> block_prepare_write() can dirty freshly created buffer. This is a problem
> for data=journal mode because data buffers shouldn't be dirty unless they
> are undergoing checkpoint. So we have to tweak get_block function for
> data=journal mode to catch the case when block_prepare_write would dirty
> the buffer, do the work instead of block_prepare_write, and properly handle
> dirty buffer as data=journal mode requires it.
>
> It might be cleaner to avoid using block_prepare_write() for data=journal
> mode writes but that would require us to duplicate most of the function
> which isn't nice either...
Ted, how about this patch? Do you agree with it? Thanks.
Honza
> CC: tytso@xxxxxxx
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/ext4/inode.c | 47 +++++++++++++++++++++++++++++++++++++++++++----
> 1 files changed, 43 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 81d6054..526404b 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1388,6 +1388,43 @@ out:
> return ret;
> }
>
> +static int ext4_journalled_get_block(struct inode *inode, sector_t iblock,
> + struct buffer_head *bh, int create)
> +{
> + handle_t *handle = ext4_journal_current_handle();
> + int ret;
> +
> + /* This function should ever be used only for real buffers */
> + BUG_ON(!bh->b_page);
> +
> + ret = ext4_get_blocks(handle, inode, iblock, 1, bh,
> + create ? EXT4_GET_BLOCKS_CREATE : 0);
> + if (ret > 0) {
> + if (buffer_new(bh)) {
> + struct page *page = bh->b_page;
> +
> + /*
> + * This is a terrible hack to avoid block_prepare_write
> + * marking our buffer as dirty
> + */
> + if (PageUptodate(page)) {
> + ret = ext4_journal_get_write_access(handle, bh);
> + if (ret < 0)
> + return ret;
> + unmap_underlying_metadata(bh->b_bdev,
> + bh->b_blocknr);
> + clear_buffer_new(bh);
> + set_buffer_uptodate(bh);
> + ret = jbd2_journal_dirty_metadata(handle, bh);
> + if (ret < 0)
> + return ret;
> + }
> + }
> + ret = 0;
> + }
> + return ret;
> +}
> +
> /*
> * `handle' can be NULL if create is zero
> */
> @@ -1599,12 +1636,14 @@ retry:
> if (ext4_should_dioread_nolock(inode))
> ret = block_write_begin(file, mapping, pos, len, flags, pagep,
> fsdata, ext4_get_block_write);
> - else
> + else if (!ext4_should_journal_data(inode))
> ret = block_write_begin(file, mapping, pos, len, flags, pagep,
> fsdata, ext4_get_block);
> -
> - if (!ret && ext4_should_journal_data(inode)) {
> - ret = walk_page_buffers(handle, page_buffers(page),
> + else {
> + ret = block_write_begin(file, mapping, pos, len, flags, pagep,
> + fsdata, ext4_journalled_get_block);
> + if (!ret)
> + ret = walk_page_buffers(handle, page_buffers(page),
> from, to, NULL, do_journal_get_write_access);
> }
>
> --
> 1.6.4.2
>
> --
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--
Jan Kara <jack@xxxxxxx>
SuSE CR Labs
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