/*
 * page.c - buffer/page management specific to NILFS
 *
 * 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.
 *
 * Written by Ryusuke Konishi and Seiji Kihara.
 */

#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/swap.h>
#include <linux/bitops.h>
#include <linux/page-flags.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/pagevec.h>
#include <linux/gfp.h>
#include "nilfs.h"
#include "page.h"
#include "mdt.h"


#define NILFS_BUFFER_INHERENT_BITS                                      \
        (BIT(BH_Uptodate) | BIT(BH_Mapped) | BIT(BH_NILFS_Node) |       \
         BIT(BH_NILFS_Volatile) | BIT(BH_NILFS_Checked))

static struct buffer_head *
__nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
                       int blkbits, unsigned long b_state)

{
        unsigned long first_block;
        struct buffer_head *bh;

        if (!page_has_buffers(page))
                create_empty_buffers(page, 1 << blkbits, b_state);

        first_block = (unsigned long)index << (PAGE_SHIFT - blkbits);
        bh = nilfs_page_get_nth_block(page, block - first_block);

        touch_buffer(bh);
        wait_on_buffer(bh);
        return bh;
}

struct buffer_head *nilfs_grab_buffer(struct inode *inode,
                                      struct address_space *mapping,
                                      unsigned long blkoff,
                                      unsigned long b_state)
{
        int blkbits = inode->i_blkbits;
        pgoff_t index = blkoff >> (PAGE_SHIFT - blkbits);
        struct page *page;
        struct buffer_head *bh;

        page = grab_cache_page(mapping, index);
        if (unlikely(!page))
                return NULL;

        bh = __nilfs_get_page_block(page, blkoff, index, blkbits, b_state);
        if (unlikely(!bh)) {
                unlock_page(page);
                put_page(page);
                return NULL;
        }
        return bh;
}

/**
 * nilfs_forget_buffer - discard dirty state
 * @inode: owner inode of the buffer
 * @bh: buffer head of the buffer to be discarded
 */
void nilfs_forget_buffer(struct buffer_head *bh)
{
        struct page *page = bh->b_page;
        const unsigned long clear_bits =
                (BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
                 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
                 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));

        lock_buffer(bh);
        set_mask_bits(&bh->b_state, clear_bits, 0);
        if (nilfs_page_buffers_clean(page))
                __nilfs_clear_page_dirty(page);

        bh->b_blocknr = -1;
        ClearPageUptodate(page);
        ClearPageMappedToDisk(page);
        unlock_buffer(bh);
        brelse(bh);
}

/**
 * nilfs_copy_buffer -- copy buffer data and flags
 * @dbh: destination buffer
 * @sbh: source buffer
 */
void nilfs_copy_buffer(struct buffer_head *dbh, struct buffer_head *sbh)
{
        void *kaddr0, *kaddr1;
        unsigned long bits;
        struct page *spage = sbh->b_page, *dpage = dbh->b_page;
        struct buffer_head *bh;

        kaddr0 = kmap_atomic(spage);
        kaddr1 = kmap_atomic(dpage);
        memcpy(kaddr1 + bh_offset(dbh), kaddr0 + bh_offset(sbh), sbh->b_size);
        kunmap_atomic(kaddr1);
        kunmap_atomic(kaddr0);

        dbh->b_state = sbh->b_state & NILFS_BUFFER_INHERENT_BITS;
        dbh->b_blocknr = sbh->b_blocknr;
        dbh->b_bdev = sbh->b_bdev;

        bh = dbh;
        bits = sbh->b_state & (BIT(BH_Uptodate) | BIT(BH_Mapped));
        while ((bh = bh->b_this_page) != dbh) {
                lock_buffer(bh);
                bits &= bh->b_state;
                unlock_buffer(bh);
        }
        if (bits & BIT(BH_Uptodate))
                SetPageUptodate(dpage);
        else
                ClearPageUptodate(dpage);
        if (bits & BIT(BH_Mapped))
                SetPageMappedToDisk(dpage);
        else
                ClearPageMappedToDisk(dpage);
}

