/*
 * Copyright (C) 2005, 2006
 * Avishay Traeger (avishay@gmail.com)
 * Copyright (C) 2008, 2009
 * Boaz Harrosh <ooo@electrozaur.com>
 *
 * Copyrights for code taken from ext2:
 *     Copyright (C) 1992, 1993, 1994, 1995
 *     Remy Card (card@masi.ibp.fr)
 *     Laboratoire MASI - Institut Blaise Pascal
 *     Universite Pierre et Marie Curie (Paris VI)
 *     from
 *     linux/fs/minix/inode.c
 *     Copyright (C) 1991, 1992  Linus Torvalds
 *
 * This file is part of exofs.
 *
 * exofs 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.  Since it is based on ext2, and the only
 * valid version of GPL for the Linux kernel is version 2, the only valid
 * version of GPL for exofs is version 2.
 *
 * exofs 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 exofs; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <linux/slab.h>

#include "exofs.h"

#define EXOFS_DBGMSG2(M...) do {} while (0)

unsigned exofs_max_io_pages(struct ore_layout *layout,
                            unsigned expected_pages)
{
        unsigned pages = min_t(unsigned, expected_pages,
                               layout->max_io_length / PAGE_SIZE);

        return pages;
}

struct page_collect {
        struct exofs_sb_info *sbi;
        struct inode *inode;
        unsigned expected_pages;
        struct ore_io_state *ios;

        struct page **pages;
        unsigned alloc_pages;
        unsigned nr_pages;
        unsigned long length;
        loff_t pg_first; /* keep 64bit also in 32-arches */
        bool read_4_write; /* This means two things: that the read is sync
                            * And the pages should not be unlocked.
                            */
        struct page *that_locked_page;
};

static void _pcol_init(struct page_collect *pcol, unsigned expected_pages,
                       struct inode *inode)
{
        struct exofs_sb_info *sbi = inode->i_sb->s_fs_info;

        pcol->sbi = sbi;
        pcol->inode = inode;
        pcol->expected_pages = expected_pages;

        pcol->ios = NULL;
        pcol->pages = NULL;
        pcol->alloc_pages = 0;
        pcol->nr_pages = 0;
        pcol->length = 0;
        pcol->pg_first = -1;
        pcol->read_4_write = false;
        pcol->that_locked_page = NULL;
}

static void _pcol_reset(struct page_collect *pcol)
{
        pcol->expected_pages -= min(pcol->nr_pages, pcol->expected_pages);

        pcol->pages = NULL;
        pcol->alloc_pages = 0;
        pcol->nr_pages = 0;
        pcol->length = 0;
        pcol->pg_first = -1;
        pcol->ios = NULL;
        pcol->that_locked_page = NULL;

        /* this is probably the end of the loop but in writes
         * it might not end here. don't be left with nothing
         */
        if (!pcol->expected_pages)
                pcol->expected_pages =
                                exofs_max_io_pages(&pcol->sbi->layout, ~0);
}

static int pcol_try_alloc(struct page_collect *pcol)
{
        unsigned pages;

        /* TODO: easily support bio chaining */
        pages =  exofs_max_io_pages(&pcol->sbi->layout, pcol->expected_pages);

        for (; pages; pages >>= 1) {
                pcol->pages = kmalloc(pages * sizeof(struct page *),
                                      GFP_KERNEL);
                if (likely(pcol->pages)) {
                        pcol->alloc_pages = pages;
                        return 0;
                }
        }

        EXOFS_ERR("Failed to kmalloc expected_pages=%u\n",
                  pcol->expected_pages);
        return -ENOMEM;
}

static void pcol_free(struct page_collect *pcol)
{
        kfree(pcol->pages);
        pcol->pages = NULL;

        if (pcol->ios) {
                ore_put_io_state(pcol->ios);
                pcol->ios = NULL;
        }
}

static int pcol_add_page(struct page_collect *pcol, struct page *page,
                         unsigned len)
{
        if (unlikely(pcol->nr_pages >= pcol->alloc_pages))
                return -ENOMEM;

        pcol->pages[pcol->nr_pages++] = page;
        pcol->length += len;
        return 0;
}

enum {PAGE_WAS_NOT_IN_IO = 17};
static int update_read_page(struct page *page, int ret)
{
        switch (ret) {
        case 0:
                /* Everything is OK */
                SetPageUptodate(page);
                if (PageError(page))
                        ClearPageError(page);
                break;
        case -EFAULT:
                /* In this case we were trying to read something that wasn't on
                 * disk yet - return a page full of zeroes.  This should be OK,
                 * because the object should be empty (if there was a write
                 * before this read, the read would be waiting with the page
                 * locked */
                clear_highpage(page);

                SetPageUptodate(page);
                if (PageError(page))
                        ClearPageError(page);
                EXOFS_DBGMSG("recovered read error\n");
                /* fall through */
        case PAGE_WAS_NOT_IN_IO:
                ret = 0; /* recovered error */
                break;
        default:
                SetPageError(page);
        }
        return ret;
}

static void update_write_page(struct page *page, int ret)
{
        if (unlikely(ret == PAGE_WAS_NOT_IN_IO))
                return; /* don't pass start don't collect $200 */

        if (ret) {
                mapping_set_error(page->mapping, ret);
                SetPageError(page);
        }
        end_page_writeback(page);
}

/* Called at the end of reads, to optionally unlock pages and update their
 * status.
 */
static int __readpages_done(struct page_collect *pcol)
{
        int i;
        u64 good_bytes;
        u64 length = 0;
        int ret = ore_check_io(pcol->ios, NULL);

        if (likely(!ret)) {
                good_bytes = pcol->length;
                ret = PAGE_WAS_NOT_IN_IO;
        } else {
                good_bytes = 0;
        }

