Re: [PATCH v2 4/4] ext4: initialize map->m_pblk in ext4_da_map_blocks()

[Jan Kara]

On Fri 30-10-26 10:13:38, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
> 
> ext4_da_map_blocks() returns a delalloc mapping through @map without
> touching map->m_pblk at all. Callers that only set up m_lblk and m_len
> of their local struct ext4_map_blocks and leave the rest to the mapping
> helper, like ext4_iomap_map_blocks() does, end up with whatever happened
> to be on their stack, so the trace_ext4_iomap_buffered_write_begin()
> tracepoint prints an uninitialized pblk for a delalloc mapping.
> 
> This has been harmless so far, ext4_da_get_block_prep() and
> ext4_set_iomap() both ignore m_pblk for a delalloc mapping, only the new
> tracepoint dumps it.
> 
> Initialize m_pblk along with m_flags at the beginning of
> ext4_da_map_blocks(), so that a delalloc mapping is always reported with
> pblk 0, the same way ext4_map_blocks() reports it.
> 
> Fixes: 008f019ab559 ("ext4: add block mapping tracepoints for iomap buffered I/O path")
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  fs/ext4/inode.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 6b2f1b07f41e6..c1c46e86bba3e 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2041,6 +2041,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map)
>  #endif
>  
>  	map->m_flags = 0;
> +	map->m_pblk = 0;
>  	ext_debug(inode, "max_blocks %u, logical block %lu\n", map->m_len,
>  		  (unsigned long) map->m_lblk);
>  
> -- 
> 2.52.0
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR