Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ryusuke/nilfs2

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ryusuke/nilfs2: (45 commits)
  nilfs2: reject filesystem with unsupported block size
  nilfs2: avoid rec_len overflow with 64KB block size
  nilfs2: simplify nilfs_get_page function
  nilfs2: reject incompatible filesystem
  nilfs2: add feature set fields to super block
  nilfs2: clarify byte offset in super block format
  nilfs2: apply read-ahead for nilfs_btree_lookup_contig
  nilfs2: introduce check flag to btree node buffer
  nilfs2: add btree get block function with readahead option
  nilfs2: add read ahead mode to nilfs_btnode_submit_block
  nilfs2: fix buffer head leak in nilfs_btnode_submit_block
  nilfs2: eliminate inline keywords in btree implementation
  nilfs2: get maximum number of child nodes from bmap object
  nilfs2: reduce repetitive calculation of max number of child nodes
  nilfs2: optimize calculation of min/max number of btree node children
  nilfs2: remove redundant pointer checks in bmap lookup functions
  nilfs2: get rid of nilfs_bmap_union
  nilfs2: unify bmap set_target_v operations
  nilfs2: get rid of nilfs_btree uses
  nilfs2: get rid of nilfs_direct uses
  ...

Documentation/filesystems/nilfs2.txt

@@ -49,7 +49,10 @@ Mount options
 NILFS2 supports the following mount options:
 (*) == default
 
-nobarrier		Disables barriers.
+barrier(*)		This enables/disables the use of write barriers.  This
+nobarrier		requires an IO stack which can support barriers, and
+			if nilfs gets an error on a barrier write, it will
+			disable again with a warning.
 errors=continue		Keep going on a filesystem error.
 errors=remount-ro(*)	Remount the filesystem read-only on an error.
 errors=panic		Panic and halt the machine if an error occurs.
@@ -74,9 +77,10 @@ norecovery		Disable recovery of the filesystem on mount.
 			This disables every write access on the device for
 			read-only mounts or snapshots.  This option will fail
 			for r/w mounts on an unclean volume.
-discard			Issue discard/TRIM commands to the underlying block
-			device when blocks are freed.  This is useful for SSD
-			devices and sparse/thinly-provisioned LUNs.
+discard			This enables/disables the use of discard/TRIM commands.
+nodiscard(*)		The discard/TRIM commands are sent to the underlying
+			block device when blocks are freed.  This is useful
+			for SSD devices and sparse/thinly-provisioned LUNs.
 
 NILFS2 usage
 ============

fs/nilfs2/bmap.c

@@ -26,6 +26,8 @@
 #include "nilfs.h"
 #include "bmap.h"
 #include "sb.h"
+#include "btree.h"
+#include "direct.h"
 #include "btnode.h"
 #include "mdt.h"
 #include "dat.h"
@@ -533,7 +535,7 @@ void nilfs_bmap_init_gc(struct nilfs_bmap *bmap)
 
 void nilfs_bmap_init_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
 {
-	memcpy(gcbmap, bmap, sizeof(union nilfs_bmap_union));
+	memcpy(gcbmap, bmap, sizeof(*bmap));
 	init_rwsem(&gcbmap->b_sem);
 	lockdep_set_class(&bmap->b_sem, &nilfs_bmap_dat_lock_key);
 	gcbmap->b_inode = &NILFS_BMAP_I(gcbmap)->vfs_inode;
@@ -541,7 +543,7 @@ void nilfs_bmap_init_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
 
 void nilfs_bmap_commit_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
 {
-	memcpy(bmap, gcbmap, sizeof(union nilfs_bmap_union));
+	memcpy(bmap, gcbmap, sizeof(*bmap));
 	init_rwsem(&bmap->b_sem);
 	lockdep_set_class(&bmap->b_sem, &nilfs_bmap_dat_lock_key);
 	bmap->b_inode = &NILFS_BMAP_I(bmap)->vfs_inode;

fs/nilfs2/bmap.h

@@ -32,11 +32,6 @@
 
 #define NILFS_BMAP_INVALID_PTR	0
 
-#define nilfs_bmap_dkey_to_key(dkey)	le64_to_cpu(dkey)
-#define nilfs_bmap_key_to_dkey(key)	cpu_to_le64(key)
-#define nilfs_bmap_dptr_to_ptr(dptr)	le64_to_cpu(dptr)
-#define nilfs_bmap_ptr_to_dptr(ptr)	cpu_to_le64(ptr)
-
 #define nilfs_bmap_keydiff_abs(diff)	((diff) < 0 ? -(diff) : (diff))
 
 
@@ -71,7 +66,7 @@ struct nilfs_bmap_operations {
 	int (*bop_delete)(struct nilfs_bmap *, __u64);
 	void (*bop_clear)(struct nilfs_bmap *);
 
-	int (*bop_propagate)(const struct nilfs_bmap *, struct buffer_head *);
+	int (*bop_propagate)(struct nilfs_bmap *, struct buffer_head *);
 	void (*bop_lookup_dirty_buffers)(struct nilfs_bmap *,
 					 struct list_head *);
 
@@ -110,6 +105,7 @@ static inline int nilfs_bmap_is_new_ptr(unsigned long ptr)
  * @b_last_allocated_ptr: last allocated ptr for data block
  * @b_ptr_type: pointer type
  * @b_state: state
+ * @b_nchildren_per_block: maximum number of child nodes for non-root nodes
  */
 struct nilfs_bmap {
 	union {
@@ -123,6 +119,7 @@ struct nilfs_bmap {
 	__u64 b_last_allocated_ptr;
 	int b_ptr_type;
 	int b_state;
+	__u16 b_nchildren_per_block;
 };
 
 /* pointer type */
@@ -224,6 +221,13 @@ static inline void nilfs_bmap_abort_end_ptr(struct nilfs_bmap *bmap,
 		nilfs_dat_abort_end(dat, &req->bpr_req);
 }
 
