linux-kernel - Re: [PATCH 4/5] mm: shmem: Convert shmem_enabled_show to use sysfs_emit

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Date:   Sun, 01 Nov 2020 14:13:52 -0800
From:   Joe Perches <joe@...ches.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] mm: shmem: Convert shmem_enabled_show to use
 sysfs_emit_at

On Sun, 2020-11-01 at 22:06 +0000, Matthew Wilcox wrote:
> Oh, ugh, sysfs_emit() should be able to work on a buffer that isn't
> page aligned.  Greg, how about this?
> 
> +++ b/fs/sysfs/file.c
> @@ -722,13 +722,13 @@ int sysfs_emit(char *buf, const char *fmt, ...)
>  {
>         va_list args;
>         int len;
> +       int start = offset_in_page(buf);

I thought of that originally and didn't want to implement it that
way as it allows sysfs_emit to be used on non-page aligned buffers.

Using two functions makes sure the buf is always page aligned and
so buf should never defectively be passed in unaligned.