linux-kernel - Re: [PATCH v2] ext4: fix direct I/O read error

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Date:   Mon, 29 Jun 2020 08:26:27 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Jiang Ying <jiangying8582@....com>,
        Wang Long <wanglong19@...tuan.com>, linux-ext4@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v2] ext4: fix direct I/O read error

> Fixes: 9fe55eea7e4b ("Fix race when checking i_size on direct i/o read").

* I suggest to move this tag to the bottom of the commit message.

* This specification is usually preferred without a dot at the line end.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=9ebcfadb0610322ac537dd7aa5d9cbc2b2894c68#n183


> This commit caused ext4 direct I/O read error when the read size is not
> alignment with block size.

Wording alternative:
aligned …


> (1) Make the file that is not alignment with block size:

… a file … aligned …


> (3) Compiling the script:

(3) Compile the source file:


> (4) Exec the script:

(4) Run the test program:


> … Thanks.

I propose to omit this word here.


> ---
>  fs/ext4/inode.c | 6 ++++++

Would you like to add patch version descriptions here?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=9ebcfadb0610322ac537dd7aa5d9cbc2b2894c68#n751


…
> @@ -3821,6 +3821,12 @@ static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
>  	struct inode *inode = mapping->host;
>  	size_t count = iov_iter_count(iter);
>  	ssize_t ret;
> +	loff_t offset = iocb->ki_pos;
> +	loff_t size;
> +
> +	size = i_size_read(inode);

How do you think about to use the following source code variant?

+	loff_t size = i_size_read(inode);


> +	if (offset >= size)
> +		return 0;

Will any further fine-tuning matter for this function implementation?

Regards,
Markus