From: Jens Axboe <axboe@suse.de>
To: blaisorblade_spam@yahoo.it
Cc: akpm@osdl.org, jdike@addtoit.com, linux-kernel@vger.kernel.org,
user-mode-linux-devel@lists.sourceforge.net
Subject: [uml-devel] Re: [patch 1/3] uml-ubd-no-empty-queue
Date: Tue, 7 Sep 2004 11:35:59 +0200 [thread overview]
Message-ID: <20040907093559.GL6323@suse.de> (raw)
In-Reply-To: <20040906174447.238788D1E@zion.localdomain>
On Mon, Sep 06 2004, blaisorblade_spam@yahoo.it wrote:
>
> Avoid using, in the UBD driver, the elv_queue_empty function. It's for
> the block layer only; in fact, the Anticipatory Scheduler can return NULL
> with elv_next_request() even if the queue is not empty, because it waits
> for the process to send another request before seeking on the disk.
>
> In fact, if (with uml-ubd-any-elevator) we let UBD use any scheduler,
> elevator=as will make the UBD driver Oops, if we don't have this patch.
>
> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
> ---
>
> uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c | 6 ++----
> 1 files changed, 2 insertions(+), 4 deletions(-)
>
> diff -puN arch/um/drivers/ubd_kern.c~uml-ubd-no-empty-queue arch/um/drivers/ubd_kern.c
> --- uml-linux-2.6.8.1/arch/um/drivers/ubd_kern.c~uml-ubd-no-empty-queue 2004-08-29 14:40:51.313410952 +0200
> +++ uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c 2004-08-29 14:40:51.315410648 +0200
> @@ -1038,8 +1038,7 @@ static void do_ubd_request(request_queue
> int err, n;
>
> if(thread_fd == -1){
> - while(!elv_queue_empty(q)){
> - req = elv_next_request(q);
> + while((req = elv_next_request(q)) != NULL){
> err = prepare_request(req, &io_req);
> if(!err){
> do_io(&io_req);
> @@ -1048,9 +1047,8 @@ static void do_ubd_request(request_queue
> }
> }
> else {
> - if(do_ubd || elv_queue_empty(q))
> + if(do_ubd || (req = elv_next_request(q)) == NULL)
> return;
> - req = elv_next_request(q);
> err = prepare_request(req, &io_req);
> if(!err){
> do_ubd = ubd_handler;
Patch is correct.
--
Jens Axboe
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WARNING: multiple messages have this Message-ID (diff)
From: Jens Axboe <axboe@suse.de>
To: blaisorblade_spam@yahoo.it
Cc: akpm@osdl.org, jdike@addtoit.com, linux-kernel@vger.kernel.org,
user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [patch 1/3] uml-ubd-no-empty-queue
Date: Tue, 7 Sep 2004 11:35:59 +0200 [thread overview]
Message-ID: <20040907093559.GL6323@suse.de> (raw)
In-Reply-To: <20040906174447.238788D1E@zion.localdomain>
On Mon, Sep 06 2004, blaisorblade_spam@yahoo.it wrote:
>
> Avoid using, in the UBD driver, the elv_queue_empty function. It's for
> the block layer only; in fact, the Anticipatory Scheduler can return NULL
> with elv_next_request() even if the queue is not empty, because it waits
> for the process to send another request before seeking on the disk.
>
> In fact, if (with uml-ubd-any-elevator) we let UBD use any scheduler,
> elevator=as will make the UBD driver Oops, if we don't have this patch.
>
> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
> ---
>
> uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c | 6 ++----
> 1 files changed, 2 insertions(+), 4 deletions(-)
>
> diff -puN arch/um/drivers/ubd_kern.c~uml-ubd-no-empty-queue arch/um/drivers/ubd_kern.c
> --- uml-linux-2.6.8.1/arch/um/drivers/ubd_kern.c~uml-ubd-no-empty-queue 2004-08-29 14:40:51.313410952 +0200
> +++ uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c 2004-08-29 14:40:51.315410648 +0200
> @@ -1038,8 +1038,7 @@ static void do_ubd_request(request_queue
> int err, n;
>
> if(thread_fd == -1){
> - while(!elv_queue_empty(q)){
> - req = elv_next_request(q);
> + while((req = elv_next_request(q)) != NULL){
> err = prepare_request(req, &io_req);
> if(!err){
> do_io(&io_req);
> @@ -1048,9 +1047,8 @@ static void do_ubd_request(request_queue
> }
> }
> else {
> - if(do_ubd || elv_queue_empty(q))
> + if(do_ubd || (req = elv_next_request(q)) == NULL)
> return;
> - req = elv_next_request(q);
> err = prepare_request(req, &io_req);
> if(!err){
> do_ubd = ubd_handler;
Patch is correct.
--
Jens Axboe
next prev parent reply other threads:[~2004-09-07 9:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-06 17:44 [uml-devel] [patch 1/3] uml-ubd-no-empty-queue blaisorblade_spam
2004-09-06 17:44 ` blaisorblade_spam
2004-09-06 21:26 ` [uml-devel] " Andrew Morton
2004-09-06 21:26 ` Andrew Morton
2004-09-07 2:26 ` [uml-devel] " Jeff Garzik
2004-09-07 2:26 ` Jeff Garzik
2004-09-07 18:04 ` [uml-devel] " BlaisorBlade
2004-09-07 18:04 ` BlaisorBlade
2004-09-07 21:23 ` Andrew Morton
2004-09-07 21:23 ` Andrew Morton
2004-09-07 9:35 ` Jens Axboe [this message]
2004-09-07 9:35 ` Jens Axboe
2004-09-07 18:50 ` [uml-devel] " BlaisorBlade
2004-09-07 18:50 ` BlaisorBlade
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