/*
 * linux/fs/ext4/page-io.c
 *
 * This contains the new page_io functions for ext4
 *
 * Written by Theodore Ts'o, 2010.
 */

#include <linux/fs.h>
#include <linux/time.h>
#include <linux/jbd2.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/mpage.h>
#include <linux/namei.h>
#include <linux/uio.h>
#include <linux/bio.h>
#include <linux/workqueue.h>
#include <linux/kernel.h>
#include <linux/slab.h>

#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"
#include "ext4_extents.h"

static struct kmem_cache *io_page_cachep, *io_end_cachep;

int __init ext4_init_pageio(void)
{
        io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT);
        if (io_page_cachep == NULL)
                return -ENOMEM;
        io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
        if (io_end_cachep == NULL) {
                kmem_cache_destroy(io_page_cachep);
                return -ENOMEM;
        }
        return 0;
}

void ext4_exit_pageio(void)
{
        kmem_cache_destroy(io_end_cachep);
        kmem_cache_destroy(io_page_cachep);
}

void ext4_ioend_wait(struct inode *inode)
{
        wait_queue_head_t *wq = ext4_ioend_wq(inode);

        wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_ioend_count) == 0));
}

static void put_io_page(struct ext4_io_page *io_page)
{
        if (atomic_dec_and_test(&io_page->p_count)) {
                end_page_writeback(io_page->p_page);
                put_page(io_page->p_page);
                kmem_cache_free(io_page_cachep, io_page);
        }
}

void ext4_free_io_end(ext4_io_end_t *io)
{
        int i;

        BUG_ON(!io);
        if (io->page)
                put_page(io->page);
        for (i = 0; i < io->num_io_pages; i++)
                put_io_page(io->pages[i]);
        io->num_io_pages = 0;
        if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count))
                wake_up_all(ext4_ioend_wq(io->inode));
        kmem_cache_free(io_end_cachep, io);
}

/*
 * check a range of space and convert unwritten extents to written.
 *
 * Called with inode->i_mutex; we depend on this when we manipulate
 * io->flag, since we could otherwise race with ext4_flush_completed_IO()
 */
int ext4_end_io_nolock(ext4_io_end_t *io)
{
        struct inode *inode = io->inode;
        loff_t offset = io->offset;
        ssize_t size = io->size;
        int ret = 0;

        ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
                   "list->prev 0x%p\n",
                   io, inode->i_ino, io->list.next, io->list.prev);

        ret = ext4_convert_unwritten_extents(inode, offset, size);
        if (ret < 0) {
                ext4_msg(inode->i_sb, KERN_EMERG,
                         "failed to convert unwritten extents to written "
                         "extents -- potential data loss!  "
                         "(inode %lu, offset %llu, size %zd, error %d)",
                         inode->i_ino, offset, size, ret);
        }

        if (io->iocb)
                aio_complete(io->iocb, io->result, 0);

        if (io->flag & EXT4_IO_END_DIRECT)
                inode_dio_done(inode);
        /* Wake up anyone waiting on unwritten extent conversion */
        if (atomic_dec_and_test(&EXT4_I(inode)->i_aiodio_unwritten))
                wake_up_all(ext4_ioend_wq(io->inode));
        return ret;
}

/*
 * work on completed aio dio IO, to convert unwritten extents to extents
 */
static void ext4_end_io_work(struct work_struct *work)
{
        ext4_io_end_t           *io = container_of(work, ext4_io_end_t, work);
        struct inode            *inode = io->inode;
        struct ext4_inode_info  *ei = EXT4_I(inode);
        unsigned long           flags;

        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
        if (io->flag & EXT4_IO_END_IN_FSYNC)
                goto requeue;
        if (list_empty(&io->list)) {
                spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
                goto free;
        }

        if (!mutex_trylock(&inode->i_mutex)) {
                bool was_queued;
requeue:
                was_queued = !!(io->flag & EXT4_IO_END_QUEUED);
                io->flag |= EXT4_IO_END_QUEUED;
                spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
                /*
                 * Requeue the work instead of waiting so that the work
                 * items queued after this can be processed.
                 */
                queue_work(EXT4_SB(inode->i_sb)->dio_unwritten_wq, &io->work);
                /*
                 * To prevent the ext4-dio-unwritten thread from keeping
                 * requeueing end_io requests and occupying cpu for too long,
                 * yield the cpu if it sees an end_io request that has already
                 * been requeued.
                 */
                if (was_queued)
                        yield();
                return;
        }
        list_del_init(&io->list);
        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
        (void) ext4_end_io_nolock(io);
        mutex_unlock(&inode->i_mutex);
free:
        ext4_free_io_end(io);
}

ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
{
        ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
        if (io) {
                atomic_inc(&EXT4_I(inode)->i_ioend_count);
                io->inode = inode;
                INIT_WORK(&io->work, ext4_end_io_work);
                INIT_LIST_HEAD(&io->list);
        }
        return io;
}

/*
 * Print an buffer I/O error compatible with the fs/buffer.c.  This
 * provides compatibility with dmesg scrapers that look for a specific
 * buffer I/O error message.  We really need a unified error reporting
 * structure to userspace ala Digital Unix's uerf system, but it's
 * probably not going to happen in my lifetime, due to LKML politics...
 */
static void buffer_io_error(struct buffer_head *bh)
{
        char b[BDEVNAME_SIZE];
        printk(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
                        bdevname(bh->b_bdev, b),
                        (unsigned long long)bh->b_blocknr);
}

static void ext4_end_bio(struct bio *bio, int error)
{
        ext4_io_end_t *io_end = bio->bi_private;
        struct workqueue_struct *wq;
        struct inode *inode;
        unsigned long flags;
        int i;
        sector_t bi_sector = bio->bi_sector;

        BUG_ON(!io_end);
        bio->bi_private = NULL;
        bio->bi_end_io = NULL;
        if (test_bit(BIO_UPTODATE, &bio->bi_flags))
                error = 0;
        bio_put(bio);

        for (i = 0; i < io_end->num_io_pages; i++) {
                struct page *page = io_end->pages[i]->p_page;
                struct buffer_head *bh, *head;
                loff_t offset;
                loff_t io_end_offset;

                if (error) {
                        SetPageError(page);
                        set_bit(AS_EIO, &page->mapping->flags);
                        head = page_buffers(page);
                        BUG_ON(!head);

                        io_end_offset = io_end->offset + io_end->size;

                        offset = (sector_t) page->index << PAGE_CACHE_SHIFT;
                        bh = head;
                        do {
                                if ((offset >= io_end->offset) &&
                                    (offset+bh->b_size <= io_end_offset))
                                        buffer_io_error(bh);

                                offset += bh->b_size;
                                bh = bh->b_this_page;
                        } while (bh != head);
                }

                put_io_page(io_end->pages[i]);
        }
        io_end->num_io_pages = 0;
        inode = io_end->inode;

        if (error) {
                io_end->flag |= EXT4_IO_END_ERROR;
                ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
                             "(offset %llu size %ld starting block %llu)",
                             inode->i_ino,
                             (unsigned long long) io_end->offset,
                             (long) io_end->size,
                             (unsigned long long)
                             bi_sector >> (inode->i_blkbits - 9));
        }

        if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
                ext4_free_io_end(io_end);
                return;
        }

        /* Add the io_end to per-inode completed io list*/
        spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
        list_add_tail(&io_end->list, &EXT4_I(inode)->i_completed_io_list);
        spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);

        wq = EXT4_SB(inode->i_sb)->dio_unwritten_wq;
        /* queue the work to convert unwritten extents to written */
        queue_work(wq, &io_end->work);
}

void ext4_io_submit(struct ext4_io_submit *io)
{
        struct bio *bio = io->io_bio;

        if (bio) {
                bio_get(io->io_bio);
                submit_bio(io->io_op, io->io_bio);
                BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
                bio_put(io->io_bio);
        }
        io->io_bio = NULL;
        io->io_op = 0;
        io->io_end = NULL;
}

static int io_submit_init(struct ext4_io_submit *io,
                          struct inode *inode,
                          struct writeback_control *wbc,
                          struct buffer_head *bh)
{
        ext4_io_end_t *io_end;
        struct page *page = bh->b_page;
        int nvecs = bio_get_nr_vecs(bh->b_bdev);
        struct bio *bio;

