Re: [PATCH 06/10] xfs: IOMAP_ZERO and IOMAP_UNSHARE already hold invalidate_lock

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Oct 08, 2024 at 10:59:17AM +0200, Christoph Hellwig wrote:
> All XFS callers of iomap_zero_range and iomap_file_unshare already hold
> invalidate_lock, so we can't take it again in
> iomap_file_buffered_write_punch_delalloc.
> 
> Use the passed in flags argument to detect if we're called from a zero
> or unshare operation and don't take the lock again in this case.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Thanks for fixing the bug I reported,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_iomap.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 4fa4d66dc37761..17170d9b9ff78a 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -1239,10 +1239,18 @@ xfs_buffered_write_iomap_end(
>  	if (start_byte >= end_byte)
>  		return 0;
>  
> -	filemap_invalidate_lock(inode->i_mapping);
> -	iomap_write_delalloc_release(inode, start_byte, end_byte, flags, iomap,
> -			xfs_buffered_write_delalloc_punch);
> -	filemap_invalidate_unlock(inode->i_mapping);
> +	/* For zeroing operations the callers already hold invalidate_lock. */
> +	if (flags & (IOMAP_UNSHARE | IOMAP_ZERO)) {
> +		rwsem_assert_held_write(&inode->i_mapping->invalidate_lock);
> +		iomap_write_delalloc_release(inode, start_byte, end_byte, flags,
> +				iomap, xfs_buffered_write_delalloc_punch);
> +	} else {
> +		filemap_invalidate_lock(inode->i_mapping);
> +		iomap_write_delalloc_release(inode, start_byte, end_byte, flags,
> +				iomap, xfs_buffered_write_delalloc_punch);
> +		filemap_invalidate_unlock(inode->i_mapping);
> +	}
> +
>  	return 0;
>  }
>  
> -- 
> 2.45.2
> 
>