fs/nilfs2/btnode.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * NILFS B-tree node cache
  *
  * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
  *
  * Originally written by Seiji Kihara.
  * Fully revised by Ryusuke Konishi for stabilization and simplification.
  *
  */

 #include <linux/types.h>
 #include <linux/buffer_head.h>
 #include <linux/mm.h>
 #include <linux/backing-dev.h>
 #include <linux/gfp.h>
 #include "nilfs.h"
 #include "mdt.h"
 #include "dat.h"
 #include "page.h"
 #include "btnode.h"


 /**
  * nilfs_init_btnc_inode - initialize B-tree node cache inode
  * @btnc_inode: inode to be initialized
  *
  * nilfs_init_btnc_inode() sets up an inode for B-tree node cache.
  */
 void nilfs_init_btnc_inode(struct inode *btnc_inode)
 {
 	struct nilfs_inode_info *ii = NILFS_I(btnc_inode);

 	btnc_inode->i_mode = S_IFREG;
 	ii->i_flags = 0;
 	memset(&ii->i_bmap_data, 0, sizeof(struct nilfs_bmap));
 	mapping_set_gfp_mask(btnc_inode->i_mapping, GFP_NOFS);
 }

 void nilfs_btnode_cache_clear(struct address_space *btnc)
 {
 	invalidate_mapping_pages(btnc, 0, -1);
 	truncate_inode_pages(btnc, 0);
 }

 struct buffer_head *
 nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
 {
 	struct inode *inode = btnc->host;
 	struct buffer_head *bh;

 	bh = nilfs_grab_buffer(inode, btnc, blocknr, BIT(BH_NILFS_Node));
 	if (unlikely(!bh))
 		return ERR_PTR(-ENOMEM);

 	if (unlikely(buffer_mapped(bh) || buffer_uptodate(bh) ||
 		     buffer_dirty(bh))) {
 		/*
 		 * The block buffer at the specified new address was already
 		 * in use.  This can happen if it is a virtual block number
 		 * and has been reallocated due to corruption of the bitmap
 		 * used to manage its allocation state (if not, the buffer
 		 * clearing of an abandoned b-tree node is missing somewhere).
 		 */
 		nilfs_error(inode->i_sb,
 			    "state inconsistency probably due to duplicate use of b-tree node block address %llu (ino=%lu)",
 			    (unsigned long long)blocknr, inode->i_ino);
 		goto failed;
 	}
 	memset(bh->b_data, 0, i_blocksize(inode));
 	bh->b_blocknr = blocknr;
 	set_buffer_mapped(bh);
 	set_buffer_uptodate(bh);

 	folio_unlock(bh->b_folio);
 	folio_put(bh->b_folio);
 	return bh;

 failed:
 	folio_unlock(bh->b_folio);
 	folio_put(bh->b_folio);
 	brelse(bh);
 	return ERR_PTR(-EIO);
 }

 int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 			      sector_t pblocknr, blk_opf_t opf,
 			      struct buffer_head **pbh, sector_t *submit_ptr)
 {
 	struct buffer_head *bh;
 	struct inode *inode = btnc->host;
 	struct folio *folio;
 	int err;

 	bh = nilfs_grab_buffer(inode, btnc, blocknr, BIT(BH_NILFS_Node));
 	if (unlikely(!bh))
 		return -ENOMEM;

 	err = -EEXIST; /* internal code */
 	folio = bh->b_folio;

 	if (buffer_uptodate(bh) || buffer_dirty(bh))
 		goto found;

 	if (pblocknr == 0) {
 		pblocknr = blocknr;
 		if (inode->i_ino != NILFS_DAT_INO) {
 			struct the_nilfs *nilfs = inode->i_sb->s_fs_info;

