
 #define min(a, b) ((a) < (b) ? (a) : (b))
 
 // Read data from inode.
-// XXX Assumes inode is from disk file system.
 int
 readi(struct inode *ip, char *dst, uint off, uint n)
 {
@@ -440,7 +435,6 @@ newblock(struct inode *ip, uint lbn)
 }
 
 // Write data to inode.
-// XXX Assumes inode is from disk file system.
 int
 writei(struct inode *ip, char *addr, uint off, uint n)
 {

fs.h

@@ -9,8 +9,8 @@
 
 // File system super block
 struct superblock {
-  uint size;         // Size of file system (bytes???) xxx
-  uint nblocks;      // Number of blocks
+  uint size;         // Size of file system image (blocks)
+  uint nblocks;      // Number of data blocks
   uint ninodes;      // Number of inodes.
 };
 

proc.c

@@ -38,7 +38,7 @@ setupsegs(struct proc *p)
   }
 
   c->gdt[0] = SEG_NULL;
-  c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024, 0); // xxx
+  c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024, 0);
   c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
   c->gdt[SEG_TSS] = SEG16(STS_T32A, (uint) &c->ts, sizeof(c->ts), 0);
   c->gdt[SEG_TSS].s = 0;