linux-kernel - Re: [PATCH 26/35] Unionfs: Privileged operations workqueue

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Message-ID: <Pine.LNX.4.61.0612061939340.16042@yvahk01.tjqt.qr>
Date:	Wed, 6 Dec 2006 19:46:50 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Josef Sipek <jsipek@....cs.sunysb.edu>
cc:	"Josef 'Jeff' Sipek" <jsipek@...sunysb.edu>,
	linux-kernel@...r.kernel.org, torvalds@...l.org, akpm@...l.org,
	hch@...radead.org, viro@....linux.org.uk,
	linux-fsdevel@...r.kernel.org, mhalcrow@...ibm.com
Subject: Re: [PATCH 26/35] Unionfs: Privileged operations workqueue


On Dec 6 2006 12:32, Josef Sipek wrote:
>> > >+int __init init_sioq(void)
>> > 
>> > Although it's just me, I'd prefer sioq_init(), sioq_exit(),
>> > sioq_run(), etc. to go in hand with what most drivers use as naming
>> > (i.e. <modulename> "_" <function>).
>> 
>> That makes sense.
> 
>Hrm. Looking at the code, I noticed that the opposite is true:
>
>destroy_filldir_cache();
>destroy_inode_cache();
>destroy_dentry_cache();
>unregister_filesystem(&unionfs_fs_type);
>
>The last one in particular...

I smell a big conspiracy! So yet again it's mixed mixed

fs$ grep __init */*.c | grep -v ' init_'
sysfs/mount.c:int __init sysfs_init(void)
sysv/inode.c:int __init sysv_init_icache(void)
proc/vmcore.c:static int __init vmcore_init(void)
proc/nommu.c:static int __init proc_nommu_init(void)
proc/proc_misc.c:void __init proc_misc_init(void)
proc/proc_tty.c:void __init proc_tty_init(void)
proc/root.c:void __init proc_root_init(void)


> 
>> > >+void __unionfs_mknod(void *data)
>> > >+{
>> > >+	struct sioq_args *args = data;
>> > >+	struct mknod_args *m = &args->mknod;
>> > 
>> > Care to make that: const struct mknod_args *m = &args->mknod;?
>> > (Same for other places)
>>  
>> Right.
> 
>If I make the *args = data line const, then gcc (4.1) yells about modifying
>a const variable 3 lines down..
>
>args->err = vfs_mknod(m->parent, m->dentry, m->mode, m->dev);
>
>Sure, I could cast, but that seems like adding cruft for no good reason.

No I despise casts more than missing consts. Why would gcc throw a warning?
Let's take this super simple program

<<<
struct inode;
struct dentry;

struct mknod_args {
    struct inode *parent;
    struct dentry *dentry;
    int mode;
    int dev;
};

extern int vfs_mknod(struct inode *, struct dentry *, int, int /*dev_t*/);

int main(void) {
    const struct mknod_args *m;
    vfs_mknod(m->parent, m->dentry, m->mode, m->dev);
    return 0;
}
>>>

As undefined-behavior as it looks, it's got the const and vfs_mknod, as well as
an approximation of dev_t. It throws no warnings when compiled with `gcc -Wall
-c test.c`. Did I miss something?



	-`J'
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