 			/* blocknr is a virtual block number */
 			err = nilfs_dat_translate(nilfs->ns_dat, blocknr,
 						  &pblocknr);
 			if (unlikely(err)) {
 				brelse(bh);
 				goto out_locked;
 			}
 		}
 	}

 	if (opf & REQ_RAHEAD) {
 		if (pblocknr != *submit_ptr + 1 || !trylock_buffer(bh)) {
 			err = -EBUSY; /* internal code */
 			brelse(bh);
 			goto out_locked;
 		}
 	} else { /* opf == REQ_OP_READ */
 		lock_buffer(bh);
 	}
 	if (buffer_uptodate(bh)) {
 		unlock_buffer(bh);
 		err = -EEXIST; /* internal code */
 		goto found;
 	}
 	set_buffer_mapped(bh);
 	bh->b_blocknr = pblocknr; /* set block address for read */
 	bh->b_end_io = end_buffer_read_sync;
 	get_bh(bh);
 	submit_bh(opf, bh);
 	bh->b_blocknr = blocknr; /* set back to the given block address */
 	*submit_ptr = pblocknr;
 	err = 0;
 found:
 	*pbh = bh;

 out_locked:
 	folio_unlock(folio);
 	folio_put(folio);
 	return err;
 }

 /**
  * nilfs_btnode_delete - delete B-tree node buffer
  * @bh: buffer to be deleted
  *
  * nilfs_btnode_delete() invalidates the specified buffer and delete the page
  * including the buffer if the page gets unbusy.
  */
 void nilfs_btnode_delete(struct buffer_head *bh)
 {
 	struct address_space *mapping;
 	struct folio *folio = bh->b_folio;
 	pgoff_t index = folio->index;
 	int still_dirty;

 	folio_get(folio);
 	folio_lock(folio);
 	folio_wait_writeback(folio);

 	nilfs_forget_buffer(bh);
 	still_dirty = folio_test_dirty(folio);
 	mapping = folio->mapping;
 	folio_unlock(folio);
 	folio_put(folio);

 	if (!still_dirty && mapping)
 		invalidate_inode_pages2_range(mapping, index, index);
 }

 /**
  * nilfs_btnode_prepare_change_key - prepare to change the search key of a
  *                                   b-tree node block
  * @btnc: page cache in which the b-tree node block is buffered
  * @ctxt: structure for exchanging context information for key change
  *
  * nilfs_btnode_prepare_change_key() prepares to move the contents of the
  * b-tree node block of the old key given in the "oldkey" member of @ctxt to
  * the position of the new key given in the "newkey" member of @ctxt in the
  * page cache @btnc.  Here, the key of the block is an index in units of
  * blocks, and if the page and block sizes match, it matches the page index
  * in the page cache.
  *
  * If the page size and block size match, this function attempts to move the
  * entire folio, and in preparation for this, inserts the original folio into
  * the new index of the cache.  If this insertion fails or if the page size
  * and block size are different, it falls back to a copy preparation using
  * nilfs_btnode_create_block(), inserts a new block at the position
  * corresponding to "newkey", and stores the buffer head pointer in the
  * "newbh" member of @ctxt.
  *
  * Note that the current implementation does not support folio sizes larger
  * than the page size.
  *
  * Return: 0 on success, or the following negative error code on failure.
  * * %-EIO	- I/O error (metadata corruption).
  * * %-ENOMEM	- Insufficient memory available.
  */
 int nilfs_btnode_prepare_change_key(struct address_space *btnc,
 				    struct nilfs_btnode_chkey_ctxt *ctxt)
 {
 	struct buffer_head *obh, *nbh;
 	struct inode *inode = btnc->host;
 	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
 	int err;

 	if (oldkey == newkey)
 		return 0;

 	obh = ctxt->bh;
 	ctxt->newbh = NULL;

 	if (inode->i_blkbits == PAGE_SHIFT) {
 		struct folio *ofolio = obh->b_folio;
 		folio_lock(ofolio);
 retry:
 		/* BUG_ON(oldkey != obh->b_folio->index); */
 		if (unlikely(oldkey != ofolio->index))
 			NILFS_FOLIO_BUG(ofolio,
 				       "invalid oldkey %lld (newkey=%lld)",
 				       (unsigned long long)oldkey,
 				       (unsigned long long)newkey);

 		xa_lock_irq(&btnc->i_pages);
 		err = __xa_insert(&btnc->i_pages, newkey, ofolio, GFP_NOFS);
 		xa_unlock_irq(&btnc->i_pages);
 		/*
 		 * Note: folio->index will not change to newkey until
 		 * nilfs_btnode_commit_change_key() will be called.
 		 * To protect the folio in intermediate state, the folio lock
 		 * is held.
 		 */
 		if (!err)
 			return 0;
 		else if (err != -EBUSY)
 			goto failed_unlock;

 		err = invalidate_inode_pages2_range(btnc, newkey, newkey);
 		if (!err)
 			goto retry;
 		/* fallback to copy mode */
 		folio_unlock(ofolio);
 	}

 	nbh = nilfs_btnode_create_block(btnc, newkey);
 	if (IS_ERR(nbh))
 		return PTR_ERR(nbh);

