If kernfs file is empty on a first read, successive read operations
using the same file descriptor will return no data, even when data is
available. Default kernfs 'seq_next' implementation advances iterator
position even when next object is not there. Kernfs 'seq_start' for
following requests will not return iterator as position is already on
the second object.
Don't set read position if valid iterator has not been returned.
Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@xxxxxxxxx>
---
fs/seq_file.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 19f532e..893db43 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -242,7 +242,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
m->count = 0;
if (unlikely(!m->count)) {
p = m->op->next(m, p, &pos);
- m->index = pos;
+ if (p && !IS_ERR(p))
+ m->index = pos;
continue;
}
if (m->count < m->size)
--
1.8.3.1
--
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