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    Subject[PATCH 001 of 3] md: Change md/bitmap file handling to use bmap to file blocks-fix

    Fix problems with new bmap based access to bitmap files.

    1/ When not using a file based bitmap, attach a NULL list of buffers
    to each page so the common free_buffer routine can cope.
    2/ Use submit_bh to read as well as write, rather than vfs_read.
    This makes read and write more symetric.
    3/ sync the file before reading, to ensure that the page cache has no
    dirty pages that might get written out later.

    Signed-off-by: Neil Brown <neilb@suse.de>

    ### Diffstat output
    ./drivers/md/bitmap.c | 46 ++++++++++++++++++++++------------------------
    1 file changed, 22 insertions(+), 24 deletions(-)

    diff ./drivers/md/bitmap.c~current~ ./drivers/md/bitmap.c
    --- ./drivers/md/bitmap.c~current~ 2006-05-16 11:09:26.000000000 +1000
    +++ ./drivers/md/bitmap.c 2006-05-16 11:09:33.000000000 +1000
    @@ -247,6 +247,8 @@ static struct page *read_sb_page(mddev_t

    if (sync_page_io(rdev->bdev, target, PAGE_SIZE, page, READ)) {
    page->index = index;
    + attach_page_buffers(page, NULL); /* so that free_buffer will
    + * quietly no-op */
    return page;
    }
    }
    @@ -349,11 +351,8 @@ static struct page *read_page(struct fil
    {
    struct page *page = NULL;
    struct inode *inode = file->f_dentry->d_inode;
    - loff_t pos = index << PAGE_SHIFT;
    - int ret;
    struct buffer_head *bh;
    sector_t block;
    - mm_segment_t oldfs;

    PRINTK("read bitmap file (%dB @ %Lu)\n", (int)PAGE_SIZE,
    (unsigned long long)index << PAGE_SHIFT);
    @@ -364,18 +363,6 @@ static struct page *read_page(struct fil
    if (IS_ERR(page))
    goto out;

    - oldfs = get_fs();
    - set_fs(KERNEL_DS);
    - ret = vfs_read(file, (char __user*) page_address(page), count, &pos);
    - set_fs(oldfs);
    -
    - if (ret >= 0 && ret != count)
    - ret = -EIO;
    - if (ret < 0) {
    - put_page(page);
    - page = ERR_PTR(ret);
    - goto out;
    - }
    bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0);
    if (!bh) {
    put_page(page);
    @@ -403,12 +390,22 @@ static struct page *read_page(struct fil

    bh->b_end_io = end_bitmap_write;
    bh->b_private = bitmap;
    + atomic_inc(&bitmap->pending_writes);
    + set_buffer_locked(bh);
    + set_buffer_mapped(bh);
    + submit_bh(READ, bh);
    }
    block++;
    bh = bh->b_this_page;
    }
    -
    page->index = index;
    +
    + wait_event(bitmap->write_wait,
    + atomic_read(&bitmap->pending_writes)==0);
    + if (bitmap->flags & BITMAP_WRITE_ERROR) {
    + free_buffers(page);
    + page = ERR_PTR(-EIO);
    + }
    out:
    if (IS_ERR(page))
    printk(KERN_ALERT "md: bitmap read error: (%dB @ %Lu): %ld\n",
    @@ -1415,15 +1412,19 @@ int bitmap_create(mddev_t *mddev)
    return -ENOMEM;

    spin_lock_init(&bitmap->lock);
    + atomic_set(&bitmap->pending_writes, 0);
    + init_waitqueue_head(&bitmap->write_wait);
    +
    bitmap->mddev = mddev;

    bitmap->file = file;
    bitmap->offset = mddev->bitmap_offset;
    - if (file) get_file(file);
    -
    - /* Ensure we read fresh data */
    - invalidate_inode_pages(file->f_dentry->d_inode->i_mapping);
    -
    + if (file) {
    + get_file(file);
    + do_sync_file_range(file, 0, LLONG_MAX,
    + SYNC_FILE_RANGE_WRITE |
    + SYNC_FILE_RANGE_WAIT_AFTER);
    + }
    /* read superblock from bitmap file (this sets bitmap->chunksize) */
    err = bitmap_read_sb(bitmap);
    if (err)
    @@ -1446,9 +1447,6 @@ int bitmap_create(mddev_t *mddev)

    bitmap->syncchunk = ~0UL;

    - atomic_set(&bitmap->pending_writes, 0);
    - init_waitqueue_head(&bitmap->write_wait);
    -
    #ifdef INJECT_FATAL_FAULT_1
    bitmap->bp = NULL;
    #else
    -
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