+static inline void nilfs_bmap_set_target_v(struct nilfs_bmap *bmap, __u64 key,
+					   __u64 ptr)
+{
+	bmap->b_last_allocated_key = key;
+	bmap->b_last_allocated_ptr = ptr;
+}
+
 __u64 nilfs_bmap_data_get_key(const struct nilfs_bmap *,
 			      const struct buffer_head *);
 

fs/nilfs2/bmap_union.h

-/*
- * bmap_union.h - NILFS block mapping.
- *
- * Copyright (C) 2006-2008 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 Koji Sato <koji@osrg.net>.
- */
-
-#ifndef _NILFS_BMAP_UNION_H
-#define _NILFS_BMAP_UNION_H
-
-#include "bmap.h"
-#include "direct.h"
-#include "btree.h"
-
-/**
- * nilfs_bmap_union -
- * @bi_bmap: bmap structure
- * @bi_btree: direct map structure
- * @bi_direct: B-tree structure
- */
-union nilfs_bmap_union {
-	struct nilfs_bmap bi_bmap;
-	struct nilfs_direct bi_direct;
-	struct nilfs_btree bi_btree;
-};
-
-#endif	/* _NILFS_BMAP_UNION_H */

fs/nilfs2/btnode.c

@@ -96,10 +96,12 @@ nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
 }
 
 int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
-			      sector_t pblocknr, struct buffer_head **pbh)
+			      sector_t pblocknr, int mode,
+			      struct buffer_head **pbh, sector_t *submit_ptr)
 {
 	struct buffer_head *bh;
 	struct inode *inode = NILFS_BTNC_I(btnc);
+	struct page *page;
 	int err;
 
 	bh = nilfs_grab_buffer(inode, btnc, blocknr, 1 << BH_NILFS_Node);
@@ -107,6 +109,7 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 		return -ENOMEM;
 
 	err = -EEXIST; /* internal code */
+	page = bh->b_page;
 
 	if (buffer_uptodate(bh) || buffer_dirty(bh))
 		goto found;
@@ -125,7 +128,16 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 			}
 		}
 	}
-	lock_buffer(bh);
+
+	if (mode == READA) {
+		if (pblocknr != *submit_ptr + 1 || !trylock_buffer(bh)) {
+			err = -EBUSY; /* internal code */
+			brelse(bh);
+			goto out_locked;
+		}
+	} else { /* mode == READ */
+		lock_buffer(bh);
+	}
 	if (buffer_uptodate(bh)) {
 		unlock_buffer(bh);
 		err = -EEXIST; /* internal code */
@@ -136,15 +148,16 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 	bh->b_blocknr = pblocknr; /* set block address for read */
 	bh->b_end_io = end_buffer_read_sync;
 	get_bh(bh);
-	submit_bh(READ, bh);
+	submit_bh(mode, bh);
 	bh->b_blocknr = blocknr; /* set back to the given block address */
+	*submit_ptr = pblocknr;
 	err = 0;
 found:
 	*pbh = bh;
 
 out_locked:
-	unlock_page(bh->b_page);
-	page_cache_release(bh->b_page);
+	unlock_page(page);
+	page_cache_release(page);
 	return err;
 }
 

fs/nilfs2/btnode.h

@@ -42,8 +42,8 @@ void nilfs_btnode_cache_init(struct address_space *, struct backing_dev_info *);
 void nilfs_btnode_cache_clear(struct address_space *);
 struct buffer_head *nilfs_btnode_create_block(struct address_space *btnc,
 					      __u64 blocknr);
-int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t,
-			      struct buffer_head **);
+int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t, int,
+			      struct buffer_head **, sector_t *);
 void nilfs_btnode_delete(struct buffer_head *);
 int nilfs_btnode_prepare_change_key(struct address_space *,
 				    struct nilfs_btnode_chkey_ctxt *);

fs/nilfs2/btree.h

@@ -30,14 +30,6 @@
 #include "btnode.h"
 #include "bmap.h"
 
-/**
- * struct nilfs_btree - B-tree structure
- * @bt_bmap: bmap base structure
- */
-struct nilfs_btree {
-	struct nilfs_bmap bt_bmap;
-};
-
 /**
  * struct nilfs_btree_path - A path on which B-tree operations are executed
  * @bp_bh: buffer head of node block
@@ -54,7 +46,7 @@ struct nilfs_btree_path {
 	union nilfs_bmap_ptr_req bp_oldreq;
 	union nilfs_bmap_ptr_req bp_newreq;
 	struct nilfs_btnode_chkey_ctxt bp_ctxt;
-	void (*bp_op)(struct nilfs_btree *, struct nilfs_btree_path *,
+	void (*bp_op)(struct nilfs_bmap *, struct nilfs_btree_path *,
 		      int, __u64 *, __u64 *);
 };
 
@@ -80,4 +72,6 @@ int nilfs_btree_convert_and_insert(struct nilfs_bmap *, __u64, __u64,
 				   const __u64 *, const __u64 *, int);
 void nilfs_btree_init_gc(struct nilfs_bmap *);
 
+int nilfs_btree_broken_node_block(struct buffer_head *bh);
+
 #endif	/* _NILFS_BTREE_H */

fs/nilfs2/dir.c

@@ -141,7 +141,7 @@ static void nilfs_check_page(struct page *page)
 	}
 	for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
 		p = (struct nilfs_dir_entry *)(kaddr + offs);
-		rec_len = le16_to_cpu(p->rec_len);
+		rec_len = nilfs_rec_len_from_disk(p->rec_len);
 
 		if (rec_len < NILFS_DIR_REC_LEN(1))
 			goto Eshort;
@@ -199,13 +199,10 @@ static void nilfs_check_page(struct page *page)
 static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
 {
 	struct address_space *mapping = dir->i_mapping;
-	struct page *page = read_cache_page(mapping, n,
-				(filler_t *)mapping->a_ops->readpage, NULL);
+	struct page *page = read_mapping_page(mapping, n, NULL);
+
 	if (!IS_ERR(page)) {
-		wait_on_page_locked(page);
 		kmap(page);
-		if (!PageUptodate(page))
-			goto fail;
 		if (!PageChecked(page))
 			nilfs_check_page(page);
 		if (PageError(page))
@@ -238,7 +235,8 @@ nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *de)
  */
 static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
 {
-	return (struct nilfs_dir_entry *)((char *)p + le16_to_cpu(p->rec_len));
+	return (struct nilfs_dir_entry *)((char *)p +
+					  nilfs_rec_len_from_disk(p->rec_len));
 }
 
 static unsigned char
@@ -329,7 +327,7 @@ static int nilfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 					goto success;
 				}
 			}
-			filp->f_pos += le16_to_cpu(de->rec_len);
+			filp->f_pos += nilfs_rec_len_from_disk(de->rec_len);
 		}
 		nilfs_put_page(page);
 	}
@@ -444,7 +442,7 @@ void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
 		    struct page *page, struct inode *inode)
 {
 	unsigned from = (char *) de - (char *) page_address(page);
-	unsigned to = from + le16_to_cpu(de->rec_len);
+	unsigned to = from + nilfs_rec_len_from_disk(de->rec_len);
 	struct address_space *mapping = page->mapping;
 	int err;
 
@@ -500,7 +498,7 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 				/* We hit i_size */
 				name_len = 0;
 				rec_len = chunk_size;
-				de->rec_len = cpu_to_le16(chunk_size);
+				de->rec_len = nilfs_rec_len_to_disk(chunk_size);
 				de->inode = 0;
 				goto got_it;
 			}
@@ -514,7 +512,7 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 			if (nilfs_match(namelen, name, de))
 				goto out_unlock;
 			name_len = NILFS_DIR_REC_LEN(de->name_len);
-			rec_len = le16_to_cpu(de->rec_len);
+			rec_len = nilfs_rec_len_from_disk(de->rec_len);
 			if (!de->inode && rec_len >= reclen)
 				goto got_it;
 			if (rec_len >= name_len + reclen)
@@ -537,8 +535,8 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 		struct nilfs_dir_entry *de1;
 
 		de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
-		de1->rec_len = cpu_to_le16(rec_len - name_len);
-		de->rec_len = cpu_to_le16(name_len);
+		de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
+		de->rec_len = nilfs_rec_len_to_disk(name_len);
 		de = de1;
 	}
 	de->name_len = namelen;
@@ -569,7 +567,8 @@ int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
 	struct inode *inode = mapping->host;
 	char *kaddr = page_address(page);
 	unsigned from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
-	unsigned to = ((char *)dir - kaddr) + le16_to_cpu(dir->rec_len);
+	unsigned to = ((char *)dir - kaddr) +
+		nilfs_rec_len_from_disk(dir->rec_len);
 	struct nilfs_dir_entry *pde = NULL;
 	struct nilfs_dir_entry *de = (struct nilfs_dir_entry *)(kaddr + from);
 	int err;
@@ -590,7 +589,7 @@ int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
 	err = nilfs_prepare_chunk(page, mapping, from, to);
 	BUG_ON(err);
 	if (pde)
-		pde->rec_len = cpu_to_le16(to - from);
+		pde->rec_len = nilfs_rec_len_to_disk(to - from);
 	dir->inode = 0;
 	nilfs_commit_chunk(page, mapping, from, to);
 	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
@@ -624,14 +623,14 @@ int nilfs_make_empty(struct inode *inode, struct inode *parent)
 	memset(kaddr, 0, chunk_size);
 	de = (struct nilfs_dir_entry *)kaddr;
 	de->name_len = 1;
-	de->rec_len = cpu_to_le16(NILFS_DIR_REC_LEN(1));
+	de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
 	memcpy(de->name, ".\0\0", 4);
 	de->inode = cpu_to_le64(inode->i_ino);
 	nilfs_set_de_type(de, inode);
 
 	de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
 	de->name_len = 2;
-	de->rec_len = cpu_to_le16(chunk_size - NILFS_DIR_REC_LEN(1));
+	de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
 	de->inode = cpu_to_le64(parent->i_ino);
 	memcpy(de->name, "..\0", 4);
 	nilfs_set_de_type(de, inode);

fs/nilfs2/direct.h

@@ -28,8 +28,6 @@
 #include "bmap.h"
 
 
-struct nilfs_direct;
-
 /**
  * struct nilfs_direct_node - direct node
  * @dn_flags: flags
@@ -40,15 +38,6 @@ struct nilfs_direct_node {
 	__u8 pad[7];
 };
 
-/**
- * struct nilfs_direct - direct mapping
- * @d_bmap: bmap structure
- */
-struct nilfs_direct {
-	struct nilfs_bmap d_bmap;
-};
-
-
 #define NILFS_DIRECT_NBLOCKS	(NILFS_BMAP_SIZE / sizeof(__le64) - 1)
 #define NILFS_DIRECT_KEY_MIN	0
 #define NILFS_DIRECT_KEY_MAX	(NILFS_DIRECT_NBLOCKS - 1)

fs/nilfs2/gcinode.c

@@ -48,6 +48,8 @@
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include "nilfs.h"
+#include "btree.h"
+#include "btnode.h"
 #include "page.h"
 #include "mdt.h"
 #include "dat.h"
@@ -149,8 +151,10 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
 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);
+	int ret;
+
+	ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
+					vbn ? : pbn, pbn, READ, out_bh, &pbn);
 	if (ret == -EEXIST) /* internal code (cache hit) */
 		ret = 0;
 	return ret;
@@ -164,10 +168,15 @@ int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
 	if (buffer_dirty(bh))
 		return -EEXIST;
 
