inode.c

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/*
 * Copyright (C) 2005, 2006
 * Avishay Traeger ([email protected])
 * Copyright (C) 2008, 2009
 * Boaz Harrosh <[email protected]>
 *
 * Copyrights for code taken from ext2:
 *     Copyright (C) 1992, 1993, 1994, 1995
 *     Remy Card ([email protected])
 *     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->read_4_write)
        _unlock_pcol_pages(pcol, ret, READ);

    pcol_free(pcol);

    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_DBGMSG("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_DBGMSG("index=0x%lx uptodate=%d\n", index, *uptodate);
        return page;
    } else {
        EXOFS_DBGMSG("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_DBGMSG("index=0x%lx\n", page->index);
        page_cache_release(page);
        return;
    }
    EXOFS_DBGMSG("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:
    _unlock_pcol_pages(pcol, ret, WRITE);
    pcol_free(pcol);
    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, to, 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 long offset)
{
    EXOFS_DBGMSG("page 0x%lx offset 0x%lx\n", page->index, offset);
    WARN_ON(1);
}

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  = NULL, /* TODO: Should be trivial to do */

    /* 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_DBGMSG("(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.
         */
        if ((ret == -ENOENT) || (ret == -EINVAL))
            ret = 0;
        goto out;
    }

    ret = extract_attr_from_ios(ios, &attrs[0]);
    if (ret) {
        EXOFS_ERR("%s: extract_attr of inode_data 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 of inode_data 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 of inode_data 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(&inode->i_data, 0);

    /* 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);
}