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SubjectRe: [PATCH] Freeze bdevs when freezing processes.
Date
On Monday, 23 October 2006 06:12, Nigel Cunningham wrote:
> XFS can continue to submit I/O from a timer routine, even after
> freezeable kernel and userspace threads are frozen. This doesn't seem to
> be an issue for current swsusp code, but is definitely an issue for
> Suspend2, where the pages being written could be overwritten by
> Suspend2's atomic copy.
>
> We can address this issue by freezing bdevs after stopping userspace
> threads, and thawing them prior to thawing userspace.

Okay, it turns out we'll probably need this, so a couple of comments follow.

> Signed-off-by: Nigel Cunningham <nigel@suspend2.net>
>
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 4a001fe..ddeeb50 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -13,6 +13,7 @@ #include <linux/interrupt.h>
> #include <linux/suspend.h>
> #include <linux/module.h>
> #include <linux/syscalls.h>
> +#include <linux/buffer_head.h>
> #include <linux/freezer.h>
>
> /*
> @@ -20,6 +21,58 @@ #include <linux/freezer.h>
> */
> #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)

I'd call it thaw_filesystems()

> +{
> + 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)

I'd call it freeze_filesystems()

> +{
> + 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);
> + if (!fs)
> + return 1;

return -ENOMEM

> + 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)
> {
> @@ -119,7 +172,7 @@ int freeze_processes(void)
> read_unlock(&tasklist_lock);
> todo += nr_user;
> if (!user_frozen && !nr_user) {
> - sys_sync();
> + freezer_make_fses_ro();
> start_time = jiffies;
> }
> user_frozen = !nr_user;
> @@ -174,6 +227,12 @@ void thaw_some_processes(int all)
> "Strange, %s not stopped\n", p->comm );
> } while_each_thread(g, p);
>
> + if (!pass) {
> + read_unlock(&tasklist_lock);
> + freezer_make_fses_rw();
> + read_lock(&tasklist_lock);
> + }
> +
> pass++;
> } while (pass < 2 && all);
>
>
>
>
>

Greetings,
Rafael


--
You never change things by fighting the existing reality.
R. Buckminster Fuller
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