 	BUG_ON(nbh == obh);
 	ctxt->newbh = nbh;
 	return 0;

  failed_unlock:
 	folio_unlock(obh->b_folio);
 	return err;
 }

 /**
  * nilfs_btnode_commit_change_key - commit the change of the search key of
  *                                  a b-tree node block
  * @btnc: page cache in which the b-tree node block is buffered
  * @ctxt: structure for exchanging context information for key change
  *
  * nilfs_btnode_commit_change_key() executes the key change based on the
  * context @ctxt prepared by nilfs_btnode_prepare_change_key().  If no valid
  * block buffer is prepared in "newbh" of @ctxt (i.e., a full folio move),
  * this function removes the folio from the old index and completes the move.
  * Otherwise, it copies the block data and inherited flag states of "oldbh"
  * to "newbh" and clears the "oldbh" from the cache.  In either case, the
  * relocated buffer is marked as dirty.
  *
  * As with nilfs_btnode_prepare_change_key(), the current implementation does
  * not support folio sizes larger than the page size.
  */
 void nilfs_btnode_commit_change_key(struct address_space *btnc,
 				    struct nilfs_btnode_chkey_ctxt *ctxt)
 {
 	struct buffer_head *obh = ctxt->bh, *nbh = ctxt->newbh;
 	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
 	struct folio *ofolio;

 	if (oldkey == newkey)
 		return;

 	if (nbh == NULL) {	/* blocksize == pagesize */
 		ofolio = obh->b_folio;
 		if (unlikely(oldkey != ofolio->index))
 			NILFS_FOLIO_BUG(ofolio,
 				       "invalid oldkey %lld (newkey=%lld)",
 				       (unsigned long long)oldkey,
 				       (unsigned long long)newkey);
 		mark_buffer_dirty(obh);

 		xa_lock_irq(&btnc->i_pages);
 		__xa_erase(&btnc->i_pages, oldkey);
 		__xa_set_mark(&btnc->i_pages, newkey, PAGECACHE_TAG_DIRTY);
 		xa_unlock_irq(&btnc->i_pages);

 		ofolio->index = obh->b_blocknr = newkey;
 		folio_unlock(ofolio);
 	} else {
 		nilfs_copy_buffer(nbh, obh);
 		mark_buffer_dirty(nbh);

 		nbh->b_blocknr = newkey;
 		ctxt->bh = nbh;
 		nilfs_btnode_delete(obh); /* will decrement bh->b_count */
 	}
 }

 /**
  * nilfs_btnode_abort_change_key - abort the change of the search key of a
  *                                 b-tree node block
  * @btnc: page cache in which the b-tree node block is buffered
  * @ctxt: structure for exchanging context information for key change
  *
  * nilfs_btnode_abort_change_key() cancels the key change associated with the
  * context @ctxt prepared via nilfs_btnode_prepare_change_key() and performs
  * any necessary cleanup.  If no valid block buffer is prepared in "newbh" of
  * @ctxt, this function removes the folio from the destination index and aborts
  * the move.  Otherwise, it clears "newbh" from the cache.
  *
  * As with nilfs_btnode_prepare_change_key(), the current implementation does
  * not support folio sizes larger than the page size.
  */
 void nilfs_btnode_abort_change_key(struct address_space *btnc,
 				   struct nilfs_btnode_chkey_ctxt *ctxt)
 {
 	struct buffer_head *nbh = ctxt->newbh;
 	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;

 	if (oldkey == newkey)
 		return;

 	if (nbh == NULL) {	/* blocksize == pagesize */
 		xa_erase_irq(&btnc->i_pages, newkey);
 		folio_unlock(ctxt->bh->b_folio);
 	} else {
 		/*
 		 * When canceling a buffer that a prepare operation has
 		 * allocated to copy a node block to another location, use
 		 * nilfs_btnode_delete() to initialize and release the buffer
 		 * so that the buffer flags will not be in an inconsistent
 		 * state when it is reallocated.
 		 */
 		nilfs_btnode_delete(nbh);
 	}
 }
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* NILFS B-tree node cache
	*
	* Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
	*
	* Originally written by Seiji Kihara.
	* Fully revised by Ryusuke Konishi for stabilization and simplification.
	*
	*/