-	if (buffer_nilfs_node(bh))
+	if (buffer_nilfs_node(bh)) {
+		if (nilfs_btree_broken_node_block(bh)) {
+			clear_buffer_uptodate(bh);
+			return -EIO;
+		}
 		nilfs_btnode_mark_dirty(bh);
-	else
+	} else {
 		nilfs_mdt_mark_buffer_dirty(bh);
+	}
 	return 0;
 }
 

fs/nilfs2/mdt.c

@@ -28,6 +28,7 @@
 #include <linux/swap.h>
 #include <linux/slab.h>
 #include "nilfs.h"
+#include "btnode.h"
 #include "segment.h"
 #include "page.h"
 #include "mdt.h"

fs/nilfs2/nilfs.h

@@ -32,7 +32,6 @@
 #include "the_nilfs.h"
 #include "sb.h"
 #include "bmap.h"
-#include "bmap_union.h"
 
 /*
  * nilfs inode data in memory
@@ -41,7 +40,7 @@ struct nilfs_inode_info {
 	__u32 i_flags;
 	unsigned long  i_state;		/* Dynamic state flags */
 	struct nilfs_bmap *i_bmap;
-	union nilfs_bmap_union i_bmap_union;
+	struct nilfs_bmap i_bmap_data;
 	__u64 i_xattr;	/* sector_t ??? */
 	__u32 i_dir_start_lookup;
 	__u64 i_cno;		/* check point number for GC inode */
@@ -71,9 +70,7 @@ static inline struct nilfs_inode_info *NILFS_I(const struct inode *inode)
 static inline struct nilfs_inode_info *
 NILFS_BMAP_I(const struct nilfs_bmap *bmap)
 {
-	return container_of((union nilfs_bmap_union *)bmap,
-			    struct nilfs_inode_info,
-			    i_bmap_union);
+	return container_of(bmap, struct nilfs_inode_info, i_bmap_data);
 }
 
 static inline struct inode *NILFS_BTNC_I(struct address_space *btnc)
@@ -106,6 +103,14 @@ enum {
 	NILFS_I_GCDAT,			/* shadow DAT, on memory only */
 };
 
+/*
+ * commit flags for nilfs_commit_super and nilfs_sync_super
+ */
+enum {
+	NILFS_SB_COMMIT = 0,	/* Commit a super block alternately */
+	NILFS_SB_COMMIT_ALL	/* Commit both super blocks */
+};
+
 /*
  * Macros to check inode numbers
  */
@@ -270,7 +275,14 @@ extern struct nilfs_super_block *
 nilfs_read_super_block(struct super_block *, u64, int, struct buffer_head **);
 extern int nilfs_store_magic_and_option(struct super_block *,
 					struct nilfs_super_block *, char *);
+extern int nilfs_check_feature_compatibility(struct super_block *,
+					     struct nilfs_super_block *);
+extern void nilfs_set_log_cursor(struct nilfs_super_block *,
+				 struct the_nilfs *);
+extern struct nilfs_super_block **nilfs_prepare_super(struct nilfs_sb_info *,
+						      int flip);
 extern int nilfs_commit_super(struct nilfs_sb_info *, int);
+extern int nilfs_cleanup_super(struct nilfs_sb_info *);
 extern int nilfs_attach_checkpoint(struct nilfs_sb_info *, __u64);
 extern void nilfs_detach_checkpoint(struct nilfs_sb_info *);
 

fs/nilfs2/page.c

@@ -37,7 +37,8 @@
 
 #define NILFS_BUFFER_INHERENT_BITS  \
 	((1UL << BH_Uptodate) | (1UL << BH_Mapped) | (1UL << BH_NILFS_Node) | \
-	 (1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Allocated))
+	 (1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Allocated) | \
+	 (1UL << BH_NILFS_Checked))
 
 static struct buffer_head *
 __nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
@@ -129,6 +130,7 @@ void nilfs_forget_buffer(struct buffer_head *bh)
 
 	lock_buffer(bh);
 	clear_buffer_nilfs_volatile(bh);
+	clear_buffer_nilfs_checked(bh);
 	clear_buffer_dirty(bh);
 	if (nilfs_page_buffers_clean(page))
 		__nilfs_clear_page_dirty(page);
@@ -480,6 +482,7 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
 				lock_buffer(bh);
 				clear_buffer_dirty(bh);
 				clear_buffer_nilfs_volatile(bh);
+				clear_buffer_nilfs_checked(bh);
 				clear_buffer_uptodate(bh);
 				clear_buffer_mapped(bh);
 				unlock_buffer(bh);

fs/nilfs2/page.h

@@ -34,11 +34,13 @@ enum {
 	BH_NILFS_Allocated = BH_PrivateStart,
 	BH_NILFS_Node,
 	BH_NILFS_Volatile,
+	BH_NILFS_Checked,
 };
 
 BUFFER_FNS(NILFS_Allocated, nilfs_allocated)	/* nilfs private buffers */
 BUFFER_FNS(NILFS_Node, nilfs_node)		/* nilfs node buffers */
 BUFFER_FNS(NILFS_Volatile, nilfs_volatile)
+BUFFER_FNS(NILFS_Checked, nilfs_checked)	/* buffer is verified */
 
 
 void nilfs_mark_buffer_dirty(struct buffer_head *bh);

fs/nilfs2/segbuf.h

@@ -54,17 +54,6 @@ struct nilfs_segsum_info {
 	sector_t		next;
 };
 
-/* macro for the flags */
-#define NILFS_SEG_HAS_SR(sum)    ((sum)->flags & NILFS_SS_SR)
-#define NILFS_SEG_LOGBGN(sum)    ((sum)->flags & NILFS_SS_LOGBGN)
-#define NILFS_SEG_LOGEND(sum)    ((sum)->flags & NILFS_SS_LOGEND)
-#define NILFS_SEG_DSYNC(sum)     ((sum)->flags & NILFS_SS_SYNDT)
-#define NILFS_SEG_SIMPLEX(sum) \
-	(((sum)->flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) == \
-	 (NILFS_SS_LOGBGN | NILFS_SS_LOGEND))
-
-#define NILFS_SEG_EMPTY(sum)	((sum)->nblocks == (sum)->nsumblk)
-
 /**
  * struct nilfs_segment_buffer - Segment buffer
  * @sb_super: back pointer to a superblock struct
@@ -141,6 +130,19 @@ int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *,
 				struct buffer_head **);
 void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *);
 
+static inline int nilfs_segbuf_simplex(struct nilfs_segment_buffer *segbuf)
+{
+	unsigned int flags = segbuf->sb_sum.flags;
+
+	return (flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) ==
+		(NILFS_SS_LOGBGN | NILFS_SS_LOGEND);
+}
+
+static inline int nilfs_segbuf_empty(struct nilfs_segment_buffer *segbuf)
+{
+	return segbuf->sb_sum.nblocks == segbuf->sb_sum.nsumblk;
+}
+
 static inline void
 nilfs_segbuf_add_segsum_buffer(struct nilfs_segment_buffer *segbuf,
 			       struct buffer_head *bh)

fs/nilfs2/segment.c

@@ -1914,12 +1914,12 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 			}
 		}
 
-		if (!NILFS_SEG_SIMPLEX(&segbuf->sb_sum)) {
-			if (NILFS_SEG_LOGBGN(&segbuf->sb_sum)) {
+		if (!nilfs_segbuf_simplex(segbuf)) {
+			if (segbuf->sb_sum.flags & NILFS_SS_LOGBGN) {
 				set_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
 				sci->sc_lseg_stime = jiffies;
 			}
-			if (NILFS_SEG_LOGEND(&segbuf->sb_sum))
+			if (segbuf->sb_sum.flags & NILFS_SS_LOGEND)
 				clear_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
 		}
 	}
@@ -1951,7 +1951,6 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 	if (update_sr) {
 		nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
 				       segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
-		set_nilfs_sb_dirty(nilfs);
 
 		clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
 		clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
@@ -2082,7 +2081,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 
 		/* Avoid empty segment */
 		if (sci->sc_stage.scnt == NILFS_ST_DONE &&
-		    NILFS_SEG_EMPTY(&sci->sc_curseg->sb_sum)) {
+		    nilfs_segbuf_empty(sci->sc_curseg)) {
 			nilfs_segctor_abort_construction(sci, nilfs, 1);
 			goto out;
 		}
@@ -2408,6 +2407,7 @@ static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 {
 	struct nilfs_sb_info *sbi = sci->sc_sbi;
 	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_super_block **sbp;
 	int err = 0;
 
 	nilfs_segctor_accept(sci);
@@ -2423,8 +2423,13 @@ static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 		if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
 		    nilfs_discontinued(nilfs)) {
 			down_write(&nilfs->ns_sem);
-			err = nilfs_commit_super(
-				sbi, nilfs_altsb_need_update(nilfs));
+			err = -EIO;
+			sbp = nilfs_prepare_super(sbi,
+						  nilfs_sb_will_flip(nilfs));
+			if (likely(sbp)) {
+				nilfs_set_log_cursor(sbp[0], nilfs);
+				err = nilfs_commit_super(sbi, NILFS_SB_COMMIT);
+			}
 			up_write(&nilfs->ns_sem);
 		}
 	}

fs/nilfs2/segment.h

@@ -234,13 +234,13 @@ extern int nilfs_attach_segment_constructor(struct nilfs_sb_info *);
 extern void nilfs_detach_segment_constructor(struct nilfs_sb_info *);
 
 /* recovery.c */
-extern int nilfs_read_super_root_block(struct super_block *, sector_t,
+extern int nilfs_read_super_root_block(struct the_nilfs *, sector_t,
 				       struct buffer_head **, int);
-extern int nilfs_search_super_root(struct the_nilfs *, struct nilfs_sb_info *,
+extern int nilfs_search_super_root(struct the_nilfs *,
 				   struct nilfs_recovery_info *);
-extern int nilfs_recover_logical_segments(struct the_nilfs *,
-					  struct nilfs_sb_info *,
-					  struct nilfs_recovery_info *);
+extern int nilfs_salvage_orphan_logs(struct the_nilfs *,
+				     struct nilfs_sb_info *,
+				     struct nilfs_recovery_info *);
 extern void nilfs_dispose_segment_list(struct list_head *);
 
 #endif /* _NILFS_SEGMENT_H */

fs/nilfs2/the_nilfs.c

@@ -38,6 +38,8 @@
 static LIST_HEAD(nilfs_objects);
 static DEFINE_SPINLOCK(nilfs_lock);
 
+static int nilfs_valid_sb(struct nilfs_super_block *sbp);
+
 void nilfs_set_last_segment(struct the_nilfs *nilfs,
 			    sector_t start_blocknr, u64 seq, __u64 cno)
 {
@@ -45,6 +47,16 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
 	nilfs->ns_last_pseg = start_blocknr;
 	nilfs->ns_last_seq = seq;
 	nilfs->ns_last_cno = cno;
+
+	if (!nilfs_sb_dirty(nilfs)) {
+		if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
+			goto stay_cursor;
+
+		set_nilfs_sb_dirty(nilfs);
+	}
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+
+ stay_cursor:
 	spin_unlock(&nilfs->ns_last_segment_lock);
 }
 
@@ -159,8 +171,7 @@ void put_nilfs(struct the_nilfs *nilfs)
 	kfree(nilfs);
 }
 
-static int nilfs_load_super_root(struct the_nilfs *nilfs,
-				 struct nilfs_sb_info *sbi, sector_t sr_block)
+static int nilfs_load_super_root(struct the_nilfs *nilfs, sector_t sr_block)
 {
 	struct buffer_head *bh_sr;
 	struct nilfs_super_root *raw_sr;
@@ -169,7 +180,7 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 	unsigned inode_size;
 	int err;
 
-	err = nilfs_read_super_root_block(sbi->s_super, sr_block, &bh_sr, 1);
+	err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);
 	if (unlikely(err))
 		return err;
 
