tolerate running out of disk blocks

1 files changed, 31 insertions, 11 deletions

diff --git a/kernel/fs.c b/kernel/fs.c
index 40c9bd4..247a86f 100644
--- a/kernel/fs.c
+++ b/kernel/fs.c
@@ -61,6 +61,7 @@ bzero(int dev, int bno)
 // Blocks.
 
 // Allocate a zeroed disk block.
+// returns 0 if out of disk space.
 static uint
 balloc(uint dev)
 {
@@ -82,7 +83,8 @@ balloc(uint dev)
     }
     brelse(bp);
   }
-  panic("balloc: out of blocks");
+  printf("balloc: out of blocks\n");
+  return 0;
 }
 
 // Free a disk block.
@@ -109,8 +111,8 @@ 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 at
-// sb.startinode. Each inode has a number, indicating its
+// The inodes are laid out sequentially on disk at block
+// sb.inodestart. Each inode has a number, indicating its
 // position on the disk.
 //
 // The kernel keeps a table of in-use inodes in memory
@@ -374,6 +376,7 @@ iunlockput(struct inode *ip)
 
 // Return the disk block address of the nth block in inode ip.
 // If there is no such block, bmap allocates one.
+// returns 0 if out of disk space.
 static uint
 bmap(struct inode *ip, uint bn)
 {
@@ -381,21 +384,32 @@ bmap(struct inode *ip, uint bn)
   struct buf *bp;
 
   if(bn < NDIRECT){
-    if((addr = ip->addrs[bn]) == 0)
-      ip->addrs[bn] = addr = balloc(ip->dev);
+    if((addr = ip->addrs[bn]) == 0){
+      addr = balloc(ip->dev);
+      if(addr == 0)
+        return 0;
+      ip->addrs[bn] = addr;
+    }
     return addr;
   }
   bn -= NDIRECT;
 
   if(bn < NINDIRECT){
     // Load indirect block, allocating if necessary.
-    if((addr = ip->addrs[NDIRECT]) == 0)
-      ip->addrs[NDIRECT] = addr = balloc(ip->dev);
+    if((addr = ip->addrs[NDIRECT]) == 0){
+      addr = balloc(ip->dev);
+      if(addr == 0)
+        return 0;
+      ip->addrs[NDIRECT] = addr;
+    }
     bp = bread(ip->dev, addr);
     a = (uint*)bp->data;
     if((addr = a[bn]) == 0){
-      a[bn] = addr = balloc(ip->dev);
-      log_write(bp);
+      addr = balloc(ip->dev);
+      if(addr){
+        a[bn] = addr;
+        log_write(bp);
+      }
     }
     brelse(bp);
     return addr;
@@ -464,7 +478,10 @@ readi(struct inode *ip, int user_dst, uint64 dst, uint off, uint n)
     n = ip->size - off;
 
   for(tot=0; tot<n; tot+=m, off+=m, dst+=m){
-    bp = bread(ip->dev, bmap(ip, off/BSIZE));
+    uint addr = bmap(ip, off/BSIZE);
+    if(addr == 0)
+      break;
+    bp = bread(ip->dev, addr);
     m = min(n - tot, BSIZE - off%BSIZE);
     if(either_copyout(user_dst, dst, bp->data + (off % BSIZE), m) == -1) {
       brelse(bp);
@@ -495,7 +512,10 @@ writei(struct inode *ip, int user_src, uint64 src, uint off, uint n)
     return -1;
 
   for(tot=0; tot<n; tot+=m, off+=m, src+=m){
-    bp = bread(ip->dev, bmap(ip, off/BSIZE));
+    uint addr = bmap(ip, off/BSIZE);
+    if(addr == 0)
+      break;
+    bp = bread(ip->dev, addr);
     m = min(n - tot, BSIZE - off%BSIZE);
     if(either_copyin(bp->data + (off % BSIZE), user_src, src, m) == -1) {
       brelse(bp);