/fs/ext4/inode.c

/*
 *  linux/fs/ext4/inode.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  64-bit file support on 64-bit platforms by Jakub Jelinek
 *	(jj@sunsite.ms.mff.cuni.cz)
 *
 *  Assorted race fixes, rewrite of ext4_get_block() by Al Viro, 2000
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/jbd2.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/mpage.h>
#include <linux/namei.h>
#include <linux/uio.h>
#include <linux/bio.h>
#include <linux/workqueue.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>

#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"
#include "ext4_extents.h"
#include "truncate.h"

#include <trace/events/ext4.h>

#define MPAGE_DA_EXTENT_TAIL 0x01

static inline int ext4_begin_ordered_truncate(struct inode *inode,
					      loff_t new_size)
{
	trace_ext4_begin_ordered_truncate(inode, new_size);
	/*
	 * If jinode is zero, then we never opened the file for
	 * writing, so there's no need to call
	 * jbd2_journal_begin_ordered_truncate() since there's no
	 * outstanding writes we need to flush.
	 */
	if (!EXT4_I(inode)->jinode)
		return 0;
	return jbd2_journal_begin_ordered_truncate(EXT4_JOURNAL(inode),
						   EXT4_I(inode)->jinode,
						   new_size);
}

static void ext4_invalidatepage(struct page *page, unsigned long offset);
static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
				   struct buffer_head *bh_result, int create);
static int ext4_set_bh_endio(struct buffer_head *bh, struct inode *inode);
static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate);
static int __ext4_journalled_writepage(struct page *page, unsigned int len);
static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);

/*
 * Test whether an inode is a fast symlink.
 */
static int ext4_inode_is_fast_symlink(struct inode *inode)
{
	int ea_blocks = EXT4_I(inode)->i_file_acl ?
		(inode->i_sb->s_blocksize >> 9) : 0;

	return (S_ISLNK(inode->i_mode) && inode->i_blocks - ea_blocks == 0);
}

/*
 * Restart the transaction associated with *handle.  This does a commit,
 * so before we call here everything must be consistently dirtied against
 * this transaction.
 */
int ext4_truncate_restart_trans(handle_t *handle, struct inode *inode,
				 int nblocks)
{
	int ret;

	/*
	 * Drop i_data_sem to avoid deadlock with ext4_map_blocks.  At this
	 * moment, get_block can be called only for blocks inside i_size since
	 * page cache has been already dropped and writes are blocked by
	 * i_mutex. So we can safely drop the i_data_sem here.
	 */
	BUG_ON(EXT4_JOURNAL(inode) == NULL);
	jbd_debug(2, "restarting handle %p\n", handle);
	up_write(&EXT4_I(inode)->i_data_sem);
	ret = ext4_journal_restart(handle, nblocks);
	down_write(&EXT4_I(inode)->i_data_sem);
	ext4_discard_preallocations(inode);

	return ret;
}

/*
 * Called at the last iput() if i_nlink is zero.
 */
void ext4_evict_inode(struct inode *inode)
{
	handle_t *handle;
	int err;

	trace_ext4_evict_inode(inode);

	ext4_ioend_wait(inode);

	if (inode->i_nlink) {
		/*
		 * When journalling data dirty buffers are tracked only in the
		 * journal. So although mm thinks everything is clean and
		 * ready for reaping the inode might still have some pages to
		 * write in the running transaction or waiting to be
		 * checkpointed. Thus calling jbd2_journal_invalidatepage()
		 * (via truncate_inode_pages()) to discard these buffers can
		 * cause data loss. Also even if we did not discard these
		 * buffers, we would have no way to find them after the inode
		 * is reaped and thus user could see stale data if he tries to
		 * read them before the transaction is checkpointed. So be
		 * careful and force everything to disk here... We use
		 * ei->i_datasync_tid to store the newest transaction
		 * containing inode's data.
		 *
		 * Note that directories do not have this problem because they
		 * don't use page cache.
		 */
		if (ext4_should_journal_data(inode) &&
		    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode))) {
			journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
			tid_t commit_tid = EXT4_I(inode)->i_datasync_tid;

			jbd2_log_start_commit(journal, commit_tid);
			jbd2_log_wait_commit(journal, commit_tid);
			filemap_write_and_wait(&inode->i_data);
		}
		truncate_inode_pages(&inode->i_data, 0);
		goto no_delete;
	}

	if (!is_bad_inode(inode))
		dquot_initialize(inode);

	if (ext4_should_order_data(inode))
		ext4_begin_ordered_truncate(inode, 0);
	truncate_inode_pages(&inode->i_data, 0);

	if (is_bad_inode(inode))
		goto no_delete;

	handle = ext4_journal_start(inode, ext4_blocks_for_truncate(inode)+3);
	if (IS_ERR(handle)) {
		ext4_std_error(inode->i_sb, PTR_ERR(handle));
		/*
		 * If we're going to skip the normal cleanup, we still need to
		 * make sure that the in-core orphan linked list is properly
		 * cleaned up.
		 */
		ext4_orphan_del(NULL, inode);
		goto no_delete;
	}

	if (IS_SYNC(inode))
		ext4_handle_sync(handle);
	inode->i_size = 0;
	err = ext4_mark_inode_dirty(handle, inode);
	if (err) {
		ext4_warning(inode->i_sb,
			     "couldn't mark inode dirty (err %d)", err);
		goto stop_handle;
	}
	if (inode->i_blocks)
		ext4_truncate(inode);

	/*
	 * ext4_ext_truncate() doesn't reserve any slop when it
	 * restarts journal transactions; therefore there may not be
	 * enough credits left in the handle to remove the inode from
	 * the orphan list and set the dtime field.
	 */
	if (!ext4_handle_has_enough_credits(handle, 3)) {
		err = ext4_journal_extend(handle, 3);
		if (err > 0)
			err = ext4_journal_restart(handle, 3);
		if (err != 0) {
			ext4_warning(inode->i_sb,
				     "couldn't extend journal (err %d)", err);
		stop_handle:
			ext4_journal_stop(handle);
			ext4_orphan_del(NULL, inode);
			goto no_delete;
		}
	}

	/*
	 * Kill off the orphan record which ext4_truncate created.
	 * AKPM: I think this can be inside the above `if'.
	 * Note that ext4_orphan_del() has to be able to cope with the
	 * deletion of a non-existent orphan - this is because we don't
	 * know if ext4_truncate() actually created an orphan record.
	 * (Well, we could do this if we need to, but heck - it works)
	 */
	ext4_orphan_del(handle, inode);
	EXT4_I(inode)->i_dtime	= get_seconds();