@@ -247,6 +258,37 @@ static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
 	nilfs_dispose_segment_list(&ri->ri_used_segments);
 }
 
+/**
+ * nilfs_store_log_cursor - load log cursor from a super block
+ * @nilfs: nilfs object
+ * @sbp: buffer storing super block to be read
+ *
+ * nilfs_store_log_cursor() reads the last position of the log
+ * containing a super root from a given super block, and initializes
+ * relevant information on the nilfs object preparatory for log
+ * scanning and recovery.
+ */
+static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
+				  struct nilfs_super_block *sbp)
+{
+	int ret = 0;
+
+	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
+	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
+	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
+
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+	nilfs->ns_seg_seq = nilfs->ns_last_seq;
+	nilfs->ns_segnum =
+		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
+	nilfs->ns_cno = nilfs->ns_last_cno + 1;
+	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
+		printk(KERN_ERR "NILFS invalid last segment number.\n");
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
 /**
  * load_nilfs - load and recover the nilfs
  * @nilfs: the_nilfs structure to be released
@@ -285,13 +327,55 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 
 	nilfs_init_recovery_info(&ri);
 
-	err = nilfs_search_super_root(nilfs, sbi, &ri);
+	err = nilfs_search_super_root(nilfs, &ri);
 	if (unlikely(err)) {
-		printk(KERN_ERR "NILFS: error searching super root.\n");
-		goto failed;
+		struct nilfs_super_block **sbp = nilfs->ns_sbp;
+		int blocksize;
+
+		if (err != -EINVAL)
+			goto scan_error;
+
+		if (!nilfs_valid_sb(sbp[1])) {
+			printk(KERN_WARNING
+			       "NILFS warning: unable to fall back to spare"
+			       "super block\n");
+			goto scan_error;
+		}
+		printk(KERN_INFO
+		       "NILFS: try rollback from an earlier position\n");
+
+		/*
+		 * restore super block with its spare and reconfigure
+		 * relevant states of the nilfs object.
+		 */
+		memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
+		nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
+		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
+
+		/* verify consistency between two super blocks */
+		blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size);
+		if (blocksize != nilfs->ns_blocksize) {
+			printk(KERN_WARNING
+			       "NILFS warning: blocksize differs between "
+			       "two super blocks (%d != %d)\n",
+			       blocksize, nilfs->ns_blocksize);
+			goto scan_error;
+		}
+
+		err = nilfs_store_log_cursor(nilfs, sbp[0]);
+		if (err)
+			goto scan_error;
+
+		/* drop clean flag to allow roll-forward and recovery */
+		nilfs->ns_mount_state &= ~NILFS_VALID_FS;
+		valid_fs = 0;
+
+		err = nilfs_search_super_root(nilfs, &ri);
+		if (err)
+			goto scan_error;
 	}
 
-	err = nilfs_load_super_root(nilfs, sbi, ri.ri_super_root);
+	err = nilfs_load_super_root(nilfs, ri.ri_super_root);
 	if (unlikely(err)) {
 		printk(KERN_ERR "NILFS: error loading super root.\n");
 		goto failed;
@@ -301,11 +385,23 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 		goto skip_recovery;
 
 	if (s_flags & MS_RDONLY) {
+		__u64 features;
+
 		if (nilfs_test_opt(sbi, NORECOVERY)) {
 			printk(KERN_INFO "NILFS: norecovery option specified. "
 			       "skipping roll-forward recovery\n");
 			goto skip_recovery;
 		}
+		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+			~NILFS_FEATURE_COMPAT_RO_SUPP;
+		if (features) {
+			printk(KERN_ERR "NILFS: couldn't proceed with "
+			       "recovery because of unsupported optional "
+			       "features (%llx)\n",
+			       (unsigned long long)features);
+			err = -EROFS;
+			goto failed_unload;
+		}
 		if (really_read_only) {
 			printk(KERN_ERR "NILFS: write access "
 			       "unavailable, cannot proceed.\n");
@@ -320,14 +416,13 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 		goto failed_unload;
 	}
 
-	err = nilfs_recover_logical_segments(nilfs, sbi, &ri);
+	err = nilfs_salvage_orphan_logs(nilfs, sbi, &ri);
 	if (err)
 		goto failed_unload;
 
 	down_write(&nilfs->ns_sem);
-	nilfs->ns_mount_state |= NILFS_VALID_FS;
-	nilfs->ns_sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
-	err = nilfs_commit_super(sbi, 1);
+	nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */
+	err = nilfs_cleanup_super(sbi);
 	up_write(&nilfs->ns_sem);
 
 	if (err) {
@@ -343,6 +438,10 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 	sbi->s_super->s_flags = s_flags;
 	return 0;
 
+ scan_error:
+	printk(KERN_ERR "NILFS: error searching super root.\n");
+	goto failed;
+
  failed_unload:
 	nilfs_mdt_destroy(nilfs->ns_cpfile);
 	nilfs_mdt_destroy(nilfs->ns_sufile);
@@ -515,8 +614,8 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
 		nilfs_swap_super_block(nilfs);
 	}
 
-	nilfs->ns_sbwtime[0] = le64_to_cpu(sbp[0]->s_wtime);
-	nilfs->ns_sbwtime[1] = valid[!swp] ? le64_to_cpu(sbp[1]->s_wtime) : 0;
+	nilfs->ns_sbwcount = 0;
+	nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
 	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
 	*sbpp = sbp[0];
 	return 0;
@@ -557,6 +656,10 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 		if (err)
 			goto out;
 
+		err = nilfs_check_feature_compatibility(sb, sbp);
+		if (err)
+			goto out;
+
 		blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
 		if (sb->s_blocksize != blocksize &&
 		    !sb_set_blocksize(sb, blocksize)) {
@@ -568,7 +671,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 		goto out;
 	}
 
-	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
+	blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
 	if (!blocksize) {
 		printk(KERN_ERR "NILFS: unable to set blocksize\n");
 		err = -EINVAL;
@@ -582,7 +685,18 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 	if (err)
 		goto failed_sbh;
 
