patch-2.0.31 linux/fs/ext2/balloc.c

• Lines: 291
• Date: Sat Aug 16 16:23:19 1997
• Orig file: v2.0.30/linux/fs/ext2/balloc.c
• Orig date: Thu Jan 4 04:14:20 1996

diff -u --recursive --new-file v2.0.30/linux/fs/ext2/balloc.c linux/fs/ext2/balloc.c
@@ -43,6 +43,10 @@
 	unsigned long desc;
 	struct ext2_group_desc * gdp;
 
+	/*
+	 * This panic should never trigger on a bad filesystem: the caller
+	 * should have verified the block/group number already.
+	 */
 	if (block_group >= sb->u.ext2_sb.s_groups_count)
 		ext2_panic (sb, "get_group_desc",
 			    "block_group >= groups_count - "
@@ -63,22 +67,37 @@
 	return gdp + desc;
 }
 
-static void read_block_bitmap (struct super_block * sb,
-			       unsigned int block_group,
-			       unsigned long bitmap_nr)
+/*
+ * Read the bitmap for a given block_group, reading into the specified 
+ * slot in the superblock's bitmap cache.
+ *
+ * Return >=0 on success or a -ve error code.
+ */
+
+static int read_block_bitmap (struct super_block * sb,
+			      unsigned int block_group,
+			      unsigned long bitmap_nr)
 {
 	struct ext2_group_desc * gdp;
 	struct buffer_head * bh;
+	int retval = 0;
 	
 	gdp = get_group_desc (sb, block_group, NULL);
 	bh = bread (sb->s_dev, gdp->bg_block_bitmap, sb->s_blocksize);
-	if (!bh)
-		ext2_panic (sb, "read_block_bitmap",
+	if (!bh) {
+		ext2_error (sb, "read_block_bitmap",
 			    "Cannot read block bitmap - "
 			    "block_group = %d, block_bitmap = %lu",
 			    block_group, (unsigned long) gdp->bg_block_bitmap);
+		retval = -EIO;
+	}
+	/*
+	 * On IO error, just leave a zero in the superblock's block pointer for
+	 * this group.  The IO will be retried next time.
+	 */
 	sb->u.ext2_sb.s_block_bitmap_number[bitmap_nr] = block_group;
 	sb->u.ext2_sb.s_block_bitmap[bitmap_nr] = bh;
+	return retval;
 }
 
 /*
@@ -91,11 +110,13 @@
  * 1/ There is one cache per mounted file system.
  * 2/ If the file system contains less than EXT2_MAX_GROUP_LOADED groups,
  *    this function reads the bitmap without maintaining a LRU cache.
+ *
+ * Return the slot used to store the bitmap, or a -ve error code.
  */
 static int load__block_bitmap (struct super_block * sb,
 			       unsigned int block_group)
 {
-	int i, j;
+	int i, j, retval = 0;
 	unsigned long block_bitmap_number;
 	struct buffer_head * block_bitmap;
 
@@ -114,7 +135,9 @@
 			else
 				return block_group;
 		} else {
-			read_block_bitmap (sb, block_group, block_group);
+			retval = read_block_bitmap (sb, block_group, block_group);
+			if (retval < 0)
+				return retval;
 			return block_group;
 		}
 	}
@@ -134,6 +157,14 @@
 		}
 		sb->u.ext2_sb.s_block_bitmap_number[0] = block_bitmap_number;
 		sb->u.ext2_sb.s_block_bitmap[0] = block_bitmap;
+
+		/*
+		 * There's still one special case here --- if block_bitmap == 0
+		 * then our last attempt to read the bitmap failed and we have
+		 * just ended up caching that failure.  Try again to read it.
+		 */
+		if (!block_bitmap)
+			retval = read_block_bitmap (sb, block_group, 0);
 	} else {
 		if (sb->u.ext2_sb.s_loaded_block_bitmaps < EXT2_MAX_GROUP_LOADED)
 			sb->u.ext2_sb.s_loaded_block_bitmaps++;
@@ -145,24 +176,71 @@
 			sb->u.ext2_sb.s_block_bitmap[j] =
 				sb->u.ext2_sb.s_block_bitmap[j - 1];
 		}
-		read_block_bitmap (sb, block_group, 0);
+		retval = read_block_bitmap (sb, block_group, 0);
 	}
-	return 0;
+	return retval;
 }
 
+/*
+ * Load the block bitmap for a given block group.  First of all do a couple
+ * of fast lookups for common cases and then pass the request onto the guts
+ * of the bitmap loader.
+ *
+ * Return the slot number of the group in the superblock bitmap cache's on
+ * success, or a -ve error code.
+ *
+ * There is still one inconsistancy here --- if the number of groups in this
+ * filesystems is <= EXT2_MAX_GROUP_LOADED, then we have no way of 
+ * differentiating between a group for which we have never performed a bitmap
+ * IO request, and a group for which the last bitmap read request failed.
+ */
 static inline int load_block_bitmap (struct super_block * sb,
 				     unsigned int block_group)
 {
-	if (sb->u.ext2_sb.s_loaded_block_bitmaps > 0 &&
-	    sb->u.ext2_sb.s_block_bitmap_number[0] == block_group)
-		return 0;
+	int slot;
 	
