/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/swap.h>
#include <linux/delay.h>
#include <linux/bio.h>
#include <linux/gfs2_ondisk.h>

#include "gfs2.h"
#include "incore.h"
#include "glock.h"
#include "glops.h"
#include "inode.h"
#include "log.h"
#include "lops.h"
#include "meta_io.h"
#include "rgrp.h"
#include "trans.h"
#include "util.h"
#include "trace_gfs2.h"

static int gfs2_aspace_writepage(struct page *page, struct writeback_control *wbc)
{
        struct buffer_head *bh, *head;
        int nr_underway = 0;
        int write_op = REQ_META | REQ_PRIO |
                (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);

        BUG_ON(!PageLocked(page));
        BUG_ON(!page_has_buffers(page));

        head = page_buffers(page);
        bh = head;

        do {
                if (!buffer_mapped(bh))
                        continue;
                /*
                 * If it's a fully non-blocking write attempt and we cannot
                 * lock the buffer then redirty the page.  Note that this can
                 * potentially cause a busy-wait loop from flusher thread and kswapd
                 * activity, but those code paths have their own higher-level
                 * throttling.
                 */
                if (wbc->sync_mode != WB_SYNC_NONE) {
                        lock_buffer(bh);
                } else if (!trylock_buffer(bh)) {
                        redirty_page_for_writepage(wbc, page);
                        continue;
                }
                if (test_clear_buffer_dirty(bh)) {
                        mark_buffer_async_write(bh);
                } else {
                        unlock_buffer(bh);
                }
        } while ((bh = bh->b_this_page) != head);

        /*
         * The page and its buffers are protected by PageWriteback(), so we can
         * drop the bh refcounts early.
         */
        BUG_ON(PageWriteback(page));
        set_page_writeback(page);

        do {
                struct buffer_head *next = bh->b_this_page;
                if (buffer_async_write(bh)) {
                        submit_bh(write_op, bh);
                        nr_underway++;
                }
                bh = next;
        } while (bh != head);
        unlock_page(page);

        if (nr_underway == 0)
                end_page_writeback(page);

        return 0;
}

const struct address_space_operations gfs2_meta_aops = {
        .writepage = gfs2_aspace_writepage,
        .releasepage = gfs2_releasepage,
};

/**
 * gfs2_getbuf - Get a buffer with a given address space
 * @gl: the glock
 * @blkno: the block number (filesystem scope)
 * @create: 1 if the buffer should be created
 *
 * Returns: the buffer
 */

struct buffer_head *gfs2_getbuf(struct gfs2_glock *gl, u64 blkno, int create)
{
        struct address_space *mapping = gfs2_glock2aspace(gl);
        struct gfs2_sbd *sdp = gl->gl_sbd;
        struct page *page;
        struct buffer_head *bh;
        unsigned int shift;
        unsigned long index;
        unsigned int bufnum;

        shift = PAGE_CACHE_SHIFT - sdp->sd_sb.sb_bsize_shift;
        index = blkno >> shift;             /* convert block to page */
        bufnum = blkno - (index << shift);  /* block buf index within page */

        if (create) {
                for (;;) {
                        page = grab_cache_page(mapping, index);
                        if (page)
                                break;
                        yield();
                }
        } else {
                page = find_lock_page(mapping, index);
                if (!page)
                        return NULL;
        }

        if (!page_has_buffers(page))
                create_empty_buffers(page, sdp->sd_sb.sb_bsize, 0);

        /* Locate header for our buffer within our page */
        for (bh = page_buffers(page); bufnum--; bh = bh->b_this_page)
                /* Do nothing */;
        get_bh(bh);

        if (!buffer_mapped(bh))
                map_bh(bh, sdp->sd_vfs, blkno);

        unlock_page(page);
        mark_page_accessed(page);
        page_cache_release(page);

        return bh;
}

static void meta_prep_new(struct buffer_head *bh)
{
        struct gfs2_meta_header *mh = (struct gfs2_meta_header *)bh->b_data;

        lock_buffer(bh);
        clear_buffer_dirty(bh);
        set_buffer_uptodate(bh);
        unlock_buffer(bh);

        mh->mh_magic = cpu_to_be32(GFS2_MAGIC);
}

/**
 * gfs2_meta_new - Get a block
 * @gl: The glock associated with this block
 * @blkno: The block number
 *
 * Returns: The buffer
 */

struct buffer_head *gfs2_meta_new(struct gfs2_glock *gl, u64 blkno)
{
        struct buffer_head *bh;
        bh = gfs2_getbuf(gl, blkno, CREATE);
        meta_prep_new(bh);
        return bh;
}

/**
 * gfs2_meta_read - Read a block from disk
 * @gl: The glock covering the block
 * @blkno: The block number
 * @flags: flags
 * @bhp: the place where the buffer is returned (NULL on failure)
 *
 * Returns: errno
 */

int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags,
                   struct buffer_head **bhp)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        struct buffer_head *bh;

        if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
                *bhp = NULL;
                return -EIO;
        }

