/*
 * segbuf.c - NILFS segment buffer
 *
 * 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>
 *
 */

#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/crc32.h>
#include "page.h"
#include "segbuf.h"


static struct kmem_cache *nilfs_segbuf_cachep;

static void nilfs_segbuf_init_once(void *obj)
{
        memset(obj, 0, sizeof(struct nilfs_segment_buffer));
}

int __init nilfs_init_segbuf_cache(void)
{
        nilfs_segbuf_cachep =
                kmem_cache_create("nilfs2_segbuf_cache",
                                  sizeof(struct nilfs_segment_buffer),
                                  0, SLAB_RECLAIM_ACCOUNT,
                                  nilfs_segbuf_init_once);

        return (nilfs_segbuf_cachep == NULL) ? -ENOMEM : 0;
}

void nilfs_destroy_segbuf_cache(void)
{
        kmem_cache_destroy(nilfs_segbuf_cachep);
}

struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *sb)
{
        struct nilfs_segment_buffer *segbuf;

        segbuf = kmem_cache_alloc(nilfs_segbuf_cachep, GFP_NOFS);
        if (unlikely(!segbuf))
                return NULL;

        segbuf->sb_super = sb;
        INIT_LIST_HEAD(&segbuf->sb_list);
        INIT_LIST_HEAD(&segbuf->sb_segsum_buffers);
        INIT_LIST_HEAD(&segbuf->sb_payload_buffers);
        return segbuf;
}

void nilfs_segbuf_free(struct nilfs_segment_buffer *segbuf)
{
        kmem_cache_free(nilfs_segbuf_cachep, segbuf);
}

void nilfs_segbuf_map(struct nilfs_segment_buffer *segbuf, __u64 segnum,
                     unsigned long offset, struct the_nilfs *nilfs)
{
        segbuf->sb_segnum = segnum;
        nilfs_get_segment_range(nilfs, segnum, &segbuf->sb_fseg_start,
                                &segbuf->sb_fseg_end);

        segbuf->sb_pseg_start = segbuf->sb_fseg_start + offset;
        segbuf->sb_rest_blocks =
                segbuf->sb_fseg_end - segbuf->sb_pseg_start + 1;
}

void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *segbuf,
                                  __u64 nextnum, struct the_nilfs *nilfs)
{
        segbuf->sb_nextnum = nextnum;
        segbuf->sb_sum.next = nilfs_get_segment_start_blocknr(nilfs, nextnum);
}

int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *segbuf)
{
        struct buffer_head *bh;

        bh = sb_getblk(segbuf->sb_super,
                       segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk);
        if (unlikely(!bh))
                return -ENOMEM;

        nilfs_segbuf_add_segsum_buffer(segbuf, bh);
        return 0;
}

int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *segbuf,
                                struct buffer_head **bhp)
{
        struct buffer_head *bh;

        bh = sb_getblk(segbuf->sb_super,
                       segbuf->sb_pseg_start + segbuf->sb_sum.nblocks);
        if (unlikely(!bh))
                return -ENOMEM;

        nilfs_segbuf_add_payload_buffer(segbuf, bh);
        *bhp = bh;
        return 0;
}

int nilfs_segbuf_reset(struct nilfs_segment_buffer *segbuf, unsigned flags,
                       time_t ctime)
{
        int err;

        segbuf->sb_sum.nblocks = segbuf->sb_sum.nsumblk = 0;
        err = nilfs_segbuf_extend_segsum(segbuf);
        if (unlikely(err))
                return err;

        segbuf->sb_sum.flags = flags;
        segbuf->sb_sum.sumbytes = sizeof(struct nilfs_segment_summary);
        segbuf->sb_sum.nfinfo = segbuf->sb_sum.nfileblk = 0;
        segbuf->sb_sum.ctime = ctime;

        segbuf->sb_io_error = 0;
        return 0;
}

/*
 * Setup segument summary
 */
void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *segbuf)
{
        struct nilfs_segment_summary *raw_sum;
        struct buffer_head *bh_sum;

        bh_sum = list_entry(segbuf->sb_segsum_buffers.next,
                            struct buffer_head, b_assoc_buffers);
        raw_sum = (struct nilfs_segment_summary *)bh_sum->b_data;

        raw_sum->ss_magic    = cpu_to_le32(NILFS_SEGSUM_MAGIC);
        raw_sum->ss_bytes    = cpu_to_le16(sizeof(*raw_sum));
        raw_sum->ss_flags    = cpu_to_le16(segbuf->sb_sum.flags);
        raw_sum->ss_seq      = cpu_to_le64(segbuf->sb_sum.seg_seq);
        raw_sum->ss_create   = cpu_to_le64(segbuf->sb_sum.ctime);
        raw_sum->ss_next     = cpu_to_le64(segbuf->sb_sum.next);
        raw_sum->ss_nblocks  = cpu_to_le32(segbuf->sb_sum.nblocks);
        raw_sum->ss_nfinfo   = cpu_to_le32(segbuf->sb_sum.nfinfo);
        raw_sum->ss_sumbytes = cpu_to_le32(segbuf->sb_sum.sumbytes);
        raw_sum->ss_pad      = 0;
}

/*
 * CRC calculation routines
 */
void nilfs_segbuf_fill_in_segsum_crc(struct nilfs_segment_buffer *segbuf,
                                     u32 seed)
{
        struct buffer_head *bh;
        struct nilfs_segment_summary *raw_sum;
        unsigned long size, bytes = segbuf->sb_sum.sumbytes;
        u32 crc;

        bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
                        b_assoc_buffers);

        raw_sum = (struct nilfs_segment_summary *)bh->b_data;
        size = min_t(unsigned long, bytes, bh->b_size);
        crc = crc32_le(seed,
                       (unsigned char *)raw_sum +
                       sizeof(raw_sum->ss_datasum) + sizeof(raw_sum->ss_sumsum),
                       size - (sizeof(raw_sum->ss_datasum) +
                               sizeof(raw_sum->ss_sumsum)));

        list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
                                     b_assoc_buffers) {
                bytes -= size;
                size = min_t(unsigned long, bytes, bh->b_size);
                crc = crc32_le(crc, bh->b_data, size);
        }
        raw_sum->ss_sumsum = cpu_to_le32(crc);
}

void nilfs_segbuf_fill_in_data_crc(struct nilfs_segment_buffer *segbuf,
                                   u32 seed)
{
        struct buffer_head *bh;
        struct nilfs_segment_summary *raw_sum;
        void *kaddr;
        u32 crc;

        bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
                        b_assoc_buffers);
        raw_sum = (struct nilfs_segment_summary *)bh->b_data;
        crc = crc32_le(seed,
                       (unsigned char *)raw_sum + sizeof(raw_sum->ss_datasum),
                       bh->b_size - sizeof(raw_sum->ss_datasum));

        list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
                                     b_assoc_buffers) {
                crc = crc32_le(crc, bh->b_data, bh->b_size);
        }
        list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
                kaddr = kmap_atomic(bh->b_page, KM_USER0);
                crc = crc32_le(crc, kaddr + bh_offset(bh), bh->b_size);
                kunmap_atomic(kaddr, KM_USER0);
        }
        raw_sum->ss_datasum = cpu_to_le32(crc);
}

void nilfs_release_buffers(struct list_head *list)
{
        struct buffer_head *bh, *n;

        list_for_each_entry_safe(bh, n, list, b_assoc_buffers) {
                list_del_init(&bh->b_assoc_buffers);
                if (buffer_nilfs_allocated(bh)) {
                        struct page *clone_page = bh->b_page;

                        /* remove clone page */
                        brelse(bh);
                        page_cache_release(clone_page); /* for each bh */
                        if (page_count(clone_page) <= 2) {
                                lock_page(clone_page);
                                nilfs_free_private_page(clone_page);
                        }
                        continue;
                }
                brelse(bh);
        }
}

/*
 * BIO operations
 */
static void nilfs_end_bio_write(struct bio *bio, int err)
{
        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct nilfs_write_info *wi = bio->bi_private;

        if (err == -EOPNOTSUPP) {
                set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
                bio_put(bio);
                /* to be detected by submit_seg_bio() */
        }

        if (!uptodate)
                atomic_inc(&wi->err);

        bio_put(bio);
        complete(&wi->bio_event);
}

static int nilfs_submit_seg_bio(struct nilfs_write_info *wi, int mode)
{
        struct bio *bio = wi->bio;
        int err;

        if (wi->nbio > 0 && bdi_write_congested(wi->bdi)) {
                wait_for_completion(&wi->bio_event);
                wi->nbio--;
                if (unlikely(atomic_read(&wi->err))) {
                        bio_put(bio);
                        err = -EIO;
                        goto failed;
                }
        }

