Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex

Hi,

On Wednesday, 15 November 2006 21:23, Pavel Machek wrote:
Hi!

There's one more thing, actually. If the on-disk data and metadata are
changed _after_ the sync we do and _before_ we create the snapshot image,
and the subsequent resume fails,

Well, but this is equivalent to a power failure immediately after the sync, so
there _must_ be a way to recover the filesystem from that, no?

Exactly.

I think I'll prepare a patch for freezing the work queues and we'll see what
to do next.

Thanks!

Okay, the patch follows.

I've been running it for some time on my boxes and it doesn't seem to break
anything. However, I don't use XFS, so well ...

Greetings,
Rafael


Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
fs/xfs/linux-2.6/xfs_buf.c | 4 ++--
include/linux/workqueue.h | 8 +++++---
kernel/workqueue.c | 20 ++++++++++++++------
3 files changed, 21 insertions(+), 11 deletions(-)

Index: linux-2.6.19-rc5-mm2/include/linux/workqueue.h
===================================================================
--- linux-2.6.19-rc5-mm2.orig/include/linux/workqueue.h 2006-09-20 05:42:06.000000000 +0200
+++ linux-2.6.19-rc5-mm2/include/linux/workqueue.h 2006-11-15 21:58:40.000000000 +0100
@@ -55,9 +55,11 @@ struct execute_work {
} while (0)

extern struct workqueue_struct *__create_workqueue(const char *name,
- int singlethread);
-#define create_workqueue(name) __create_workqueue((name), 0)
-#define create_singlethread_workqueue(name) __create_workqueue((name), 1)
+ int singlethread,
+ int freezeable);
+#define create_workqueue(name) __create_workqueue((name), 0, 0)
+#define create_freezeable_workqueue(name) __create_workqueue((name), 0, 1)
+#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)

extern void destroy_workqueue(struct workqueue_struct *wq);

Index: linux-2.6.19-rc5-mm2/kernel/workqueue.c
===================================================================
--- linux-2.6.19-rc5-mm2.orig/kernel/workqueue.c 2006-11-15 21:32:13.000000000 +0100
+++ linux-2.6.19-rc5-mm2/kernel/workqueue.c 2006-11-15 22:27:40.000000000 +0100
@@ -31,6 +31,7 @@
#include <linux/mempolicy.h>
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
+#include <linux/freezer.h>

/*
* The per-CPU workqueue (if single thread, we always use the first
@@ -57,6 +58,8 @@ struct cpu_workqueue_struct {
struct task_struct *thread;

int run_depth; /* Detect run_workqueue() recursion depth */
+
+ int freezeable; /* Freeze the thread during suspend */
} ____cacheline_aligned;

/*
@@ -251,7 +254,8 @@ static int worker_thread(void *__cwq)
struct k_sigaction sa;
sigset_t blocked;

- current->flags |= PF_NOFREEZE;
+ if (!cwq->freezeable)
+ current->flags |= PF_NOFREEZE;

set_user_nice(current, -5);

@@ -274,6 +278,9 @@ static int worker_thread(void *__cwq)

set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
+ if (cwq->freezeable)
+ try_to_freeze();
+
add_wait_queue(&cwq->more_work, &wait);
if (list_empty(&cwq->worklist))
schedule();
@@ -350,7 +357,7 @@ void fastcall flush_workqueue(struct wor
EXPORT_SYMBOL_GPL(flush_workqueue);

static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
- int cpu)
+ int cpu, int freezeable)
{
struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
struct task_struct *p;
@@ -360,6 +367,7 @@ static struct task_struct *create_workqu
cwq->thread = NULL;
cwq->insert_sequence = 0;
cwq->remove_sequence = 0;
+ cwq->freezeable = freezeable;
INIT_LIST_HEAD(&cwq->worklist);
init_waitqueue_head(&cwq->more_work);
init_waitqueue_head(&cwq->work_done);
@@ -375,7 +383,7 @@ static struct task_struct *create_workqu
}

struct workqueue_struct *__create_workqueue(const char *name,
- int singlethread)
+ int singlethread, int freezeable)
{
int cpu, destroy = 0;
struct workqueue_struct *wq;
@@ -395,7 +403,7 @@ struct workqueue_struct *__create_workqu
mutex_lock(&workqueue_mutex);
if (singlethread) {
INIT_LIST_HEAD(&wq->list);
- p = create_workqueue_thread(wq, singlethread_cpu);
+ p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
if (!p)
destroy = 1;
else
@@ -403,7 +411,7 @@ struct workqueue_struct *__create_workqu
} else {
list_add(&wq->list, &workqueues);
for_each_online_cpu(cpu) {
- p = create_workqueue_thread(wq, cpu);
+ p = create_workqueue_thread(wq, cpu, freezeable);
if (p) {
kthread_bind(p, cpu);
wake_up_process(p);
@@ -657,7 +665,7 @@ static int __devinit workqueue_cpu_callb
mutex_lock(&workqueue_mutex);
/* Create a new workqueue thread for it. */
list_for_each_entry(wq, &workqueues, list) {
- if (!create_workqueue_thread(wq, hotcpu)) {
+ if (!create_workqueue_thread(wq, hotcpu, 0)) {
printk("workqueue for %i failed\n", hotcpu);
return NOTIFY_BAD;
}
Index: linux-2.6.19-rc5-mm2/fs/xfs/linux-2.6/xfs_buf.c
===================================================================
--- linux-2.6.19-rc5-mm2.orig/fs/xfs/linux-2.6/xfs_buf.c 2006-11-15 21:32:08.000000000 +0100
+++ linux-2.6.19-rc5-mm2/fs/xfs/linux-2.6/xfs_buf.c 2006-11-15 22:12:43.000000000 +0100
@@ -1826,11 +1826,11 @@ xfs_buf_init(void)
if (!xfs_buf_zone)
goto out_free_trace_buf;

- xfslogd_workqueue = create_workqueue("xfslogd");
+ xfslogd_workqueue = create_freezeable_workqueue("xfslogd");
if (!xfslogd_workqueue)
goto out_free_buf_zone;

- xfsdatad_workqueue = create_workqueue("xfsdatad");
+ xfsdatad_workqueue = create_freezeable_workqueue("xfsdatad");
if (!xfsdatad_workqueue)
goto out_destroy_xfslogd_workqueue;

-
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