        io_end = ext4_init_io_end(inode, GFP_NOFS);
        if (!io_end)
                return -ENOMEM;
        bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
        bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
        bio->bi_bdev = bh->b_bdev;
        bio->bi_private = io->io_end = io_end;
        bio->bi_end_io = ext4_end_bio;

        io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);

        io->io_bio = bio;
        io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
        io->io_next_block = bh->b_blocknr;
        return 0;
}

static int io_submit_add_bh(struct ext4_io_submit *io,
                            struct ext4_io_page *io_page,
                            struct inode *inode,
                            struct writeback_control *wbc,
                            struct buffer_head *bh)
{
        ext4_io_end_t *io_end;
        int ret;

        if (buffer_new(bh)) {
                clear_buffer_new(bh);
                unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
        }

        if (!buffer_mapped(bh) || buffer_delay(bh)) {
                if (!buffer_mapped(bh))
                        clear_buffer_dirty(bh);
                if (io->io_bio)
                        ext4_io_submit(io);
                return 0;
        }

        if (io->io_bio && bh->b_blocknr != io->io_next_block) {
submit_and_retry:
                ext4_io_submit(io);
        }
        if (io->io_bio == NULL) {
                ret = io_submit_init(io, inode, wbc, bh);
                if (ret)
                        return ret;
        }
        io_end = io->io_end;
        if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
            (io_end->pages[io_end->num_io_pages-1] != io_page))
                goto submit_and_retry;
        if (buffer_uninit(bh))
                ext4_set_io_unwritten_flag(inode, io_end);
        io->io_end->size += bh->b_size;
        io->io_next_block++;
        ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
        if (ret != bh->b_size)
                goto submit_and_retry;
        if ((io_end->num_io_pages == 0) ||
            (io_end->pages[io_end->num_io_pages-1] != io_page)) {
                io_end->pages[io_end->num_io_pages++] = io_page;
                atomic_inc(&io_page->p_count);
        }
        return 0;
}

int ext4_bio_write_page(struct ext4_io_submit *io,
                        struct page *page,
                        int len,
                        struct writeback_control *wbc)
{
        struct inode *inode = page->mapping->host;
        unsigned block_start, block_end, blocksize;
        struct ext4_io_page *io_page;
        struct buffer_head *bh, *head;
        int ret = 0;

        blocksize = 1 << inode->i_blkbits;

        BUG_ON(!PageLocked(page));
        BUG_ON(PageWriteback(page));

        io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
        if (!io_page) {
                set_page_dirty(page);
                unlock_page(page);
                return -ENOMEM;
        }
        io_page->p_page = page;
        atomic_set(&io_page->p_count, 1);
        get_page(page);
        set_page_writeback(page);
        ClearPageError(page);

        for (bh = head = page_buffers(page), block_start = 0;
             bh != head || !block_start;
             block_start = block_end, bh = bh->b_this_page) {

                block_end = block_start + blocksize;
                if (block_start >= len) {
                        /*
                         * Comments copied from block_write_full_page_endio:
                         *
                         * The page straddles i_size.  It must be zeroed out on
                         * each and every writepage invocation because it may
                         * be mmapped.  "A file is mapped in multiples of the
                         * page size.  For a file that is not a multiple of
                         * the  page size, the remaining memory is zeroed when
                         * mapped, and writes to that region are not written
                         * out to the file."
                         */
                        zero_user_segment(page, block_start, block_end);
                        clear_buffer_dirty(bh);
                        set_buffer_uptodate(bh);
                        continue;
                }
                clear_buffer_dirty(bh);
                ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
                if (ret) {
                        /*
                         * We only get here on ENOMEM.  Not much else
                         * we can do but mark the page as dirty, and
                         * better luck next time.
                         */
                        set_page_dirty(page);
                        break;
                }
        }
        unlock_page(page);
        /*
         * If the page was truncated before we could do the writeback,
         * or we had a memory allocation error while trying to write
         * the first buffer head, we won't have submitted any pages for
         * I/O.  In that case we need to make sure we've cleared the
         * PageWriteback bit from the page to prevent the system from
         * wedging later on.
         */
        put_io_page(io_page);
        return ret;
}