Re: [RFC][PATCH] swsusp: support creating bigger images

Nigel Cunningham
2006-04-26T00:50:43Z

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Hi.

On Wednesday 26 April 2006 08:43, Rafael J. Wysocki wrote:
> Hi,
>
> On Wednesday 26 April 2006 00:25, Pavel Machek wrote:
> > > > It does apply to all of the LRU pages. This is what I've been doing
> > > > for years now. The only corner case I've come across is XFS. It still
> > > > wants to write data even when there's nothing to do and it's threads
> > > > are frozen (IIRC - haven't looked at it for a while). I got around
> > > > that by freezing bdevs when freezing processes.
> > >
> > > This means if we freeze bdevs, we'll be able to save all of the LRU
> > > pages, except for the pages mapped by the current task, without
> > > copying. I think we can try to do this, but we'll need a patch to
> > > freeze bdevs for this purpose. ;-)
> >
> > ...adding more dependencies to how vm/blockdevs work. I'd say current
> > code is complex enough...
>
> Well, why don't we see the patch? If it's too complex, we can just decide
> not to use it. :-)

In Suspend2, I'm still using a different version of process.c to what you guys
have. In my version, I thaw kernelspace, then thaw bdevs, then thaw userspace.
The version below just thaws bdevs after thawing all processes. I think that
might need modification, but thought I'd post this now so you can see how
complicated or otherwise it is.

Regards,

Nigel

diff -ruN linux-2.6.17-rc2/kernel/power/process.c bdev-freeze/kernel/power/process.c
--- linux-2.6.17-rc2/kernel/power/process.c 2006-04-19 14:27:36.000000000 +1000
+++ bdev-freeze/kernel/power/process.c 2006-04-26 10:44:56.000000000 +1000
@@ -19,6 +19,56 @@
*/
#define TIMEOUT (20 * HZ)

+struct frozen_fs
+{
+ struct list_head fsb_list;
+ struct super_block *sb;
+};
+
+LIST_HEAD(frozen_fs_list);
+
+void freezer_make_fses_rw(void)
+{
+ struct frozen_fs *fs, *next_fs;
+
+ list_for_each_entry_safe(fs, next_fs, &frozen_fs_list, fsb_list) {
+ thaw_bdev(fs->sb->s_bdev, fs->sb);
+
+ list_del(&fs->fsb_list);
+ kfree(fs);
+ }
+}
+
+/*
+ * Done after userspace is frozen, so there should be no danger of
+ * fses being unmounted while we're in here.
+ */
+int freezer_make_fses_ro(void)
+{
+ struct frozen_fs *fs;
+ struct super_block *sb;
+
+ /* Generate the list */
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ if (!sb->s_root || !sb->s_bdev ||
+ (sb->s_frozen == SB_FREEZE_TRANS) ||
+ (sb->s_flags & MS_RDONLY))
+ continue;
+
+ fs = kmalloc(sizeof(struct frozen_fs), GFP_ATOMIC);
+ fs->sb = sb;
+ list_add_tail(&fs->fsb_list, &frozen_fs_list);
+ };
+
+ /* Do the freezing in reverse order so filesystems dependant
+ * upon others are frozen in the right order. (Eg loopback
+ * on ext3). */
+ list_for_each_entry_reverse(fs, &frozen_fs_list, fsb_list)
+ freeze_bdev(fs->sb->s_bdev);
+
+ return 0;
+}
+

static inline int freezeable(struct task_struct * p)
{
@@ -77,6 +127,7 @@
printk( "Stopping tasks: " );
start_time = jiffies;
user_frozen = 0;
+ bdevs_frozen = 0;
do {
nr_user = todo = 0;
read_lock(&tasklist_lock);
@@ -107,6 +158,10 @@
start_time = jiffies;
}
user_frozen = !nr_user;
+
+ if (user_frozen && !bdevs_frozen)
+ freezer_make_fses_ro();
+
yield(); /* Yield is okay here */
if (todo && time_after(jiffies, start_time + TIMEOUT))
break;
@@ -156,6 +211,8 @@
printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
} while_each_thread(g, p);

+ freezer_make_fses_rw();
+
read_unlock(&tasklist_lock);
schedule();
printk( " done\n" );

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