From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>,
Greg KH <gregkh@linuxfoundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/6] seq_file: add seq_read_iter
Date: Wed, 11 Nov 2020 22:21:16 +0000 [thread overview]
Message-ID: <20201111222116.GA919131@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20201111215220.GA3576660@ZenIV.linux.org.uk>
On Wed, Nov 11, 2020 at 09:52:20PM +0000, Al Viro wrote:
> That can be done, but I would rather go with
> n = copy_to_iter(m->buf + m->from, m->count, iter);
> m->count -= n;
> m->from += n;
> copied += n;
> if (!size)
> goto Done;
> if (m->count)
> goto Efault;
> if we do it that way. Let me see if I can cook something
> reasonable along those lines...
Something like below (build-tested only):
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 3b20e21604e7..07b33c1f34a9 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -168,7 +168,6 @@ EXPORT_SYMBOL(seq_read);
ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct seq_file *m = iocb->ki_filp->private_data;
- size_t size = iov_iter_count(iter);
size_t copied = 0;
size_t n;
void *p;
@@ -208,14 +207,11 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
}
/* if not empty - flush it first */
if (m->count) {
- n = min(m->count, size);
- if (copy_to_iter(m->buf + m->from, n, iter) != n)
- goto Efault;
+ n = copy_to_iter(m->buf + m->from, m->count, iter);
m->count -= n;
m->from += n;
- size -= n;
copied += n;
- if (!size)
+ if (!iov_iter_count(iter) || m->count)
goto Done;
}
/* we need at least one record in buffer */
@@ -249,6 +245,7 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
goto Done;
Fill:
/* they want more? let's try to get some more */
+ /* m->count is positive and there's space left in iter */
while (1) {
size_t offs = m->count;
loff_t pos = m->index;
@@ -263,7 +260,7 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
err = PTR_ERR(p);
break;
}
- if (m->count >= size)
+ if (m->count >= iov_iter_count(iter))
break;
err = m->op->show(m, p);
if (seq_has_overflowed(m) || err) {
@@ -273,16 +270,14 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
}
}
m->op->stop(m, p);
- n = min(m->count, size);
- if (copy_to_iter(m->buf, n, iter) != n)
- goto Efault;
+ n = copy_to_iter(m->buf, m->count, iter);
copied += n;
m->count -= n;
m->from = n;
Done:
- if (!copied)
- copied = err;
- else {
+ if (unlikely(!copied)) {
+ copied = m->count ? -EFAULT : err;
+ } else {
iocb->ki_pos += copied;
m->read_pos += copied;
}
@@ -291,9 +286,6 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
Enomem:
err = -ENOMEM;
goto Done;
-Efault:
- err = -EFAULT;
- goto Done;
}
EXPORT_SYMBOL(seq_read_iter);
next prev parent reply other threads:[~2020-11-11 22:21 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 8:27 support splice reads on seq_file based procfs files v2 Christoph Hellwig
2020-11-04 8:27 ` [PATCH 1/6] seq_file: add seq_read_iter Christoph Hellwig
2020-11-10 21:32 ` Al Viro
2020-11-10 21:35 ` Al Viro
2020-11-10 23:20 ` Al Viro
2020-11-11 7:55 ` Christoph Hellwig
2020-11-11 17:54 ` Linus Torvalds
2020-11-11 21:52 ` Al Viro
2020-11-11 22:21 ` Al Viro [this message]
2020-11-11 22:27 ` Linus Torvalds
2020-11-11 23:00 ` Al Viro
2020-11-13 23:54 ` Nathan Chancellor
2020-11-14 1:17 ` Al Viro
2020-11-14 3:01 ` Nathan Chancellor
2020-11-14 3:54 ` Al Viro
2020-11-14 4:14 ` Nathan Chancellor
2020-11-14 5:50 ` Al Viro
2020-11-14 6:19 ` Nathan Chancellor
2020-11-14 7:00 ` Al Viro
2020-11-14 20:50 ` Al Viro
2020-11-15 15:53 ` Al Viro
2020-11-15 16:56 ` Linus Torvalds
2020-11-15 21:41 ` Nathan Chancellor
2020-11-15 23:38 ` Al Viro
2020-11-15 23:51 ` Nathan Chancellor
2020-11-16 0:25 ` Al Viro
2020-11-16 0:34 ` Nathan Chancellor
2020-11-16 3:29 ` Al Viro
2020-11-27 16:29 ` Christoph Hellwig
2020-12-08 16:35 ` Christoph Hellwig
2020-12-08 18:34 ` Linus Torvalds
2020-12-08 19:49 ` Al Viro
2020-12-08 20:25 ` Linus Torvalds
2020-12-08 20:53 ` Al Viro
2020-12-08 21:01 ` Linus Torvalds
2020-12-08 19:49 ` Greg KH
2020-11-14 21:44 ` Al Viro
2020-11-04 8:27 ` [PATCH 2/6] proc: wire up generic_file_splice_read for iter ops Christoph Hellwig
2020-11-04 8:27 ` [PATCH 3/6] proc/cpuinfo: switch to ->read_iter Christoph Hellwig
2020-11-04 8:27 ` [PATCH 4/6] proc/stat: " Christoph Hellwig
2020-11-04 8:27 ` [PATCH 5/6] proc "single files": " Christoph Hellwig
2020-11-04 8:27 ` [PATCH 6/6] proc "seq " Christoph Hellwig
2020-11-04 17:53 ` support splice reads on seq_file based procfs files v2 Linus Torvalds
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