new helper: single_open_size()

Same as single_open(), but preallocates the buffer of given size.
Doesn't make any sense for sizes up to PAGE_SIZE and doesn't make
sense if output of show() exceeds PAGE_SIZE only rarely - seq_read()
will take care of growing the buffer and redoing show().  If you
_know_ that it will be large, it might make more sense to look into
saner iterator, rather than go with single-shot one.  If that's
impossible, single_open_size() might be for you.

Again, don't use that without a good reason; occasionally that's really
the best way to go, but very often there are better solutions.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 68a04a343ca..2da29ac178f 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -123,6 +123,7 @@ static inline int seq_nodemask_list(struct seq_file *m, nodemask_t *mask)
 }
 
 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);
 int seq_open_private(struct file *, const struct seq_operations *, int);