nilfs2: segment constructor

This adds the segment constructor (also called log writer).

The segment constructor collects dirty buffers for every dirty inode,
makes summaries of the buffers, assigns disk block addresses to the
buffers, and then submits BIOs for the buffers.

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>

fs/nilfs2/file.c

@@ -73,10 +73,66 @@ nilfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
 	return ret;
 }
 
-static int nilfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+static int nilfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
-	if (!(vma->vm_flags & (VM_WRITE | VM_MAYWRITE)))
-		return -EPERM;
+	struct page *page = vmf->page;
+	struct inode *inode = vma->vm_file->f_dentry->d_inode;
+	struct nilfs_transaction_info ti;
+	int ret;
+
+	if (unlikely(nilfs_near_disk_full(NILFS_SB(inode->i_sb)->s_nilfs)))
+		return VM_FAULT_SIGBUS; /* -ENOSPC */
+
+	lock_page(page);
+	if (page->mapping != inode->i_mapping ||
+	    page_offset(page) >= i_size_read(inode) || !PageUptodate(page)) {
+		unlock_page(page);
+		return VM_FAULT_NOPAGE; /* make the VM retry the fault */
+	}
+
+	/*
+	 * check to see if the page is mapped already (no holes)
+	 */
+	if (PageMappedToDisk(page)) {
+		unlock_page(page);
+		goto mapped;
+	}
+	if (page_has_buffers(page)) {
+		struct buffer_head *bh, *head;
+		int fully_mapped = 1;
+
+		bh = head = page_buffers(page);
+		do {
+			if (!buffer_mapped(bh)) {
+				fully_mapped = 0;
+				break;
+			}
+		} while (bh = bh->b_this_page, bh != head);
+
+		if (fully_mapped) {
+			SetPageMappedToDisk(page);
+			unlock_page(page);
+			goto mapped;
+		}
+	}
+	unlock_page(page);
+
+	/*
+	 * fill hole blocks
+	 */
+	ret = nilfs_transaction_begin(inode->i_sb, &ti, 1);
+	/* never returns -ENOMEM, but may return -ENOSPC */
+	if (unlikely(ret))
+		return VM_FAULT_SIGBUS;
+
+	ret = block_page_mkwrite(vma, vmf, nilfs_get_block);
+	if (unlikely(ret)) {
+		nilfs_transaction_abort(inode->i_sb);
+		return ret;
+	}
+	nilfs_transaction_commit(inode->i_sb);
+
+ mapped:
 	SetPageChecked(page);
 	wait_on_page_writeback(page);
 	return 0;

fs/nilfs2/seglist.h

@@ -0,0 +1,85 @@
+/*
+ * seglist.h - expediential structure and routines to handle list of segments
+ *             (would be removed in a future release)
+ *
+ * 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 Ryusuke Konishi <ryusuke@osrg.net>
+ *
+ */
+#ifndef _NILFS_SEGLIST_H
+#define _NILFS_SEGLIST_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/nilfs2_fs.h>
+#include "sufile.h"
+
+struct nilfs_segment_entry {
+	__u64			segnum;
+
+#define NILFS_SLH_FREED		0x0001	/* The segment was freed provisonally.
+					   It must be cancelled if
+					   construction aborted */
+
+	unsigned		flags;
+	struct list_head	list;
+	struct buffer_head     *bh_su;
+	struct nilfs_segment_usage *raw_su;
+};
+
+
+void nilfs_dispose_segment_list(struct list_head *);
+
+static inline struct nilfs_segment_entry *
+nilfs_alloc_segment_entry(__u64 segnum)
+{
+	struct nilfs_segment_entry *ent = kmalloc(sizeof(*ent), GFP_NOFS);
+
+	if (likely(ent)) {
+		ent->segnum = segnum;
+		ent->flags = 0;
+		ent->bh_su = NULL;
+		ent->raw_su = NULL;
+		INIT_LIST_HEAD(&ent->list);
+	}
+	return ent;
+}
+
+static inline int nilfs_open_segment_entry(struct nilfs_segment_entry *ent,
+					   struct inode *sufile)
+{
+	return nilfs_sufile_get_segment_usage(sufile, ent->segnum,
+					      &ent->raw_su, &ent->bh_su);
+}
+
+static inline void nilfs_close_segment_entry(struct nilfs_segment_entry *ent,
+					     struct inode *sufile)
+{
+	if (!ent->bh_su)
+		return;
+	nilfs_sufile_put_segment_usage(sufile, ent->segnum, ent->bh_su);
+	ent->bh_su = NULL;
+	ent->raw_su = NULL;
+}
+
+static inline void nilfs_free_segment_entry(struct nilfs_segment_entry *ent)
+{
+	kfree(ent);
+}
+
+#endif /* _NILFS_SEGLIST_H */