Re: [PATCH linux-2.6-14-mm2] block: problem unloading I/O-Scheduler Module

[Jens Axboe]

On Thu, Nov 17 2005, Dirk Henning Gerdes wrote:
> If you have compiled an I/O-Scheduler as module you cannot unload it,
> because of a memory-error.
> 
> Signed-off-by: Dirk Gerdes mail@xxxxxxxxxxxxxx
> 
> --- linux-2.6.14-mm2-pagecache/block/elevator.c	2005-11-17
> 12:37:10.000000000 +0100
> +++ linux-2.6.14-mm2-pagecache_fix/block/elevator.c	2005-11-17
> 14:05:41.000000000 +0100
> @@ -656,7 +656,7 @@
>  		struct io_context *ioc = p->io_context;
>  		struct cfq_io_context *cic;
>  
> -		if (ioc->cic_root.rb_node != NULL) {
> +		if (ioc != NULL && ioc->cic_root.rb_node != NULL) {
>  			cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context,
> rb_node);
>  			cic->exit(ioc);
>  			cic->dtor(ioc);

Shouldn't that just read

        if (!ioc)
                continue;

instead? Otherwise you'd crash on 'as' exit next. Ah, it already has
that. Ok, so I prefer this (what I merged).


diff --git a/block/elevator.c b/block/elevator.c
index 5720409..0c389a0 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -652,13 +652,16 @@ void elv_unregister(struct elevator_type
 		struct io_context *ioc = p->io_context;
 		struct cfq_io_context *cic;
 
+		if (!ioc)
+			continue;
+
 		if (ioc->cic_root.rb_node != NULL) {
 			cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
 			cic->exit(ioc);
 			cic->dtor(ioc);
 		}
 
-		if (ioc && ioc->aic) {
+		if (ioc->aic) {
 			ioc->aic->exit(ioc->aic);
 			ioc->aic->dtor(ioc->aic);
 			ioc->aic = NULL;

-- 
Jens Axboe

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