Adds a seq_reserve function to allow users of the seq_file interface to
increase the initial size of the buffer. Avoids repeated allocations and
calls to the show function in cases where large buffers of known size are
needed.
Signed-off-by: Colin Cross <ccross@xxxxxxxxxxx>
---
fs/seq_file.c | 30 ++++++++++++++++++++++++++++++
include/linux/seq_file.h | 1 +
2 files changed, 31 insertions(+), 0 deletions(-)
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 05d6b0e..8d9778c 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -62,6 +62,36 @@ int seq_open(struct file *file, const struct seq_operations *op)
}
EXPORT_SYMBOL(seq_open);
+/**
+ * seq_reserve - increase initial buffer for sequential file
+ * @m: target buffer
+ * @size: size in bytes to reserve
+ *
+ * seq_reserve() increases the initial size of the seq_file buffer. Can
+ * be used to avoid future allocations and repeated calls to the show
+ * function for large buffers of known size.
+ * Returns 0 on success, or -ENOMEM if the buffer cannot be allocated.
+ */
+int seq_reserve(struct seq_file *m, size_t size)
+{
+ void *buf;
+
+ /* don't ask for more than the kmalloc() max size */
+ if (size > KMALLOC_MAX_SIZE)
+ size = KMALLOC_MAX_SIZE;
+
+ buf = kmalloc(size, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ kfree(m->buf);
+ m->buf = buf;
+ m->size = size;
+
+ return 0;
+}
+EXPORT_SYMBOL(seq_reserve);
+
static int traverse(struct seq_file *m, loff_t offset)
{
loff_t pos = 0, index;
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 03c0232..ad93319 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -75,6 +75,7 @@ static inline void seq_commit(struct seq_file *m, int num)
char *mangle_path(char *s, char *p, char *esc);
int seq_open(struct file *, const struct seq_operations *);
+int seq_reserve(struct seq_file *m, size_t size);
ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
loff_t seq_lseek(struct file *, loff_t, int);
int seq_release(struct inode *, struct file *);
--
1.7.4.1
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