	#include <linux/types.h>
	#include <linux/buffer_head.h>
	#include <linux/mm.h>
	#include <linux/backing-dev.h>
	#include <linux/gfp.h>
	#include "nilfs.h"
	#include "mdt.h"
	#include "dat.h"
	#include "page.h"
	#include "btnode.h"


	/**
	* nilfs_init_btnc_inode - initialize B-tree node cache inode
	* @btnc_inode: inode to be initialized
	*
	* nilfs_init_btnc_inode() sets up an inode for B-tree node cache.
	*/
	void nilfs_init_btnc_inode(struct inode *btnc_inode)
	{
	struct nilfs_inode_info *ii = NILFS_I(btnc_inode);

	btnc_inode->i_mode = S_IFREG;
	ii->i_flags = 0;
	memset(&ii->i_bmap_data, 0, sizeof(struct nilfs_bmap));
	mapping_set_gfp_mask(btnc_inode->i_mapping, GFP_NOFS);
	}

	void nilfs_btnode_cache_clear(struct address_space *btnc)
	{
	invalidate_mapping_pages(btnc, 0, -1);
	truncate_inode_pages(btnc, 0);
	}

	struct buffer_head *
	nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
	{
	struct inode *inode = btnc->host;
	struct buffer_head *bh;

	bh = nilfs_grab_buffer(inode, btnc, blocknr, BIT(BH_NILFS_Node));
	if (unlikely(!bh))
	return ERR_PTR(-ENOMEM);

	if (unlikely(buffer_mapped(bh) \|\| buffer_uptodate(bh) \|\|
	buffer_dirty(bh))) {
	/*
	* The block buffer at the specified new address was already
	* in use. This can happen if it is a virtual block number
	* and has been reallocated due to corruption of the bitmap
	* used to manage its allocation state (if not, the buffer
	* clearing of an abandoned b-tree node is missing somewhere).
	*/
	nilfs_error(inode->i_sb,
	"state inconsistency probably due to duplicate use of b-tree node block address %llu (ino=%lu)",
	(unsigned long long)blocknr, inode->i_ino);
	goto failed;
	}
	memset(bh->b_data, 0, i_blocksize(inode));
	bh->b_blocknr = blocknr;
	set_buffer_mapped(bh);
	set_buffer_uptodate(bh);

	folio_unlock(bh->b_folio);
	folio_put(bh->b_folio);
	return bh;

	failed:
	folio_unlock(bh->b_folio);
	folio_put(bh->b_folio);
	brelse(bh);
	return ERR_PTR(-EIO);
	}

	int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
	sector_t pblocknr, blk_opf_t opf,
	struct buffer_head *pbh, sector_t submit_ptr)
	{
	struct buffer_head *bh;
	struct inode *inode = btnc->host;
	struct folio *folio;
	int err;

	bh = nilfs_grab_buffer(inode, btnc, blocknr, BIT(BH_NILFS_Node));
	if (unlikely(!bh))
	return -ENOMEM;

	err = -EEXIST; /* internal code */
	folio = bh->b_folio;

	if (buffer_uptodate(bh) \|\| buffer_dirty(bh))
	goto found;

	if (pblocknr == 0) {
	pblocknr = blocknr;
	if (inode->i_ino != NILFS_DAT_INO) {
	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;