-	if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED && 
-	    sb->u.ext2_sb.s_block_bitmap_number[block_group] == block_group &&
-	    sb->u.ext2_sb.s_block_bitmap[block_group]) 
-		return block_group;
+	/*
+	 * Do the lookup for the slot.  First of all, check if we're asking
+	 * for the same slot as last time, and did we succeed that last time?
+	 */
+	if (sb->u.ext2_sb.s_loaded_block_bitmaps > 0 &&
+	    sb->u.ext2_sb.s_block_bitmap_number[0] == block_group &&
+	    sb->u.ext2_sb.s_block_bitmap[block_group]) {
+		slot = 0;
+	}
+	/*
+	 * Or can we do a fast lookup based on a loaded group on a filesystem
+	 * small enough to be mapped directly into the superblock?
+	 */
+	else if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED && 
+		 sb->u.ext2_sb.s_block_bitmap_number[block_group] == block_group &&
+		 sb->u.ext2_sb.s_block_bitmap[block_group]) {
+		slot = block_group;
+	} 
+	/*
+	 * If not, then do a full lookup for this block group.
+	 */
+	else {
+		slot = load__block_bitmap (sb, block_group);
+	}
 
-	return load__block_bitmap (sb, block_group);
+	/*
+	 * <0 means we just got an error
+	 */
+	if (slot < 0)
+		return slot;
+	
+	/*
+	 * If it's a valid slot, we may still have cached a previous IO error,
+	 * in which case the bh in the superblock cache will be zero.
+	 */
+	if (!sb->u.ext2_sb.s_block_bitmap[slot])
+		return -EIO;
+	
+	/*
+	 * Must have been read in OK to get this far.
+	 */
+	return slot;
 }
 
 void ext2_free_blocks (const struct inode * inode, unsigned long block,
@@ -199,12 +277,19 @@
 	block_group = (block - es->s_first_data_block) /
 		      EXT2_BLOCKS_PER_GROUP(sb);
 	bit = (block - es->s_first_data_block) % EXT2_BLOCKS_PER_GROUP(sb);
-	if (bit + count > EXT2_BLOCKS_PER_GROUP(sb))
-		ext2_panic (sb, "ext2_free_blocks",
+	if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
+		ext2_error (sb, "ext2_free_blocks",
 			    "Freeing blocks across group boundary - "
 			    "Block = %lu, count = %lu",
 			    block, count);
+		unlock_super (sb);
+		return;
+	}
+	
 	bitmap_nr = load_block_bitmap (sb, block_group);
+	if (bitmap_nr < 0)
+		goto error_return;
+		
 	bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
 	gdp = get_group_desc (sb, block_group, &bh2);
 
@@ -214,11 +299,14 @@
 	     in_range (block, gdp->bg_inode_table,
 		       sb->u.ext2_sb.s_itb_per_group) ||
 	     in_range (block + count - 1, gdp->bg_inode_table,
-		       sb->u.ext2_sb.s_itb_per_group)))
-		ext2_panic (sb, "ext2_free_blocks",
+		       sb->u.ext2_sb.s_itb_per_group))) {
+		ext2_error (sb, "ext2_free_blocks",
 			    "Freeing blocks in system zones - "
 			    "Block = %lu, count = %lu",
 			    block, count);
+		unlock_super (sb);
+		return;
+	}
 
 	for (i = 0; i < count; i++) {
 		if (!clear_bit (bit + i, bh->b_data))
@@ -242,6 +330,7 @@
 		wait_on_buffer (bh);
 	}
 	sb->s_dirt = 1;
+error_return:
 	unlock_super (sb);
 	return;
 }
@@ -301,6 +390,12 @@
 			goal_attempts++;
 #endif
 		bitmap_nr = load_block_bitmap (sb, i);
+		if (bitmap_nr < 0) {
+			*err = -EIO;
+			unlock_super (sb);
+			return 0;
+		}
+		
 		bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
 
 		ext2_debug ("goal is at %d:%d.\n", i, j);
@@ -372,7 +467,14 @@
 		unlock_super (sb);
 		return 0;
 	}
+
 	bitmap_nr = load_block_bitmap (sb, i);
+	if (bitmap_nr < 0) {
+		*err = -EIO;
+		unlock_super (sb);
+		return 0;
+	}
+		
 	bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
 	r = memscan(bh->b_data, 0, EXT2_BLOCKS_PER_GROUP(sb) >> 3);
 	j = (r - bh->b_data) << 3;
@@ -415,10 +517,14 @@
 	if (test_opt (sb, CHECK_STRICT) &&
 	    (tmp == gdp->bg_block_bitmap ||
 	     tmp == gdp->bg_inode_bitmap ||
-	     in_range (tmp, gdp->bg_inode_table, sb->u.ext2_sb.s_itb_per_group)))
-		ext2_panic (sb, "ext2_new_block",
+	     in_range (tmp, gdp->bg_inode_table, sb->u.ext2_sb.s_itb_per_group))) {
+		ext2_error (sb, "ext2_new_block",
 			    "Allocating block in system zone - "
 			    "block = %u", tmp);
+		unlock_super (sb);
+		*err = -EIO;
+		return 0;
+	}
 
 	if (set_bit (j, bh->b_data)) {
 		ext2_warning (sb, "ext2_new_block",
@@ -511,7 +617,11 @@
 	for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++) {
 		gdp = get_group_desc (sb, i, NULL);
 		desc_count += gdp->bg_free_blocks_count;
+
 		bitmap_nr = load_block_bitmap (sb, i);
+		if (bitmap_nr < 0)
+			continue;
+		
 		x = ext2_count_free (sb->u.ext2_sb.s_block_bitmap[bitmap_nr],
 				     sb->s_blocksize);
 		printk ("group %d: stored = %d, counted = %lu\n",
@@ -556,6 +666,9 @@
 		gdp = get_group_desc (sb, i, NULL);
 		desc_count += gdp->bg_free_blocks_count;
 		bitmap_nr = load_block_bitmap (sb, i);
+		if (bitmap_nr < 0)
+			continue;
+
 		bh = sb->u.ext2_sb.s_block_bitmap[bitmap_nr];
 
 		if (!test_bit (0, bh->b_data))