From: Matthew Wilcox <willy@infradead.org>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrii Nakryiko <andrii@kernel.org>,
Shaurya Rane <ssrane_b23@ee.vjti.ac.in>,
"Darrick J . Wong" <djwong@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Meta kernel team <kernel-team@meta.com>,
bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH bpf v2] lib/buildid: use __kernel_read() for sleepable context
Date: Fri, 19 Dec 2025 04:07:51 +0000 [thread overview]
Message-ID: <aUTPl35UPcjc66l3@casper.infradead.org> (raw)
In-Reply-To: <3lf3ed3xn2oaenvlqjmypuewtm6gakzbecc7kgqsadggyvdtkr@uyw4boj6igqu>
On Thu, Dec 18, 2025 at 04:16:40PM -0800, Shakeel Butt wrote:
> On Thu, Dec 18, 2025 at 11:55:39PM +0000, Matthew Wilcox wrote:
> > On Thu, Dec 18, 2025 at 12:55:05PM -0800, Shakeel Butt wrote:
> > > + do {
> > > + ret = __kernel_read(r->file, buf, sz, &pos);
> > > + if (ret <= 0) {
> > > + r->err = ret ?: -EIO;
> > > + return NULL;
> > > + }
> > > + buf += ret;
> > > + sz -= ret;
> > > + } while (sz > 0);
> >
> > Why are you doing a loop around __kernel_read()? eg kernel_read() does
> > not do a read around __kernel_read(). The callers of kernel_read()
> > don't do a loop either. So what makes you think it needs to have a loop
> > around it?
>
> I am assuming that __kernel_read() can return less data than the
> requested. Is that assumption incorrect?
I think it can, but I don't think a second call will get any more data.
For example, it could hit EOF. What led you to think that calling it in
a loop was the right approach?
next prev parent reply other threads:[~2025-12-19 4:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-18 20:55 Shakeel Butt
2025-12-18 21:21 ` Andrew Morton
2025-12-18 23:55 ` Matthew Wilcox
2025-12-19 0:16 ` Shakeel Butt
2025-12-19 4:07 ` Matthew Wilcox [this message]
2025-12-19 5:58 ` Shakeel Butt
2025-12-19 17:42 ` Andrii Nakryiko
2025-12-22 5:33 ` Matthew Wilcox
2025-12-22 5:31 ` Matthew Wilcox
2025-12-22 19:41 ` Shakeel Butt
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