Re: [PATCH v4 15/23] ext4: add block mapping tracepoints for iomap buffered I/O path
From: Ojaswin Mujoo
Date: Wed May 27 2026 - 09:15:22 EST
On Mon, May 11, 2026 at 03:23:35PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
>
> Add tracepoints for iomap buffered read, write, partial block zeroing,
> and writeback operations to help debug the iomap buffered I/O path.
>
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Looks good, feel free to add:
Reviewed-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
Regards,
Ojaswin
> ---
> fs/ext4/inode.c | 6 +++++
> include/trace/events/ext4.h | 45 +++++++++++++++++++++++++++++++++++++
> 2 files changed, 51 insertions(+)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index e0dae2501292..239d387ffaf2 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3961,6 +3961,8 @@ static int ext4_iomap_buffered_read_begin(struct inode *inode, loff_t offset,
> if (ret < 0)
> return ret;
>
> + trace_ext4_iomap_buffered_read_begin(inode, &map, offset, length,
> + flags);
> ext4_set_iomap(inode, iomap, &map, offset, length, flags);
> return 0;
> }
> @@ -4034,6 +4036,8 @@ static int ext4_iomap_buffered_do_write_begin(struct inode *inode,
> if (ret < 0)
> return ret;
>
> + trace_ext4_iomap_buffered_write_begin(inode, &map, offset, length,
> + flags);
> ext4_set_iomap(inode, iomap, &map, offset, length, flags);
> return 0;
> }
> @@ -4136,6 +4140,7 @@ static int ext4_iomap_zero_begin(struct inode *inode,
> map.m_len = (start >> blkbits) - map.m_lblk;
> }
>
> + trace_ext4_iomap_zero_begin(inode, &map, offset, length, flags);
> ext4_set_iomap(inode, iomap, &map, offset, length, flags);
> iomap->flags |= iomap_flags;
>
> @@ -4308,6 +4313,7 @@ static int ext4_iomap_map_writeback_range(struct iomap_writepage_ctx *wpc,
> return ret;
> }
> out:
> + trace_ext4_iomap_map_writeback_range(inode, &map, offset, dirty_len, 0);
> ext4_set_iomap(inode, &wpc->iomap, &map, offset, dirty_len, 0);
> return 0;
> }
> diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
> index f493642cf121..ebafa06cd191 100644
> --- a/include/trace/events/ext4.h
> +++ b/include/trace/events/ext4.h
> @@ -3096,6 +3096,51 @@ TRACE_EVENT(ext4_move_extent_exit,
> __entry->ret)
> );
>
> +DECLARE_EVENT_CLASS(ext4_set_iomap_class,
> + TP_PROTO(struct inode *inode, struct ext4_map_blocks *map,
> + loff_t offset, loff_t length, unsigned int flags),
> + TP_ARGS(inode, map, offset, length, flags),
> + TP_STRUCT__entry(
> + __field(dev_t, dev)
> + __field(u64, ino)
> + __field(ext4_lblk_t, m_lblk)
> + __field(unsigned int, m_len)
> + __field(unsigned int, m_flags)
> + __field(u64, m_seq)
> + __field(loff_t, offset)
> + __field(loff_t, length)
> + __field(unsigned int, iomap_flags)
> + ),
> + TP_fast_assign(
> + __entry->dev = inode->i_sb->s_dev;
> + __entry->ino = inode->i_ino;
> + __entry->m_lblk = map->m_lblk;
> + __entry->m_len = map->m_len;
> + __entry->m_flags = map->m_flags;
> + __entry->m_seq = map->m_seq;
> + __entry->offset = offset;
> + __entry->length = length;
> + __entry->iomap_flags = flags;
> +
> + ),
> + TP_printk("dev %d:%d ino %llu m_lblk %u m_len %u m_flags %s m_seq %llu orig_off 0x%llx orig_len 0x%llx iomap_flags 0x%x",
> + MAJOR(__entry->dev), MINOR(__entry->dev),
> + __entry->ino, __entry->m_lblk, __entry->m_len,
> + show_mflags(__entry->m_flags), __entry->m_seq,
> + __entry->offset, __entry->length, __entry->iomap_flags)
> +)
> +
> +#define DEFINE_SET_IOMAP_EVENT(name) \
> +DEFINE_EVENT(ext4_set_iomap_class, name, \
> + TP_PROTO(struct inode *inode, struct ext4_map_blocks *map, \
> + loff_t offset, loff_t length, unsigned int flags), \
> + TP_ARGS(inode, map, offset, length, flags))
> +
> +DEFINE_SET_IOMAP_EVENT(ext4_iomap_buffered_read_begin);
> +DEFINE_SET_IOMAP_EVENT(ext4_iomap_buffered_write_begin);
> +DEFINE_SET_IOMAP_EVENT(ext4_iomap_map_writeback_range);
> +DEFINE_SET_IOMAP_EVENT(ext4_iomap_zero_begin);
> +
> #endif /* _TRACE_EXT4_H */
>
> /* This part must be outside protection */
> --
> 2.52.0
>