linux-ext4 - Re: [PATCHv4 5/8] iomap: simplify direct io validity check

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Message-ID: <aP-c5gPjrpsn0vJA@google.com>
Date: Mon, 27 Oct 2025 16:25:10 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Keith Busch <kbusch@...a.com>
Cc: linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org, hch@....de,
	axboe@...nel.dk, Keith Busch <kbusch@...nel.org>,
	Hannes Reinecke <hare@...e.de>,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCHv4 5/8] iomap: simplify direct io validity check

On Wed, Aug 27, 2025 at 07:12:55AM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@...nel.org>
> 
> The block layer checks all the segments for validity later, so no need
> for an early check. Just reduce it to a simple position and total length
> check, and defer the more invasive segment checks to the block layer.
> 
> Signed-off-by: Keith Busch <kbusch@...nel.org>
> Reviewed-by: Hannes Reinecke <hare@...e.de>
> Reviewed-by: Martin K. Petersen <martin.petersen@...cle.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> ---
>  fs/iomap/direct-io.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index fea23fa6a402f..c06e41fd4d0af 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -337,8 +337,7 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
>  	u64 copied = 0;
>  	size_t orig_count;
>  
> -	if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1) ||
> -	    !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter))
> +	if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1))
>  		return -EINVAL;
>  
>  	if (dio->flags & IOMAP_DIO_WRITE) {
> -- 
> 2.47.3
> 

Hey Keith, I'be bisected an LTP issue down to this patch. There is a
O_DIRECT read test that expects EINVAL for a bad buffer alignment.
However, if I understand the patchset correctly, this is intentional
move which makes this LTP test obsolete, correct?

The broken test is "test 5" here:
https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/read/read02.c

... and this is what I get now:
  read02.c:87: TFAIL: read() failed unexpectedly, expected EINVAL: EIO (5)

Cheers,
Carlos Llamas