	/*
	 * One subtle ordering requirement: if anything has gone wrong
	 * (transaction abort, IO errors, whatever), then we can still
	 * do these next steps (the fs will already have been marked as
	 * having errors), but we can't free the inode if the mark_dirty
	 * fails.
	 */
	if (ext4_mark_inode_dirty(handle, inode))
		/* If that failed, just do the required in-core inode clear. */
		ext4_clear_inode(inode);
	else
		ext4_free_inode(handle, inode);
	ext4_journal_stop(handle);
	return;
no_delete:
	ext4_clear_inode(inode);	/* We must guarantee clearing of inode... */
}

#ifdef CONFIG_QUOTA
qsize_t *ext4_get_reserved_space(struct inode *inode)
{
	return &EXT4_I(inode)->i_reserved_quota;
}
#endif

/*
 * Calculate the number of metadata blocks need to reserve
 * to allocate a block located at @lblock
 */
static int ext4_calc_metadata_amount(struct inode *inode, ext4_lblk_t lblock)
{
	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
		return ext4_ext_calc_metadata_amount(inode, lblock);

	return ext4_ind_calc_metadata_amount(inode, lblock);
}

/*
 * Called with i_data_sem down, which is important since we can call
 * ext4_discard_preallocations() from here.
 */
void ext4_da_update_reserve_space(struct inode *inode,
					int used, int quota_claim)
{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct ext4_inode_info *ei = EXT4_I(inode);

	spin_lock(&ei->i_block_reservation_lock);
	trace_ext4_da_update_reserve_space(inode, used);
	if (unlikely(used > ei->i_reserved_data_blocks)) {
		ext4_msg(inode->i_sb, KERN_NOTICE, "%s: ino %lu, used %d "
			 "with only %d reserved data blocks\n",
			 __func__, inode->i_ino, used,
			 ei->i_reserved_data_blocks);
		WARN_ON(1);
		used = ei->i_reserved_data_blocks;
	}

	/* Update per-inode reservations */
	ei->i_reserved_data_blocks -= used;
	ei->i_reserved_meta_blocks -= ei->i_allocated_meta_blocks;
	percpu_counter_sub(&sbi->s_dirtyblocks_counter,
			   used + ei->i_allocated_meta_blocks);
	ei->i_allocated_meta_blocks = 0;

	if (ei->i_reserved_data_blocks == 0) {
		/*
		 * We can release all of the reserved metadata blocks
		 * only when we have written all of the delayed
		 * allocation blocks.
		 */
		percpu_counter_sub(&sbi->s_dirtyblocks_counter,
				   ei->i_reserved_meta_blocks);
		ei->i_reserved_meta_blocks = 0;
		ei->i_da_metadata_calc_len = 0;
	}
	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);

	/* Update quota subsystem for data blocks */
	if (quota_claim)
		dquot_claim_block(inode, used);
	else {
		/*
		 * We did fallocate with an offset that is already delayed
		 * allocated. So on delayed allocated writeback we should
		 * not re-claim the quota for fallocated blocks.
		 */
		dquot_release_reservation_block(inode, used);
	}

	/*
	 * If we have done all the pending block allocations and if
	 * there aren't any writers on the inode, we can discard the
	 * inode's preallocations.
	 */
	if ((ei->i_reserved_data_blocks == 0) &&
	    (atomic_read(&inode->i_writecount) == 0))
		ext4_discard_preallocations(inode);
}

static int __check_block_validity(struct inode *inode, const char *func,
				unsigned int line,
				struct ext4_map_blocks *map)
{
	if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), map->m_pblk,
				   map->m_len)) {
		ext4_error_inode(inode, func, line, map->m_pblk,
				 "lblock %lu mapped to illegal pblock "
				 "(length %d)", (unsigned long) map->m_lblk,
				 map->m_len);
		return -EIO;
	}
	return 0;
}

#define check_block_validity(inode, map)	\
	__check_block_validity((inode), __func__, __LINE__, (map))

/*
 * Return the number of contiguous dirty pages in a given inode
 * starting at page frame idx.
 */
static pgoff_t ext4_num_dirty_pages(struct inode *inode, pgoff_t idx,
				    unsigned int max_pages)
{
	struct address_space *mapping = inode->i_mapping;
	pgoff_t	index;
	struct pagevec pvec;
	pgoff_t num = 0;
	int i, nr_pages, done = 0;

	if (max_pages == 0)
		return 0;
	pagevec_init(&pvec, 0);
	while (!done) {
		index = idx;
		nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
					      PAGECACHE_TAG_DIRTY,
					      (pgoff_t)PAGEVEC_SIZE);
		if (nr_pages == 0)
			break;
		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];
			struct buffer_head *bh, *head;

			lock_page(page);
			if (unlikely(page->mapping != mapping) ||
			    !PageDirty(page) ||
			    PageWriteback(page) ||
			    page->index != idx) {
				done = 1;
				unlock_page(page);
				break;
			}
			if (page_has_buffers(page)) {
				bh = head = page_buffers(page);
				do {
					if (!buffer_delay(bh) &&
					    !buffer_unwritten(bh))
						done = 1;
					bh = bh->b_this_page;
				} while (!done && (bh != head));
			}
			unlock_page(page);
			if (done)
				break;
			idx++;
			num++;
			if (num >= max_pages) {
				done = 1;
				break;
			}
		}
		pagevec_release(&pvec);
	}
	return num;
}

/*
 * The ext4_map_blocks() function tries to look up the requested blocks,
 * and returns if the blocks are already mapped.
 *
 * Otherwise it takes the write lock of the i_data_sem and allocate blocks
 * and store the allocated blocks in the result buffer head and mark it
 * mapped.
 *
 * If file type is extents based, it will call ext4_ext_map_blocks(),
 * Otherwise, call with ext4_ind_map_blocks() to handle indirect mapping
 * based files
 *
 * On success, it returns the number of blocks being mapped or allocate.
 * if create==0 and the blocks are pre-allocated and uninitialized block,
 * the result buffer head is unmapped. If the create ==1, it will make sure
 * the buffer head is mapped.
 *
 * It returns 0 if plain look up failed (blocks have not been allocated), in
 * that casem, buffer head is unmapped
 *
 * It returns the error in case of allocation failure.
 */
int ext4_map_blocks(handle_t *handle, struct inode *inode,
		    struct ext4_map_blocks *map, int flags)
{
	int retval;

	map->m_flags = 0;
	ext_debug("ext4_map_blocks(): inode %lu, flag %d, max_blocks %u,"
		  "logical block %lu\n", inode->i_ino, flags, map->m_len,
		  (unsigned long) map->m_lblk);
	/*
	 * Try to see if we can get the block without requesting a new
	 * file system block.
	 */
	down_read((&EXT4_I(inode)->i_data_sem));
	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
		retval = ext4_ext_map_blocks(handle, inode, map, 0);
	} else {
		retval = ext4_ind_map_blocks(handle, inode, map, 0);
	}
	up_read((&EXT4_I(inode)->i_data_sem));

	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
		int ret = check_block_validity(inode, map);
		if (ret != 0)
			return ret;
	}

	/* If it is only a block(s) look up */
	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
		return retval;

	/*
	 * Returns if the blocks have already allocated
	 *
	 * Note that if blocks have been preallocated
	 * ext4_ext_get_block() returns th create = 0
	 * with buffer head unmapped.
	 */
	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)
		return retval;

	/*
	 * When we call get_blocks without the create flag, the
	 * BH_Unwritten flag could have gotten set if the blocks
	 * requested were part of a uninitialized extent.  We need to
	 * clear this flag now that we are committed to convert all or
	 * part of the uninitialized extent to be an initialized
	 * extent.  This is because we need to avoid the combination
	 * of BH_Unwritten and BH_Mapped flags being simultaneously
	 * set on the buffer_head.
	 */
	map->m_flags &= ~EXT4_MAP_UNWRITTEN;

	/*
	 * New blocks allocate and/or writing to uninitialized extent
	 * will possibly result in updating i_data, so we take
	 * the write lock of i_data_sem, and call get_blocks()
	 * with create == 1 flag.
	 */
	down_write((&EXT4_I(inode)->i_data_sem));

	/*
	 * if the caller is from delayed allocation writeout path
	 * we have already reserved fs blocks for allocation
	 * let the underlying get_block() function know to
	 * avoid double accounting
	 */
	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
		ext4_set_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED);
	/*
	 * We need to check for EXT4 here because migrate
	 * could have changed the inode type in between
	 */
	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
		retval = ext4_ext_map_blocks(handle, inode, map, flags);
	} else {
		retval = ext4_ind_map_blocks(handle, inode, map, flags);

		if (retval > 0 && map->m_flags & EXT4_MAP_NEW) {
			/*
			 * We allocated new blocks which will result in
			 * i_data's format changing.  Force the migrate
			 * to fail by clearing migrate flags
			 */
			ext4_clear_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
		}

		/*
		 * Update reserved blocks/metadata blocks after successful
		 * block allocation which had been deferred till now. We don't
		 * support fallocate for non extent files. So we can update
		 * reserve space here.
		 */
		if ((retval > 0) &&
			(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE))
			ext4_da_update_reserve_space(inode, retval, 1);
	}
	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
		ext4_clear_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED);

	up_write((&EXT4_I(inode)->i_data_sem));
	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
		int ret = check_block_validity(inode, map);
		if (ret != 0)
			return ret;
	}
	return retval;
}

/* Maximum number of blocks we map for direct IO at once. */
#define DIO_MAX_BLOCKS 4096

static int _ext4_get_block(struct inode *inode, sector_t iblock,
			   struct buffer_head *bh, int flags)
{
	handle_t *handle = ext4_journal_current_handle();
	struct ext4_map_blocks map;
	int ret = 0, started = 0;
	int dio_credits;

	map.m_lblk = iblock;
	map.m_len = bh->b_size >> inode->i_blkbits;

	if (flags && !handle) {
		/* Direct IO write... */
		if (map.m_len > DIO_MAX_BLOCKS)
			map.m_len = DIO_MAX_BLOCKS;
		dio_credits = ext4_chunk_trans_blocks(inode, map.m_len);
		handle = ext4_journal_start(inode, dio_credits);
		if (IS_ERR(handle)) {
			ret = PTR_ERR(handle);
			return ret;
		}
		started = 1;
	}

	ret = ext4_map_blocks(handle, inode, &map, flags);
	if (ret > 0) {
		map_bh(bh, inode->i_sb, map.m_pblk);
		bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
		ret = 0;
	}
	if (started)
		ext4_journal_stop(handle);
	return ret;
}

int ext4_get_block(struct inode *inode, sector_t iblock,
		   struct buffer_head *bh, int create)
{
	return _ext4_get_block(inode, iblock, bh,
			       create ? EXT4_GET_BLOCKS_CREATE : 0);
}

/*
 * `handle' can be NULL if create is zero
 */
struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
				ext4_lblk_t block, int create, int *errp)
{
	struct ext4_map_blocks map;
	struct buffer_head *bh;
	int fatal = 0, err;

	J_ASSERT(handle != NULL || create == 0);

	map.m_lblk = block;
	map.m_len = 1;
	err = ext4_map_blocks(handle, inode, &map,
			      create ? EXT4_GET_BLOCKS_CREATE : 0);

	if (err < 0)
		*errp = err;
	if (err <= 0)
		return NULL;
	*errp = 0;

	bh = sb_getblk(inode->i_sb, map.m_pblk);
	if (!bh) {
		*errp = -EIO;
		return NULL;
	}
	if (map.m_flags & EXT4_MAP_NEW) {
		J_ASSERT(create != 0);
		J_ASSERT(handle != NULL);

		/*
		 * Now that we do not always journal data, we should
		 * keep in mind whether this should always journal the
		 * new buffer as metadata.  For now, regular file
		 * writes use ext4_get_block instead, so it's not a
		 * problem.
		 */
		lock_buffer(bh);
		BUFFER_TRACE(bh, "call get_create_access");
		fatal = ext4_journal_get_create_access(handle, bh);
		if (!fatal && !buffer_uptodate(bh)) {
			memset(bh->b_data, 0, inode->i_sb->s_blocksize);
			set_buffer_uptodate(bh);
		}
		unlock_buffer(bh);
		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
		err = ext4_handle_dirty_metadata(handle, inode, bh);
		if (!fatal)
			fatal = err;
	} else {
		BUFFER_TRACE(bh, "not a new buffer");
	}
	if (fatal) {
		*errp = fatal;
		brelse(bh);
		bh = NULL;
	}
	return bh;
}

struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
			       ext4_lblk_t block, int create, int *err)
{
	struct buffer_head *bh;

	bh = ext4_getblk(handle, inode, block, create, err);
	if (!bh)
		return bh;
	if (buffer_uptodate(bh))
		return bh;
	ll_rw_block(READ_META, 1, &bh);
	wait_on_buffer(bh);
	if (buffer_uptodate(bh))
		return bh;
	put_bh(bh);
	*err = -EIO;
	return NULL;
}

static int walk_page_buffers(handle_t *handle,
			     struct buffer_head *head,
			     unsigned from,
			     unsigned to,
			     int *partial,
			     int (*fn)(handle_t *handle,
				       struct buffer_head *bh))
{
	struct buffer_head *bh;
	unsigned block_start, block_end;
	unsigned blocksize = head->b_size;
	int err, ret = 0;
	struct buffer_head *next;

	for (bh = head, block_start = 0;
	     ret == 0 && (bh != head || !block_start);
	     block_start = block_end, bh = next) {
		next = bh->b_this_page;
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (partial && !buffer_uptodate(bh))
				*partial = 1;
			continue;
		}
		err = (*fn)(handle, bh);
		if (!ret)
			ret = err;
	}
	return ret;
}

