page-io.c

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/*
 * 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);
    BUG_ON(!list_empty(&io->list));
    BUG_ON(io->flag & EXT4_IO_END_UNWRITTEN);

    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. */
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;
    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_unwritten))
        wake_up_all(ext4_ioend_wq(io->inode));
    return ret;
}

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

    if (list_empty(&EXT4_I(inode)->i_completed_io_list)) {
        ext4_debug("inode %lu completed_io list is empty\n",
               inode->i_ino);
        return;
    }

    ext4_debug("Dump inode %lu completed_io list\n", inode->i_ino);
    list_for_each_entry(io, &EXT4_I(inode)->i_completed_io_list, 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. */
void ext4_add_complete_io(ext4_io_end_t *io_end)
{
    struct ext4_inode_info *ei = EXT4_I(io_end->inode);
    struct workqueue_struct *wq;
    unsigned long flags;

    BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
    wq = EXT4_SB(io_end->inode->i_sb)->dio_unwritten_wq;

    spin_lock_irqsave(&ei->i_completed_io_lock, flags);
    if (list_empty(&ei->i_completed_io_list)) {
        io_end->flag |= EXT4_IO_END_QUEUED;
        queue_work(wq, &io_end->work);
    }
    list_add_tail(&io_end->list, &ei->i_completed_io_list);
    spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
}

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

    INIT_LIST_HEAD(&complete);
    INIT_LIST_HEAD(&to_free);

    spin_lock_irqsave(&ei->i_completed_io_lock, flags);
    dump_completed_IO(inode);
    list_replace_init(&ei->i_completed_io_list, &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;

        list_add_tail(&io->list, &complete);
    }
    spin_lock_irqsave(&ei->i_completed_io_lock, flags);
    while (!list_empty(&complete)) {
        io = list_entry(complete.next, ext4_io_end_t, list);
        io->flag &= ~EXT4_IO_END_UNWRITTEN;
        /* end_io context can not be destroyed now because it still
         * used by queued worker. Worker thread will destroy it later */
        if (io->flag & EXT4_IO_END_QUEUED)
            list_del_init(&io->list);
        else
            list_move(&io->list, &to_free);
    }
    /* If we are called from worker context, it is time to clear queued
     * flag, and destroy it's end_io if it was converted already */
    if (work_io) {
        work_io->flag &= ~EXT4_IO_END_QUEUED;
        if (!(work_io->flag & EXT4_IO_END_UNWRITTEN))
            list_add_tail(&work_io->list, &to_free);
    }
    spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

    while (!list_empty(&to_free)) {
        io = list_entry(to_free.next, ext4_io_end_t, list);
        list_del_init(&io->list);
        ext4_free_io_end(io);
    }
    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);
    ext4_do_flush_completed_IO(io->inode, io);
}

int ext4_flush_unwritten_io(struct inode *inode)
{
    int ret;
    WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex) &&
             !(inode->i_state & I_FREEING));
    ret = ext4_do_flush_completed_IO(inode, NULL);
    ext4_unwritten_wait(inode);
    return ret;
}

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 inode *inode;
    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;
    }

    ext4_add_complete_io(io_end);
}

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;
}