| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20060720170054.GB27601@sergelap.austin.ibm.com>
Date: Thu, 20 Jul 2006 12:00:54 -0500
From: "Serge E. Hallyn" <serue@...ibm.com>
To: Andrew Morton <akpm@...l.org>
Cc: "Serge E. Hallyn" <serue@...ibm.com>, hugh@...itas.com,
torvalds@...l.org, linux-kernel@...r.kernel.org
Subject: Re: please revert kthread from loop.c
Quoting Andrew Morton (akpm@...l.org):
> On Thu, 13 Jul 2006 08:36:02 -0500
> "Serge E. Hallyn" <serue@...ibm.com> wrote:
>
> > Quoting Andrew Morton (akpm@...l.org):
> >
> > > Again: why is this so hard? It shouldn't be. Perhaps because loop is
> > > using completions in bizarre ways where it should be using
> > > wake_up_process(), wait_event(), etc.
> >
> > Ah.
> >
> > wait_event() actually seems like the way to go - I'll try to follow the
> > example in fs/ocfs2/journal.c.
>
> I suspect quite a lot of changes to loop.c would fall out. For a start, in
> a sufficiently-simplified implementation lo_pending would perhaps go away -
> just test the NULLness of the top of the list of BIOs.
True - here is an attempt at that:
Subject: [PATCH] kthread: convert loop.c to kthread
From: Serge E. Hallyn <hallyn@...gelap.(none)>
Date: 1153345222 -0500
Convert loop.c from the deprecated kernel_thread to kthread.
This patch simplifies the code quite a bit and passes similar
testing to the previous submission on both emulated x86 and
s390.
Changes since last submission:
switched to using a rather simple loop based on
wait_event_interruptible.
Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
---
drivers/block/loop.c | 69 +++++++++++++++++---------------------------------
include/linux/loop.h | 5 +---
2 files changed, 26 insertions(+), 48 deletions(-)
c5f5e9d7016d6fb2b43aa4b13aea302ac367a28c
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 7b3b94d..0468785 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -72,6 +72,7 @@
#include <linux/completion.h>
#include <linux/highmem.h>
#include <linux/gfp.h>
+#include <linux/kthread.h>
#include <asm/uaccess.h>
@@ -522,15 +523,12 @@ static int loop_make_request(request_que
goto out;
if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
goto out;
- lo->lo_pending++;
loop_add_bio(lo, old_bio);
+ wake_up(&lo->lo_event);
spin_unlock_irq(&lo->lo_lock);
- complete(&lo->lo_bh_done);
return 0;
out:
- if (lo->lo_pending == 0)
- complete(&lo->lo_bh_done);
spin_unlock_irq(&lo->lo_lock);
bio_io_error(old_bio, old_bio->bi_size);
return 0;
@@ -570,14 +568,18 @@ static inline void loop_handle_bio(struc
* to avoid blocking in our make_request_fn. it also does loop decrypting
* on reads for block backed loop, as that is too heavy to do from
* b_end_io context where irqs may be disabled.
+ *
+ * Loop explanation: loop_clr_fd() sets lo_state to Lo_rundown before
+ * calling kthread_stop(). Therefore once kthread_should_stop() is
+ * true, make_request will not place any more requests. Therefore
+ * once kthread_should_stop() is true and lo_bio is NULL, we are
+ * done with the loop.
*/
static int loop_thread(void *data)
{
struct loop_device *lo = data;
struct bio *bio;
- daemonize("loop%d", lo->lo_number);
-
/*
* loop can be used in an encrypted device,
* hence, it mustn't be stopped at all
@@ -587,47 +589,21 @@ static int loop_thread(void *data)
set_user_nice(current, -20);
- lo->lo_state = Lo_bound;
- lo->lo_pending = 1;
-
- /*
- * complete it, we are running
- */
- complete(&lo->lo_done);
+ while (!kthread_should_stop() || lo->lo_bio) {
- for (;;) {
- int pending;
+ wait_event_interruptible(lo->lo_event,
+ lo->lo_bio || kthread_should_stop());
- if (wait_for_completion_interruptible(&lo->lo_bh_done))
+ if (!lo->lo_bio)
continue;
-
spin_lock_irq(&lo->lo_lock);
-
- /*
- * could be completed because of tear-down, not pending work
- */
- if (unlikely(!lo->lo_pending)) {
- spin_unlock_irq(&lo->lo_lock);
- break;
- }
-
bio = loop_get_bio(lo);
- lo->lo_pending--;
- pending = lo->lo_pending;
spin_unlock_irq(&lo->lo_lock);
BUG_ON(!bio);
loop_handle_bio(lo, bio);
-
- /*
- * upped both for pending work and tear-down, lo_pending
- * will hit zero then
- */
- if (unlikely(!pending))
- break;
}
- complete(&lo->lo_done);
return 0;
}
@@ -837,10 +813,15 @@ static int loop_set_fd(struct loop_devic
set_blocksize(bdev, lo_blocksize);
- error = kernel_thread(loop_thread, lo, CLONE_KERNEL);
- if (error < 0)
+ lo->lo_thread = kthread_create(loop_thread, lo, "loop%d",
+ lo->lo_number);
+ if (IS_ERR(lo->lo_thread)) {
+ error = PTR_ERR(lo->lo_thread);
+ lo->lo_thread = NULL;
goto out_putf;
- wait_for_completion(&lo->lo_done);
+ }
+ lo->lo_state = Lo_bound;
+ wake_up_process(lo->lo_thread);
return 0;
out_putf:
@@ -904,12 +885,9 @@ static int loop_clr_fd(struct loop_devic
spin_lock_irq(&lo->lo_lock);
lo->lo_state = Lo_rundown;
- lo->lo_pending--;
- if (!lo->lo_pending)
- complete(&lo->lo_bh_done);
spin_unlock_irq(&lo->lo_lock);
- wait_for_completion(&lo->lo_done);
+ kthread_stop(lo->lo_thread);
lo->lo_backing_file = NULL;
@@ -922,6 +900,7 @@ static int loop_clr_fd(struct loop_devic
lo->lo_sizelimit = 0;
lo->lo_encrypt_key_size = 0;
lo->lo_flags = 0;
+ lo->lo_thread = NULL;
memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
memset(lo->lo_file_name, 0, LO_NAME_SIZE);
@@ -1284,9 +1263,9 @@ static int __init loop_init(void)
if (!lo->lo_queue)
goto out_mem4;
mutex_init(&lo->lo_ctl_mutex);
- init_completion(&lo->lo_done);
- init_completion(&lo->lo_bh_done);
lo->lo_number = i;
+ lo->lo_thread = NULL;
+ init_waitqueue_head(&lo->lo_event);
spin_lock_init(&lo->lo_lock);
disk->major = LOOP_MAJOR;
disk->first_minor = i;
diff --git a/include/linux/loop.h b/include/linux/loop.h
index e76c761..191a595 100644
--- a/include/linux/loop.h
+++ b/include/linux/loop.h
@@ -59,10 +59,9 @@ struct loop_device {
struct bio *lo_bio;
struct bio *lo_biotail;
int lo_state;
- struct completion lo_done;
- struct completion lo_bh_done;
struct mutex lo_ctl_mutex;
- int lo_pending;
+ struct task_struct *lo_thread;
+ wait_queue_head_t lo_event;
request_queue_t *lo_queue;
};
--
1.1.6
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists