* [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
@ 2017-05-06 5:22 markus
2017-05-08 15:47 ` Bart Van Assche
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: markus @ 2017-05-06 5:22 UTC (permalink / raw)
To: Bart Van Assche; +Cc: linux-block, axboe
Trying to switch to a non-existing elevator currently results in garbled
dmesg output, e.g.:
# echo " foo" > /sys/block/sda/queue/scheduler
elevator: type foo not found
elevator: switch to foo
failed
(note the leading whitespace and unintended line break.)
Fix by removing the leading whitespace and stripping the trailing newline.
Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>
diff --git a/block/elevator.c b/block/elevator.c
index bf11e70f008b..3e1a42192519 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -1054,7 +1054,6 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
*/
static int __elevator_change(struct request_queue *q, const char *name)
{
- char elevator_name[ELV_NAME_MAX];
struct elevator_type *e;
/*
@@ -1063,15 +1062,14 @@ static int __elevator_change(struct request_queue *q, const char *name)
if (q->mq_ops && !strncmp(name, "none", 4))
return elevator_switch(q, NULL);
- strlcpy(elevator_name, name, sizeof(elevator_name));
- e = elevator_get(strstrip(elevator_name), true);
+ e = elevator_get(name, true);
if (!e) {
- printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
+ printk(KERN_ERR "elevator: type %s not found\n", name);
return -EINVAL;
}
if (q->elevator &&
- !strcmp(elevator_name, q->elevator->type->elevator_name)) {
+ !strcmp(name, q->elevator->type->elevator_name)) {
elevator_put(e);
return 0;
}
@@ -1112,16 +1110,19 @@ static inline bool elv_support_iosched(struct request_queue *q)
ssize_t elv_iosched_store(struct request_queue *q, const char *name,
size_t count)
{
+ char elevator_name[ELV_NAME_MAX];
int ret;
if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q))
return count;
- ret = __elevator_change(q, name);
+ strlcpy(elevator_name, skip_spaces(name), sizeof(elevator_name));
+ strstrip(elevator_name);
+ ret = __elevator_change(q, elevator_name);
if (!ret)
return count;
- printk(KERN_ERR "elevator: switch to %s failed\n", name);
+ printk(KERN_ERR "elevator: switch to %s failed\n", elevator_name);
return ret;
}
--
Markus
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-06 5:22 [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message markus
@ 2017-05-08 15:47 ` Bart Van Assche
2017-05-08 16:48 ` markus
2017-05-08 16:53 ` Jens Axboe
2017-05-09 2:18 ` Elliott, Robert (Persistent Memory)
2 siblings, 1 reply; 9+ messages in thread
From: Bart Van Assche @ 2017-05-08 15:47 UTC (permalink / raw)
To: markus; +Cc: linux-block, axboe
On Sat, 2017-05-06 at 07:22 +0200, markus@trippelsdorf.de wrote:
> - ret =3D __elevator_change(q, name);
> + strlcpy(elevator_name, skip_spaces(name), sizeof(elevator_name));
Hello Markus,
Please include the version number of a patch in the e-mail subject line whe=
n
posting a second or later version. Regarding the strlcpy() call, in the
FreeBSD strlcpy() man page I found the following: "If the src and dst strin=
gs
overlap, the behavior is undefined." Since the Linux kernel implementation =
of
strlcpy() uses memcpy() and since the ANSI C standard does not allow that
memcpy() input and output buffers overlap, please rework this code. See e.g=
.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/memcpy.html
Thanks,
Bart.=
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-08 15:47 ` Bart Van Assche
@ 2017-05-08 16:48 ` markus
2017-05-08 16:52 ` Bart Van Assche
0 siblings, 1 reply; 9+ messages in thread
From: markus @ 2017-05-08 16:48 UTC (permalink / raw)
To: Bart Van Assche; +Cc: linux-block, axboe
On 2017.05.08 at 15:47 +0000, Bart Van Assche wrote:
> On Sat, 2017-05-06 at 07:22 +0200, markus@trippelsdorf.de wrote:
> > - ret = __elevator_change(q, name);
> > + strlcpy(elevator_name, skip_spaces(name), sizeof(elevator_name));
>
> Please include the version number of a patch in the e-mail subject line when
> posting a second or later version. Regarding the strlcpy() call, in the
> FreeBSD strlcpy() man page I found the following: "If the src and dst strings
> overlap, the behavior is undefined." Since the Linux kernel implementation of
> strlcpy() uses memcpy() and since the ANSI C standard does not allow that
> memcpy() input and output buffers overlap, please rework this code. See e.g.
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/memcpy.html
I don't see how src and dst could possibly overlap here.
--
Markus
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-08 16:48 ` markus
@ 2017-05-08 16:52 ` Bart Van Assche
0 siblings, 0 replies; 9+ messages in thread
From: Bart Van Assche @ 2017-05-08 16:52 UTC (permalink / raw)
To: markus; +Cc: linux-block, axboe
On Mon, 2017-05-08 at 18:48 +0200, markus@trippelsdorf.de wrote:
> On 2017.05.08 at 15:47 +0000, Bart Van Assche wrote:
> > On Sat, 2017-05-06 at 07:22 +0200, markus@trippelsdorf.de wrote:
> > > - ret =3D __elevator_change(q, name);
> > > + strlcpy(elevator_name, skip_spaces(name), sizeof(elevator_name));
> >=20
> > Please include the version number of a patch in the e-mail subject line=
when
> > posting a second or later version. Regarding the strlcpy() call, in the
> > FreeBSD strlcpy() man page I found the following: "If the src and dst s=
trings
> > overlap, the behavior is undefined." Since the Linux kernel implementat=
ion of
> > strlcpy() uses memcpy() and since the ANSI C standard does not allow th=
at
> > memcpy() input and output buffers overlap, please rework this code. See=
e.g.
> > http://pubs.opengroup.org/onlinepubs/9699919799/functions/memcpy.html
>=20
> I don't see how src and dst could possibly overlap here.
Hello Markus,
Sorry - I misread your patch. Since that was the only comment I had:
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>=
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-06 5:22 [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message markus
2017-05-08 15:47 ` Bart Van Assche
@ 2017-05-08 16:53 ` Jens Axboe
2017-05-09 2:18 ` Elliott, Robert (Persistent Memory)
2 siblings, 0 replies; 9+ messages in thread
From: Jens Axboe @ 2017-05-08 16:53 UTC (permalink / raw)
To: markus, Bart Van Assche; +Cc: linux-block
On 05/05/2017 11:22 PM, markus@trippelsdorf.de wrote:
>
> Trying to switch to a non-existing elevator currently results in garbled
> dmesg output, e.g.:
>
> # echo " foo" > /sys/block/sda/queue/scheduler
>
> elevator: type foo not found
> elevator: switch to foo
> failed
>
> (note the leading whitespace and unintended line break.)
>
> Fix by removing the leading whitespace and stripping the trailing newline.
Added, thanks.
--
Jens Axboe
^ permalink raw reply [flat|nested] 9+ messages in thread
* RE: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-06 5:22 [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message markus
2017-05-08 15:47 ` Bart Van Assche
2017-05-08 16:53 ` Jens Axboe
@ 2017-05-09 2:18 ` Elliott, Robert (Persistent Memory)
2017-05-09 2:22 ` Jens Axboe
2 siblings, 1 reply; 9+ messages in thread
From: Elliott, Robert (Persistent Memory) @ 2017-05-09 2:18 UTC (permalink / raw)
To: markus, Bart Van Assche; +Cc: linux-block, axboe
> -----Original Message-----
> From: linux-block-owner@vger.kernel.org [mailto:linux-block-
> owner@vger.kernel.org] On Behalf Of markus@trippelsdorf.de
> Sent: Saturday, May 06, 2017 12:23 AM
> To: Bart Van Assche <Bart.VanAssche@sandisk.com>
> Cc: linux-block@vger.kernel.org; axboe@kernel.dk
> Subject: [PATCH] block: Remove leading whitespace and trailing
> newline in elevator switch error message
>=20
>=20
> Trying to switch to a non-existing elevator currently results in
> garbled
> dmesg output, e.g.:
>=20
> # echo " foo" > /sys/block/sda/queue/scheduler
>=20
> elevator: type foo not found
> elevator: switch to foo
> failed
...
