From: Greg KH <gregkh@linuxfoundation.org>
To: Jaewon Kim <jaewon31.kim@samsung.com>
Cc: leon@kernel.org, vbabka@suse.cz, adobriyan@gmail.com,
akpm@linux-foundation.org, labbott@redhat.com,
sumit.semwal@linaro.org, minchan@kernel.org, ngupta@vflare.org,
sergey.senozhatsky.work@gmail.com, kasong@redhat.com,
bhe@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
jaewon31.kim@gmail.com, linux-api@vger.kernel.org,
kexec@lists.infradead.org
Subject: Re: [RFC PATCH v2 1/3] meminfo_extra: introduce meminfo extra
Date: Tue, 24 Mar 2020 11:11:10 +0100 [thread overview]
Message-ID: <20200324101110.GA2218981@kroah.com> (raw)
In-Reply-To: <5E79CEB5.8070308@samsung.com>
On Tue, Mar 24, 2020 at 06:11:17PM +0900, Jaewon Kim wrote:
> On 2020년 03월 23일 18:53, Greg KH wrote:
> >> +int register_meminfo_extra(atomic_long_t *val, int shift, const char *name)
> >> +{
> >> + struct meminfo_extra *meminfo, *memtemp;
> >> + int len;
> >> + int error = 0;
> >> +
> >> + meminfo = kzalloc(sizeof(*meminfo), GFP_KERNEL);
> >> + if (!meminfo) {
> >> + error = -ENOMEM;
> >> + goto out;
> >> + }
> >> +
> >> + meminfo->val = val;
> >> + meminfo->shift_for_page = shift;
> >> + strncpy(meminfo->name, name, NAME_SIZE);
> >> + len = strlen(meminfo->name);
> >> + meminfo->name[len] = ':';
> >> + strncpy(meminfo->name_pad, meminfo->name, NAME_BUF_SIZE);
> >> + while (++len < NAME_BUF_SIZE - 1)
> >> + meminfo->name_pad[len] = ' ';
> >> +
> >> + spin_lock(&meminfo_lock);
> >> + list_for_each_entry_rcu(memtemp, &meminfo_head, list) {
> >> + if (memtemp->val == val) {
> >> + error = -EINVAL;
> >> + break;
> >> + }
> >> + }
> >> + if (!error)
> >> + list_add_tail_rcu(&meminfo->list, &meminfo_head);
> >> + spin_unlock(&meminfo_lock);
> > If you have a lock, why are you needing rcu?
> I think _rcu should be removed out of list_for_each_entry_rcu.
> But I'm confused about what you meant.
> I used rcu_read_lock on __meminfo_extra,
> and I think spin_lock is also needed for addition and deletion to handle multiple modifiers.
If that's the case, then that's fine, it just didn't seem like that was
needed. Or I might have been reading your rcu logic incorrectly...
> >> + if (error)
> >> + kfree(meminfo);
> >> +out:
> >> +
> >> + return error;
> >> +}
> >> +EXPORT_SYMBOL(register_meminfo_extra);
> > EXPORT_SYMBOL_GPL()? I have to ask :)
> I can use EXPORT_SYMBOL_GPL.
> >
> > thanks,
> >
> > greg k-h
> >
> >
>
> Hello
> Thank you for your comment.
>
> By the way there was not resolved discussion on v1 patch as I mentioned on cover page.
> I'd like to hear your opinion on this /proc/meminfo_extra node.
I think it is the propagation of an old and obsolete interface that you
will have to support for the next 20+ years and yet not actually be
useful :)
> Do you think this is meaningful or cannot co-exist with other future
> sysfs based API.
What sysfs-based API?
I still don't know _why_ you want this. The ION stuff is not needed as
that code is about to be deleted, so who else wants this? What is the
use-case for it that is so desperately needed that parsing
yet-another-proc file is going to solve the problem?
thanks,
greg k-h
next prev parent reply other threads:[~2020-03-24 10:11 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200323080507epcas1p44cdb9ecb70a7a7395b3acddeda3cfd89@epcas1p4.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 0/3] meminfo_extra: introduce meminfo extra Jaewon Kim
[not found] ` <CGME20200323080508epcas1p387c9c19b480da53be40fe5d51e76a477@epcas1p3.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 1/3] " Jaewon Kim
2020-03-23 9:53 ` Greg KH
2020-03-24 9:11 ` Jaewon Kim
2020-03-24 10:11 ` Greg KH [this message]
2020-03-24 11:37 ` Jaewon Kim
2020-03-24 11:46 ` Greg KH
2020-03-24 12:53 ` Jaewon Kim
2020-03-24 13:19 ` Greg KH
2020-03-26 8:21 ` Jaewon Kim
2020-03-29 7:19 ` Leon Romanovsky
2020-03-29 7:23 ` Greg KH
2020-03-29 8:19 ` Leon Romanovsky
2020-03-25 18:23 ` Alexey Dobriyan
2020-03-23 12:00 ` Dave Young
[not found] ` <CGME20200323080508epcas1p2dfe6517169a65936e5ab10c4e63a19a7@epcas1p2.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 2/3] mm: zsmalloc: include zs page size in " Jaewon Kim
[not found] ` <CGME20200323080508epcas1p3c68190cd46635b9ff026a4ae70fc7a3b@epcas1p3.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 3/3] android: ion: include system heap " Jaewon Kim
2020-03-23 9:49 ` Greg KH
2020-03-25 18:12 ` [RFC PATCH v2 0/3] meminfo_extra: introduce " Alexey Dobriyan
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