Re: [PATCH] drivers: Conversions from kmalloc+memset to k(z|c)alloc.

From: Daniel K.
Date: Fri Jul 21 2006 - 06:23:18 EST

Rolf Eike Beer wrote:
Am Donnerstag, 20. Juli 2006 21:05 schrieb Panagiotis Issaris:
@@ -443,12 +442,11 @@ int con_clear_unimap(struct vc_data *vc,
p = (struct uni_pagedir *)*vc->vc_uni_pagedir_loc;
if (p && p->readonly) return -EIO;
if (!p || --p->refcount) {
- q = (struct uni_pagedir *)kmalloc(sizeof(*p), GFP_KERNEL);
+ q = kzalloc(sizeof(*p), GFP_KERNEL);
if (!q) {
if (p) p->refcount++;
return -ENOMEM;
- memset(q, 0, sizeof(*q));
*vc->vc_uni_pagedir_loc = (unsigned long)q;
} else {

This one still changes the way the code works. Before your patch *p will be always zeroed out. Now if p is there before it will keep it's contents.

No, it doesn't, the data at *p is/was not zeroed inside the if { .. } block.
Read carefully, the multiple statements on one line obfuscations might
have thrown you off.

However, it is slightly confusing that the value assigned to `q' is
kzalloced using sizeof(*p). It is an improvement though, as the old version
kmalloced using sizeof(*p), and memset using sizeof(*q).
That was really strange.

Daniel K.
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