/**
 * nilfs_page_buffers_clean - check if a page has dirty buffers or not.
 * @page: page to be checked
 *
 * nilfs_page_buffers_clean() returns zero if the page has dirty buffers.
 * Otherwise, it returns non-zero value.
 */
int nilfs_page_buffers_clean(struct page *page)
{
        struct buffer_head *bh, *head;

        bh = head = page_buffers(page);
        do {
                if (buffer_dirty(bh))
                        return 0;
                bh = bh->b_this_page;
        } while (bh != head);
        return 1;
}

void nilfs_page_bug(struct page *page)
{
        struct address_space *m;
        unsigned long ino;

        if (unlikely(!page)) {
                printk(KERN_CRIT "NILFS_PAGE_BUG(NULL)\n");
                return;
        }

        m = page->mapping;
        ino = m ? m->host->i_ino : 0;

        printk(KERN_CRIT "NILFS_PAGE_BUG(%p): cnt=%d index#=%llu flags=0x%lx "
               "mapping=%p ino=%lu\n",
               page, page_ref_count(page),
               (unsigned long long)page->index, page->flags, m, ino);

        if (page_has_buffers(page)) {
                struct buffer_head *bh, *head;
                int i = 0;

                bh = head = page_buffers(page);
                do {
                        printk(KERN_CRIT
                               " BH[%d] %p: cnt=%d block#=%llu state=0x%lx\n",
                               i++, bh, atomic_read(&bh->b_count),
                               (unsigned long long)bh->b_blocknr, bh->b_state);
                        bh = bh->b_this_page;
                } while (bh != head);
        }
}

/**
 * nilfs_copy_page -- copy the page with buffers
 * @dst: destination page
 * @src: source page
 * @copy_dirty: flag whether to copy dirty states on the page's buffer heads.
 *
 * This function is for both data pages and btnode pages.  The dirty flag
 * should be treated by caller.  The page must not be under i/o.
 * Both src and dst page must be locked
 */
static void nilfs_copy_page(struct page *dst, struct page *src, int copy_dirty)
{
        struct buffer_head *dbh, *dbufs, *sbh, *sbufs;
        unsigned long mask = NILFS_BUFFER_INHERENT_BITS;

        BUG_ON(PageWriteback(dst));

        sbh = sbufs = page_buffers(src);
        if (!page_has_buffers(dst))
                create_empty_buffers(dst, sbh->b_size, 0);

        if (copy_dirty)
                mask |= BIT(BH_Dirty);

        dbh = dbufs = page_buffers(dst);
        do {
                lock_buffer(sbh);
                lock_buffer(dbh);
                dbh->b_state = sbh->b_state & mask;
                dbh->b_blocknr = sbh->b_blocknr;
                dbh->b_bdev = sbh->b_bdev;
                sbh = sbh->b_this_page;
                dbh = dbh->b_this_page;
        } while (dbh != dbufs);

        copy_highpage(dst, src);

        if (PageUptodate(src) && !PageUptodate(dst))
                SetPageUptodate(dst);
        else if (!PageUptodate(src) && PageUptodate(dst))
                ClearPageUptodate(dst);
        if (PageMappedToDisk(src) && !PageMappedToDisk(dst))
                SetPageMappedToDisk(dst);
        else if (!PageMappedToDisk(src) && PageMappedToDisk(dst))
                ClearPageMappedToDisk(dst);

        do {
                unlock_buffer(sbh);
                unlock_buffer(dbh);
                sbh = sbh->b_this_page;
                dbh = dbh->b_this_page;
        } while (dbh != dbufs);
}

int nilfs_copy_dirty_pages(struct address_space *dmap,
                           struct address_space *smap)
{
        struct pagevec pvec;
        unsigned int i;
        pgoff_t index = 0;
        int err = 0;

        pagevec_init(&pvec);
repeat:
        if (!pagevec_lookup_tag(&pvec, smap, &index, PAGECACHE_TAG_DIRTY))
                return 0;

        for (i = 0; i < pagevec_count(&pvec); i++) {
                struct page *page = pvec.pages[i], *dpage;

                lock_page(page);
                if (unlikely(!PageDirty(page)))
                        NILFS_PAGE_BUG(page, "inconsistent dirty state");

                dpage = grab_cache_page(dmap, page->index);
                if (unlikely(!dpage)) {
                        /* No empty page is added to the page cache */
                        err = -ENOMEM;
                        unlock_page(page);
                        break;
                }
                if (unlikely(!page_has_buffers(page)))
                        NILFS_PAGE_BUG(page,
                                       "found empty page in dat page cache");

                nilfs_copy_page(dpage, page, 1);
                __set_page_dirty_nobuffers(dpage);

