nilfs2: get rid of GCDAT inode

This applies prepared rollback function and redirect function of
metadata file to DAT file, and eliminates GCDAT inode.

Signed-off-by: Ryusuke Konishi <[e-mail]>

fs/nilfs2/Makefile

···
 nilfs2-y := inode.o file.o dir.o super.o namei.o page.o mdt.o \
 	btnode.o bmap.o btree.o direct.o dat.o recovery.o \
 	the_nilfs.o segbuf.o segment.o cpfile.o sufile.o \
-	ifile.o alloc.o gcinode.o ioctl.o gcdat.o
+	ifile.o alloc.o gcinode.o ioctl.o

fs/nilfs2/bmap.c

···
 	nilfs_btree_init_gc(bmap);
 }
 
-void nilfs_bmap_init_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
-{
-	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;
-}
-
-void nilfs_bmap_commit_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
-{
-	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;
-}
-
 void nilfs_bmap_save(const struct nilfs_bmap *bmap,
 		     struct nilfs_bmap_store *store)
 {

fs/nilfs2/bmap.h

···
 int nilfs_bmap_mark(struct nilfs_bmap *, __u64, int);
 
 void nilfs_bmap_init_gc(struct nilfs_bmap *);
-void nilfs_bmap_init_gcdat(struct nilfs_bmap *, struct nilfs_bmap *);
-void nilfs_bmap_commit_gcdat(struct nilfs_bmap *, struct nilfs_bmap *);
 
 void nilfs_bmap_save(const struct nilfs_bmap *, struct nilfs_bmap_store *);
 void nilfs_bmap_restore(struct nilfs_bmap *, const struct nilfs_bmap_store *);

fs/nilfs2/dat.c

···
 struct nilfs_dat_info {
 	struct nilfs_mdt_info mi;
 	struct nilfs_palloc_cache palloc_cache;
+	struct nilfs_shadow_map shadow;
 };
 
 static inline struct nilfs_dat_info *NILFS_DAT_I(struct inode *dat)
···
 	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
 	if (ret < 0)
 		return ret;
+
+	/*
+	 * The given disk block number (blocknr) is not yet written to
+	 * the device at this point.
+	 *
+	 * To prevent nilfs_dat_translate() from returning the
+	 * uncommited block number, this makes a copy of the entry
+	 * buffer and redirects nilfs_dat_translate() to the copy.
+	 */
+	if (!buffer_nilfs_redirected(entry_bh)) {
+		ret = nilfs_mdt_freeze_buffer(dat, entry_bh);
+		if (ret) {
+			brelse(entry_bh);
+			return ret;
+		}
+	}
+
 	kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
 	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
 	if (unlikely(entry->de_blocknr == cpu_to_le64(0))) {
···
  */
 int nilfs_dat_translate(struct inode *dat, __u64 vblocknr, sector_t *blocknrp)
 {
-	struct buffer_head *entry_bh;
+	struct buffer_head *entry_bh, *bh;
 	struct nilfs_dat_entry *entry;
 	sector_t blocknr;
 	void *kaddr;
···
 	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
 	if (ret < 0)
 		return ret;
+
+	if (!nilfs_doing_gc() && buffer_nilfs_redirected(entry_bh)) {
+		bh = nilfs_mdt_get_frozen_buffer(dat, entry_bh);
+		if (bh) {
+			WARN_ON(!buffer_uptodate(bh));
+			brelse(entry_bh);
+			entry_bh = bh;
+		}
+	}
 
 	kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
 	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
···
 		di = NILFS_DAT_I(dat);
 		lockdep_set_class(&di->mi.mi_sem, &dat_lock_key);
 		nilfs_palloc_setup_cache(dat, &di->palloc_cache);
+		nilfs_mdt_setup_shadow_map(dat, &di->shadow);
 	}
 	return dat;
 }

