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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-04-06 22:01:45 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-07 11:31:17 -0400
commit047180f2d7bf95ff5699ca04da639a7556e23435 (patch)
tree28f66f0880426ffae01892df531e820064ff7f6f
parent47420c799830d4676e544dbec56b2a7f787528f5 (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.c21
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 @@
1/* 1/*
2 * gcinode.c - NILFS memory inode for GC 2 * gcinode.c - dummy inodes to buffer blocks for garbage collection
3 * 3 *
4 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation. 4 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
5 * 5 *
@@ -22,6 +22,25 @@
22 * Revised by Ryusuke Konishi <ryusuke@osrg.net>. 22 * Revised by Ryusuke Konishi <ryusuke@osrg.net>.
23 * 23 *
24 */ 24 */
25/*
26 * This file adds the cache of on-disk blocks to be moved in garbage
27 * collection. The disk blocks are held with dummy inodes (called
28 * gcinodes), and this file provides lookup function of the dummy
29 * inodes and their buffer read function.
30 *
31 * Since NILFS2 keeps up multiple checkpoints/snapshots accross GC, it
32 * has to treat blocks that belong to a same file but have different
33 * checkpoint numbers. To avoid interference among generations, dummy
34 * inodes are managed separatly from actual inodes, and their lookup
35 * function (nilfs_gc_iget) is designed to be specified with a
36 * checkpoint number argument as well as an inode number.
37 *
38 * Buffers and pages held by the dummy inodes will be released each
39 * time after they are copied to a new log. Dirty blocks made on the
40 * current generation and the blocks to be moved by GC never overlap
41 * because the dirty blocks make a new generation; they rather must be
42 * written individually.
43 */
25 44
26#include <linux/buffer_head.h> 45#include <linux/buffer_head.h>
27#include <linux/mpage.h> 46#include <linux/mpage.h>