svn commit: r253341 - head/sys/ufs/ffs

[Kirk McKusick]

Author: mckusick
Date: Sun Jul 14 18:44:33 2013
New Revision: 253341
URL: http://svnweb.freebsd.org/changeset/base/253341

Log:
  Update to comments describing block allocation policy.
  
  Submitted by: Bruce Evans

Modified:
  head/sys/ufs/ffs/ffs_alloc.c

Modified: head/sys/ufs/ffs/ffs_alloc.c
==============================================================================
--- head/sys/ufs/ffs/ffs_alloc.c	Sun Jul 14 18:26:47 2013	(r253340)
+++ head/sys/ufs/ffs/ffs_alloc.c	Sun Jul 14 18:44:33 2013	(r253341)
@@ -1196,7 +1196,8 @@ ffs_dirpref(pip)
 /*
  * Select the desired position for the next block in a file.  The file is
  * logically divided into sections. The first section is composed of the
- * direct blocks. Each additional section contains fs_maxbpg blocks.
+ * direct blocks and the next fs_maxbpg blocks. Each additional section
+ * contains fs_maxbpg blocks.
  *
  * If no blocks have been allocated in the first section, the policy is to
  * request a block in the same cylinder group as the inode that describes
@@ -1214,14 +1215,12 @@ ffs_dirpref(pip)
  * cylinder group from which the previous allocation was made. The sweep
  * continues until a cylinder group with greater than the average number
  * of free blocks is found. If the allocation is for the first block in an
- * indirect block, the information on the previous allocation is unavailable;
- * here a best guess is made based upon the logical block number being
- * allocated.
+ * indirect block or the previous block is a hole, then the information on
+ * the previous allocation is unavailable; here a best guess is made based
+ * on the logical block number being allocated.
  *
  * If a section is already partially allocated, the policy is to
- * contiguously allocate fs_maxcontig blocks. The end of one of these
- * contiguous blocks and the beginning of the next is laid out
- * contiguously if possible.
+ * allocate blocks contiguously within the section if possible.
  */
 ufs2_daddr_t
 ffs_blkpref_ufs1(ip, lbn, indx, bap)