                unlock_page(dpage);
                put_page(dpage);
                unlock_page(page);
        }
        pagevec_release(&pvec);
        cond_resched();

        if (likely(!err))
                goto repeat;
        return err;
}

/**
 * nilfs_copy_back_pages -- copy back pages to original cache from shadow cache
 * @dmap: destination page cache
 * @smap: source page cache
 *
 * No pages must no be added to the cache during this process.
 * This must be ensured by the caller.
 */
void nilfs_copy_back_pages(struct address_space *dmap,
                           struct address_space *smap)
{
        struct pagevec pvec;
        unsigned int i, n;
        pgoff_t index = 0;
        int err;

        pagevec_init(&pvec);
repeat:
        n = pagevec_lookup(&pvec, smap, &index);
        if (!n)
                return;

        for (i = 0; i < pagevec_count(&pvec); i++) {
                struct page *page = pvec.pages[i], *dpage;
                pgoff_t offset = page->index;

                lock_page(page);
                dpage = find_lock_page(dmap, offset);
                if (dpage) {
                        /* override existing page on the destination cache */
                        WARN_ON(PageDirty(dpage));
                        nilfs_copy_page(dpage, page, 0);
                        unlock_page(dpage);
                        put_page(dpage);
                } else {
                        struct page *page2;

                        /* move the page to the destination cache */
                        xa_lock_irq(&smap->i_pages);
                        page2 = radix_tree_delete(&smap->i_pages, offset);
                        WARN_ON(page2 != page);

                        smap->nrpages--;
                        xa_unlock_irq(&smap->i_pages);

                        xa_lock_irq(&dmap->i_pages);
                        err = radix_tree_insert(&dmap->i_pages, offset, page);
                        if (unlikely(err < 0)) {
                                WARN_ON(err == -EEXIST);
                                page->mapping = NULL;
                                put_page(page); /* for cache */
                        } else {
                                page->mapping = dmap;
                                dmap->nrpages++;
                                if (PageDirty(page))
                                        radix_tree_tag_set(&dmap->i_pages,
                                                           offset,
                                                           PAGECACHE_TAG_DIRTY);
                        }
                        xa_unlock_irq(&dmap->i_pages);
                }
                unlock_page(page);
        }
        pagevec_release(&pvec);
        cond_resched();

        goto repeat;
}

/**
 * nilfs_clear_dirty_pages - discard dirty pages in address space
 * @mapping: address space with dirty pages for discarding
 * @silent: suppress [true] or print [false] warning messages
 */
void nilfs_clear_dirty_pages(struct address_space *mapping, bool silent)
{
        struct pagevec pvec;
        unsigned int i;
        pgoff_t index = 0;

        pagevec_init(&pvec);

        while (pagevec_lookup_tag(&pvec, mapping, &index,
                                        PAGECACHE_TAG_DIRTY)) {
                for (i = 0; i < pagevec_count(&pvec); i++) {
                        struct page *page = pvec.pages[i];

                        lock_page(page);
                        nilfs_clear_dirty_page(page, silent);
                        unlock_page(page);
                }
                pagevec_release(&pvec);
                cond_resched();
        }
}

/**
 * nilfs_clear_dirty_page - discard dirty page
 * @page: dirty page that will be discarded
 * @silent: suppress [true] or print [false] warning messages
 */
void nilfs_clear_dirty_page(struct page *page, bool silent)
{
        struct inode *inode = page->mapping->host;
        struct super_block *sb = inode->i_sb;

        BUG_ON(!PageLocked(page));

        if (!silent)
                nilfs_msg(sb, KERN_WARNING,
                          "discard dirty page: offset=%lld, ino=%lu",
                          page_offset(page), inode->i_ino);

        ClearPageUptodate(page);
        ClearPageMappedToDisk(page);

        if (page_has_buffers(page)) {
                struct buffer_head *bh, *head;
                const unsigned long clear_bits =
                        (BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
                         BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
                         BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));

                bh = head = page_buffers(page);
                do {
                        lock_buffer(bh);
                        if (!silent)
                                nilfs_msg(sb, KERN_WARNING,
                                          "discard dirty block: blocknr=%llu, size=%zu",
                                          (u64)bh->b_blocknr, bh->b_size);

                        set_mask_bits(&bh->b_state, clear_bits, 0);
                        unlock_buffer(bh);
                } while (bh = bh->b_this_page, bh != head);
        }