+	err = nilfs_check_feature_compatibility(sb, sbp);
+	if (err)
+		goto failed_sbh;
+
 	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
+	if (blocksize < NILFS_MIN_BLOCK_SIZE ||
+	    blocksize > NILFS_MAX_BLOCK_SIZE) {
+		printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
+		       "filesystem blocksize %d\n", blocksize);
+		err = -EINVAL;
+		goto failed_sbh;
+	}
 	if (sb->s_blocksize != blocksize) {
 		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);
 
@@ -604,6 +718,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 			   when reloading fails. */
 	}
 	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
+	nilfs->ns_blocksize = blocksize;
 
 	err = nilfs_store_disk_layout(nilfs, sbp);
 	if (err)
@@ -616,23 +731,9 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 	bdi = nilfs->ns_bdev->bd_inode->i_mapping->backing_dev_info;
 	nilfs->ns_bdi = bdi ? : &default_backing_dev_info;
 
-	/* Finding last segment */
-	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
-	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
-	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
-
-	nilfs->ns_seg_seq = nilfs->ns_last_seq;
-	nilfs->ns_segnum =
-		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
-	nilfs->ns_cno = nilfs->ns_last_cno + 1;
-	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
-		printk(KERN_ERR "NILFS invalid last segment number.\n");
-		err = -EINVAL;
+	err = nilfs_store_log_cursor(nilfs, sbp);
+	if (err)
 		goto failed_sbh;
-	}
-	/* Dummy values  */
-	nilfs->ns_free_segments_count =
-		nilfs->ns_nsegments - (nilfs->ns_segnum + 1);
 
 	/* Initialize gcinode cache */
 	err = nilfs_init_gccache(nilfs);

fs/nilfs2/the_nilfs.h

@@ -57,7 +57,8 @@ enum {
  * @ns_current: back pointer to current mount
  * @ns_sbh: buffer heads of on-disk super blocks
  * @ns_sbp: pointers to super block data
- * @ns_sbwtime: previous write time of super blocks
+ * @ns_sbwtime: previous write time of super block
+ * @ns_sbwcount: write count of super block
  * @ns_sbsize: size of valid data in super block
  * @ns_supers: list of nilfs super block structs
  * @ns_seg_seq: segment sequence counter
@@ -73,7 +74,7 @@ enum {
  * @ns_last_seq: sequence value of the latest segment
  * @ns_last_cno: checkpoint number of the latest segment
  * @ns_prot_seq: least sequence number of segments which must not be reclaimed
- * @ns_free_segments_count: counter of free segments
+ * @ns_prev_seq: base sequence number used to decide if advance log cursor
  * @ns_segctor_sem: segment constructor semaphore
  * @ns_dat: DAT file inode
  * @ns_cpfile: checkpoint file inode
@@ -82,6 +83,7 @@ enum {
  * @ns_gc_inodes: dummy inodes to keep live blocks
  * @ns_gc_inodes_h: hash list to keep dummy inode holding live blocks
  * @ns_blocksize_bits: bit length of block size
+ * @ns_blocksize: block size
  * @ns_nsegments: number of segments in filesystem
  * @ns_blocks_per_segment: number of blocks per segment
  * @ns_r_segments_percentage: reserved segments percentage
@@ -119,7 +121,8 @@ struct the_nilfs {
 	 */
 	struct buffer_head     *ns_sbh[2];
 	struct nilfs_super_block *ns_sbp[2];
-	time_t			ns_sbwtime[2];
+	time_t			ns_sbwtime;
+	unsigned		ns_sbwcount;
 	unsigned		ns_sbsize;
 	unsigned		ns_mount_state;
 
@@ -149,7 +152,7 @@ struct the_nilfs {
 	u64			ns_last_seq;
 	__u64			ns_last_cno;
 	u64			ns_prot_seq;
-	unsigned long		ns_free_segments_count;
+	u64			ns_prev_seq;
 
 	struct rw_semaphore	ns_segctor_sem;
 
@@ -168,6 +171,7 @@ struct the_nilfs {
 
 	/* Disk layout information (static) */
 	unsigned int		ns_blocksize_bits;
+	unsigned int		ns_blocksize;
 	unsigned long		ns_nsegments;
 	unsigned long		ns_blocks_per_segment;
 	unsigned long		ns_r_segments_percentage;
@@ -203,20 +207,17 @@ THE_NILFS_FNS(SB_DIRTY, sb_dirty)
 
 /* Minimum interval of periodical update of superblocks (in seconds) */
 #define NILFS_SB_FREQ		10
-#define NILFS_ALTSB_FREQ	60  /* spare superblock */
 
 static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
 {
 	u64 t = get_seconds();
-	return t < nilfs->ns_sbwtime[0] ||
-		 t > nilfs->ns_sbwtime[0] + NILFS_SB_FREQ;
+	return t < nilfs->ns_sbwtime || t > nilfs->ns_sbwtime + NILFS_SB_FREQ;
 }
 
-static inline int nilfs_altsb_need_update(struct the_nilfs *nilfs)
+static inline int nilfs_sb_will_flip(struct the_nilfs *nilfs)
 {
-	u64 t = get_seconds();
-	struct nilfs_super_block **sbp = nilfs->ns_sbp;
-	return sbp[1] && t > nilfs->ns_sbwtime[1] + NILFS_ALTSB_FREQ;
+	int flip_bits = nilfs->ns_sbwcount & 0x0FL;
+	return (flip_bits != 0x08 && flip_bits != 0x0F);
 }
 
 void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);

include/linux/nilfs2_fs.h

@@ -160,7 +160,7 @@ struct nilfs_super_root {
  * struct nilfs_super_block - structure of super block on disk
  */
 struct nilfs_super_block {
-	__le32	s_rev_level;		/* Revision level */
+/*00*/	__le32	s_rev_level;		/* Revision level */
 	__le16	s_minor_rev_level;	/* minor revision level */
 	__le16	s_magic;		/* Magic signature */
 
