On Tue 09-04-13 11:14:20, Lukas Czerner wrote:
> This reverts commit ccb4d7af914e0fe9b2f1022f8ea6c300463fd5e6.
>
> This commit reintroduces functions ext4_block_truncate_page() and
> ext4_block_zero_page_range() which has been previously removed in favour
> of ext4_discard_partial_page_buffers().
>
> In future commits we want to reintroduce those function and remove
> ext4_discard_partial_page_buffers() since it is duplicating some code
> and also partially duplicating work of truncate_pagecache_range(),
> moreover the old implementation was much clearer.
>
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
When checking the functions, I've noticed one thing:
> + if (ext4_should_journal_data(inode)) {
> + BUFFER_TRACE(bh, "get write access");
> + err = ext4_journal_get_write_access(handle, bh);
> + if (err)
> + goto unlock;
> + }
> +
> + zero_user(page, offset, length);
> +
> + BUFFER_TRACE(bh, "zeroed end of block");
> +
> + err = 0;
> + if (ext4_should_journal_data(inode)) {
> + err = ext4_handle_dirty_metadata(handle, inode, bh);
> + } else
> + mark_buffer_dirty(bh);
I think we should call also ext4_jbd2_file_inode() in data=ordered mode.
Otherwise a crash after the truncate transaction has committed could still
result in the tail of the block not being zeroed on disk...
Honza
> +
> +unlock:
> + unlock_page(page);
> + page_cache_release(page);
> + return err;
> +}
> +
> int ext4_can_truncate(struct inode *inode)
> {
> if (S_ISREG(inode->i_mode))
> --
> 1.7.7.6
>
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--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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