        EXOFS_DBGMSG2("readpages_done(0x%lx) good_bytes=0x%llx"
                     " length=0x%lx nr_pages=%u\n",
                     pcol->inode->i_ino, _LLU(good_bytes), pcol->length,
                     pcol->nr_pages);

        for (i = 0; i < pcol->nr_pages; i++) {
                struct page *page = pcol->pages[i];
                struct inode *inode = page->mapping->host;
                int page_stat;

                if (inode != pcol->inode)
                        continue; /* osd might add more pages at end */

                if (likely(length < good_bytes))
                        page_stat = 0;
                else
                        page_stat = ret;

                EXOFS_DBGMSG2("    readpages_done(0x%lx, 0x%lx) %s\n",
                          inode->i_ino, page->index,
                          page_stat ? "bad_bytes" : "good_bytes");

                ret = update_read_page(page, page_stat);
                if (!pcol->read_4_write)
                        unlock_page(page);
                length += PAGE_SIZE;
        }

        pcol_free(pcol);
        EXOFS_DBGMSG2("readpages_done END\n");
        return ret;
}

/* callback of async reads */
static void readpages_done(struct ore_io_state *ios, void *p)
{
        struct page_collect *pcol = p;

        __readpages_done(pcol);
        atomic_dec(&pcol->sbi->s_curr_pending);
        kfree(pcol);
}

static void _unlock_pcol_pages(struct page_collect *pcol, int ret, int rw)
{
        int i;

        for (i = 0; i < pcol->nr_pages; i++) {
                struct page *page = pcol->pages[i];

                if (rw == READ)
                        update_read_page(page, ret);
                else
                        update_write_page(page, ret);

                unlock_page(page);
        }
}

static int _maybe_not_all_in_one_io(struct ore_io_state *ios,
        struct page_collect *pcol_src, struct page_collect *pcol)
{
        /* length was wrong or offset was not page aligned */
        BUG_ON(pcol_src->nr_pages < ios->nr_pages);

        if (pcol_src->nr_pages > ios->nr_pages) {
                struct page **src_page;
                unsigned pages_less = pcol_src->nr_pages - ios->nr_pages;
                unsigned long len_less = pcol_src->length - ios->length;
                unsigned i;
                int ret;

                /* This IO was trimmed */
                pcol_src->nr_pages = ios->nr_pages;
                pcol_src->length = ios->length;

                /* Left over pages are passed to the next io */
                pcol->expected_pages += pages_less;
                pcol->nr_pages = pages_less;
                pcol->length = len_less;
                src_page = pcol_src->pages + pcol_src->nr_pages;
                pcol->pg_first = (*src_page)->index;

                ret = pcol_try_alloc(pcol);
                if (unlikely(ret))
                        return ret;

                for (i = 0; i < pages_less; ++i)
                        pcol->pages[i] = *src_page++;

                EXOFS_DBGMSG("Length was adjusted nr_pages=0x%x "
                        "pages_less=0x%x expected_pages=0x%x "
                        "next_offset=0x%llx next_len=0x%lx\n",
                        pcol_src->nr_pages, pages_less, pcol->expected_pages,
                        pcol->pg_first * PAGE_SIZE, pcol->length);
        }
        return 0;
}

static int read_exec(struct page_collect *pcol)
{
        struct exofs_i_info *oi = exofs_i(pcol->inode);
        struct ore_io_state *ios;
        struct page_collect *pcol_copy = NULL;
        int ret;

        if (!pcol->pages)
                return 0;

        if (!pcol->ios) {
                int ret = ore_get_rw_state(&pcol->sbi->layout, &oi->oc, true,
                                             pcol->pg_first << PAGE_CACHE_SHIFT,
                                             pcol->length, &pcol->ios);

                if (ret)
                        return ret;
        }

        ios = pcol->ios;
        ios->pages = pcol->pages;

        if (pcol->read_4_write) {
                ore_read(pcol->ios);
                return __readpages_done(pcol);
        }

        pcol_copy = kmalloc(sizeof(*pcol_copy), GFP_KERNEL);
        if (!pcol_copy) {
                ret = -ENOMEM;
                goto err;
        }

        *pcol_copy = *pcol;
        ios->done = readpages_done;
        ios->private = pcol_copy;

        /* pages ownership was passed to pcol_copy */
        _pcol_reset(pcol);

        ret = _maybe_not_all_in_one_io(ios, pcol_copy, pcol);
        if (unlikely(ret))
                goto err;

        EXOFS_DBGMSG2("read_exec(0x%lx) offset=0x%llx length=0x%llx\n",
                pcol->inode->i_ino, _LLU(ios->offset), _LLU(ios->length));

        ret = ore_read(ios);
        if (unlikely(ret))
                goto err;

        atomic_inc(&pcol->sbi->s_curr_pending);

        return 0;

err:
        if (!pcol_copy) /* Failed before ownership transfer */
                pcol_copy = pcol;
        _unlock_pcol_pages(pcol_copy, ret, READ);
        pcol_free(pcol_copy);
        kfree(pcol_copy);

        return ret;
}

/* readpage_strip is called either directly from readpage() or by the VFS from
 * within read_cache_pages(), to add one more page to be read. It will try to
 * collect as many contiguous pages as posible. If a discontinuity is
 * encountered, or it runs out of resources, it will submit the previous segment
 * and will start a new collection. Eventually caller must submit the last
 * segment if present.
 */
static int readpage_strip(void *data, struct page *page)
{
        struct page_collect *pcol = data;
        struct inode *inode = pcol->inode;
        struct exofs_i_info *oi = exofs_i(inode);
        loff_t i_size = i_size_read(inode);
        pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
        size_t len;
        int ret;

        BUG_ON(!PageLocked(page));

        /* FIXME: Just for debugging, will be removed */
        if (PageUptodate(page))
                EXOFS_ERR("PageUptodate(0x%lx, 0x%lx)\n", pcol->inode->i_ino,
                          page->index);

        pcol->that_locked_page = page;

        if (page->index < end_index)
                len = PAGE_CACHE_SIZE;
        else if (page->index == end_index)
                len = i_size & ~PAGE_CACHE_MASK;
        else
                len = 0;

        if (!len || !obj_created(oi)) {
                /* this will be out of bounds, or doesn't exist yet.
                 * Current page is cleared and the request is split
                 */
                clear_highpage(page);

                SetPageUptodate(page);
                if (PageError(page))
                        ClearPageError(page);

                if (!pcol->read_4_write)
                        unlock_page(page);
                EXOFS_DBGMSG("readpage_strip(0x%lx) empty page len=%zx "
                             "read_4_write=%d index=0x%lx end_index=0x%lx "
                             "splitting\n", inode->i_ino, len,
                             pcol->read_4_write, page->index, end_index);

                return read_exec(pcol);
        }

try_again:

        if (unlikely(pcol->pg_first == -1)) {
                pcol->pg_first = page->index;
        } else if (unlikely((pcol->pg_first + pcol->nr_pages) !=
                   page->index)) {
                /* Discontinuity detected, split the request */
                ret = read_exec(pcol);
                if (unlikely(ret))
                        goto fail;
                goto try_again;
        }

        if (!pcol->pages) {
                ret = pcol_try_alloc(pcol);
                if (unlikely(ret))
                        goto fail;
        }

        if (len != PAGE_CACHE_SIZE)
                zero_user(page, len, PAGE_CACHE_SIZE - len);

        EXOFS_DBGMSG2("    readpage_strip(0x%lx, 0x%lx) len=0x%zx\n",
                     inode->i_ino, page->index, len);

        ret = pcol_add_page(pcol, page, len);
        if (ret) {
                EXOFS_DBGMSG2("Failed pcol_add_page pages[i]=%p "
                          "this_len=0x%zx nr_pages=%u length=0x%lx\n",
                          page, len, pcol->nr_pages, pcol->length);

                /* split the request, and start again with current page */
                ret = read_exec(pcol);
                if (unlikely(ret))
                        goto fail;

                goto try_again;
        }

        return 0;

fail:
        /* SetPageError(page); ??? */
        unlock_page(page);
        return ret;
}

static int exofs_readpages(struct file *file, struct address_space *mapping,
                           struct list_head *pages, unsigned nr_pages)
{
        struct page_collect pcol;
        int ret;

        _pcol_init(&pcol, nr_pages, mapping->host);

        ret = read_cache_pages(mapping, pages, readpage_strip, &pcol);
        if (ret) {
                EXOFS_ERR("read_cache_pages => %d\n", ret);
                return ret;
        }

        ret = read_exec(&pcol);
        if (unlikely(ret))
                return ret;

        return read_exec(&pcol);
}

static int _readpage(struct page *page, bool read_4_write)
{
        struct page_collect pcol;
        int ret;

        _pcol_init(&pcol, 1, page->mapping->host);

        pcol.read_4_write = read_4_write;
        ret = readpage_strip(&pcol, page);
        if (ret) {
                EXOFS_ERR("_readpage => %d\n", ret);
                return ret;
        }

        return read_exec(&pcol);
}

/*
 * We don't need the file
 */
static int exofs_readpage(struct file *file, struct page *page)
{
        return _readpage(page, false);
}

/* Callback for osd_write. All writes are asynchronous */
static void writepages_done(struct ore_io_state *ios, void *p)
{
        struct page_collect *pcol = p;
        int i;
        u64  good_bytes;
        u64  length = 0;
        int ret = ore_check_io(ios, NULL);

        atomic_dec(&pcol->sbi->s_curr_pending);

        if (likely(!ret)) {
                good_bytes = pcol->length;
                ret = PAGE_WAS_NOT_IN_IO;
        } else {
                good_bytes = 0;
        }

        EXOFS_DBGMSG2("writepages_done(0x%lx) good_bytes=0x%llx"
                     " length=0x%lx nr_pages=%u\n",
                     pcol->inode->i_ino, _LLU(good_bytes), pcol->length,
                     pcol->nr_pages);

        for (i = 0; i < pcol->nr_pages; i++) {
                struct page *page = pcol->pages[i];
                struct inode *inode = page->mapping->host;
                int page_stat;

                if (inode != pcol->inode)
                        continue; /* osd might add more pages to a bio */

                if (likely(length < good_bytes))
                        page_stat = 0;
                else
                        page_stat = ret;

                update_write_page(page, page_stat);
                unlock_page(page);
                EXOFS_DBGMSG2("    writepages_done(0x%lx, 0x%lx) status=%d\n",
                             inode->i_ino, page->index, page_stat);

                length += PAGE_SIZE;
        }

        pcol_free(pcol);
        kfree(pcol);
        EXOFS_DBGMSG2("writepages_done END\n");
}

static struct page *__r4w_get_page(void *priv, u64 offset, bool *uptodate)
{
        struct page_collect *pcol = priv;
        pgoff_t index = offset / PAGE_SIZE;

        if (!pcol->that_locked_page ||
            (pcol->that_locked_page->index != index)) {
                struct page *page;
                loff_t i_size = i_size_read(pcol->inode);

                if (offset >= i_size) {
                        *uptodate = true;
                        EXOFS_DBGMSG2("offset >= i_size index=0x%lx\n", index);
                        return ZERO_PAGE(0);
                }

                page =  find_get_page(pcol->inode->i_mapping, index);
                if (!page) {
                        page = find_or_create_page(pcol->inode->i_mapping,
                                                   index, GFP_NOFS);
                        if (unlikely(!page)) {
                                EXOFS_DBGMSG("grab_cache_page Failed "
                                        "index=0x%llx\n", _LLU(index));
                                return NULL;
                        }
                        unlock_page(page);
                }
                if (PageDirty(page) || PageWriteback(page))
                        *uptodate = true;
                else
                        *uptodate = PageUptodate(page);
                EXOFS_DBGMSG2("index=0x%lx uptodate=%d\n", index, *uptodate);
                return page;
        } else {
                EXOFS_DBGMSG2("YES that_locked_page index=0x%lx\n",
                             pcol->that_locked_page->index);
                *uptodate = true;
                return pcol->that_locked_page;
        }
}