/*
 * To preserve ordering, it is essential that the hole instantiation and
 * the data write be encapsulated in a single transaction.  We cannot
 * close off a transaction and start a new one between the ext4_get_block()
 * and the commit_write().  So doing the jbd2_journal_start at the start of
 * prepare_write() is the right place.
 *
 * Also, this function can nest inside ext4_writepage() ->
 * block_write_full_page(). In that case, we *know* that ext4_writepage()
 * has generated enough buffer credits to do the whole page.  So we won't
 * block on the journal in that case, which is good, because the caller may
 * be PF_MEMALLOC.
 *
 * By accident, ext4 can be reentered when a transaction is open via
 * quota file writes.  If we were to commit the transaction while thus
 * reentered, there can be a deadlock - we would be holding a quota
 * lock, and the commit would never complete if another thread had a
 * transaction open and was blocking on the quota lock - a ranking
 * violation.
 *
 * So what we do is to rely on the fact that jbd2_journal_stop/journal_start
 * will _not_ run commit under these circumstances because handle->h_ref
 * is elevated.  We'll still have enough credits for the tiny quotafile
 * write.
 */
static int do_journal_get_write_access(handle_t *handle,
				       struct buffer_head *bh)
{
	int dirty = buffer_dirty(bh);
	int ret;

	if (!buffer_mapped(bh) || buffer_freed(bh))
		return 0;
	/*
	 * __block_write_begin() could have dirtied some buffers. Clean
	 * the dirty bit as jbd2_journal_get_write_access() could complain
	 * otherwise about fs integrity issues. Setting of the dirty bit
	 * by __block_write_begin() isn't a real problem here as we clear
	 * the bit before releasing a page lock and thus writeback cannot
	 * ever write the buffer.
	 */
	if (dirty)
		clear_buffer_dirty(bh);
	ret = ext4_journal_get_write_access(handle, bh);
	if (!ret && dirty)
		ret = ext4_handle_dirty_metadata(handle, NULL, bh);
	return ret;
}

static int ext4_get_block_write(struct inode *inode, sector_t iblock,
		   struct buffer_head *bh_result, int create);
static int ext4_write_begin(struct file *file, struct address_space *mapping,
			    loff_t pos, unsigned len, unsigned flags,
			    struct page **pagep, void **fsdata)
{
	struct inode *inode = mapping->host;
	int ret, needed_blocks;
	handle_t *handle;
	int retries = 0;
	struct page *page;
	pgoff_t index;
	unsigned from, to;

	trace_ext4_write_begin(inode, pos, len, flags);
	/*
	 * Reserve one block more for addition to orphan list in case
	 * we allocate blocks but write fails for some reason
	 */
	needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
	index = pos >> PAGE_CACHE_SHIFT;
	from = pos & (PAGE_CACHE_SIZE - 1);
	to = from + len;

retry:
	handle = ext4_journal_start(inode, needed_blocks);
	if (IS_ERR(handle)) {
		ret = PTR_ERR(handle);
		goto out;
	}

	/* We cannot recurse into the filesystem as the transaction is already
	 * started */
	flags |= AOP_FLAG_NOFS;

	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page) {
		ext4_journal_stop(handle);
		ret = -ENOMEM;
		goto out;
	}
	*pagep = page;

	if (ext4_should_dioread_nolock(inode))
		ret = __block_write_begin(page, pos, len, ext4_get_block_write);
	else
		ret = __block_write_begin(page, pos, len, ext4_get_block);

	if (!ret && ext4_should_journal_data(inode)) {
		ret = walk_page_buffers(handle, page_buffers(page),
				from, to, NULL, do_journal_get_write_access);
	}

	if (ret) {
		unlock_page(page);
		page_cache_release(page);
		/*
		 * __block_write_begin may have instantiated a few blocks
		 * outside i_size.  Trim these off again. Don't need
		 * i_size_read because we hold i_mutex.
		 *
		 * Add inode to orphan list in case we crash before
		 * truncate finishes
		 */
		if (pos + len > inode->i_size && ext4_can_truncate(inode))
			ext4_orphan_add(handle, inode);

		ext4_journal_stop(handle);
		if (pos + len > inode->i_size) {
			ext4_truncate_failed_write(inode);
			/*
			 * If truncate failed early the inode might
			 * still be on the orphan list; we need to
			 * make sure the inode is removed from the
			 * orphan list in that case.
			 */
			if (inode->i_nlink)
				ext4_orphan_del(NULL, inode);
		}
	}

	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
		goto retry;
out:
	return ret;
}

/* For write_end() in data=journal mode */
static int write_end_fn(handle_t *handle, struct buffer_head *bh)
{
	if (!buffer_mapped(bh) || buffer_freed(bh))
		return 0;
	set_buffer_uptodate(bh);
	return ext4_handle_dirty_metadata(handle, NULL, bh);
}

static int ext4_generic_write_end(struct file *file,
				  struct address_space *mapping,
				  loff_t pos, unsigned len, unsigned copied,
				  struct page *page, void *fsdata)
{
	int i_size_changed = 0;
	struct inode *inode = mapping->host;
	handle_t *handle = ext4_journal_current_handle();

	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);

	/*
	 * No need to use i_size_read() here, the i_size
	 * cannot change under us because we hold i_mutex.
	 *
	 * But it's important to update i_size while still holding page lock:
	 * page writeout could otherwise come in and zero beyond i_size.
	 */
	if (pos + copied > inode->i_size) {
		i_size_write(inode, pos + copied);
		i_size_changed = 1;
	}

	if (pos + copied >  EXT4_I(inode)->i_disksize) {
		/* We need to mark inode dirty even if
		 * new_i_size is less that inode->i_size
		 * bu greater than i_disksize.(hint delalloc)
		 */
		ext4_update_i_disksize(inode, (pos + copied));
		i_size_changed = 1;
	}
	unlock_page(page);
	page_cache_release(page);

	/*
	 * Don't mark the inode dirty under page lock. First, it unnecessarily
	 * makes the holding time of page lock longer. Second, it forces lock
	 * ordering of page lock and transaction start for journaling
	 * filesystems.
	 */
	if (i_size_changed)
		ext4_mark_inode_dirty(handle, inode);

	return copied;
}

/*
 * We need to pick up the new inode size which generic_commit_write gave us
 * `file' can be NULL - eg, when called from page_symlink().
 *
 * ext4 never places buffers on inode->i_mapping->private_list.  metadata
 * buffers are managed internally.
 */
static int ext4_ordered_write_end(struct file *file,
				  struct address_space *mapping,
				  loff_t pos, unsigned len, unsigned copied,
				  struct page *page, void *fsdata)
{
	handle_t *handle = ext4_journal_current_handle();
	struct inode *inode = mapping->host;
	int ret = 0, ret2;

	trace_ext4_ordered_write_end(inode, pos, len, copied);
	ret = ext4_jbd2_file_inode(handle, inode);

	if (ret == 0) {
		ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
							page, fsdata);
		copied = ret2;
		if (pos + len > inode->i_size && ext4_can_truncate(inode))
			/* if we have allocated more blocks and copied
			 * less. We will have blocks allocated outside
			 * inode->i_size. So truncate them
			 */
			ext4_orphan_add(handle, inode);
		if (ret2 < 0)
			ret = ret2;
	}
	ret2 = ext4_journal_stop(handle);
	if (!ret)
		ret = ret2;

	if (pos + len > inode->i_size) {
		ext4_truncate_failed_write(inode);
		/*
		 * If truncate failed early the inode might still be
		 * on the orphan list; we need to make sure the inode
		 * is removed from the orphan list in that case.
		 */
		if (inode->i_nlink)
			ext4_orphan_del(NULL, inode);
	}


	return ret ? ret : copied;
}

static int ext4_writeback_write_end(struct file *file,
				    struct address_space *mapping,
				    loff_t pos, unsigned len, unsigned copied,
				    struct page *page, void *fsdata)
{
	handle_t *handle = ext4_journal_current_handle();
	struct inode *inode = mapping->host;
	int ret = 0, ret2;

	trace_ext4_writeback_write_end(inode, pos, len, copied);
	ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
							page, fsdata);
	copied = ret2;
	if (pos + len > inode->i_size && ext4_can_truncate(inode))
		/* if we have allocated more blocks and copied
		 * less. We will have blocks allocated outside
		 * inode->i_size. So truncate them
		 */
		ext4_orphan_add(handle, inode);

	if (ret2 < 0)
		ret = ret2;

	ret2 = ext4_journal_stop(handle);
	if (!ret)
		ret = ret2;

	if (pos + len > inode->i_size) {
		ext4_truncate_failed_write(inode);
		/*
		 * If truncate failed early the inode might still be
		 * on the orphan list; we need to make sure the inode
		 * is removed from the orphan list in that case.
		 */
		if (inode->i_nlink)
			ext4_orphan_del(NULL, inode);
	}

	return ret ? ret : copied;
}

static int ext4_journalled_write_end(struct file *file,
				     struct address_space *mapping,
				     loff_t pos, unsigned len, unsigned copied,
				     struct page *page, void *fsdata)
{
	handle_t *handle = ext4_journal_current_handle();
	struct inode *inode = mapping->host;
	int ret = 0, ret2;
	int partial = 0;
	unsigned from, to;
	loff_t new_i_size;

	trace_ext4_journalled_write_end(inode, pos, len, copied);
	from = pos & (PAGE_CACHE_SIZE - 1);
	to = from + len;

	BUG_ON(!ext4_handle_valid(handle));

	if (copied < len) {
		if (!PageUptodate(page))
			copied = 0;
		page_zero_new_buffers(page, from+copied, to);
	}

	ret = walk_page_buffers(handle, page_buffers(page), from,
				to, &partial, write_end_fn);
	if (!partial)
		SetPageUptodate(page);
	new_i_size = pos + copied;
	if (new_i_size > inode->i_size)
		i_size_write(inode, pos+copied);
	ext4_set_inode_state(inode, EXT4_STATE_JDATA);
	EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
	if (new_i_size > EXT4_I(inode)->i_disksize) {
		ext4_update_i_disksize(inode, new_i_size);
		ret2 = ext4_mark_inode_dirty(handle, inode);
		if (!ret)
			ret = ret2;
	}

	unlock_page(page);
	page_cache_release(page);
	if (pos + len > inode->i_size && ext4_can_truncate(inode))
		/* if we have allocated more blocks and copied
		 * less. We will have blocks allocated outside
		 * inode->i_size. So truncate them
		 */
		ext4_orphan_add(handle, inode);

	ret2 = ext4_journal_stop(handle);
	if (!ret)
		ret = ret2;
	if (pos + len > inode->i_size) {
		ext4_truncate_failed_write(inode);
		/*
		 * If truncate failed early the inode might still be
		 * on the orphan list; we need to make sure the inode
		 * is removed from the orphan list in that case.
		 */
		if (inode->i_nlink)
			ext4_orphan_del(NULL, inode);
	}

	return ret ? ret : copied;
}

/*
 * Reserve a single block located at lblock
 */
static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
{
	int retries = 0;
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct ext4_inode_info *ei = EXT4_I(inode);
	unsigned long md_needed;
	int ret;

	/*
	 * recalculate the amount of metadata blocks to reserve
	 * in order to allocate nrblocks
	 * worse case is one extent per block
	 */
repeat:
	spin_lock(&ei->i_block_reservation_lock);
	md_needed = ext4_calc_metadata_amount(inode, lblock);
	trace_ext4_da_reserve_space(inode, md_needed);
	spin_unlock(&ei->i_block_reservation_lock);

	/*
	 * We will charge metadata quota at writeout time; this saves
	 * us from metadata over-estimation, though we may go over by
	 * a small amount in the end.  Here we just reserve for data.
	 */
	ret = dquot_reserve_block(inode, 1);
	if (ret)
		return ret;
	/*
	 * We do still charge estimated metadata to the sb though;
	 * we cannot afford to run out of free blocks.
	 */
	if (ext4_claim_free_blocks(sbi, md_needed + 1, 0)) {
		dquot_release_reservation_block(inode, 1);
		if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
			yield();
			goto repeat;
		}
		return -ENOSPC;
	}
	spin_lock(&ei->i_block_reservation_lock);
	ei->i_reserved_data_blocks++;
	ei->i_reserved_meta_blocks += md_needed;
	spin_unlock(&ei->i_block_reservation_lock);

	return 0;       /* success */
}

static void ext4_da_release_space(struct inode *inode, int to_free)
{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct ext4_inode_info *ei = EXT4_I(inode);

	if (!to_free)
		return;		/* Nothing to release, exit */

	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);

	trace_ext4_da_release_space(inode, to_free);
	if (unlikely(to_free > ei->i_reserved_data_blocks)) {
		/*
		 * if there aren't enough reserved blocks, then the
		 * counter is messed up somewhere.  Since this
		 * function is called from invalidate page, it's
		 * harmless to return without any action.
		 */
		ext4_msg(inode->i_sb, KERN_NOTICE, "ext4_da_release_space: "
			 "ino %lu, to_free %d with only %d reserved "
			 "data blocks\n", inode->i_ino, to_free,
			 ei->i_reserved_data_blocks);
		WARN_ON(1);
		to_free = ei->i_reserved_data_blocks;
	}
	ei->i_reserved_data_blocks -= to_free;

	if (ei->i_reserved_data_blocks == 0) {
		/*
		 * We can release all of the reserved metadata blocks
		 * only when we have written all of the delayed
		 * allocation blocks.
		 */
		percpu_counter_sub(&sbi->s_dirtyblocks_counter,
				   ei->i_reserved_meta_blocks);
		ei->i_reserved_meta_blocks = 0;
		ei->i_da_metadata_calc_len = 0;
	}

	/* update fs dirty data blocks counter */
	percpu_counter_sub(&sbi->s_dirtyblocks_counter, to_free);

	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);

	dquot_release_reservation_block(inode, to_free);
}

static void ext4_da_page_release_reservation(struct page *page,
					     unsigned long offset)
{
	int to_release = 0;
	struct buffer_head *head, *bh;
	unsigned int curr_off = 0;

	head = page_buffers(page);
	bh = head;
	do {
		unsigned int next_off = curr_off + bh->b_size;

		if ((offset <= curr_off) && (buffer_delay(bh))) {
			to_release++;
			clear_buffer_delay(bh);
		}
		curr_off = next_off;
	} while ((bh = bh->b_this_page) != head);
	ext4_da_release_space(page->mapping->host, to_release);
}

/*
 * Delayed allocation stuff
 */

/*
 * mpage_da_submit_io - walks through extent of pages and try to write
 * them with writepage() call back
 *
 * @mpd->inode: inode
 * @mpd->first_page: first page of the extent
 * @mpd->next_page: page after the last page of the extent
 *
 * By the time mpage_da_submit_io() is called we expect all blocks
 * to be allocated. this may be wrong if allocation failed.
 *
 * As pages are already locked by write_cache_pages(), we can't use it
 */
static int mpage_da_submit_io(struct mpage_da_data *mpd,
			      struct ext4_map_blocks *map)
{
	struct pagevec pvec;
	unsigned long index, end;
	int ret = 0, err, nr_pages, i;
	struct inode *inode = mpd->inode;
	struct address_space *mapping = inode->i_mapping;
	loff_t size = i_size_read(inode);
	unsigned int len, block_start;
	struct buffer_head *bh, *page_bufs = NULL;
	int journal_data = ext4_should_journal_data(inode);
	sector_t pblock = 0, cur_logical = 0;
	struct ext4_io_submit io_submit;

	BUG_ON(mpd->next_page <= mpd->first_page);
	memset(&io_submit, 0, sizeof(io_submit));
	/*
	 * We need to start from the first_page to the next_page - 1
	 * to make sure we also write the mapped dirty buffer_heads.
	 * If we look at mpd->b_blocknr we would only be looking
	 * at the currently mapped buffer_heads.
	 */
	index = mpd->first_page;
	end = mpd->next_page - 1;

	pagevec_init(&pvec, 0);
	while (index <= end) {
		nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
		if (nr_pages == 0)
			break;
		for (i = 0; i < nr_pages; i++) {
			int commit_write = 0, skip_page = 0;
			struct page *page = pvec.pages[i];

			index = page->index;
			if (index > end)
				break;

			if (index == size >> PAGE_CACHE_SHIFT)
				len = size & ~PAGE_CACHE_MASK;
			else
				len = PAGE_CACHE_SIZE;
			if (map) {
				cur_logical = index << (PAGE_CACHE_SHIFT -
							inode->i_blkbits);
				pblock = map->m_pblk + (cur_logical -
							map->m_lblk);
			}
			index++;

			BUG_ON(!PageLocked(page));
			BUG_ON(PageWriteback(page));

			/*
			 * If the page does not have buffers (for
			 * whatever reason), try to create them using
			 * __block_write_begin.  If this fails,
			 * skip the page and move on.
			 */
			if (!page_has_buffers(page)) {
				if (__block_write_begin(page, 0, len,
						noalloc_get_block_write)) {
				skip_page:
					unlock_page(page);
					continue;
				}
				commit_write = 1;
			}

			bh = page_bufs = page_buffers(page);
			block_start = 0;
			do {
				if (!bh)
					goto skip_page;
				if (map && (cur_logical >= map->m_lblk) &&
				    (cur_logical <= (map->m_lblk +
						     (map->m_len - 1)))) {
					if (buffer_delay(bh)) {
						clear_buffer_delay(bh);
						bh->b_blocknr = pblock;
					}
					if (buffer_unwritten(bh) ||
					    buffer_mapped(bh))
						BUG_ON(bh->b_blocknr != pblock);
					if (map->m_flags & EXT4_MAP_UNINIT)
						set_buffer_uninit(bh);
					clear_buffer_unwritten(bh);
				}

				/* skip page if block allocation undone */
				if (buffer_delay(bh) || buffer_unwritten(bh))
					skip_page = 1;
				bh = bh->b_this_page;
				block_start += bh->b_size;
				cur_logical++;
				pblock++;
			} while (bh != page_bufs);

			if (skip_page)
				goto skip_page;

			if (commit_write)
				/* mark the buffer_heads as dirty & uptodate */
				block_commit_write(page, 0, len);

			clear_page_dirty_for_io(page);
			/*
			 * Delalloc doesn't support data journalling,
			 * but eventually maybe we'll lift this
			 * restriction.
			 */
			if (unlikely(journal_data && PageChecked(page)))
				err = __ext4_journalled_writepage(page, len);
			else if (test_opt(inode->i_sb, MBLK_IO_SUBMIT))
				err = ext4_bio_write_page(&io_submit, page,
							  len, mpd->wbc);
			else if (buffer_uninit(page_bufs)) {
				ext4_set_bh_endio(page_bufs, inode);
				err = block_write_full_page_endio(page,
					noalloc_get_block_write,
					mpd->wbc, ext4_end_io_buffer_write);
			} else
				err = block_write_full_page(page,
					noalloc_get_block_write, mpd->wbc);

			if (!err)
				mpd->pages_written++;
			/*
			 * In error case, we have to continue because
			 * remaining pages are still locked
			 */
			if (ret == 0)
				ret = err;
		}
		pagevec_release(&pvec);
	}
	ext4_io_submit(&io_submit);
	return ret;
}

static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd)
{
	int nr_pages, i;
	pgoff_t index, end;
	struct pagevec pvec;
	struct inode *inode = mpd->inode;
	struct address_space *mapping = inode->i_mapping;

