[XFS] Fix for large allocation groups, so that extent

sizes will not overflow pagebuf lengths.

SGI Modid: xfs-linux:xfs-kern:164827a

fs/xfs/linux/xfs_aops.c

@@ -407,8 +407,10 @@ map_unwritten(
 	offset <<= PAGE_CACHE_SHIFT;
 	offset += p_offset;
 
-	pb = pagebuf_lookup(iomapp->iomap_target,
-			    iomapp->iomap_offset, iomapp->iomap_bsize, 0);
+	/* get an "empty" pagebuf to manage IO completion
+	 * Proper values will be set before returning */
+	pb = pagebuf_lookup(iomapp->iomap_target, 0, 0, 0);
+
 	if (!pb)
 		return -EAGAIN;
 
@@ -471,6 +473,11 @@ map_unwritten(
 			nblocks += bs;
 			atomic_add(bs, &pb->pb_io_remaining);
 			convert_page(inode, page, iomapp, pb, startio, all_bh);
+                        /* stop if converting the next page might add
+			 * enough blocks that the corresponding byte
+			 * count won't fit in our ulong page buf length */
+			if (nblocks >= ((ULONG_MAX - PAGE_SIZE) >> block_bits))
+				goto enough;
 		}
 
 		if (tindex == tlast &&
@@ -481,16 +488,20 @@ map_unwritten(
 				nblocks += bs;
 				atomic_add(bs, &pb->pb_io_remaining);
 				convert_page(inode, page, iomapp, pb, startio, all_bh);
+				if (nblocks >= ((ULONG_MAX - PAGE_SIZE) >> block_bits))
+					goto enough;
 			}
 		}
 	}
 
+enough:
 	size = nblocks;		/* NB: using 64bit number here */
 	size <<= block_bits;	/* convert fsb's to byte range */
 
 	XFS_BUF_DATAIO(pb);
 	XFS_BUF_ASYNC(pb);
 	XFS_BUF_SET_SIZE(pb, size);
+	XFS_BUF_SET_COUNT(pb, size);
 	XFS_BUF_SET_OFFSET(pb, offset);
 	XFS_BUF_SET_FSPRIVATE(pb, LINVFS_GET_VP(inode));
 	XFS_BUF_SET_IODONE_FUNC(pb, linvfs_unwritten_convert);
@@ -925,8 +936,10 @@ linvfs_get_block_core(
 	}
 
 	if (blocks) {
-		size = (iomap.iomap_bsize - iomap.iomap_delta); 
-		bh_result->b_size = min_t(ssize_t, size, blocks << inode->i_blkbits);
+		loff_t iosize;
+		iosize = (iomap.iomap_bsize - iomap.iomap_delta);
+		bh_result->b_size =
+		    (ssize_t)min(iosize, (loff_t)(blocks << inode->i_blkbits));
 	}
 
 	return 0;

fs/xfs/xfs_iomap.h

@@ -66,27 +66,26 @@ typedef enum {
 /*
  * xfs_iomap_t:  File system I/O map
  *
- * The iomap_bn, iomap_offset and iomap_length fields are expressed in disk blocks.
- * The iomap_length field specifies the size of the underlying backing store
- * for the particular mapping.
+ * The iomap_bn field is expressed in 512-byte blocks, and is where the 
+ * mapping starts on disk.
  *
- * The iomap_bsize, iomap_size and iomap_delta fields are in bytes and indicate
- * the size of the mapping, the number of bytes that are valid to access
- * (read or write), and the offset into the mapping, given the offset
- * supplied to the file I/O map routine.  iomap_delta is the offset of the
- * desired data from the beginning of the mapping.
+ * The iomap_offset, iomap_bsize and iomap_delta fields are in bytes.
+ * iomap_offset is the offset of the mapping in the file itself.
+ * iomap_bsize is the size of the mapping,  iomap_delta is the 
+ * desired data's offset into the mapping, given the offset supplied 
+ * to the file I/O map routine.
  *
  * When a request is made to read beyond the logical end of the object,
- * iomap_size may be set to 0, but iomap_offset and iomap_length should be set to
- * the actual amount of underlying storage that has been allocated, if any.
+ * iomap_size may be set to 0, but iomap_offset and iomap_length should be set
+ * to the actual amount of underlying storage that has been allocated, if any.
  */
 
 typedef struct xfs_iomap {
-	xfs_daddr_t		iomap_bn;
+	xfs_daddr_t		iomap_bn;	/* first 512b blk of mapping */
 	xfs_buftarg_t		*iomap_target;
-	loff_t			iomap_offset;
-	size_t			iomap_delta;
-	size_t			iomap_bsize;
+	loff_t			iomap_offset;	/* offset of mapping, bytes */
+	loff_t			iomap_bsize;	/* size of mapping, bytes */
+	size_t			iomap_delta;	/* offset into mapping, bytes */
 	iomap_flags_t		iomap_flags;
 } xfs_iomap_t;