static void __r4w_put_page(void *priv, struct page *page)
{
        struct page_collect *pcol = priv;

        if ((pcol->that_locked_page != page) && (ZERO_PAGE(0) != page)) {
                EXOFS_DBGMSG2("index=0x%lx\n", page->index);
                page_cache_release(page);
                return;
        }
        EXOFS_DBGMSG2("that_locked_page index=0x%lx\n",
                     ZERO_PAGE(0) == page ? -1 : page->index);
}

static const struct _ore_r4w_op _r4w_op = {
        .get_page = &__r4w_get_page,
        .put_page = &__r4w_put_page,
};

static int write_exec(struct page_collect *pcol)
{
        struct exofs_i_info *oi = exofs_i(pcol->inode);
        struct ore_io_state *ios;
        struct page_collect *pcol_copy = NULL;
        int ret;

        if (!pcol->pages)
                return 0;

        BUG_ON(pcol->ios);
        ret = ore_get_rw_state(&pcol->sbi->layout, &oi->oc, false,
                                 pcol->pg_first << PAGE_CACHE_SHIFT,
                                 pcol->length, &pcol->ios);
        if (unlikely(ret))
                goto err;

        pcol_copy = kmalloc(sizeof(*pcol_copy), GFP_KERNEL);
        if (!pcol_copy) {
                EXOFS_ERR("write_exec: Failed to kmalloc(pcol)\n");
                ret = -ENOMEM;
                goto err;
        }

        *pcol_copy = *pcol;

        ios = pcol->ios;
        ios->pages = pcol_copy->pages;
        ios->done = writepages_done;
        ios->r4w = &_r4w_op;
        ios->private = pcol_copy;

        /* pages ownership was passed to pcol_copy */
        _pcol_reset(pcol);

        ret = _maybe_not_all_in_one_io(ios, pcol_copy, pcol);
        if (unlikely(ret))
                goto err;

        EXOFS_DBGMSG2("write_exec(0x%lx) offset=0x%llx length=0x%llx\n",
                pcol->inode->i_ino, _LLU(ios->offset), _LLU(ios->length));

        ret = ore_write(ios);
        if (unlikely(ret)) {
                EXOFS_ERR("write_exec: ore_write() Failed\n");
                goto err;
        }

        atomic_inc(&pcol->sbi->s_curr_pending);
        return 0;

err:
        if (!pcol_copy) /* Failed before ownership transfer */
                pcol_copy = pcol;
        _unlock_pcol_pages(pcol_copy, ret, WRITE);
        pcol_free(pcol_copy);
        kfree(pcol_copy);

        return ret;
}

/* writepage_strip is called either directly from writepage() or by the VFS from
 * within write_cache_pages(), to add one more page to be written to storage.
 * It will try to collect as many contiguous pages as possible. If a
 * discontinuity is encountered or it runs out of resources it will submit the
 * previous segment and will start a new collection.
 * Eventually caller must submit the last segment if present.
 */
static int writepage_strip(struct page *page,
                           struct writeback_control *wbc_unused, void *data)
{
        struct page_collect *pcol = data;
        struct inode *inode = pcol->inode;
        struct exofs_i_info *oi = exofs_i(inode);
        loff_t i_size = i_size_read(inode);
        pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
        size_t len;
        int ret;

        BUG_ON(!PageLocked(page));

        ret = wait_obj_created(oi);
        if (unlikely(ret))
                goto fail;

        if (page->index < end_index)
                /* in this case, the page is within the limits of the file */
                len = PAGE_CACHE_SIZE;
        else {
                len = i_size & ~PAGE_CACHE_MASK;

                if (page->index > end_index || !len) {
                        /* in this case, the page is outside the limits
                         * (truncate in progress)
                         */
                        ret = write_exec(pcol);
                        if (unlikely(ret))
                                goto fail;
                        if (PageError(page))
                                ClearPageError(page);
                        unlock_page(page);
                        EXOFS_DBGMSG("writepage_strip(0x%lx, 0x%lx) "
                                     "outside the limits\n",
                                     inode->i_ino, page->index);
                        return 0;
                }
        }

try_again:

        if (unlikely(pcol->pg_first == -1)) {
                pcol->pg_first = page->index;
        } else if (unlikely((pcol->pg_first + pcol->nr_pages) !=
                   page->index)) {
                /* Discontinuity detected, split the request */
                ret = write_exec(pcol);
                if (unlikely(ret))
                        goto fail;

                EXOFS_DBGMSG("writepage_strip(0x%lx, 0x%lx) Discontinuity\n",
                             inode->i_ino, page->index);
                goto try_again;
        }

        if (!pcol->pages) {
                ret = pcol_try_alloc(pcol);
                if (unlikely(ret))
                        goto fail;
        }

        EXOFS_DBGMSG2("    writepage_strip(0x%lx, 0x%lx) len=0x%zx\n",
                     inode->i_ino, page->index, len);

        ret = pcol_add_page(pcol, page, len);
        if (unlikely(ret)) {
                EXOFS_DBGMSG2("Failed pcol_add_page "
                             "nr_pages=%u total_length=0x%lx\n",
                             pcol->nr_pages, pcol->length);

                /* split the request, next loop will start again */
                ret = write_exec(pcol);
                if (unlikely(ret)) {
                        EXOFS_DBGMSG("write_exec failed => %d", ret);
                        goto fail;
                }

                goto try_again;
        }

        BUG_ON(PageWriteback(page));
        set_page_writeback(page);

        return 0;

fail:
        EXOFS_DBGMSG("Error: writepage_strip(0x%lx, 0x%lx)=>%d\n",
                     inode->i_ino, page->index, ret);
        set_bit(AS_EIO, &page->mapping->flags);
        unlock_page(page);
        return ret;
}

static int exofs_writepages(struct address_space *mapping,
                       struct writeback_control *wbc)
{
        struct page_collect pcol;
        long start, end, expected_pages;
        int ret;

        start = wbc->range_start >> PAGE_CACHE_SHIFT;
        end = (wbc->range_end == LLONG_MAX) ?
                        start + mapping->nrpages :
                        wbc->range_end >> PAGE_CACHE_SHIFT;

        if (start || end)
                expected_pages = end - start + 1;
        else
                expected_pages = mapping->nrpages;

        if (expected_pages < 32L)
                expected_pages = 32L;

