Re: [PATCH 16/16] btrfs: btree_writepages lock extents before pages

[Josef Bacik <josef@toxicpanda.com>]

On Tue, Nov 15, 2022 at 12:00:34PM -0600, Goldwyn Rodrigues wrote:
> Lock extents before pages while performing btree_writepages().
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  fs/btrfs/disk-io.c | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 8ac9612f8f27..b7e7c4c9d404 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -858,8 +858,25 @@ static int btree_migrate_folio(struct address_space *mapping,
>  static int btree_writepages(struct address_space *mapping,
>  			    struct writeback_control *wbc)
>  {
> +	u64 start, end;
> +	struct btrfs_inode *inode = BTRFS_I(mapping->host);
> +        struct extent_state *cached = NULL;
>  	struct btrfs_fs_info *fs_info;
>  	int ret;
> +	u64 isize = round_up(i_size_read(&inode->vfs_inode), PAGE_SIZE) - 1;
> +
> +	if (wbc->range_cyclic) {
> +		start = mapping->writeback_index << PAGE_SHIFT;
> +		end = isize;
> +	} else {
> +		start = round_down(wbc->range_start, PAGE_SIZE);
> +		end = round_up(wbc->range_end, PAGE_SIZE) - 1;
> +		end = min(isize, end);
> +	}

Same comment here as the extent_writepages case, we need to handle the
possibility of ->writeback_index changing between now and
btree_write_cache_pages.  Thanks,

Josef