Re: [patch 1/1] PM: Adds remount fs ro at suspend

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Christoph Hellwig wrote:
On Fri, Feb 02, 2007 at 01:50:10PM -1000, [email protected] wrote:

This adds the ability for the file system to remounted as read only during a
system suspend. Log the mount points so when the resume occurs, they can be remounted back to their original states. This is so in an advent of a power
failure, we try our best to keep data from being corrupted or lost.

Can you please explain why this can't be done in userspace?

I am sure it can. The idea came from customer inputs, speed is my guess. echo mem > /sys/../state seems a whole lot simpler and cleaner than having userspace figure out what it mounted and then doing echo mem.

In fact
all existing suspend solutions seem to be doing fine doing things like
this in userspace.

I guess I missed that boat. If you don't mind, could you point at one solution.


+static struct suspremount *suspremount_list;
+
< snipped>

+void suspend_remount_all_fs_ro(void)
+{
+	suspremount_list = NULL;
+	emergency_remount();

NACK.  emergency_remount is exactly what it sais and should never ever
be used for a system that you want to keep on using later on.

The code "emergency_remount" is almost identical to what we have been using. I wanted to reuse existing code rather than dup it.

If you
look at it's implementation it's not correct and can't serve as more than
a bandaid for susrq.

From our customer experience, we have not gotten an bad feedback on it. It seems to address there needs.

 In fact we should probably just remove it..

+EXPORT_SYMBOL(suspend_remount_all_fs_ro);

And something like this for sure should not be exported.

+EXPORT_SYMBOL(resume_remount_fs_rw);

ditto.


All the code corrects have been address in my upcoming version.

Many thanks for you time and feedback.

Armin
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