        EXOFS_DBGMSG2("inode(0x%lx) wbc->start=0x%llx wbc->end=0x%llx "
                     "nrpages=%lu start=0x%lx end=0x%lx expected_pages=%ld\n",
                     mapping->host->i_ino, wbc->range_start, wbc->range_end,
                     mapping->nrpages, start, end, expected_pages);

        _pcol_init(&pcol, expected_pages, mapping->host);

        ret = write_cache_pages(mapping, wbc, writepage_strip, &pcol);
        if (unlikely(ret)) {
                EXOFS_ERR("write_cache_pages => %d\n", ret);
                return ret;
        }

        ret = write_exec(&pcol);
        if (unlikely(ret))
                return ret;

        if (wbc->sync_mode == WB_SYNC_ALL) {
                return write_exec(&pcol); /* pump the last reminder */
        } else if (pcol.nr_pages) {
                /* not SYNC let the reminder join the next writeout */
                unsigned i;

                for (i = 0; i < pcol.nr_pages; i++) {
                        struct page *page = pcol.pages[i];

                        end_page_writeback(page);
                        set_page_dirty(page);
                        unlock_page(page);
                }
        }
        return 0;
}

/*
static int exofs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct page_collect pcol;
        int ret;

        _pcol_init(&pcol, 1, page->mapping->host);

        ret = writepage_strip(page, NULL, &pcol);
        if (ret) {
                EXOFS_ERR("exofs_writepage => %d\n", ret);
                return ret;
        }

        return write_exec(&pcol);
}
*/
/* i_mutex held using inode->i_size directly */
static void _write_failed(struct inode *inode, loff_t to)
{
        if (to > inode->i_size)
                truncate_pagecache(inode, inode->i_size);
}

int exofs_write_begin(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned flags,
                struct page **pagep, void **fsdata)
{
        int ret = 0;
        struct page *page;

        page = *pagep;
        if (page == NULL) {
                ret = simple_write_begin(file, mapping, pos, len, flags, pagep,
                                         fsdata);
                if (ret) {
                        EXOFS_DBGMSG("simple_write_begin failed\n");
                        goto out;
                }

                page = *pagep;
        }

         /* read modify write */
        if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
                loff_t i_size = i_size_read(mapping->host);
                pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
                size_t rlen;

                if (page->index < end_index)
                        rlen = PAGE_CACHE_SIZE;
                else if (page->index == end_index)
                        rlen = i_size & ~PAGE_CACHE_MASK;
                else
                        rlen = 0;

                if (!rlen) {
                        clear_highpage(page);
                        SetPageUptodate(page);
                        goto out;
                }

                ret = _readpage(page, true);
                if (ret) {
                        /*SetPageError was done by _readpage. Is it ok?*/
                        unlock_page(page);
                        EXOFS_DBGMSG("__readpage failed\n");
                }
        }
out:
        if (unlikely(ret))
                _write_failed(mapping->host, pos + len);

        return ret;
}

static int exofs_write_begin_export(struct file *file,
                struct address_space *mapping,
                loff_t pos, unsigned len, unsigned flags,
                struct page **pagep, void **fsdata)
{
        *pagep = NULL;

        return exofs_write_begin(file, mapping, pos, len, flags, pagep,
                                        fsdata);
}

static int exofs_write_end(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
{
        struct inode *inode = mapping->host;
        /* According to comment in simple_write_end i_mutex is held */
        loff_t i_size = inode->i_size;
        int ret;

        ret = simple_write_end(file, mapping,pos, len, copied, page, fsdata);
        if (unlikely(ret))
                _write_failed(inode, pos + len);

        /* TODO: once simple_write_end marks inode dirty remove */
        if (i_size != inode->i_size)
                mark_inode_dirty(inode);
        return ret;
}

static int exofs_releasepage(struct page *page, gfp_t gfp)
{
        EXOFS_DBGMSG("page 0x%lx\n", page->index);
        WARN_ON(1);
        return 0;
}

static void exofs_invalidatepage(struct page *page, unsigned int offset,
                                 unsigned int length)
{
        EXOFS_DBGMSG("page 0x%lx offset 0x%x length 0x%x\n",
                     page->index, offset, length);
        WARN_ON(1);
}


 /* TODO: Should be easy enough to do proprly */
static ssize_t exofs_direct_IO(int rw, struct kiocb *iocb,
                struct iov_iter *iter, loff_t offset)
{
        return 0;
}

const struct address_space_operations exofs_aops = {
        .readpage       = exofs_readpage,
        .readpages      = exofs_readpages,
        .writepage      = NULL,
        .writepages     = exofs_writepages,
        .write_begin    = exofs_write_begin_export,
        .write_end      = exofs_write_end,
        .releasepage    = exofs_releasepage,
        .set_page_dirty = __set_page_dirty_nobuffers,
        .invalidatepage = exofs_invalidatepage,

        /* Not implemented Yet */
        .bmap           = NULL, /* TODO: use osd's OSD_ACT_READ_MAP */
        .direct_IO      = exofs_direct_IO,

        /* With these NULL has special meaning or default is not exported */
        .get_xip_mem    = NULL,
        .migratepage    = NULL,
        .launder_page   = NULL,
        .is_partially_uptodate = NULL,
        .error_remove_page = NULL,
};

/******************************************************************************
 * INODE OPERATIONS
 *****************************************************************************/

/*
 * Test whether an inode is a fast symlink.

