/*
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Written by Ryusuke Konishi <ryusuke@osrg.net>,
 *            Seiji Kihara <kihara@osrg.net>.
 */

#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 "nilfs.h"
#include "page.h"
#include "mdt.h"


#define NILFS_BUFFER_INHERENT_BITS  \
        ((1UL << BH_Uptodate) | (1UL << BH_Mapped) | (1UL << BH_NILFS_Node) | \
         (1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Allocated))

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_CACHE_SHIFT - blkbits);
        bh = nilfs_page_get_nth_block(page, block - first_block);

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

/*
 * Since the page cache of B-tree node pages or data page cache of pseudo
 * inodes does not have a valid mapping->host pointer, calling
 * mark_buffer_dirty() for their buffers causes a NULL pointer dereference;
 * it calls __mark_inode_dirty(NULL) through __set_page_dirty().
 * To avoid this problem, the old style mark_buffer_dirty() is used instead.
 */
void nilfs_mark_buffer_dirty(struct buffer_head *bh)
{
        if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
                __set_page_dirty_nobuffers(bh->b_page);
}

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_CACHE_SHIFT - blkbits);
        struct page *page, *opage;
        struct buffer_head *bh, *obh;

        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);
                page_cache_release(page);
                return NULL;
        }
        if (!buffer_uptodate(bh) && mapping->assoc_mapping != NULL) {
                /*
                 * Shadow page cache uses assoc_mapping to point its original
                 * page cache.  The following code tries the original cache
                 * if the given cache is a shadow and it didn't hit.
                 */
                opage = find_lock_page(mapping->assoc_mapping, index);
                if (!opage)
                        return bh;

                obh = __nilfs_get_page_block(opage, blkoff, index, blkbits,
                                             b_state);
                if (buffer_uptodate(obh)) {
                        nilfs_copy_buffer(bh, obh);
                        if (buffer_dirty(obh)) {
                                nilfs_mark_buffer_dirty(bh);
                                if (!buffer_nilfs_node(bh) && NILFS_MDT(inode))
                                        nilfs_mdt_mark_dirty(inode);
                        }
                }
                brelse(obh);
                unlock_page(opage);
                page_cache_release(opage);
        }
        return bh;
}

/**
 * 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;

        lock_buffer(bh);
        clear_buffer_nilfs_volatile(bh);
        clear_buffer_dirty(bh);
        if (nilfs_page_buffers_clean(page))
                __nilfs_clear_page_dirty(page);

        clear_buffer_uptodate(bh);
        clear_buffer_mapped(bh);
        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, KM_USER0);
        kaddr1 = kmap_atomic(dpage, KM_USER1);
        memcpy(kaddr1 + bh_offset(dbh), kaddr0 + bh_offset(sbh), sbh->b_size);
        kunmap_atomic(kaddr1, KM_USER1);
        kunmap_atomic(kaddr0, KM_USER0);

        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 & ((1UL << BH_Uptodate) | (1UL << BH_Mapped));
        while ((bh = bh->b_this_page) != dbh) {
                lock_buffer(bh);
                bits &= bh->b_state;
                unlock_buffer(bh);
        }
        if (bits & (1UL << BH_Uptodate))
                SetPageUptodate(dpage);
        else
                ClearPageUptodate(dpage);
        if (bits & (1UL << 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 = 0;

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

        m = page->mapping;
        if (m) {
                struct inode *inode = NILFS_AS_I(m);
                if (inode != NULL)
                        ino = inode->i_ino;
        }
        printk(KERN_CRIT "NILFS_PAGE_BUG(%p): cnt=%d index#=%llu flags=0x%lx "
               "mapping=%p ino=%lu\n",
               page, atomic_read(&page->_count),
               (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_alloc_private_page - allocate a private page with buffer heads
 *
 * Return Value: On success, a pointer to the allocated page is returned.
 * On error, NULL is returned.
 */
struct page *nilfs_alloc_private_page(struct block_device *bdev, int size,
                                      unsigned long state)
{
        struct buffer_head *bh, *head, *tail;
        struct page *page;

        page = alloc_page(GFP_NOFS); /* page_count of the returned page is 1 */
        if (unlikely(!page))
                return NULL;

        lock_page(page);
        head = alloc_page_buffers(page, size, 0);
        if (unlikely(!head)) {
                unlock_page(page);
                __free_page(page);
                return NULL;
        }

        bh = head;
        do {
                bh->b_state = (1UL << BH_NILFS_Allocated) | state;
                tail = bh;
                bh->b_bdev = bdev;
                bh = bh->b_this_page;
        } while (bh);

        tail->b_this_page = head;
        attach_page_buffers(page, head);

        return page;
}

void nilfs_free_private_page(struct page *page)
{
        BUG_ON(!PageLocked(page));
        BUG_ON(page->mapping);

        if (page_has_buffers(page) && !try_to_free_buffers(page))
                NILFS_PAGE_BUG(page, "failed to free page");

        unlock_page(page);
        __free_page(page);
}

/**
 * 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 fuction 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 |= (1UL << 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, 0);
repeat:
        if (!pagevec_lookup_tag(&pvec, smap, &index, PAGECACHE_TAG_DIRTY,
                                PAGEVEC_SIZE))
                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);
                page_cache_release(dpage);
                unlock_page(page);
        }
        pagevec_release(&pvec);
        cond_resched();

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

/**
 * nilfs_copy_back_pages -- copy back pages to orignal 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, 0);
repeat:
        n = pagevec_lookup(&pvec, smap, index, PAGEVEC_SIZE);
        if (!n)
                return;
        index = pvec.pages[n - 1]->index + 1;

        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);
                        page_cache_release(dpage);
                } else {
                        struct page *page2;

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

                        smap->nrpages--;
                        spin_unlock_irq(&smap->tree_lock);

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

        goto repeat;
}

void nilfs_clear_dirty_pages(struct address_space *mapping)
{
        struct pagevec pvec;
        unsigned int i;
        pgoff_t index = 0;

        pagevec_init(&pvec, 0);

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

                        lock_page(page);
                        ClearPageUptodate(page);
                        ClearPageMappedToDisk(page);
                        bh = head = page_buffers(page);
                        do {
                                lock_buffer(bh);
                                clear_buffer_dirty(bh);
                                clear_buffer_nilfs_volatile(bh);
                                clear_buffer_uptodate(bh);
                                clear_buffer_mapped(bh);
                                unlock_buffer(bh);
                                bh = bh->b_this_page;
                        } while (bh != head);

                        __nilfs_clear_page_dirty(page);
                        unlock_page(page);
                }
                pagevec_release(&pvec);
                cond_resched();
        }
}

unsigned nilfs_page_count_clean_buffers(struct page *page,
                                        unsigned from, unsigned to)
{
        unsigned block_start, block_end;
        struct buffer_head *bh, *head;
        unsigned 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;
}

/*
 * 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) {
                spin_lock_irq(&mapping->tree_lock);
                if (test_bit(PG_dirty, &page->flags)) {
                        radix_tree_tag_clear(&mapping->page_tree,
                                             page_index(page),
                                             PAGECACHE_TAG_DIRTY);
                        spin_unlock_irq(&mapping->tree_lock);
                        return clear_page_dirty_for_io(page);
                }
                spin_unlock_irq(&mapping->tree_lock);
                return 0;
        }
        return TestClearPageDirty(page);
}