	index = mpd->first_page;
	end   = mpd->next_page - 1;
	while (index <= end) {
		nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
		if (nr_pages == 0)
			break;
		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];
			if (page->index > end)
				break;
			BUG_ON(!PageLocked(page));
			BUG_ON(PageWriteback(page));
			block_invalidatepage(page, 0);
			ClearPageUptodate(page);
			unlock_page(page);
		}
		index = pvec.pages[nr_pages - 1]->index + 1;
		pagevec_release(&pvec);
	}
	return;
}

static void ext4_print_free_blocks(struct inode *inode)
{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	printk(KERN_CRIT "Total free blocks count %lld\n",
	       ext4_count_free_blocks(inode->i_sb));
	printk(KERN_CRIT "Free/Dirty block details\n");
	printk(KERN_CRIT "free_blocks=%lld\n",
	       (long long) percpu_counter_sum(&sbi->s_freeblocks_counter));
	printk(KERN_CRIT "dirty_blocks=%lld\n",
	       (long long) percpu_counter_sum(&sbi->s_dirtyblocks_counter));
	printk(KERN_CRIT "Block reservation details\n");
	printk(KERN_CRIT "i_reserved_data_blocks=%u\n",
	       EXT4_I(inode)->i_reserved_data_blocks);
	printk(KERN_CRIT "i_reserved_meta_blocks=%u\n",
	       EXT4_I(inode)->i_reserved_meta_blocks);
	return;
}

/*
 * mpage_da_map_and_submit - go through given space, map them
 *       if necessary, and then submit them for I/O
 *
 * @mpd - bh describing space
 *
 * The function skips space we know is already mapped to disk blocks.
 *
 */
static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
{
	int err, blks, get_blocks_flags;
	struct ext4_map_blocks map, *mapp = NULL;
	sector_t next = mpd->b_blocknr;
	unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
	loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
	handle_t *handle = NULL;

	/*
	 * If the blocks are mapped already, or we couldn't accumulate
	 * any blocks, then proceed immediately to the submission stage.
	 */
	if ((mpd->b_size == 0) ||
	    ((mpd->b_state  & (1 << BH_Mapped)) &&
	     !(mpd->b_state & (1 << BH_Delay)) &&
	     !(mpd->b_state & (1 << BH_Unwritten))))
		goto submit_io;

	handle = ext4_journal_current_handle();
	BUG_ON(!handle);

	/*
	 * Call ext4_map_blocks() to allocate any delayed allocation
	 * blocks, or to convert an uninitialized extent to be
	 * initialized (in the case where we have written into
	 * one or more preallocated blocks).
	 *
	 * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
	 * indicate that we are on the delayed allocation path.  This
	 * affects functions in many different parts of the allocation
	 * call path.  This flag exists primarily because we don't
	 * want to change *many* call functions, so ext4_map_blocks()
	 * will set the EXT4_STATE_DELALLOC_RESERVED flag once the
	 * inode's allocation semaphore is taken.
	 *
	 * If the blocks in questions were delalloc blocks, set
	 * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
	 * variables are updated after the blocks have been allocated.
	 */
	map.m_lblk = next;
	map.m_len = max_blocks;
	get_blocks_flags = EXT4_GET_BLOCKS_CREATE;
	if (ext4_should_dioread_nolock(mpd->inode))
		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
	if (mpd->b_state & (1 << BH_Delay))
		get_blocks_flags |= EXT4_GET_BLOCKS_DELALLOC_RESERVE;

	blks = ext4_map_blocks(handle, mpd->inode, &map, get_blocks_flags);
	if (blks < 0) {
		struct super_block *sb = mpd->inode->i_sb;

		err = blks;
		/*
		 * If get block returns EAGAIN or ENOSPC and there
		 * appears to be free blocks we will just let
		 * mpage_da_submit_io() unlock all of the pages.
		 */
		if (err == -EAGAIN)
			goto submit_io;

		if (err == -ENOSPC &&
		    ext4_count_free_blocks(sb)) {
			mpd->retval = err;
			goto submit_io;
		}

		/*
		 * get block failure will cause us to loop in
		 * writepages, because a_ops->writepage won't be able
		 * to make progress. The page will be redirtied by
		 * writepage and writepages will again try to write
		 * the same.
		 */
		if (!(EXT4_SB(sb)->s_mount_flags & EXT4_MF_FS_ABORTED)) {
			ext4_msg(sb, KERN_CRIT,
				 "delayed block allocation failed for inode %lu "
				 "at logical offset %llu with max blocks %zd "
				 "with error %d", mpd->inode->i_ino,
				 (unsigned long long) next,
				 mpd->b_size >> mpd->inode->i_blkbits, err);
			ext4_msg(sb, KERN_CRIT,
				"This should not happen!! Data will be lost\n");
			if (err == -ENOSPC)
				ext4_print_free_blocks(mpd->inode);
		}
		/* invalidate all the pages */
		ext4_da_block_invalidatepages(mpd);

		/* Mark this page range as having been completed */
		mpd->io_done = 1;
		return;
	}
	BUG_ON(blks == 0);

	mapp = &map;
	if (map.m_flags & EXT4_MAP_NEW) {
		struct block_device *bdev = mpd->inode->i_sb->s_bdev;
		int i;

		for (i = 0; i < map.m_len; i++)
			unmap_underlying_metadata(bdev, map.m_pblk + i);
	}

	if (ext4_should_order_data(mpd->inode)) {
		err = ext4_jbd2_file_inode(handle, mpd->inode);
		if (err)
			/* This only happens if the journal is aborted */
			return;
	}

	/*
	 * Update on-disk size along with block allocation.
	 */
	disksize = ((loff_t) next + blks) << mpd->inode->i_blkbits;
	if (disksize > i_size_read(mpd->inode))
		disksize = i_size_read(mpd->inode);
	if (disksize > EXT4_I(mpd->inode)->i_disksize) {
		ext4_update_i_disksize(mpd->inode, disksize);
		err = ext4_mark_inode_dirty(handle, mpd->inode);
		if (err)
			ext4_error(mpd->inode->i_sb,
				   "Failed to mark inode %lu dirty",
				   mpd->inode->i_ino);
	}

submit_io:
	mpage_da_submit_io(mpd, mapp);
	mpd->io_done = 1;
}

#define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
		(1 << BH_Delay) | (1 << BH_Unwritten))

