kernfs: fix regression in kernfs_fop_write caused by wrong type

[ Upstream commit ba87977a49913129962af8ac35b0e13e0fa4382d ]

Commit b7ce40cff0b9 ("kernfs: cache atomic_write_len in
kernfs_open_file") changes type of local variable 'len' from ssize_t
to size_t. This change caused that the *ppos value is updated also
when the previous write callback failed.

Mentioned snippet:
...
len = ops->write(...); <- return value can be negative
...
if (len > 0)           <- true here in this case
        *ppos += len;
...

Fixes: b7ce40cff0b9 ("kernfs: cache atomic_write_len in kernfs_open_file")
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 9ff28bc294c0aa2b433ce1db3bafb40a97ec421b..5d084638e1f889b956f6063aad4e2c859a711870 100644 (file)
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -272,7 +272,7 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
 {
        struct kernfs_open_file *of = kernfs_of(file);
        const struct kernfs_ops *ops;
-       size_t len;
+       ssize_t len;
        char *buf;
 
        if (of->atomic_write_len) {