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[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: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2008-08-24 07:45:33 -04:00
parent 59af1584bf
commit 4cdfe84b51
1 changed files with 9 additions and 2 deletions
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11
fs/seq_file.c
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@ -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 */
pos = m->index;
p = m->op->start(m, &pos);
while (1) {
pos = m->index;
p = m->op->start(m, &pos);
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;