 */
static inline int exofs_inode_is_fast_symlink(struct inode *inode)
{
        struct exofs_i_info *oi = exofs_i(inode);

        return S_ISLNK(inode->i_mode) && (oi->i_data[0] != 0);
}

static int _do_truncate(struct inode *inode, loff_t newsize)
{
        struct exofs_i_info *oi = exofs_i(inode);
        struct exofs_sb_info *sbi = inode->i_sb->s_fs_info;
        int ret;

        inode->i_mtime = inode->i_ctime = CURRENT_TIME;

        ret = ore_truncate(&sbi->layout, &oi->oc, (u64)newsize);
        if (likely(!ret))
                truncate_setsize(inode, newsize);

        EXOFS_DBGMSG2("(0x%lx) size=0x%llx ret=>%d\n",
                     inode->i_ino, newsize, ret);
        return ret;
}

/*
 * Set inode attributes - update size attribute on OSD if needed,
 *                        otherwise just call generic functions.
 */
int exofs_setattr(struct dentry *dentry, struct iattr *iattr)
{
        struct inode *inode = dentry->d_inode;
        int error;

        /* if we are about to modify an object, and it hasn't been
         * created yet, wait
         */
        error = wait_obj_created(exofs_i(inode));
        if (unlikely(error))
                return error;

        error = inode_change_ok(inode, iattr);
        if (unlikely(error))
                return error;

        if ((iattr->ia_valid & ATTR_SIZE) &&
            iattr->ia_size != i_size_read(inode)) {
                error = _do_truncate(inode, iattr->ia_size);
                if (unlikely(error))
                        return error;
        }

        setattr_copy(inode, iattr);
        mark_inode_dirty(inode);
        return 0;
}

static const struct osd_attr g_attr_inode_file_layout = ATTR_DEF(
        EXOFS_APAGE_FS_DATA,
        EXOFS_ATTR_INODE_FILE_LAYOUT,
        0);
static const struct osd_attr g_attr_inode_dir_layout = ATTR_DEF(
        EXOFS_APAGE_FS_DATA,
        EXOFS_ATTR_INODE_DIR_LAYOUT,
        0);

/*
 * Read the Linux inode info from the OSD, and return it as is. In exofs the
 * inode info is in an application specific page/attribute of the osd-object.
 */
static int exofs_get_inode(struct super_block *sb, struct exofs_i_info *oi,
                    struct exofs_fcb *inode)
{
        struct exofs_sb_info *sbi = sb->s_fs_info;
        struct osd_attr attrs[] = {
                [0] = g_attr_inode_data,
                [1] = g_attr_inode_file_layout,
                [2] = g_attr_inode_dir_layout,
        };
        struct ore_io_state *ios;
        struct exofs_on_disk_inode_layout *layout;
        int ret;

        ret = ore_get_io_state(&sbi->layout, &oi->oc, &ios);
        if (unlikely(ret)) {
                EXOFS_ERR("%s: ore_get_io_state failed.\n", __func__);
                return ret;
        }

        attrs[1].len = exofs_on_disk_inode_layout_size(sbi->oc.numdevs);
        attrs[2].len = exofs_on_disk_inode_layout_size(sbi->oc.numdevs);

        ios->in_attr = attrs;
        ios->in_attr_len = ARRAY_SIZE(attrs);

        ret = ore_read(ios);
        if (unlikely(ret)) {
                EXOFS_ERR("object(0x%llx) corrupted, return empty file=>%d\n",
                          _LLU(oi->one_comp.obj.id), ret);
                memset(inode, 0, sizeof(*inode));
                inode->i_mode = 0040000 | (0777 & ~022);
                /* If object is lost on target we might as well enable it's
                 * delete.
                 */
                ret = 0;
                goto out;
        }

        ret = extract_attr_from_ios(ios, &attrs[0]);
        if (ret) {
                EXOFS_ERR("%s: extract_attr 0 of inode failed\n", __func__);
                goto out;
        }
        WARN_ON(attrs[0].len != EXOFS_INO_ATTR_SIZE);
        memcpy(inode, attrs[0].val_ptr, EXOFS_INO_ATTR_SIZE);

        ret = extract_attr_from_ios(ios, &attrs[1]);
        if (ret) {
                EXOFS_ERR("%s: extract_attr 1 of inode failed\n", __func__);
                goto out;
        }
        if (attrs[1].len) {
                layout = attrs[1].val_ptr;
                if (layout->gen_func != cpu_to_le16(LAYOUT_MOVING_WINDOW)) {
                        EXOFS_ERR("%s: unsupported files layout %d\n",
                                __func__, layout->gen_func);
                        ret = -ENOTSUPP;
                        goto out;
                }
        }

        ret = extract_attr_from_ios(ios, &attrs[2]);
        if (ret) {
                EXOFS_ERR("%s: extract_attr 2 of inode failed\n", __func__);
                goto out;
        }
        if (attrs[2].len) {
                layout = attrs[2].val_ptr;
                if (layout->gen_func != cpu_to_le16(LAYOUT_MOVING_WINDOW)) {
                        EXOFS_ERR("%s: unsupported meta-data layout %d\n",
                                __func__, layout->gen_func);
                        ret = -ENOTSUPP;
                        goto out;
                }
        }

out:
        ore_put_io_state(ios);
        return ret;
}

static void __oi_init(struct exofs_i_info *oi)
{
        init_waitqueue_head(&oi->i_wq);
        oi->i_flags = 0;
}
/*
 * Fill in an inode read from the OSD and set it up for use
 */
struct inode *exofs_iget(struct super_block *sb, unsigned long ino)
{
        struct exofs_i_info *oi;
        struct exofs_fcb fcb;
        struct inode *inode;
        int ret;

        inode = iget_locked(sb, ino);
        if (!inode)
                return ERR_PTR(-ENOMEM);
        if (!(inode->i_state & I_NEW))
                return inode;
        oi = exofs_i(inode);
        __oi_init(oi);
        exofs_init_comps(&oi->oc, &oi->one_comp, sb->s_fs_info,
                         exofs_oi_objno(oi));

