hi, Elliott thanks for your reply. :) On 2015年07月23日 22:53, Elliott, Robert (Server Storage) wrote: >> -----Original Message----- >> From: linux-kernel-ow...@vger.kernel.org [mailto:linux-kernel- >> ow...@vger.kernel.org] On Behalf Of Pan Xinhui >> Sent: Thursday, July 23, 2015 4:54 AM >> To: linux-kernel@vger.kernel.org >> Subject: [PATCH] x86/mm/pat: Do a small optimization when dump PAT memtype >> list > ... >> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c >> index 268b2c8..6302119 100644 >> --- a/arch/x86/mm/pat.c >> +++ b/arch/x86/mm/pat.c >> @@ -1001,45 +1001,42 @@ EXPORT_SYMBOL_GPL(pgprot_writethrough); >> >> #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT) >> >> -static struct memtype *memtype_get_idx(loff_t pos) >> +static struct memtype *memtype_get_idx(struct memtype *entry, loff_t pos) >> { >> - struct memtype *print_entry; >> int ret; >> >> - print_entry = kzalloc(sizeof(struct memtype), GFP_KERNEL); >> - if (!print_entry) >> - return NULL; >> - >> spin_lock(&memtype_lock); >> - ret = rbt_memtype_copy_nth_element(print_entry, pos); >> + ret = rbt_memtype_copy_nth_element(entry, pos); >> spin_unlock(&memtype_lock); >> >> - if (!ret) { >> - return print_entry; >> - } else { >> - kfree(print_entry); >> - return NULL; >> - } >> + return ret ? NULL : entry; >> } >> > ... >> static void memtype_seq_stop(struct seq_file *seq, void *v) >> { >> + kfree(seq->private); >> } >> > > Consider adding > seq->private = NULL; > so the stale pointer isn't left around. There's probably not > much risk of accessing it, but NULL is safer in case it is. > I know exactly what are you worrying about. start and stop callback is still not the best place to alloc/free the *entry*. you are worrying about that some codes might touch it.
seq_file.c has offered seq_open_private and seq_release_private. we can make use of them. :) I will work out patch v2, this time I will Cc you. I am very happy if you could review it at any free time. :) thanks xinhui > --- > Robert Elliott, HP Server Storage > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/