[PATCH 1/2] seq_file: Add __seq_open_private_bufsize for seq file_operation sizes

From: Joe Perches
Date: Sat Aug 20 2016 - 04:00:30 EST


Specifying an initial output buffer size can reduce the
number of regenerations of the seq_<output> buffers when
the buffer overflows.

Add another version of __seq_open_private that takes an
initial buffer size.

Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
---
fs/seq_file.c | 31 +++++++++++++++++++++++++++++++
include/linux/seq_file.h | 3 +++
2 files changed, 34 insertions(+)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index b8ac757e..d98fa77 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -652,6 +652,37 @@ int seq_open_private(struct file *filp, const struct seq_operations *ops,
}
EXPORT_SYMBOL(seq_open_private);

+void *__seq_open_private_bufsize(struct file *f,
+ const struct seq_operations *ops,
+ int psize, size_t bufsize)
+{
+ int rc;
+ void *private;
+ struct seq_file *seq;
+
+ private = kzalloc(psize, GFP_KERNEL);
+ if (private == NULL)
+ goto out;
+
+ rc = seq_open(f, ops);
+ if (rc < 0)
+ goto out_free;
+
+ seq = f->private_data;
+ seq->private = private;
+
+ kfree(seq->buf);
+ seq->buf = seq_buf_alloc(seq->size = round_up(bufsize, PAGE_SIZE));
+
+ return private;
+
+out_free:
+ kfree(private);
+out:
+ return NULL;
+}
+EXPORT_SYMBOL(__seq_open_private_bufsize);
+
void seq_putc(struct seq_file *m, char c)
{
if (m->count >= m->size)
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index e305b66..719f1b8 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -136,6 +136,9 @@ int single_open(struct file *, int (*)(struct seq_file *, void *), void *);
int single_open_size(struct file *, int (*)(struct seq_file *, void *), void *, size_t);
int single_release(struct inode *, struct file *);
void *__seq_open_private(struct file *, const struct seq_operations *, int);
+void *__seq_open_private_bufsize(struct file *f,
+ const struct seq_operations *ops,
+ int psize, size_t bufsize);
int seq_open_private(struct file *, const struct seq_operations *, int);
int seq_release_private(struct inode *, struct file *);

--
2.8.0.rc4.16.g56331f8