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

[sashiko-bot@kernel.org]

> From: Zhang Yi <yi.zhang@huawei.com>
> 
> 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@huawei.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261026115131.1735014-1-yi.zhang@huaweicloud.com?part=4