        bio->bi_end_io = nilfs_end_bio_write;
        bio->bi_private = wi;
        bio_get(bio);
        submit_bio(mode, bio);
        if (bio_flagged(bio, BIO_EOPNOTSUPP)) {
                bio_put(bio);
                err = -EOPNOTSUPP;
                goto failed;
        }
        wi->nbio++;
        bio_put(bio);

        wi->bio = NULL;
        wi->rest_blocks -= wi->end - wi->start;
        wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
        wi->start = wi->end;
        return 0;

 failed:
        wi->bio = NULL;
        return err;
}

/**
 * nilfs_alloc_seg_bio - allocate a bio for writing segment.
 * @sb: super block
 * @start: beginning disk block number of this BIO.
 * @nr_vecs: request size of page vector.
 *
 * alloc_seg_bio() allocates a new BIO structure and initialize it.
 *
 * Return Value: On success, pointer to the struct bio is returned.
 * On error, NULL is returned.
 */
static struct bio *nilfs_alloc_seg_bio(struct super_block *sb, sector_t start,
                                       int nr_vecs)
{
        struct bio *bio;

        bio = bio_alloc(GFP_NOIO, nr_vecs);
        if (bio == NULL) {
                while (!bio && (nr_vecs >>= 1))
                        bio = bio_alloc(GFP_NOIO, nr_vecs);
        }
        if (likely(bio)) {
                bio->bi_bdev = sb->s_bdev;
                bio->bi_sector = (sector_t)start << (sb->s_blocksize_bits - 9);
        }
        return bio;
}

void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *segbuf,
                                struct nilfs_write_info *wi)
{
        wi->bio = NULL;
        wi->rest_blocks = segbuf->sb_sum.nblocks;
        wi->max_pages = bio_get_nr_vecs(wi->sb->s_bdev);
        wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
        wi->start = wi->end = 0;
        wi->nbio = 0;
        wi->blocknr = segbuf->sb_pseg_start;

        atomic_set(&wi->err, 0);
        init_completion(&wi->bio_event);
}

static int nilfs_submit_bh(struct nilfs_write_info *wi, struct buffer_head *bh,
                           int mode)
{
        int len, err;

        BUG_ON(wi->nr_vecs <= 0);
 repeat:
        if (!wi->bio) {
                wi->bio = nilfs_alloc_seg_bio(wi->sb, wi->blocknr + wi->end,
                                              wi->nr_vecs);
                if (unlikely(!wi->bio))
                        return -ENOMEM;
        }

        len = bio_add_page(wi->bio, bh->b_page, bh->b_size, bh_offset(bh));
        if (len == bh->b_size) {
                wi->end++;
                return 0;
        }
        /* bio is FULL */
        err = nilfs_submit_seg_bio(wi, mode);
        /* never submit current bh */
        if (likely(!err))
                goto repeat;
        return err;
}

int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
                       struct nilfs_write_info *wi)
{
        struct buffer_head *bh;
        int res, rw = WRITE;

        list_for_each_entry(bh, &segbuf->sb_segsum_buffers, b_assoc_buffers) {
                res = nilfs_submit_bh(wi, bh, rw);
                if (unlikely(res))
                        goto failed_bio;
        }

        list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
                res = nilfs_submit_bh(wi, bh, rw);
                if (unlikely(res))
                        goto failed_bio;
        }

        if (wi->bio) {
                /*
                 * Last BIO is always sent through the following
                 * submission.
                 */
                rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
                res = nilfs_submit_seg_bio(wi, rw);
                if (unlikely(res))
                        goto failed_bio;
        }

        res = 0;
 out:
        return res;

 failed_bio:
        atomic_inc(&wi->err);
        goto out;
}

/**
 * nilfs_segbuf_wait - wait for completion of requested BIOs
 * @wi: nilfs_write_info
 *
 * Return Value: On Success, 0 is returned. On Error, one of the following
 * negative error code is returned.
 *
 * %-EIO - I/O error
 */
int nilfs_segbuf_wait(struct nilfs_segment_buffer *segbuf,
                      struct nilfs_write_info *wi)
{
        int err = 0;

        if (!wi->nbio)
                return 0;

        do {
                wait_for_completion(&wi->bio_event);
        } while (--wi->nbio > 0);

        if (unlikely(atomic_read(&wi->err) > 0)) {
                printk(KERN_ERR "NILFS: IO error writing segment\n");
                err = -EIO;
                segbuf->sb_io_error = 1;
        }
        return err;
}