fs/nilfs2/gcdat.c

···
-/*
- * gcdat.c - NILFS shadow DAT 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 <[e-mail]>, Amagai Yoshiji <[e-mail]>,
- *            and Ryusuke Konishi <[e-mail]>.
- *
- */
-
-#include <linux/buffer_head.h>
-#include "nilfs.h"
-#include "page.h"
-#include "mdt.h"
-
-int nilfs_init_gcdat_inode(struct the_nilfs *nilfs)
-{
-	struct inode *dat = nilfs->ns_dat, *gcdat = nilfs->ns_gc_dat;
-	struct nilfs_inode_info *dii = NILFS_I(dat), *gii = NILFS_I(gcdat);
-	int err;
-
-	gcdat->i_state = 0;
-	gcdat->i_blocks = dat->i_blocks;
-	gii->i_flags = dii->i_flags;
-	gii->i_state = dii->i_state | (1 << NILFS_I_GCDAT);
-	gii->i_cno = 0;
-	nilfs_bmap_init_gcdat(gii->i_bmap, dii->i_bmap);
-	err = nilfs_copy_dirty_pages(gcdat->i_mapping, dat->i_mapping);
-	if (unlikely(err))
-		return err;
-
-	return nilfs_copy_dirty_pages(&gii->i_btnode_cache,
-				      &dii->i_btnode_cache);
-}
-
-void nilfs_commit_gcdat_inode(struct the_nilfs *nilfs)
-{
-	struct inode *dat = nilfs->ns_dat, *gcdat = nilfs->ns_gc_dat;
-	struct nilfs_inode_info *dii = NILFS_I(dat), *gii = NILFS_I(gcdat);
-	struct address_space *mapping = dat->i_mapping;
-	struct address_space *gmapping = gcdat->i_mapping;
-
-	down_write(&NILFS_MDT(dat)->mi_sem);
-	dat->i_blocks = gcdat->i_blocks;
-	dii->i_flags = gii->i_flags;
-	dii->i_state = gii->i_state & ~(1 << NILFS_I_GCDAT);
-
-	nilfs_bmap_commit_gcdat(gii->i_bmap, dii->i_bmap);
-
-	nilfs_palloc_clear_cache(dat);
-	nilfs_palloc_clear_cache(gcdat);
-	nilfs_clear_dirty_pages(mapping);
-	nilfs_copy_back_pages(mapping, gmapping);
-	/* note: mdt dirty flags should be cleared by segctor. */
-
-	nilfs_clear_dirty_pages(&dii->i_btnode_cache);
-	nilfs_copy_back_pages(&dii->i_btnode_cache, &gii->i_btnode_cache);
-
-	up_write(&NILFS_MDT(dat)->mi_sem);
-}
-
-void nilfs_clear_gcdat_inode(struct the_nilfs *nilfs)
-{
-	struct inode *gcdat = nilfs->ns_gc_dat;
-	struct nilfs_inode_info *gii = NILFS_I(gcdat);
-
-	gcdat->i_state = I_FREEING | I_CLEAR;
-	gii->i_flags = 0;
-
-	nilfs_palloc_clear_cache(gcdat);
-	truncate_inode_pages(gcdat->i_mapping, 0);
-	truncate_inode_pages(&gii->i_btnode_cache, 0);
-}

fs/nilfs2/mdt.c

···
 	sb = inode->i_sb;
 	nilfs = NILFS_MDT(inode)->mi_nilfs;
 
-	if (page->mapping->assoc_mapping)
-		return 0; /* Do not request flush for shadow page cache */
 	if (!sb) {
 		down_read(&nilfs->ns_writer_sem);
 		writer = nilfs->ns_writer;
···
 	mi->mi_entry_size = entry_size;
 	mi->mi_entries_per_block = (1 << inode->i_blkbits) / entry_size;
 	mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
-}
-
-void nilfs_mdt_set_shadow(struct inode *orig, struct inode *shadow)
-{
-	shadow->i_mapping->assoc_mapping = orig->i_mapping;
-	NILFS_I(shadow)->i_btnode_cache.assoc_mapping =
-		&NILFS_I(orig)->i_btnode_cache;
 }
 
 static const struct address_space_operations shadow_map_aops = {

fs/nilfs2/mdt.h

···
 				   ino_t);
 void nilfs_mdt_destroy(struct inode *);
 void nilfs_mdt_set_entry_size(struct inode *, unsigned, unsigned);
-void nilfs_mdt_set_shadow(struct inode *, struct inode *);
 
 int nilfs_mdt_setup_shadow_map(struct inode *inode,
 			       struct nilfs_shadow_map *shadow);

fs/nilfs2/nilfs.h

···
 	NILFS_I_INODE_DIRTY,		/* write_inode is requested */
 	NILFS_I_BMAP,			/* has bmap and btnode_cache */
 	NILFS_I_GCINODE,		/* inode for GC, on memory only */
-	NILFS_I_GCDAT,			/* shadow DAT, on memory only */
 };
 
 /*
···
 
 static inline struct inode *nilfs_dat_inode(const struct the_nilfs *nilfs)
 {
-	return nilfs_doing_gc() ? nilfs->ns_gc_dat : nilfs->ns_dat;
+	return nilfs->ns_dat;
 }
 
 /*
···
 int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *);
 int nilfs_init_gcinode(struct inode *inode);
 void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs);
-
-/* gcdat.c */
-int nilfs_init_gcdat_inode(struct the_nilfs *);
-void nilfs_commit_gcdat_inode(struct the_nilfs *);
-void nilfs_clear_gcdat_inode(struct the_nilfs *);
 
