linux-kernel - Re: [PATCH v3 5/7] fs: remove no

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Date:   Thu, 30 Jun 2022 09:45:04 +0300
From:   Nikolay Borisov <n.borisov.lkml@...il.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk
Subject: Re: [PATCH v3 5/7] fs: remove no_llseek



On 29.06.22 г. 16:07 ч., Jason A. Donenfeld wrote:
> Now that all callers of ->llseek are going through vfs_llseek(), we
> don't gain anything by keeping no_llseek around. Nothing compares it or
> calls it.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
>   fs/read_write.c    | 17 +++--------------
>   include/linux/fs.h |  1 -
>   2 files changed, 3 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/read_write.c b/fs/read_write.c
> index b1b1cdfee9d3..69cd8d72d91e 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -227,12 +227,6 @@ loff_t noop_llseek(struct file *file, loff_t offset, int whence)
>   }
>   EXPORT_SYMBOL(noop_llseek);
>   
> -loff_t no_llseek(struct file *file, loff_t offset, int whence)
> -{
> -	return -ESPIPE;
> -}
> -EXPORT_SYMBOL(no_llseek);
> -
>   loff_t default_llseek(struct file *file, loff_t offset, int whence)
>   {
>   	struct inode *inode = file_inode(file);
> @@ -290,14 +284,9 @@ EXPORT_SYMBOL(default_llseek);
>   
>   loff_t vfs_llseek(struct file *file, loff_t offset, int whence)
>   {
> -	loff_t (*fn)(struct file *, loff_t, int);
> -
> -	fn = no_llseek;
> -	if (file->f_mode & FMODE_LSEEK) {
> -		if (file->f_op->llseek)
> -			fn = file->f_op->llseek;
> -	}
> -	return fn(file, offset, whence);
> +	if (!(file->f_mode & FMODE_LSEEK) || !file->f_op->llseek)

Is it not sufficient here to just check for the presence of FMODE_LSEEK? 
NULL  llseek shall result in FMODE_LSEEK not being set when the file is 
opened?

> +		return -ESPIPE;
> +	return file->f_op->llseek(file, offset, whence);
>   }
>   EXPORT_SYMBOL(vfs_llseek);
>   
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9ad5e3520fae..0cb5a1706e1f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3022,7 +3022,6 @@ extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
>   extern void
>   file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
>   extern loff_t noop_llseek(struct file *file, loff_t offset, int whence);
> -extern loff_t no_llseek(struct file *file, loff_t offset, int whence);
>   extern loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize);
>   extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
>   extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,