        /* read the inode from the osd */
        ret = exofs_get_inode(sb, oi, &fcb);
        if (ret)
                goto bad_inode;

        set_obj_created(oi);

        /* copy stuff from on-disk struct to in-memory struct */
        inode->i_mode = le16_to_cpu(fcb.i_mode);
        i_uid_write(inode, le32_to_cpu(fcb.i_uid));
        i_gid_write(inode, le32_to_cpu(fcb.i_gid));
        set_nlink(inode, le16_to_cpu(fcb.i_links_count));
        inode->i_ctime.tv_sec = (signed)le32_to_cpu(fcb.i_ctime);
        inode->i_atime.tv_sec = (signed)le32_to_cpu(fcb.i_atime);
        inode->i_mtime.tv_sec = (signed)le32_to_cpu(fcb.i_mtime);
        inode->i_ctime.tv_nsec =
                inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = 0;
        oi->i_commit_size = le64_to_cpu(fcb.i_size);
        i_size_write(inode, oi->i_commit_size);
        inode->i_blkbits = EXOFS_BLKSHIFT;
        inode->i_generation = le32_to_cpu(fcb.i_generation);

        oi->i_dir_start_lookup = 0;

        if ((inode->i_nlink == 0) && (inode->i_mode == 0)) {
                ret = -ESTALE;
                goto bad_inode;
        }

        if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
                if (fcb.i_data[0])
                        inode->i_rdev =
                                old_decode_dev(le32_to_cpu(fcb.i_data[0]));
                else
                        inode->i_rdev =
                                new_decode_dev(le32_to_cpu(fcb.i_data[1]));
        } else {
                memcpy(oi->i_data, fcb.i_data, sizeof(fcb.i_data));
        }

        inode->i_mapping->backing_dev_info = sb->s_bdi;
        if (S_ISREG(inode->i_mode)) {
                inode->i_op = &exofs_file_inode_operations;
                inode->i_fop = &exofs_file_operations;
                inode->i_mapping->a_ops = &exofs_aops;
        } else if (S_ISDIR(inode->i_mode)) {
                inode->i_op = &exofs_dir_inode_operations;
                inode->i_fop = &exofs_dir_operations;
                inode->i_mapping->a_ops = &exofs_aops;
        } else if (S_ISLNK(inode->i_mode)) {
                if (exofs_inode_is_fast_symlink(inode))
                        inode->i_op = &exofs_fast_symlink_inode_operations;
                else {
                        inode->i_op = &exofs_symlink_inode_operations;
                        inode->i_mapping->a_ops = &exofs_aops;
                }
        } else {
                inode->i_op = &exofs_special_inode_operations;
                if (fcb.i_data[0])
                        init_special_inode(inode, inode->i_mode,
                           old_decode_dev(le32_to_cpu(fcb.i_data[0])));
                else
                        init_special_inode(inode, inode->i_mode,
                           new_decode_dev(le32_to_cpu(fcb.i_data[1])));
        }

        unlock_new_inode(inode);
        return inode;

bad_inode:
        iget_failed(inode);
        return ERR_PTR(ret);
}

int __exofs_wait_obj_created(struct exofs_i_info *oi)
{
        if (!obj_created(oi)) {
                EXOFS_DBGMSG("!obj_created\n");
                BUG_ON(!obj_2bcreated(oi));
                wait_event(oi->i_wq, obj_created(oi));
                EXOFS_DBGMSG("wait_event done\n");
        }
        return unlikely(is_bad_inode(&oi->vfs_inode)) ? -EIO : 0;
}

/*
 * Callback function from exofs_new_inode().  The important thing is that we
 * set the obj_created flag so that other methods know that the object exists on
 * the OSD.
 */
static void create_done(struct ore_io_state *ios, void *p)
{
        struct inode *inode = p;
        struct exofs_i_info *oi = exofs_i(inode);
        struct exofs_sb_info *sbi = inode->i_sb->s_fs_info;
        int ret;

        ret = ore_check_io(ios, NULL);
        ore_put_io_state(ios);

        atomic_dec(&sbi->s_curr_pending);

        if (unlikely(ret)) {
                EXOFS_ERR("object=0x%llx creation failed in pid=0x%llx",
                          _LLU(exofs_oi_objno(oi)),
                          _LLU(oi->one_comp.obj.partition));
                /*TODO: When FS is corrupted creation can fail, object already
                 * exist. Get rid of this asynchronous creation, if exist
                 * increment the obj counter and try the next object. Until we
                 * succeed. All these dangling objects will be made into lost
                 * files by chkfs.exofs
                 */
        }

        set_obj_created(oi);

        wake_up(&oi->i_wq);
}

/*
 * Set up a new inode and create an object for it on the OSD
 */
struct inode *exofs_new_inode(struct inode *dir, umode_t mode)
{
        struct super_block *sb = dir->i_sb;
        struct exofs_sb_info *sbi = sb->s_fs_info;
        struct inode *inode;
        struct exofs_i_info *oi;
        struct ore_io_state *ios;
        int ret;

        inode = new_inode(sb);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        oi = exofs_i(inode);
        __oi_init(oi);

        set_obj_2bcreated(oi);

        inode->i_mapping->backing_dev_info = sb->s_bdi;
        inode_init_owner(inode, dir, mode);
        inode->i_ino = sbi->s_nextid++;
        inode->i_blkbits = EXOFS_BLKSHIFT;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        oi->i_commit_size = inode->i_size = 0;
        spin_lock(&sbi->s_next_gen_lock);
        inode->i_generation = sbi->s_next_generation++;
        spin_unlock(&sbi->s_next_gen_lock);
        insert_inode_hash(inode);