@@ -169,50 +169,53 @@ struct nilfs_super_block {
 					   is excluded. */
 	__le16  s_flags;		/* flags */
 	__le32  s_crc_seed;		/* Seed value of CRC calculation */
-	__le32	s_sum;			/* Check sum of super block */
+/*10*/	__le32	s_sum;			/* Check sum of super block */
 
 	__le32	s_log_block_size;	/* Block size represented as follows
 					   blocksize =
 					       1 << (s_log_block_size + 10) */
 	__le64  s_nsegments;		/* Number of segments in filesystem */
-	__le64  s_dev_size;		/* block device size in bytes */
+/*20*/	__le64  s_dev_size;		/* block device size in bytes */
 	__le64	s_first_data_block;	/* 1st seg disk block number */
-	__le32  s_blocks_per_segment;   /* number of blocks per full segment */
+/*30*/	__le32  s_blocks_per_segment;   /* number of blocks per full segment */
 	__le32	s_r_segments_percentage; /* Reserved segments percentage */
 
 	__le64  s_last_cno;		/* Last checkpoint number */
-	__le64  s_last_pseg;		/* disk block addr pseg written last */
+/*40*/	__le64  s_last_pseg;		/* disk block addr pseg written last */
 	__le64  s_last_seq;             /* seq. number of seg written last */
-	__le64	s_free_blocks_count;	/* Free blocks count */
+/*50*/	__le64	s_free_blocks_count;	/* Free blocks count */
 
 	__le64	s_ctime;		/* Creation time (execution time of
 					   newfs) */
-	__le64	s_mtime;		/* Mount time */
+/*60*/	__le64	s_mtime;		/* Mount time */
 	__le64	s_wtime;		/* Write time */
-	__le16	s_mnt_count;		/* Mount count */
+/*70*/	__le16	s_mnt_count;		/* Mount count */
 	__le16	s_max_mnt_count;	/* Maximal mount count */
 	__le16	s_state;		/* File system state */
 	__le16	s_errors;		/* Behaviour when detecting errors */
 	__le64	s_lastcheck;		/* time of last check */
 
-	__le32	s_checkinterval;	/* max. time between checks */
+/*80*/	__le32	s_checkinterval;	/* max. time between checks */
 	__le32	s_creator_os;		/* OS */
 	__le16	s_def_resuid;		/* Default uid for reserved blocks */
 	__le16	s_def_resgid;		/* Default gid for reserved blocks */
 	__le32	s_first_ino;		/* First non-reserved inode */
 
-	__le16  s_inode_size;		/* Size of an inode */
+/*90*/	__le16  s_inode_size;		/* Size of an inode */
 	__le16  s_dat_entry_size;       /* Size of a dat entry */
 	__le16  s_checkpoint_size;      /* Size of a checkpoint */
 	__le16	s_segment_usage_size;	/* Size of a segment usage */
 
-	__u8	s_uuid[16];		/* 128-bit uuid for volume */
-	char	s_volume_name[80];	/* volume name */
+/*98*/	__u8	s_uuid[16];		/* 128-bit uuid for volume */
+/*A8*/	char	s_volume_name[80];	/* volume name */
 
-	__le32  s_c_interval;           /* Commit interval of segment */
+/*F8*/	__le32  s_c_interval;           /* Commit interval of segment */
 	__le32  s_c_block_max;          /* Threshold of data amount for
 					   the segment construction */
-	__u32	s_reserved[192];	/* padding to the end of the block */
+/*100*/	__le64  s_feature_compat;	/* Compatible feature set */
+	__le64  s_feature_compat_ro;	/* Read-only compatible feature set */
+	__le64  s_feature_incompat;	/* Incompatible feature set */
+	__u32	s_reserved[186];	/* padding to the end of the block */
 };
 
 /*
@@ -227,6 +230,16 @@ struct nilfs_super_block {
 #define NILFS_CURRENT_REV	2	/* current major revision */
 #define NILFS_MINOR_REV		0	/* minor revision */
 
+/*
+ * Feature set definitions
+ *
+ * If there is a bit set in the incompatible feature set that the kernel
+ * doesn't know about, it should refuse to mount the filesystem.
+ */
+#define NILFS_FEATURE_COMPAT_SUPP	0ULL
+#define NILFS_FEATURE_COMPAT_RO_SUPP	0ULL
+#define NILFS_FEATURE_INCOMPAT_SUPP	0ULL
+
 /*
  * Bytes count of super_block for CRC-calculation
  */
@@ -273,6 +286,12 @@ struct nilfs_super_block {
 
 #define NILFS_NAME_LEN 255
 
+/*
+ * Block size limitations
+ */
+#define NILFS_MIN_BLOCK_SIZE		1024
+#define NILFS_MAX_BLOCK_SIZE		65536
+
 /*
  * The new version of the directory entry.  Since V0 structures are
  * stored in intel byte order, and the name_len field could never be
@@ -313,7 +332,25 @@ enum {
 #define NILFS_DIR_ROUND			(NILFS_DIR_PAD - 1)
 #define NILFS_DIR_REC_LEN(name_len)	(((name_len) + 12 + NILFS_DIR_ROUND) & \
 					~NILFS_DIR_ROUND)
+#define NILFS_MAX_REC_LEN		((1<<16)-1)
 
+static inline unsigned nilfs_rec_len_from_disk(__le16 dlen)
+{
+	unsigned len = le16_to_cpu(dlen);
+
+	if (len == NILFS_MAX_REC_LEN)
+		return 1 << 16;
+	return len;
+}
+
+static inline __le16 nilfs_rec_len_to_disk(unsigned len)
+{
+	if (len == (1 << 16))
+		return cpu_to_le16(NILFS_MAX_REC_LEN);
+	else if (len > (1 << 16))
+		BUG();
+	return cpu_to_le16(len);
+}
 
 /**
  * struct nilfs_finfo - file information