| Message ID | 20170501162928.GB291@x4 (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 2017-05-01 at 18:29 +0200, markus@trippelsdorf.de wrote: > + strlcpy(elevator_name, name, sizeof(elevator_name)); > + strstrip(elevator_name); > + ret = __elevator_change(q, elevator_name); Hello Markus, Are you aware that the current implementation of __elevator_change() strips leading whitespace but that with your patch applied leading whitespace is no longer removed from the elevator name? If you have a look at strim() in lib/string.c you will see that in case of leading whitespace that function does not remove the leading whitespace but returns a pointer to the first non-whitespace character. Otherwise this patch looks fine to me. Bart.
On 2017.05.05 at 20:05 +0000, Bart Van Assche wrote: > On Mon, 2017-05-01 at 18:29 +0200, markus@trippelsdorf.de wrote: > > + strlcpy(elevator_name, name, sizeof(elevator_name)); > > + strstrip(elevator_name); > > + ret = __elevator_change(q, elevator_name); > > > Are you aware that the current implementation of __elevator_change() strips > leading whitespace but that with your patch applied leading whitespace is no > longer removed from the elevator name? If you have a look at strim() in > lib/string.c you will see that in case of leading whitespace that function > does not remove the leading whitespace but returns a pointer to the first > non-whitespace character. Well, only in the call to elevator_get(). The dmesg output does contain leading whitespace. But the fix is simple. I will send a new patch.
diff --git a/block/elevator.c b/block/elevator.c index bf11e70f008b..1af23eee4395 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, 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; }
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 unintended line break.) Fix by stripping the trailing newline. Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>