/*
 * 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/aio.h>
#include <linux/uio.h>
#include <linux/bio.h>
#include <linux/workqueue.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/ratelimit.h>

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

static struct kmem_cache *io_end_cachep;

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

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

/*
 * 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_ratelimited(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_finish_bio(struct bio *bio)
{
        int i;
        int error = !test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct bio_vec *bvec;

        bio_for_each_segment_all(bvec, bio, i) {
                struct page *page = bvec->bv_page;
                struct buffer_head *bh, *head;
                unsigned bio_start = bvec->bv_offset;
                unsigned bio_end = bio_start + bvec->bv_len;
                unsigned under_io = 0;
                unsigned long flags;

                if (!page)
                        continue;

                if (error) {
                        SetPageError(page);
                        set_bit(AS_EIO, &page->mapping->flags);
                }
                bh = head = page_buffers(page);
                /*
                 * We check all buffers in the page under BH_Uptodate_Lock
                 * to avoid races with other end io clearing async_write flags
                 */
                local_irq_save(flags);
                bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
                do {
                        if (bh_offset(bh) < bio_start ||
                            bh_offset(bh) + bh->b_size > bio_end) {
                                if (buffer_async_write(bh))
                                        under_io++;
                                continue;
                        }
                        clear_buffer_async_write(bh);
                        if (error)
                                buffer_io_error(bh);
                } while ((bh = bh->b_this_page) != head);
                bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
                local_irq_restore(flags);
                if (!under_io)
                        end_page_writeback(page);
        }
}

static void ext4_release_io_end(ext4_io_end_t *io_end)
{
        struct bio *bio, *next_bio;

        BUG_ON(!list_empty(&io_end->list));
        BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
        WARN_ON(io_end->handle);

        if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
                wake_up_all(ext4_ioend_wq(io_end->inode));

        for (bio = io_end->bio; bio; bio = next_bio) {
                next_bio = bio->bi_private;
                ext4_finish_bio(bio);
                bio_put(bio);
        }
        kmem_cache_free(io_end_cachep, io_end);
}

static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
{
        struct inode *inode = io_end->inode;

        io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
        /* Wake up anyone waiting on unwritten extent conversion */
        if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
                wake_up_all(ext4_ioend_wq(inode));
}

/*
 * Check a range of space and convert unwritten extents to written. Note that
 * we are protected from truncate touching same part of extent tree by the
 * fact that truncate code waits for all DIO to finish (thus exclusion from
 * direct IO is achieved) and also waits for PageWriteback bits. Thus we
 * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
 * completed (happens from ext4_free_ioend()).
 */
static int ext4_end_io(ext4_io_end_t *io)
{
        struct inode *inode = io->inode;
        loff_t offset = io->offset;
        ssize_t size = io->size;
        handle_t *handle = io->handle;
        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);

        io->handle = NULL;      /* Following call will use up the handle */
        ret = ext4_convert_unwritten_extents(handle, 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);
        }
        ext4_clear_io_unwritten_flag(io);
        ext4_release_io_end(io);
        return ret;
}

static void dump_completed_IO(struct inode *inode, struct list_head *head)
{
#ifdef  EXT4FS_DEBUG
        struct list_head *cur, *before, *after;
        ext4_io_end_t *io, *io0, *io1;

        if (list_empty(head))
                return;

        ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
        list_for_each_entry(io, head, list) {
                cur = &io->list;
                before = cur->prev;
                io0 = container_of(before, ext4_io_end_t, list);
                after = cur->next;
                io1 = container_of(after, ext4_io_end_t, list);

                ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
                            io, inode->i_ino, io0, io1);
        }
#endif
}

/* Add the io_end to per-inode completed end_io list. */
static void ext4_add_complete_io(ext4_io_end_t *io_end)
{
        struct ext4_inode_info *ei = EXT4_I(io_end->inode);
        struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);
        struct workqueue_struct *wq;
        unsigned long flags;

        /* Only reserved conversions from writeback should enter here */
        WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
        WARN_ON(!io_end->handle && sbi->s_journal);
        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
        wq = sbi->rsv_conversion_wq;
        if (list_empty(&ei->i_rsv_conversion_list))
                queue_work(wq, &ei->i_rsv_conversion_work);
        list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
}

static int ext4_do_flush_completed_IO(struct inode *inode,
                                      struct list_head *head)
{
        ext4_io_end_t *io;
        struct list_head unwritten;
        unsigned long flags;
        struct ext4_inode_info *ei = EXT4_I(inode);
        int err, ret = 0;

        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
        dump_completed_IO(inode, head);
        list_replace_init(head, &unwritten);
        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

        while (!list_empty(&unwritten)) {
                io = list_entry(unwritten.next, ext4_io_end_t, list);
                BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
                list_del_init(&io->list);

                err = ext4_end_io(io);
                if (unlikely(!ret && err))
                        ret = err;
        }
        return ret;
}

/*
 * work on completed IO, to convert unwritten extents to extents
 */
void ext4_end_io_rsv_work(struct work_struct *work)
{
        struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
                                                  i_rsv_conversion_work);
        ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
}