/*
 * mpage_add_bh_to_extent - try to add one more block to extent of blocks
 *
 * @mpd->lbh - extent of blocks
 * @logical - logical number of the block in the file
 * @bh - bh of the block (used to access block's state)
 *
 * the function is used to collect contig. blocks in same state
 */
static void mpage_add_bh_to_extent(struct mpage_da_data *mpd,
				   sector_t logical, size_t b_size,
				   unsigned long b_state)
{
	sector_t next;
	int nrblocks = mpd->b_size >> mpd->inode->i_blkbits;

	/*
	 * XXX Don't go larger than mballoc is willing to allocate
	 * This is a stopgap solution.  We eventually need to fold
	 * mpage_da_submit_io() into this function and then call
	 * ext4_map_blocks() multiple times in a loop
	 */
	if (nrblocks >= 8*1024*1024/mpd->inode->i_sb->s_blocksize)
		goto flush_it;

	/* check if thereserved journal credits might overflow */
	if (!(ext4_test_inode_flag(mpd->inode, EXT4_INODE_EXTENTS))) {
		if (nrblocks >= EXT4_MAX_TRANS_DATA) {
			/*
			 * With non-extent format we are limited by the journal
			 * credit available.  Total credit needed to insert
			 * nrblocks contiguous blocks is dependent on the
			 * nrblocks.  So limit nrblocks.
			 */
			goto flush_it;
		} else if ((nrblocks + (b_size >> mpd->inode->i_blkbits)) >
				EXT4_MAX_TRANS_DATA) {
			/*
			 * Adding the new buffer_head would make it cross the
			 * allowed limit for which we have journal credit
			 * reserved. So limit the new bh->b_size
			 */
			b_size = (EXT4_MAX_TRANS_DATA - nrblocks) <<
						mpd->inode->i_blkbits;
			/* we will do mpage_da_submit_io in the next loop */
		}
	}
	/*
	 * First block in the extent
	 */
	if (mpd->b_size == 0) {
		mpd->b_blocknr = logical;
		mpd->b_size = b_size;
		mpd->b_state = b_state & BH_FLAGS;
		return;
	}

	next = mpd->b_blocknr + nrblocks;
	/*
	 * Can we merge the block to our big extent?
	 */
	if (logical == next && (b_state & BH_FLAGS) == mpd->b_state) {
		mpd->b_size += b_size;
		return;
	}

flush_it:
	/*
	 * We couldn't merge the block to our extent, so we
	 * need to flush current  extent and start new one
	 */
	mpage_da_map_and_submit(mpd);
	return;
}

static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh)
{
	return (buffer_delay(bh) || buffer_unwritten(bh)) && buffer_dirty(bh);
}

/*
 * This is a special get_blocks_t callback which is used by
 * ext4_da_write_begin().  It will either return mapped block or
 * reserve space for a single block.
 *
 * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set.
 * We also have b_blocknr = -1 and b_bdev initialized properly
 *
 * For unwritten buffer_head we have BH_Mapped, BH_New, BH_Unwritten set.
 * We also have b_blocknr = physicalblock mapping unwritten extent and b_bdev
 * initialized properly.
 */
static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
				  struct buffer_head *bh, int create)
{
	struct ext4_map_blocks map;
	int ret = 0;
	sector_t invalid_block = ~((sector_t) 0xffff);

	if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
		invalid_block = ~0;

	BUG_ON(create == 0);
	BUG_ON(bh->b_size != inode->i_sb->s_blocksize);

	map.m_lblk = iblock;
	map.m_len = 1;

	/*
	 * first, we need to know whether the block is allocated already
	 * preallocated blocks are unmapped but should treated
	 * the same as allocated blocks.
	 */
	ret = ext4_map_blocks(NULL, inode, &map, 0);
	if (ret < 0)
		return ret;
	if (ret == 0) {
		if (buffer_delay(bh))
			return 0; /* Not sure this could or should happen */
		/*
		 * XXX: __block_write_begin() unmaps passed block, is it OK?
		 */
		ret = ext4_da_reserve_space(inode, iblock);
		if (ret)
			/* not enough space to reserve */
			return ret;

		map_bh(bh, inode->i_sb, invalid_block);
		set_buffer_new(bh);
		set_buffer_delay(bh);
		return 0;
	}

	map_bh(bh, inode->i_sb, map.m_pblk);
	bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;

	if (buffer_unwritten(bh)) {
		/* A delayed write to unwritten bh should be marked
		 * new and mapped.  Mapped ensures that we don't do
		 * get_block multiple times when we write to the same
		 * offset and new ensures that we do proper zero out
		 * for partial write.
		 */
		set_buffer_new(bh);
		set_buffer_mapped(bh);
	}
	return 0;
}

/*
 * This function is used as a standard get_block_t calback function
 * when there is no desire to allocate any blocks.  It is used as a
 * callback function for block_write_begin() and block_write_full_page().
 * These functions should only try to map a single block at a time.
 *
 * Since this function doesn't do block allocations even if the caller
 * requests it by passing in create=1, it is critically important that
 * any caller checks to make sure that any buffer heads are returned
 * by this function are either all already mapped or marked for
 * delayed allocation before calling  block_write_full_page().  Otherwise,
 * b_blocknr could be left unitialized, and the page write functions will
 * be taken by surprise.
 */
static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
				   struct buffer_head *bh_result, int create)
{
	BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
	return _ext4_get_block(inode, iblock, bh_result, 0);
}

static int bget_one(handle_t *handle, struct buffer_head *bh)
{
	get_bh(bh);
	return 0;
}

static int bput_one(handle_t *handle, struct buffer_head *bh)
{
	put_bh(bh);
	return 0;
}

static int __ext4_journalled_writepage(struct page *page,
				       unsigned int len)
{
	struct address_space *mapping = page->mapping;
	struct inode *inode = mapping->host;
	struct buffer_head *page_bufs;
	handle_t *handle = NULL;
	int ret = 0;
	int err;

	ClearPageChecked(page);
	page_bufs = page_buffers(page);
	BUG_ON(!page_bufs);
	walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
	/* As soon as we unlock the page, it can go away, but we have
	 * references to buffers so we are safe */
	unlock_page(page);

	handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
	if (IS_ERR(handle)) {
		ret = PTR_ERR(handle);
		goto out;
	}

	BUG_ON(!ext4_handle_valid(handle));

	ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
				do_journal_get_write_access);

	err = walk_page_buffers(handle, page_bufs, 0, len, NULL,
				write_end_fn);
	if (ret == 0)
		ret = err;
	EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
	err = ext4_journal_stop(handle);
	if (!ret)
		ret = err;

	walk_page_buffers(handle, page_bufs, 0, len, NULL, bput_one);
	ext4_set_inode_state(inode, EXT4_STATE_JDATA);
out:
	return ret;
}

static int ext4_set_bh_endio(struct buffer_head *bh, struct inode *inode);
static void ext4_end_io_buffer_write(struct buffer_head *