> @@ -1063,15 +1062,14 @@ static int __elevator_change(struct
> request_queue *q, const char *name)
> if (q->mq_ops && !strncmp(name, "none", 4))
> return elevator_switch(q, NULL);
>=20
> - strlcpy(elevator_name, name, sizeof(elevator_name));
> - e =3D elevator_get(strstrip(elevator_name), true);
> + e =3D elevator_get(name, true);
> if (!e) {
> - printk(KERN_ERR "elevator: type %s not found\n",
> elevator_name);
> + printk(KERN_ERR "elevator: type %s not found\n", name);
> return -EINVAL;
> }
...
> @@ -1112,16 +1110,19 @@ static inline bool elv_support_iosched(struct
> request_queue *q)
> ssize_t elv_iosched_store(struct request_queue *q, const char *name,
> size_t count)
> {
...
> + strlcpy(elevator_name, skip_spaces(name),
> sizeof(elevator_name));
> + strstrip(elevator_name);
> + ret =3D __elevator_change(q, elevator_name);
> if (!ret)
> return count;
>=20
> - printk(KERN_ERR "elevator: switch to %s failed\n", name);
> + printk(KERN_ERR "elevator: switch to %s failed\n",
> elevator_name);
> return ret;
> }
That leaves two lines of error prints for a single error, and
the second line doesn't convey additional information.
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-09 2:18 ` Elliott, Robert (Persistent Memory)
@ 2017-05-09 2:22 ` Jens Axboe
2017-05-09 4:42 ` markus
0 siblings, 1 reply; 9+ messages in thread
From: Jens Axboe @ 2017-05-09 2:22 UTC (permalink / raw)
To: Elliott, Robert (Persistent Memory); +Cc: markus, Bart Van Assche, linux-block
> On May 8, 2017, at 8:18 PM, Elliott, Robert (Persistent Memory) <elliott@h=
pe.com> wrote:
>=20
>=20
>=20
>> -----Original Message-----
>> From: linux-block-owner@vger.kernel.org [mailto:linux-block-
>> owner@vger.kernel.org] On Behalf Of markus@trippelsdorf.de
>> Sent: Saturday, May 06, 2017 12:23 AM
>> To: Bart Van Assche <Bart.VanAssche@sandisk.com>
>> Cc: linux-block@vger.kernel.org; axboe@kernel.dk
>> Subject: [PATCH] block: Remove leading whitespace and trailing
>> newline in elevator switch error message
>>=20
>>=20
>> Trying to switch to a non-existing elevator currently results in
>> garbled
>> dmesg output, e.g.:
>>=20
>> # echo " foo" > /sys/block/sda/queue/scheduler
>>=20
>> elevator: type foo not found
>> elevator: switch to foo
>> failed
> ...
>> @@ -1063,15 +1062,14 @@ static int __elevator_change(struct
>> request_queue *q, const char *name)
>> if (q->mq_ops && !strncmp(name, "none", 4))
>> return elevator_switch(q, NULL);
>>=20
>> - strlcpy(elevator_name, name, sizeof(elevator_name));
>> - e =3D elevator_get(strstrip(elevator_name), true);
>> + e =3D elevator_get(name, true);
>> if (!e) {
>> - printk(KERN_ERR "elevator: type %s not found\n",
>> elevator_name);
>> + printk(KERN_ERR "elevator: type %s not found\n", name);
>> return -EINVAL;
>> }
> ...
>> @@ -1112,16 +1110,19 @@ static inline bool elv_support_iosched(struct
>> request_queue *q)
>> ssize_t elv_iosched_store(struct request_queue *q, const char *name,
>> size_t count)
>> {
> ...