 /*
  * Inodes and files operations

fs/nilfs2/page.c

···
 {
 	int blkbits = inode->i_blkbits;
 	pgoff_t index = blkoff >> (PAGE_CACHE_SHIFT - blkbits);
-	struct page *page, *opage;
-	struct buffer_head *bh, *obh;
+	struct page *page;
+	struct buffer_head *bh;
 
 	page = grab_cache_page(mapping, index);
 	if (unlikely(!page))
···
 		unlock_page(page);
 		page_cache_release(page);
 		return NULL;
-	}
-	if (!buffer_uptodate(bh) && mapping->assoc_mapping != NULL) {
-		/*
-		 * Shadow page cache uses assoc_mapping to point its original
-		 * page cache.  The following code tries the original cache
-		 * if the given cache is a shadow and it didn't hit.
-		 */
-		opage = find_lock_page(mapping->assoc_mapping, index);
-		if (!opage)
-			return bh;
-
-		obh = __nilfs_get_page_block(opage, blkoff, index, blkbits,
-					     b_state);
-		if (buffer_uptodate(obh)) {
-			nilfs_copy_buffer(bh, obh);
-			if (buffer_dirty(obh)) {
-				nilfs_mark_buffer_dirty(bh);
-				if (!buffer_nilfs_node(bh) && NILFS_MDT(inode))
-					nilfs_mdt_mark_dirty(inode);
-			}
-		}
-		brelse(obh);
-		unlock_page(opage);
-		page_cache_release(opage);
 	}
 	return bh;
 }

fs/nilfs2/segment.c

···
 
 	nilfs_drop_collected_inodes(&sci->sc_dirty_files);
 
-	if (nilfs_doing_gc()) {
+	if (nilfs_doing_gc())
 		nilfs_drop_collected_inodes(&sci->sc_gc_inodes);
-		if (update_sr)
-			nilfs_commit_gcdat_inode(nilfs);
-	} else
+	else
 		nilfs->ns_nongc_ctime = sci->sc_seg_ctime;
 
 	sci->sc_nblk_inc += sci->sc_nblk_this_inc;
···
 
 	nilfs_transaction_lock(sbi, &ti, 1);
 
-	err = nilfs_init_gcdat_inode(nilfs);
+	err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);
 	if (unlikely(err))
 		goto out_unlock;
 
 	err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs);
-	if (unlikely(err))
+	if (unlikely(err)) {
+		nilfs_mdt_restore_from_shadow_map(nilfs->ns_dat);
 		goto out_unlock;
+	}
 
 	sci->sc_freesegs = kbufs[4];
 	sci->sc_nfreesegs = argv[4].v_nmembs;
···
  out_unlock:
 	sci->sc_freesegs = NULL;
 	sci->sc_nfreesegs = 0;
-	nilfs_clear_gcdat_inode(nilfs);
+	nilfs_mdt_clear_shadow_map(nilfs->ns_dat);
 	nilfs_transaction_unlock(sbi);
 	return err;
 }

fs/nilfs2/the_nilfs.c

···
 		nilfs_mdt_destroy(nilfs->ns_sufile);
 		nilfs_mdt_destroy(nilfs->ns_cpfile);
 		nilfs_mdt_destroy(nilfs->ns_dat);
-		nilfs_mdt_destroy(nilfs->ns_gc_dat);
 	}
 	if (nilfs_init(nilfs)) {
 		brelse(nilfs->ns_sbh[0]);
···
 	if (unlikely(!nilfs->ns_dat))
 		goto failed;
 
-	nilfs->ns_gc_dat = nilfs_dat_new(nilfs, dat_entry_size);
-	if (unlikely(!nilfs->ns_gc_dat))
-		goto failed_dat;
-
 	nilfs->ns_cpfile = nilfs_cpfile_new(nilfs, checkpoint_size);
 	if (unlikely(!nilfs->ns_cpfile))
-		goto failed_gc_dat;
+		goto failed_dat;
 
 	nilfs->ns_sufile = nilfs_sufile_new(nilfs, segment_usage_size);
 	if (unlikely(!nilfs->ns_sufile))
 		goto failed_cpfile;
-
-	nilfs_mdt_set_shadow(nilfs->ns_dat, nilfs->ns_gc_dat);
 
 	err = nilfs_dat_read(nilfs->ns_dat, (void *)bh_sr->b_data +
 			     NILFS_SR_DAT_OFFSET(inode_size));
···
 
  failed_cpfile:
 	nilfs_mdt_destroy(nilfs->ns_cpfile);
-
- failed_gc_dat:
-	nilfs_mdt_destroy(nilfs->ns_gc_dat);
 
  failed_dat:
 	nilfs_mdt_destroy(nilfs->ns_dat);
···
 	nilfs_mdt_destroy(nilfs->ns_cpfile);
 	nilfs_mdt_destroy(nilfs->ns_sufile);
 	nilfs_mdt_destroy(nilfs->ns_dat);
-	nilfs_mdt_destroy(nilfs->ns_gc_dat);
 
  failed:
 	nilfs_clear_recovery_info(&ri);

fs/nilfs2/the_nilfs.h

···
  * @ns_dat: DAT file inode
  * @ns_cpfile: checkpoint file inode
  * @ns_sufile: segusage file inode
- * @ns_gc_dat: shadow inode of the DAT file inode for GC
  * @ns_cptree: rb-tree of all mounted checkpoints (nilfs_root)
  * @ns_cptree_lock: lock protecting @ns_cptree
  * @ns_gc_inodes: dummy inodes to keep live blocks
···
 	struct inode	       *ns_dat;
 	struct inode	       *ns_cpfile;
 	struct inode	       *ns_sufile;
-	struct inode	       *ns_gc_dat;
 
 	/* Checkpoint tree */
 	struct rb_root		ns_cptree;