[PATCH RFC 02/27] jfs: let procfs copy in writes to the loglevel file

[Christian Brauner]

Implement ->proc_write_buf() so procfs copies in what is written before
it pins the entry, and take the level from that copy. Writes larger than
PAGE_SIZE - 1 bytes fail with -EINVAL now and so do empty writes, which
looked at a byte that wasn't written before.

Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>
---
 fs/jfs/jfs_debug.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/fs/jfs/jfs_debug.c b/fs/jfs/jfs_debug.c
index 5eb35b0d420f..e1c0211a6a32 100644
--- a/fs/jfs/jfs_debug.c
+++ b/fs/jfs/jfs_debug.c
@@ -23,13 +23,10 @@ static int jfs_loglevel_proc_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static ssize_t jfs_loglevel_proc_write(struct file *file,
-		const char __user *buffer, size_t count, loff_t *ppos)
+static ssize_t jfs_loglevel_proc_write(struct file *file, char *buffer,
+		size_t count, loff_t *ppos)
 {
-	char c;
-
-	if (get_user(c, buffer))
-		return -EFAULT;
+	char c = buffer[0];
 
 	/* yes, I know this is an ASCIIism.  --hch */
 	if (c < '0' || c > '9')
@@ -40,7 +37,7 @@ static ssize_t jfs_loglevel_proc_write(struct file *file,
 
 static const struct proc_ops jfs_loglevel_proc_ops = {
 	.proc_show	= jfs_loglevel_proc_show,
-	.proc_write	= jfs_loglevel_proc_write,
+	.proc_write_buf	= jfs_loglevel_proc_write,
 };
 #endif
 

-- 
2.53.0