        exofs_init_comps(&oi->oc, &oi->one_comp, sb->s_fs_info,
                         exofs_oi_objno(oi));
        exofs_sbi_write_stats(sbi); /* Make sure new sbi->s_nextid is on disk */

        mark_inode_dirty(inode);

        ret = ore_get_io_state(&sbi->layout, &oi->oc, &ios);
        if (unlikely(ret)) {
                EXOFS_ERR("exofs_new_inode: ore_get_io_state failed\n");
                return ERR_PTR(ret);
        }

        ios->done = create_done;
        ios->private = inode;

        ret = ore_create(ios);
        if (ret) {
                ore_put_io_state(ios);
                return ERR_PTR(ret);
        }
        atomic_inc(&sbi->s_curr_pending);

        return inode;
}

/*
 * struct to pass two arguments to update_inode's callback
 */
struct updatei_args {
        struct exofs_sb_info    *sbi;
        struct exofs_fcb        fcb;
};

/*
 * Callback function from exofs_update_inode().
 */
static void updatei_done(struct ore_io_state *ios, void *p)
{
        struct updatei_args *args = p;

        ore_put_io_state(ios);

        atomic_dec(&args->sbi->s_curr_pending);

        kfree(args);
}

/*
 * Write the inode to the OSD.  Just fill up the struct, and set the attribute
 * synchronously or asynchronously depending on the do_sync flag.
 */
static int exofs_update_inode(struct inode *inode, int do_sync)
{
        struct exofs_i_info *oi = exofs_i(inode);
        struct super_block *sb = inode->i_sb;
        struct exofs_sb_info *sbi = sb->s_fs_info;
        struct ore_io_state *ios;
        struct osd_attr attr;
        struct exofs_fcb *fcb;
        struct updatei_args *args;
        int ret;

        args = kzalloc(sizeof(*args), GFP_KERNEL);
        if (!args) {
                EXOFS_DBGMSG("Failed kzalloc of args\n");
                return -ENOMEM;
        }

        fcb = &args->fcb;

        fcb->i_mode = cpu_to_le16(inode->i_mode);
        fcb->i_uid = cpu_to_le32(i_uid_read(inode));
        fcb->i_gid = cpu_to_le32(i_gid_read(inode));
        fcb->i_links_count = cpu_to_le16(inode->i_nlink);
        fcb->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
        fcb->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
        fcb->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
        oi->i_commit_size = i_size_read(inode);
        fcb->i_size = cpu_to_le64(oi->i_commit_size);
        fcb->i_generation = cpu_to_le32(inode->i_generation);

        if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
                if (old_valid_dev(inode->i_rdev)) {
                        fcb->i_data[0] =
                                cpu_to_le32(old_encode_dev(inode->i_rdev));
                        fcb->i_data[1] = 0;
                } else {
                        fcb->i_data[0] = 0;
                        fcb->i_data[1] =
                                cpu_to_le32(new_encode_dev(inode->i_rdev));
                        fcb->i_data[2] = 0;
                }
        } else
                memcpy(fcb->i_data, oi->i_data, sizeof(fcb->i_data));

        ret = ore_get_io_state(&sbi->layout, &oi->oc, &ios);
        if (unlikely(ret)) {
                EXOFS_ERR("%s: ore_get_io_state failed.\n", __func__);
                goto free_args;
        }

        attr = g_attr_inode_data;
        attr.val_ptr = fcb;
        ios->out_attr_len = 1;
        ios->out_attr = &attr;

        wait_obj_created(oi);

        if (!do_sync) {
                args->sbi = sbi;
                ios->done = updatei_done;
                ios->private = args;
        }

        ret = ore_write(ios);
        if (!do_sync && !ret) {
                atomic_inc(&sbi->s_curr_pending);
                goto out; /* deallocation in updatei_done */
        }

        ore_put_io_state(ios);
free_args:
        kfree(args);
out:
        EXOFS_DBGMSG("(0x%lx) do_sync=%d ret=>%d\n",
                     inode->i_ino, do_sync, ret);
        return ret;
}

int exofs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        /* FIXME: fix fsync and use wbc->sync_mode == WB_SYNC_ALL */
        return exofs_update_inode(inode, 1);
}

/*
 * Callback function from exofs_delete_inode() - don't have much cleaning up to
 * do.
 */
static void delete_done(struct ore_io_state *ios, void *p)
{
        struct exofs_sb_info *sbi = p;

        ore_put_io_state(ios);

        atomic_dec(&sbi->s_curr_pending);
}

/*
 * Called when the refcount of an inode reaches zero.  We remove the object
 * from the OSD here.  We make sure the object was created before we try and
 * delete it.
 */
void exofs_evict_inode(struct inode *inode)
{
        struct exofs_i_info *oi = exofs_i(inode);
        struct super_block *sb = inode->i_sb;
        struct exofs_sb_info *sbi = sb->s_fs_info;
        struct ore_io_state *ios;
        int ret;

        truncate_inode_pages_final(&inode->i_data);

        /* TODO: should do better here */
        if (inode->i_nlink || is_bad_inode(inode))
                goto no_delete;

        inode->i_size = 0;
        clear_inode(inode);

        /* if we are deleting an obj that hasn't been created yet, wait.
         * This also makes sure that create_done cannot be called with an
         * already evicted inode.
         */
        wait_obj_created(oi);
        /* ignore the error, attempt a remove anyway */

        /* Now Remove the OSD objects */
        ret = ore_get_io_state(&sbi->layout, &oi->oc, &ios);
        if (unlikely(ret)) {
                EXOFS_ERR("%s: ore_get_io_state failed\n", __func__);
                return;
        }

        ios->done = delete_done;
        ios->private = sbi;

        ret = ore_remove(ios);
        if (ret) {
                EXOFS_ERR("%s: ore_remove failed\n", __func__);
                ore_put_io_state(ios);
                return;
        }
        atomic_inc(&sbi->s_curr_pending);

        return;

no_delete:
        clear_inode(inode);
}