diff options
| author | Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> | 2009-04-06 19:01:45 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-07 08:31:17 -0700 |
| commit | 047180f2d7bf95ff5699ca04da639a7556e23435 (patch) | |
| tree | 28f66f0880426ffae01892df531e820064ff7f6f | |
| parent | 47420c799830d4676e544dbec56b2a7f787528f5 (diff) | |
nilfs2: insert explanations in gcinode file
The file gcinode.c gives buffer cache functions for on-disk blocks
moved in garbage collection. Joern Engel has suggested inserting its
explanations in the source file (Message-ID:
<20080917144146.GD8750@logfs.org> and
<20080917224953.GB14644@logfs.org>).
This follows the comment.
Cc: Joern Engel <joern@logfs.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/nilfs2/gcinode.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c index 001395266325..77615aabc7e2 100644 --- a/fs/nilfs2/gcinode.c +++ b/fs/nilfs2/gcinode.c @@ -1,5 +1,5 @@ /* - * gcinode.c - NILFS memory inode for GC + * gcinode.c - dummy inodes to buffer blocks for garbage collection * * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation. * @@ -22,6 +22,25 @@ * Revised by Ryusuke Konishi <ryusuke@osrg.net>. * */ +/* + * This file adds the cache of on-disk blocks to be moved in garbage + * collection. The disk blocks are held with dummy inodes (called + * gcinodes), and this file provides lookup function of the dummy + * inodes and their buffer read function. + * + * Since NILFS2 keeps up multiple checkpoints/snapshots accross GC, it + * has to treat blocks that belong to a same file but have different + * checkpoint numbers. To avoid interference among generations, dummy + * inodes are managed separatly from actual inodes, and their lookup + * function (nilfs_gc_iget) is designed to be specified with a + * checkpoint number argument as well as an inode number. + * + * Buffers and pages held by the dummy inodes will be released each + * time after they are copied to a new log. Dirty blocks made on the + * current generation and the blocks to be moved by GC never overlap + * because the dirty blocks make a new generation; they rather must be + * written individually. + */ #include <linux/buffer_head.h> #include <linux/mpage.h> |