From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Joe Perches <joe@perches.com>, Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] mm: shmem: Convert shmem_enabled_show to use sysfs_emit_at
Date: Mon, 2 Nov 2020 14:33:43 +0100 [thread overview]
Message-ID: <20201102133343.GA1011963@kroah.com> (raw)
In-Reply-To: <20201101220604.GI27442@casper.infradead.org>
On Sun, Nov 01, 2020 at 10:06:04PM +0000, Matthew Wilcox wrote:
> On Sun, Nov 01, 2020 at 01:43:13PM -0800, Joe Perches wrote:
> > > Why did you change this?
> >
> > Are you asking about the function argument alignment or the commit message?
>
> The indentation. Don't change the fucking indentation, Joe.
>
> > > Look, this isn't performance sensitive code. Just do something simple.
> > >
> > > if (shmem_huge == values[i])
> > > buf += sysfs_emit(buf, "[%s]",
> > > shmem_format_huge(values[i]));
> > > else
> > > buf += sysfs_emit(buf, "%s",
> > > shmem_format_huge(values[i]));
> > > if (i == ARRAY_SIZE(values) - 1)
> > > buf += sysfs_emit(buf, "\n");
> > > else
> > > buf += sysfs_emit(buf, " ");
> > >
> > > Shame there's no sysfs_emitc, but there you go.
> >
> > I think what's there is simple.
>
> Again, you're wrong.
>
> > And your suggested code doesn't work.
> > sysfs_emit is used for single emits.
> > sysfs_emit_at is used for multiple emits.
>
> Oh, ugh, sysfs_emit() should be able to work on a buffer that isn't
> page aligned. Greg, how about this?
How can sysfs_emit() be called on a non-page-aligned buffer? It's being
used on the buffer that was passed to the sysfs call.
And if you are writing multiple values to a single sysfs file output,
well, not good...
>
> +++ 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);
>
> - if (WARN(!buf || offset_in_page(buf),
> - "invalid sysfs_emit: buf:%p\n", buf))
> + if (WARN(!buf, "invalid sysfs_emit: buf:%p\n", buf))
> return 0;
>
> va_start(args, fmt);
> - len = vscnprintf(buf, PAGE_SIZE, fmt, args);
> + len = vscnprintf(buf, PAGE_SIZE - start, fmt, args);
That's a bit too 'tricky' for my taste, why is it somehow needed?
thanks,
greg k-h
next prev parent reply other threads:[~2020-11-02 13:32 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-01 20:12 [PATCH 0/5] mm: Convert sysfs sprintf family to sysfs_emit Joe Perches
2020-11-01 20:12 ` [PATCH 1/5] mm: Use sysfs_emit for struct kobject * uses Joe Perches
2020-11-01 20:12 ` [PATCH 2/5] mm: huge_memory: Convert remaining use of sprintf to sysfs_emit and neatening Joe Perches
2020-11-01 20:12 ` [PATCH 3/5] mm:backing-dev: Use sysfs_emit in macro defining functions Joe Perches
2020-11-01 20:12 ` [PATCH 4/5] mm: shmem: Convert shmem_enabled_show to use sysfs_emit_at Joe Perches
2020-11-01 20:48 ` Matthew Wilcox
2020-11-01 21:04 ` Joe Perches
2020-11-01 21:19 ` Matthew Wilcox
2020-11-01 21:43 ` Joe Perches
2020-11-01 22:06 ` Matthew Wilcox
2020-11-01 22:08 ` Joe Perches
2020-11-01 22:13 ` Joe Perches
2020-11-01 22:14 ` Joe Perches
2020-11-02 13:33 ` Greg Kroah-Hartman [this message]
2020-11-02 14:08 ` Matthew Wilcox
2020-11-02 14:32 ` Greg Kroah-Hartman
2020-11-02 14:40 ` Matthew Wilcox
2020-11-02 17:01 ` Joe Perches
2020-11-01 20:12 ` [PATCH 5/5] mm: slub: Convert sysfs sprintf family to sysfs_emit/sysfs_emit_at Joe Perches
2020-11-13 12:10 ` [mm] b6efe2fcc4: BUG:kernel_NULL_pointer_dereference,address kernel test robot
2020-11-13 16:13 ` Joe Perches
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