nilfs2: block cache for garbage collection

This 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.
Signed-off-by: Seiji Kihara <kihara.seiji@lab.ntt.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Yoshiji Amagai <amagai.yoshiji@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/gcinode.c

+/*
+ * gcinode.c - NILFS memory inode for GC
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * Written by Seiji Kihara <kihara@osrg.net>, Amagai Yoshiji <amagai@osrg.net>,
+ *            and Ryusuke Konishi <ryusuke@osrg.net>.
+ * Revised by Ryusuke Konishi <ryusuke@osrg.net>.
+ *
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mpage.h>
+#include <linux/hash.h>
+#include <linux/swap.h>
+#include "nilfs.h"
+#include "page.h"
+#include "mdt.h"
+#include "dat.h"
+#include "ifile.h"
+
+static struct address_space_operations def_gcinode_aops = {};
+/* XXX need def_gcinode_iops/fops? */
+
+/*
+ * nilfs_gccache_submit_read_data() - add data buffer and submit read request
+ * @inode - gc inode
+ * @blkoff - dummy offset treated as the key for the page cache
+ * @pbn - physical block number of the block
+ * @vbn - virtual block number of the block, 0 for non-virtual block
+ * @out_bh - indirect pointer to a buffer_head struct to receive the results
+ *
+ * Description: nilfs_gccache_submit_read_data() registers the data buffer
+ * specified by @pbn to the GC pagecache with the key @blkoff.
+ * This function sets @vbn (@pbn if @vbn is zero) in b_blocknr of the buffer.
+ *
+ * Return Value: On success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - The block specified with @pbn does not exist.
+ */
+int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
+				   sector_t pbn, __u64 vbn,
+				   struct buffer_head **out_bh)
+{
+	struct buffer_head *bh;
+	int err;
+
+	bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
+	if (unlikely(!bh))
+		return -ENOMEM;
+
+	if (buffer_uptodate(bh))
+		goto out;
+
+	if (pbn == 0) {
+		struct inode *dat_inode = NILFS_I_NILFS(inode)->ns_dat;
+					  /* use original dat, not gc dat. */
+		err = nilfs_dat_translate(dat_inode, vbn, &pbn);
+		if (unlikely(err)) { /* -EIO, -ENOMEM, -ENOENT */
+			brelse(bh);
+			goto failed;
+		}
+	}
+
+	lock_buffer(bh);
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		goto out;
+	}
+
+	if (!buffer_mapped(bh)) {
+		bh->b_bdev = NILFS_I_NILFS(inode)->ns_bdev;
+		set_buffer_mapped(bh);
+	}
+	bh->b_blocknr = pbn;
+	bh->b_end_io = end_buffer_read_sync;
+	get_bh(bh);
+	submit_bh(READ, bh);
+	if (vbn)
+		bh->b_blocknr = vbn;
+ out:
+	err = 0;
+	*out_bh = bh;
+
+ failed:
+	unlock_page(bh->b_page);
+	page_cache_release(bh->b_page);
+	return err;
+}
+
+/*
+ * nilfs_gccache_submit_read_node() - add node buffer and submit read request
+ * @inode - gc inode
+ * @pbn - physical block number for the block
+ * @vbn - virtual block number for the block
+ * @out_bh - indirect pointer to a buffer_head struct to receive the results
+ *
+ * Description: nilfs_gccache_submit_read_node() registers the node buffer
+ * specified by @vbn to the GC pagecache.  @pbn can be supplied by the
+ * caller to avoid translation of the disk block address.
+ *
+ * Return Value: On success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_gccache_submit_read_node(struct inode *inode, sector_t pbn,
+				   __u64 vbn, struct buffer_head **out_bh)
+{
+	int ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
+					    vbn ? : pbn, pbn, out_bh, 0);
+	if (ret == -EEXIST) /* internal code (cache hit) */
+		ret = 0;
+	return ret;
+}
+
+int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
+{
+	wait_on_buffer(bh);
+	if (!buffer_uptodate(bh))
+		return -EIO;
+	if (buffer_dirty(bh))
+		return -EEXIST;
+
+	if (buffer_nilfs_node(bh))
+		nilfs_btnode_mark_dirty(bh);
+	else
+		nilfs_mdt_mark_buffer_dirty(bh);
+	return 0;
+}
+
+/*
+ * nilfs_init_gccache() - allocate and initialize gc_inode hash table
+ * @nilfs - the_nilfs
+ *
+ * Return Value: On success, 0.
