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Commit 4cdfe84b authored by Al Viro's avatar Al Viro
Browse files

[PATCH] deal with the first call of ->show() generating no output 



seq_read() has a subtle bug - we want the first loop there to go
until at least one *non-empty* record had fit entirely into buffer.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 59af1584

fs/seq_file.c

+9 −2
Original line number Diff line number Diff line
@@ -108,9 +108,9 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) 
			goto Done;

	}

	/* we need at least one record in buffer */

	while (1) {

	pos = m->index;

	p = m->op->start(m, &pos);

	while (1) {

		err = PTR_ERR(p);

		if (!p || IS_ERR(p))

			break;
@@ -119,6 +119,11 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) 
			break;

		if (unlikely(err))

			m->count = 0;

		if (unlikely(!m->count)) {

			p = m->op->next(m, p, &pos);

			m->index = pos;

			continue;

		}

		if (m->count < m->size)

			goto Fill;

		m->op->stop(m, p);
@@ -128,6 +133,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) 
			goto Enomem;

		m->count = 0;

		m->version = 0;

		pos = m->index;

		p = m->op->start(m, &pos);

	}

	m->op->stop(m, p);

	m->count = 0;