	/* blocknr is a virtual block number */
	err = nilfs_dat_translate(nilfs->ns_dat, blocknr,
	&pblocknr);
	if (unlikely(err)) {
	brelse(bh);
	goto out_locked;
	}
	}
	}

	if (opf & REQ_RAHEAD) {
	if (pblocknr != *submit_ptr + 1 \|\| !trylock_buffer(bh)) {
	err = -EBUSY; /* internal code */
	brelse(bh);
	goto out_locked;
	}
	} else { /* opf == REQ_OP_READ */
	lock_buffer(bh);
	}
	if (buffer_uptodate(bh)) {
	unlock_buffer(bh);
	err = -EEXIST; /* internal code */
	goto found;
	}
	set_buffer_mapped(bh);
	bh->b_blocknr = pblocknr; /* set block address for read */
	bh->b_end_io = end_buffer_read_sync;
	get_bh(bh);
	submit_bh(opf, bh);
	bh->b_blocknr = blocknr; /* set back to the given block address */
	*submit_ptr = pblocknr;
	err = 0;
	found:
	*pbh = bh;

	out_locked:
	folio_unlock(folio);
	folio_put(folio);
	return err;
	}

	/**
	* nilfs_btnode_delete - delete B-tree node buffer
	* @bh: buffer to be deleted
	*
	* nilfs_btnode_delete() invalidates the specified buffer and delete the page
	* including the buffer if the page gets unbusy.
	*/
	void nilfs_btnode_delete(struct buffer_head *bh)
	{
	struct address_space *mapping;
	struct folio *folio = bh->b_folio;
	pgoff_t index = folio->index;
	int still_dirty;

	folio_get(folio);
	folio_lock(folio);
	folio_wait_writeback(folio);

	nilfs_forget_buffer(bh);
	still_dirty = folio_test_dirty(folio);
	mapping = folio->mapping;
	folio_unlock(folio);
	folio_put(folio);

	if (!still_dirty && mapping)
	invalidate_inode_pages2_range(mapping, index, index);
	}

	/**
	* nilfs_btnode_prepare_change_key - prepare to change the search key of a
	* b-tree node block
	* @btnc: page cache in which the b-tree node block is buffered
	* @ctxt: structure for exchanging context information for key change
	*
	* nilfs_btnode_prepare_change_key() prepares to move the contents of the
	* b-tree node block of the old key given in the "oldkey" member of @ctxt to
	* the position of the new key given in the "newkey" member of @ctxt in the
	* page cache @btnc. Here, the key of the block is an index in units of
	* blocks, and if the page and block sizes match, it matches the page index
	* in the page cache.
	*
	* If the page size and block size match, this function attempts to move the
	* entire folio, and in preparation for this, inserts the original folio into
	* the new index of the cache. If this insertion fails or if the page size
	* and block size are different, it falls back to a copy preparation using
	* nilfs_btnode_create_block(), inserts a new block at the position
	* corresponding to "newkey", and stores the buffer head pointer in the
	* "newbh" member of @ctxt.
	*
	* Note that the current implementation does not support folio sizes larger
	* than the page size.
	*
	* Return: 0 on success, or the following negative error code on failure.
	* * %-EIO - I/O error (metadata corruption).
	* * %-ENOMEM - Insufficient memory available.
	*/
	int nilfs_btnode_prepare_change_key(struct address_space *btnc,
	struct nilfs_btnode_chkey_ctxt *ctxt)
	{
	struct buffer_head obh, nbh;
	struct inode *inode = btnc->host;
	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
	int err;

	if (oldkey == newkey)
	return 0;

	obh = ctxt->bh;
	ctxt->newbh = NULL;

	if (inode->i_blkbits == PAGE_SHIFT) {
	struct folio *ofolio = obh->b_folio;
	folio_lock(ofolio);
	retry:
	/* BUG_ON(oldkey != obh->b_folio->index); */
	if (unlikely(oldkey != ofolio->index))
	NILFS_FOLIO_BUG(ofolio,
	"invalid oldkey %lld (newkey=%lld)",
	(unsigned long long)oldkey,
	(unsigned long long)newkey);

	xa_lock_irq(&btnc->i_pages);
	err = __xa_insert(&btnc->i_pages, newkey, ofolio, GFP_NOFS);
	xa_unlock_irq(&btnc->i_pages);
	/*
	* Note: folio->index will not change to newkey until
	* nilfs_btnode_commit_change_key() will be called.
	* To protect the folio in intermediate state, the folio lock
	* is held.
	*/
	if (!err)
	return 0;
	else if (err != -EBUSY)
	goto failed_unlock;

	err = invalidate_inode_pages2_range(btnc, newkey, newkey);
	if (!err)
	goto retry;
	/* fallback to copy mode */
	folio_unlock(ofolio);
	}

	nbh = nilfs_btnode_create_block(btnc, newkey);
	if (IS_ERR(nbh))
	return PTR_ERR(nbh);

	BUG_ON(nbh == obh);
	ctxt->newbh = nbh;
	return 0;

	failed_unlock:
	folio_unlock(obh->b_folio);
	return err;
	}

	/**
	* nilfs_btnode_commit_change_key - commit the change of the search key of
	* a b-tree node block
	* @btnc: page cache in which the b-tree node block is buffered
	* @ctxt: structure for exchanging context information for key change
	*
	* nilfs_btnode_commit_change_key() executes the key change based on the
	* context @ctxt prepared by nilfs_btnode_prepare_change_key(). If no valid
	* block buffer is prepared in "newbh" of @ctxt (i.e., a full folio move),
	* this function removes the folio from the old index and completes the move.
	* Otherwise, it copies the block data and inherited flag states of "oldbh"
	* to "newbh" and clears the "oldbh" from the cache. In either case, the
	* relocated buffer is marked as dirty.
	*
	* As with nilfs_btnode_prepare_change_key(), the current implementation does
	* not support folio sizes larger than the page size.
	*/
	void nilfs_btnode_commit_change_key(struct address_space *btnc,
	struct nilfs_btnode_chkey_ctxt *ctxt)
	{
	struct buffer_head obh = ctxt->bh, nbh = ctxt->newbh;
	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
	struct folio *ofolio;

	if (oldkey == newkey)
	return;

	if (nbh == NULL) { /* blocksize == pagesize */
	ofolio = obh->b_folio;
	if (unlikely(oldkey != ofolio->index))
	NILFS_FOLIO_BUG(ofolio,
	"invalid oldkey %lld (newkey=%lld)",
	(unsigned long long)oldkey,
	(unsigned long long)newkey);
	mark_buffer_dirty(obh);

	xa_lock_irq(&btnc->i_pages);
	__xa_erase(&btnc->i_pages, oldkey);
	__xa_set_mark(&btnc->i_pages, newkey, PAGECACHE_TAG_DIRTY);
	xa_unlock_irq(&btnc->i_pages);

	ofolio->index = obh->b_blocknr = newkey;
	folio_unlock(ofolio);
	} else {
	nilfs_copy_buffer(nbh, obh);
	mark_buffer_dirty(nbh);

	nbh->b_blocknr = newkey;
	ctxt->bh = nbh;
	nilfs_btnode_delete(obh); /* will decrement bh->b_count */
	}
	}

	/**
	* nilfs_btnode_abort_change_key - abort the change of the search key of a
	* b-tree node block
	* @btnc: page cache in which the b-tree node block is buffered
	* @ctxt: structure for exchanging context information for key change
	*
	* nilfs_btnode_abort_change_key() cancels the key change associated with the
	* context @ctxt prepared via nilfs_btnode_prepare_change_key() and performs
	* any necessary cleanup. If no valid block buffer is prepared in "newbh" of
	* @ctxt, this function removes the folio from the destination index and aborts
	* the move. Otherwise, it clears "newbh" from the cache.
	*
	* As with nilfs_btnode_prepare_change_key(), the current implementation does
	* not support folio sizes larger than the page size.
	*/
	void nilfs_btnode_abort_change_key(struct address_space *btnc,
	struct nilfs_btnode_chkey_ctxt *ctxt)
	{
	struct buffer_head *nbh = ctxt->newbh;
	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;

	if (oldkey == newkey)
	return;

	if (nbh == NULL) { /* blocksize == pagesize */
	xa_erase_irq(&btnc->i_pages, newkey);
	folio_unlock(ctxt->bh->b_folio);
	} else {
	/*
	* When canceling a buffer that a prepare operation has
	* allocated to copy a node block to another location, use
	* nilfs_btnode_delete() to initialize and release the buffer
	* so that the buffer flags will not be in an inconsistent
	* state when it is reallocated.
	*/
	nilfs_btnode_delete(nbh);
	}
	}