+ * On error, a negative error code is returned.
+ */
+int nilfs_init_gccache(struct the_nilfs *nilfs)
+{
+	int loop;
+
+	BUG_ON(nilfs->ns_gc_inodes_h);
+
+	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
+
+	nilfs->ns_gc_inodes_h =
+		kmalloc(sizeof(struct hlist_head) * NILFS_GCINODE_HASH_SIZE,
+			GFP_NOFS);
+	if (nilfs->ns_gc_inodes_h == NULL)
+		return -ENOMEM;
+
+	for (loop = 0; loop < NILFS_GCINODE_HASH_SIZE; loop++)
+		INIT_HLIST_HEAD(&nilfs->ns_gc_inodes_h[loop]);
+	return 0;
+}
+
+/*
+ * nilfs_destroy_gccache() - free gc_inode hash table
+ * @nilfs - the nilfs
+ */
+void nilfs_destroy_gccache(struct the_nilfs *nilfs)
+{
+	if (nilfs->ns_gc_inodes_h) {
+		nilfs_remove_all_gcinode(nilfs);
+		kfree(nilfs->ns_gc_inodes_h);
+		nilfs->ns_gc_inodes_h = NULL;
+	}
+}
+
+static struct inode *alloc_gcinode(struct the_nilfs *nilfs, ino_t ino,
+				   __u64 cno)
+{
+	struct inode *inode = nilfs_mdt_new_common(nilfs, NULL, ino, GFP_NOFS);
+	struct nilfs_inode_info *ii;
+
+	if (!inode)
+		return NULL;
+
+	inode->i_op = NULL;
+	inode->i_fop = NULL;
+	inode->i_mapping->a_ops = &def_gcinode_aops;
+
+	ii = NILFS_I(inode);
+	ii->i_cno = cno;
+	ii->i_flags = 0;
+	ii->i_state = 1 << NILFS_I_GCINODE;
+	ii->i_bh = NULL;
+	ii->i_dtime = 0;
+	nilfs_bmap_init_gc(ii->i_bmap);
+
+	return inode;
+}
+
+static unsigned long ihash(ino_t ino, __u64 cno)
+{
+	return hash_long((unsigned long)((ino << 2) + cno),
+			 NILFS_GCINODE_HASH_BITS);
+}
+
+/*
+ * nilfs_gc_iget() - find or create gc inode with specified (ino,cno)
+ */
+struct inode *nilfs_gc_iget(struct the_nilfs *nilfs, ino_t ino, __u64 cno)
+{
+	struct hlist_head *head = nilfs->ns_gc_inodes_h + ihash(ino, cno);
+	struct hlist_node *node;
+	struct inode *inode;
+
+	hlist_for_each_entry(inode, node, head, i_hash) {
+		if (inode->i_ino == ino && NILFS_I(inode)->i_cno == cno)
+			return inode;
+	}
+
+	inode = alloc_gcinode(nilfs, ino, cno);
+	if (likely(inode)) {
+		hlist_add_head(&inode->i_hash, head);
+		list_add(&NILFS_I(inode)->i_dirty, &nilfs->ns_gc_inodes);
+	}
+	return inode;
+}
+
+/*
+ * nilfs_clear_gcinode() - clear and free a gc inode
+ */
+void nilfs_clear_gcinode(struct inode *inode)
+{
+	nilfs_mdt_clear(inode);
+	nilfs_mdt_destroy(inode);
+}
+
+/*
+ * nilfs_remove_all_gcinode() - remove all inodes from the_nilfs
+ */
+void nilfs_remove_all_gcinode(struct the_nilfs *nilfs)
+{
+	struct hlist_head *head = nilfs->ns_gc_inodes_h;
+	struct hlist_node *node, *n;
+	struct inode *inode;
+	int loop;
+
+	for (loop = 0; loop < NILFS_GCINODE_HASH_SIZE; loop++, head++) {
+		hlist_for_each_entry_safe(inode, node, n, head, i_hash) {
+			hlist_del_init(&inode->i_hash);
+			list_del_init(&NILFS_I(inode)->i_dirty);
+			nilfs_clear_gcinode(inode); /* might sleep */
+		}
+	}
+}