        *bhp = bh = gfs2_getbuf(gl, blkno, CREATE);

        lock_buffer(bh);
        if (buffer_uptodate(bh)) {
                unlock_buffer(bh);
                return 0;
        }
        bh->b_end_io = end_buffer_read_sync;
        get_bh(bh);
        submit_bh(READ_SYNC | REQ_META | REQ_PRIO, bh);
        if (!(flags & DIO_WAIT))
                return 0;

        wait_on_buffer(bh);
        if (unlikely(!buffer_uptodate(bh))) {
                struct gfs2_trans *tr = current->journal_info;
                if (tr && tr->tr_touched)
                        gfs2_io_error_bh(sdp, bh);
                brelse(bh);
                *bhp = NULL;
                return -EIO;
        }

        return 0;
}

/**
 * gfs2_meta_wait - Reread a block from disk
 * @sdp: the filesystem
 * @bh: The block to wait for
 *
 * Returns: errno
 */

int gfs2_meta_wait(struct gfs2_sbd *sdp, struct buffer_head *bh)
{
        if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
                return -EIO;

        wait_on_buffer(bh);

        if (!buffer_uptodate(bh)) {
                struct gfs2_trans *tr = current->journal_info;
                if (tr && tr->tr_touched)
                        gfs2_io_error_bh(sdp, bh);
                return -EIO;
        }
        if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
                return -EIO;

        return 0;
}

void gfs2_remove_from_journal(struct buffer_head *bh, struct gfs2_trans *tr, int meta)
{
        struct address_space *mapping = bh->b_page->mapping;
        struct gfs2_sbd *sdp = gfs2_mapping2sbd(mapping);
        struct gfs2_bufdata *bd = bh->b_private;
        int was_pinned = 0;

        if (test_clear_buffer_pinned(bh)) {
                trace_gfs2_pin(bd, 0);
                atomic_dec(&sdp->sd_log_pinned);
                list_del_init(&bd->bd_list);
                if (meta) {
                        gfs2_assert_warn(sdp, sdp->sd_log_num_buf);
                        sdp->sd_log_num_buf--;
                        tr->tr_num_buf_rm++;
                } else {
                        gfs2_assert_warn(sdp, sdp->sd_log_num_databuf);
                        sdp->sd_log_num_databuf--;
                        tr->tr_num_databuf_rm++;
                }
                tr->tr_touched = 1;
                was_pinned = 1;
                brelse(bh);
        }
        if (bd) {
                spin_lock(&sdp->sd_ail_lock);
                if (bd->bd_tr) {
                        gfs2_trans_add_revoke(sdp, bd);
                } else if (was_pinned) {
                        bh->b_private = NULL;
                        kmem_cache_free(gfs2_bufdata_cachep, bd);
                }
                spin_unlock(&sdp->sd_ail_lock);
        }
        clear_buffer_dirty(bh);
        clear_buffer_uptodate(bh);
}

/**
 * gfs2_meta_wipe - make inode's buffers so they aren't dirty/pinned anymore
 * @ip: the inode who owns the buffers
 * @bstart: the first buffer in the run
 * @blen: the number of buffers in the run
 *
 */

void gfs2_meta_wipe(struct gfs2_inode *ip, u64 bstart, u32 blen)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct buffer_head *bh;

        while (blen) {
                bh = gfs2_getbuf(ip->i_gl, bstart, NO_CREATE);
                if (bh) {
                        lock_buffer(bh);
                        gfs2_log_lock(sdp);
                        gfs2_remove_from_journal(bh, current->journal_info, 1);
                        gfs2_log_unlock(sdp);
                        unlock_buffer(bh);
                        brelse(bh);
                }

                bstart++;
                blen--;
        }
}

/**
 * gfs2_meta_indirect_buffer - Get a metadata buffer
 * @ip: The GFS2 inode
 * @height: The level of this buf in the metadata (indir addr) tree (if any)
 * @num: The block number (device relative) of the buffer
 * @bhp: the buffer is returned here
 *
 * Returns: errno
 */

int gfs2_meta_indirect_buffer(struct gfs2_inode *ip, int height, u64 num,
                              struct buffer_head **bhp)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        struct gfs2_glock *gl = ip->i_gl;
        struct buffer_head *bh;
        int ret = 0;
        u32 mtype = height ? GFS2_METATYPE_IN : GFS2_METATYPE_DI;

        ret = gfs2_meta_read(gl, num, DIO_WAIT, &bh);
        if (ret == 0 && gfs2_metatype_check(sdp, bh, mtype)) {
                brelse(bh);
                ret = -EIO;
        }
        *bhp = bh;
        return ret;
}

/**
 * gfs2_meta_ra - start readahead on an extent of a file
 * @gl: the glock the blocks belong to
 * @dblock: the starting disk block
 * @extlen: the number of blocks in the extent
 *
 * returns: the first buffer in the extent
 */

struct buffer_head *gfs2_meta_ra(struct gfs2_glock *gl, u64 dblock, u32 extlen)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        struct buffer_head *first_bh, *bh;
        u32 max_ra = gfs2_tune_get(sdp, gt_max_readahead) >>
                          sdp->sd_sb.sb_bsize_shift;

        BUG_ON(!extlen);

        if (max_ra < 1)
                max_ra = 1;
        if (extlen > max_ra)
                extlen = max_ra;

        first_bh = gfs2_getbuf(gl, dblock, CREATE);

        if (buffer_uptodate(first_bh))
                goto out;
        if (!buffer_locked(first_bh))
                ll_rw_block(READ_SYNC | REQ_META, 1, &first_bh);

        dblock++;
        extlen--;

        while (extlen) {
                bh = gfs2_getbuf(gl, dblock, CREATE);

                if (!buffer_uptodate(bh) && !buffer_locked(bh))
                        ll_rw_block(READA | REQ_META, 1, &bh);
                brelse(bh);
                dblock++;
                extlen--;
                if (!buffer_locked(first_bh) && buffer_uptodate(first_bh))
                        goto out;
        }

        wait_on_buffer(first_bh);
out:
        return first_bh;
}