/*
 * btnode.c - NILFS B-tree node cache
 *
 * 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.
 *
 * 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"

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 = NILFS_BTNC_I(btnc);
        struct buffer_head *bh;

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

        if (unlikely(buffer_mapped(bh) || buffer_uptodate(bh) ||
                     buffer_dirty(bh))) {
                brelse(bh);
                BUG();
        }
        memset(bh->b_data, 0, 1 << inode->i_blkbits);
        bh->b_bdev = inode->i_sb->s_bdev;
        bh->b_blocknr = blocknr;
        set_buffer_mapped(bh);
        set_buffer_uptodate(bh);

        unlock_page(bh->b_page);
        put_page(bh->b_page);
        return bh;
}

int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
                              sector_t pblocknr, int mode, int mode_flags,
                              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, BIT(BH_NILFS_Node));
        if (unlikely(!bh))
                return -ENOMEM;

        err = -EEXIST; /* internal code */
        page = bh->b_page;

        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 (mode_flags & REQ_RAHEAD) {
                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 */
                goto found;
        }
        set_buffer_mapped(bh);
        bh->b_bdev = inode->i_sb->s_bdev;
        bh->b_blocknr = pblocknr; /* set block address for read */
        bh->b_end_io = end_buffer_read_sync;
        get_bh(bh);
        submit_bh(mode, mode_flags, bh);
        bh->b_blocknr = blocknr; /* set back to the given block address */
        *submit_ptr = pblocknr;
        err = 0;
found:
        *pbh = bh;

out_locked:
        unlock_page(page);
        put_page(page);
        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 page *page = bh->b_page;
        pgoff_t index = page_index(page);
        int still_dirty;

        get_page(page);
        lock_page(page);
        wait_on_page_writeback(page);

        nilfs_forget_buffer(bh);
        still_dirty = PageDirty(page);
        mapping = page->mapping;
        unlock_page(page);
        put_page(page);

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

/**
 * nilfs_btnode_prepare_change_key
 *  prepare to move contents of the block for old key to one of new key.
 *  the old buffer will not be removed, but might be reused for new buffer.
 *  it might return -ENOMEM because of memory allocation errors,
 *  and might return -EIO because of disk read errors.
 */
int nilfs_btnode_prepare_change_key(struct address_space *btnc,
                                    struct nilfs_btnode_chkey_ctxt *ctxt)
{
        struct buffer_head *obh, *nbh;
        struct inode *inode = NILFS_BTNC_I(btnc);
        __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) {
                lock_page(obh->b_page);
                /*
                 * We cannot call radix_tree_preload for the kernels older
                 * than 2.6.23, because it is not exported for modules.
                 */
retry:
                err = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
                if (err)
                        goto failed_unlock;
                /* BUG_ON(oldkey != obh->b_page->index); */
                if (unlikely(oldkey != obh->b_page->index))
                        NILFS_PAGE_BUG(obh->b_page,
                                       "invalid oldkey %lld (newkey=%lld)",
                                       (unsigned long long)oldkey,
                                       (unsigned long long)newkey);

                spin_lock_irq(&btnc->tree_lock);
                err = radix_tree_insert(&btnc->page_tree, newkey, obh->b_page);
                spin_unlock_irq(&btnc->tree_lock);
                /*
                 * Note: page->index will not change to newkey until
                 * nilfs_btnode_commit_change_key() will be called.
                 * To protect the page in intermediate state, the page lock
                 * is held.
                 */
                radix_tree_preload_end();
                if (!err)
                        return 0;
                else if (err != -EEXIST)
                        goto failed_unlock;

                err = invalidate_inode_pages2_range(btnc, newkey, newkey);
                if (!err)
                        goto retry;
                /* fallback to copy mode */
                unlock_page(obh->b_page);
        }

        nbh = nilfs_btnode_create_block(btnc, newkey);
        if (!nbh)
                return -ENOMEM;

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

 failed_unlock:
        unlock_page(obh->b_page);
        return err;
}

/**
 * nilfs_btnode_commit_change_key
 *  commit the change_key operation prepared by prepare_change_key().
 */
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 page *opage;

        if (oldkey == newkey)
                return;

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

                spin_lock_irq(&btnc->tree_lock);
                radix_tree_delete(&btnc->page_tree, oldkey);
                radix_tree_tag_set(&btnc->page_tree, newkey,
                                   PAGECACHE_TAG_DIRTY);
                spin_unlock_irq(&btnc->tree_lock);

                opage->index = obh->b_blocknr = newkey;
                unlock_page(opage);
        } 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_key operation prepared by prepare_change_key().
 */
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 */
                spin_lock_irq(&btnc->tree_lock);
                radix_tree_delete(&btnc->page_tree, newkey);
                spin_unlock_irq(&btnc->tree_lock);
                unlock_page(ctxt->bh->b_page);
        } else
                brelse(nbh);
}