x86: cpuid: correct return value on partial operations

Return the correct return value when the CPUID driver partially
completes a request (we should return the number of bytes actually
read or written, instead of the error code.)

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 23e8316c8357a151b3bdf197e2e78d2e1be466fe..8e9cd6a8ec120951c4683b410572d63b0c3d0824 100644 (file)
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -89,7 +89,8 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
        struct cpuid_regs cmd;
        int cpu = iminor(file->f_path.dentry->d_inode);
        u64 pos = *ppos;
-       int err;
+       ssize_t bytes = 0;
+       int err = 0;
 
        if (count % 16)
                return -EINVAL; /* Invalid chunk size */
@@ -99,14 +100,17 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
                cmd.ecx = pos >> 32;
                err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
                if (err)
-                       return err;
-               if (copy_to_user(tmp, &cmd, 16))
-                       return -EFAULT;
+                       break;
+               if (copy_to_user(tmp, &cmd, 16)) {
+                       err = -EFAULT;
+                       break;
+               }
                tmp += 16;
+               bytes += 16;
                *ppos = ++pos;
        }
 
-       return tmp - buf;
+       return bytes ? bytes : err;
 }
 
 static int cpuid_open(struct inode *inode, struct file *file)