>> + strlcpy(elevator_name, skip_spaces(name),
>> sizeof(elevator_name));
>> + strstrip(elevator_name);
>> + ret =3D __elevator_change(q, elevator_name);
>> if (!ret)
>> return count;
>>=20
>> - printk(KERN_ERR "elevator: switch to %s failed\n", name);
>> + printk(KERN_ERR "elevator: switch to %s failed\n",
>> elevator_name);
>> return ret;
>> }
>=20
> That leaves two lines of error prints for a single error, and
> the second line doesn't convey additional information.
Yeah good point. Honestly I think we should just kill both lines. None of th=
em add value.=20
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-09 2:22 ` Jens Axboe
@ 2017-05-09 4:42 ` markus
2017-05-09 14:57 ` Jens Axboe
0 siblings, 1 reply; 9+ messages in thread
From: markus @ 2017-05-09 4:42 UTC (permalink / raw)
To: Jens Axboe
Cc: Elliott, Robert (Persistent Memory), Bart Van Assche, linux-block
On 2017.05.08 at 20:22 -0600, Jens Axboe wrote:
>
> > On May 8, 2017, at 8:18 PM, Elliott, Robert (Persistent Memory)
> > <elliott@hpe.com> wrote:
> >> + printk(KERN_ERR "elevator: type %s not found\n", name);
> > ...
> >> + printk(KERN_ERR "elevator: switch to %s failed\n",
> >
> > That leaves two lines of error prints for a single error, and
> > the second line doesn't convey additional information.
>
> Yeah good point. Honestly I think we should just kill both lines. None
> of them add value.
They at least help debugging of udev rules, e.g. on Gentoo they have:
# set noop on solid state drives
SUBSYSTEM=="block", ACTION=="add", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="noop"
And this will of course fail for mq. But how will you notice it without
any dmesg error message?
--
Markus
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message
2017-05-09 4:42 ` markus
@ 2017-05-09 14:57 ` Jens Axboe
0 siblings, 0 replies; 9+ messages in thread
From: Jens Axboe @ 2017-05-09 14:57 UTC (permalink / raw)
To: markus; +Cc: Elliott, Robert (Persistent Memory), Bart Van Assche, linux-block
On 05/08/2017 10:42 PM, markus@trippelsdorf.de wrote:
> On 2017.05.08 at 20:22 -0600, Jens Axboe wrote:
>>
>>> On May 8, 2017, at 8:18 PM, Elliott, Robert (Persistent Memory)
>>> <elliott@hpe.com> wrote:
>>>> + printk(KERN_ERR "elevator: type %s not found\n", name);
>>> ...
>>>> + printk(KERN_ERR "elevator: switch to %s failed\n",
>>>
>>> That leaves two lines of error prints for a single error, and
>>> the second line doesn't convey additional information.
>>
>> Yeah good point. Honestly I think we should just kill both lines. None
>> of them add value.
>
> They at least help debugging of udev rules, e.g. on Gentoo they have:
>
> # set noop on solid state drives
> SUBSYSTEM=="block", ACTION=="add", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="noop"
>
> And this will of course fail for mq. But how will you notice it without
> any dmesg error message?
The echo to the sysfs file fails. udev should report such failures. Using
dmesg as the channel to report and discover errors like that is not a
great idea, and it was a mistake to put that code in the switch path
in the first place.
--
Jens Axboe
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2017-05-09 14:57 UTC | newest]
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-- links below jump to the message on this page --
2017-05-06 5:22 [PATCH] block: Remove leading whitespace and trailing newline in elevator switch error message markus
2017-05-08 15:47 ` Bart Van Assche
2017-05-08 16:48 ` markus
2017-05-08 16:52 ` Bart Van Assche
2017-05-08 16:53 ` Jens Axboe
2017-05-09 2:18 ` Elliott, Robert (Persistent Memory)
2017-05-09 2:22 ` Jens Axboe
2017-05-09 4:42 ` markus
2017-05-09 14:57 ` Jens Axboe
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