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_LIST_HEAD(&io->list);
                atomic_set(&io->count, 1);
        }
        return io;
}

void ext4_put_io_end_defer(ext4_io_end_t *io_end)
{
        if (atomic_dec_and_test(&io_end->count)) {
                if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
                        ext4_release_io_end(io_end);
                        return;
                }
                ext4_add_complete_io(io_end);
        }
}

int ext4_put_io_end(ext4_io_end_t *io_end)
{
        int err = 0;

        if (atomic_dec_and_test(&io_end->count)) {
                if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
                        err = ext4_convert_unwritten_extents(io_end->handle,
                                                io_end->inode, io_end->offset,
                                                io_end->size);
                        io_end->handle = NULL;
                        ext4_clear_io_unwritten_flag(io_end);
                }
                ext4_release_io_end(io_end);
        }
        return err;
}

ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
{
        atomic_inc(&io_end->count);
        return io_end;
}

/* BIO completion function for page writeback */
static void ext4_end_bio(struct bio *bio, int error)
{
        ext4_io_end_t *io_end = bio->bi_private;
        sector_t bi_sector = bio->bi_iter.bi_sector;

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

        if (error) {
                struct inode *inode = io_end->inode;

                ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
                             "(offset %llu size %ld starting block %llu)",
                             error, inode->i_ino,
                             (unsigned long long) io_end->offset,
                             (long) io_end->size,
                             (unsigned long long)
                             bi_sector >> (inode->i_blkbits - 9));
                mapping_set_error(inode->i_mapping, error);
        }

        if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
                /*
                 * Link bio into list hanging from io_end. We have to do it
                 * atomically as bio completions can be racing against each
                 * other.
                 */
                bio->bi_private = xchg(&io_end->bio, bio);
                ext4_put_io_end_defer(io_end);
        } else {
                /*
                 * Drop io_end reference early. Inode can get freed once
                 * we finish the bio.
                 */
                ext4_put_io_end_defer(io_end);
                ext4_finish_bio(bio);
                bio_put(bio);
        }
}

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;
}

void ext4_io_submit_init(struct ext4_io_submit *io,
                         struct writeback_control *wbc)
{
        io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
        io->io_bio = NULL;
        io->io_end = NULL;
}

static int io_submit_init_bio(struct ext4_io_submit *io,
                              struct buffer_head *bh)
{
        int nvecs = bio_get_nr_vecs(bh->b_bdev);
        struct bio *bio;

        bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
        if (!bio)
                return -ENOMEM;
        bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
        bio->bi_bdev = bh->b_bdev;
        bio->bi_end_io = ext4_end_bio;
        bio->bi_private = ext4_get_io_end(io->io_end);
        io->io_bio = bio;
        io->io_next_block = bh->b_blocknr;
        return 0;
}

static int io_submit_add_bh(struct ext4_io_submit *io,
                            struct inode *inode,
                            struct buffer_head *bh)
{
        int ret;

        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_bio(io, bh);
                if (ret)
                        return ret;
        }
        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;
        io->io_next_block++;
        return 0;
}

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

        blocksize = 1 << inode->i_blkbits;

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

        if (keep_towrite)
                set_page_writeback_keepwrite(page);
        else
                set_page_writeback(page);
        ClearPageError(page);

        /*
         * Comments copied from block_write_full_page:
         *
         * 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."
         */
        if (len < PAGE_CACHE_SIZE)
                zero_user_segment(page, len, PAGE_CACHE_SIZE);
        /*
         * In the first loop we prepare and mark buffers to submit. We have to
         * mark all buffers in the page before submitting so that
         * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
         * on the first buffer finishes and we are still working on submitting
         * the second buffer.
         */
        bh = head = page_buffers(page);
        do {
                block_start = bh_offset(bh);
                if (block_start >= len) {
                        clear_buffer_dirty(bh);
                        set_buffer_uptodate(bh);
                        continue;
                }
                if (!buffer_dirty(bh) || buffer_delay(bh) ||
                    !buffer_mapped(bh) || buffer_unwritten(bh)) {
                        /* A hole? We can safely clear the dirty bit */
                        if (!buffer_mapped(bh))
                                clear_buffer_dirty(bh);
                        if (io->io_bio)
                                ext4_io_submit(io);
                        continue;
                }
                if (buffer_new(bh)) {
                        clear_buffer_new(bh);
                        unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
                }
                set_buffer_async_write(bh);
        } while ((bh = bh->b_this_page) != head);

        /* Now submit buffers to write */
        bh = head = page_buffers(page);
        do {
                if (!buffer_async_write(bh))
                        continue;
                ret = io_submit_add_bh(io, inode, 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.
                         */
                        redirty_page_for_writepage(wbc, page);
                        break;
                }
                nr_submitted++;
                clear_buffer_dirty(bh);
        } while ((bh = bh->b_this_page) != head);

        /* Error stopped previous loop? Clean up buffers... */
        if (ret) {
                do {
                        clear_buffer_async_write(bh);
                        bh = bh->b_this_page;
                } while (bh != head);
        }
        unlock_page(page);
        /* Nothing submitted - we have to end page writeback */
        if (!nr_submitted)
                end_page_writeback(page);
        return ret;
}