        __nilfs_clear_page_dirty(page);
}

unsigned int nilfs_page_count_clean_buffers(struct page *page,
                                            unsigned int from, unsigned int to)
{
        unsigned int block_start, block_end;
        struct buffer_head *bh, *head;
        unsigned int nc = 0;

        for (bh = head = page_buffers(page), block_start = 0;
             bh != head || !block_start;
             block_start = block_end, bh = bh->b_this_page) {
                block_end = block_start + bh->b_size;
                if (block_end > from && block_start < to && !buffer_dirty(bh))
                        nc++;
        }
        return nc;
}

void nilfs_mapping_init(struct address_space *mapping, struct inode *inode)
{
        mapping->host = inode;
        mapping->flags = 0;
        mapping_set_gfp_mask(mapping, GFP_NOFS);
        mapping->private_data = NULL;
        mapping->a_ops = &empty_aops;
}

/*
 * NILFS2 needs clear_page_dirty() in the following two cases:
 *
 * 1) For B-tree node pages and data pages of the dat/gcdat, NILFS2 clears
 *    page dirty flags when it copies back pages from the shadow cache
 *    (gcdat->{i_mapping,i_btnode_cache}) to its original cache
 *    (dat->{i_mapping,i_btnode_cache}).
 *
 * 2) Some B-tree operations like insertion or deletion may dispose buffers
 *    in dirty state, and this needs to cancel the dirty state of their pages.
 */
int __nilfs_clear_page_dirty(struct page *page)
{
        struct address_space *mapping = page->mapping;

        if (mapping) {
                xa_lock_irq(&mapping->i_pages);
                if (test_bit(PG_dirty, &page->flags)) {
                        radix_tree_tag_clear(&mapping->i_pages,
                                             page_index(page),
                                             PAGECACHE_TAG_DIRTY);
                        xa_unlock_irq(&mapping->i_pages);
                        return clear_page_dirty_for_io(page);
                }
                xa_unlock_irq(&mapping->i_pages);
                return 0;
        }
        return TestClearPageDirty(page);
}

/**
 * nilfs_find_uncommitted_extent - find extent of uncommitted data
 * @inode: inode
 * @start_blk: start block offset (in)
 * @blkoff: start offset of the found extent (out)
 *
 * This function searches an extent of buffers marked "delayed" which
 * starts from a block offset equal to or larger than @start_blk.  If
 * such an extent was found, this will store the start offset in
 * @blkoff and return its length in blocks.  Otherwise, zero is
 * returned.
 */
unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
                                            sector_t start_blk,
                                            sector_t *blkoff)
{
        unsigned int i;
        pgoff_t index;
        unsigned int nblocks_in_page;
        unsigned long length = 0;
        sector_t b;
        struct pagevec pvec;
        struct page *page;

        if (inode->i_mapping->nrpages == 0)
                return 0;

        index = start_blk >> (PAGE_SHIFT - inode->i_blkbits);
        nblocks_in_page = 1U << (PAGE_SHIFT - inode->i_blkbits);

        pagevec_init(&pvec);

repeat:
        pvec.nr = find_get_pages_contig(inode->i_mapping, index, PAGEVEC_SIZE,
                                        pvec.pages);
        if (pvec.nr == 0)
                return length;

        if (length > 0 && pvec.pages[0]->index > index)
                goto out;

        b = pvec.pages[0]->index << (PAGE_SHIFT - inode->i_blkbits);
        i = 0;
        do {
                page = pvec.pages[i];

                lock_page(page);
                if (page_has_buffers(page)) {
                        struct buffer_head *bh, *head;

                        bh = head = page_buffers(page);
                        do {
                                if (b < start_blk)
                                        continue;
                                if (buffer_delay(bh)) {
                                        if (length == 0)
                                                *blkoff = b;
                                        length++;
                                } else if (length > 0) {
                                        goto out_locked;
                                }
                        } while (++b, bh = bh->b_this_page, bh != head);
                } else {
                        if (length > 0)
                                goto out_locked;

                        b += nblocks_in_page;
                }
                unlock_page(page);

        } while (++i < pagevec_count(&pvec));

        index = page->index + 1;
        pagevec_release(&pvec);
        cond_resched();
        goto repeat;

out_locked:
        unlock_page(page);
out:
        pagevec_release(&pvec);
        return length;
}