lkml.org 
[lkml]   [2009]   [Feb]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH V4] Allow SysRq emergency thaw to thaw frozen filesystems
Andrew Morton wrote:
> On Mon, 02 Feb 2009 16:55:18 -0600
> Eric Sandeen <sandeen@redhat.com> wrote:
>
>> (this version fixes a couple small issues raised by Randy Dunlap)
>> (and adds sb_lock locking I forgot, as akpm pointed out)
>> (Randy's CONFIG_BLOCK fix should still apply over this)
>
> <converts it to a delta so I can see what you did>

Sorry, didn't know if you want deltas on top of old patches or new
respun patches. Guess now I know :)

> --- a/fs/buffer.c~allow-sysrq-emergency-thaw-to-thaw-frozen-filesystems-v4
> +++ a/fs/buffer.c
> @@ -263,11 +263,13 @@ void do_thaw_all(unsigned long unused)
> struct super_block *sb;
> char b[BDEVNAME_SIZE];
>
> + spin_lock(&sb_lock);
> list_for_each_entry(sb, &super_blocks, s_list) {
> while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
> printk(KERN_WARNING "Emergency Thaw on %s\n",
> bdevname(sb->s_bdev, b));
> }
> + spin_unlock(&sb_lock);
> printk(KERN_WARNING "Emergency Thaw complete\n");
> }
>
> _
>
>
> Can't call thaw_bdev() under spinlock.

Oh, sigh, I've come full circle to what I started with that didn't work,
didn't I.

> If we're going to do this, I think it will need the whole
> sb_lock/s_count/s_umount song-n-dance.
>
> It's a pretty common operation. What you want is, I think, identical
> to sync_supers(), only with one line changed.
>
> so we could do
>
> void apply_to_all_supers(void (fn)(struct super_block *))
> {
> struct super_block *sb;
>
> spin_lock(&sb_lock);
> restart:
> list_for_each_entry(sb, &super_blocks, s_list) {
> if (sb->s_dirt) {
> sb->s_count++;
> spin_unlock(&sb_lock);
> down_read(&sb->s_umount);
> (*fn)(sb);
> up_read(&sb->s_umount);
> spin_lock(&sb_lock);
> if (__put_super_and_need_restart(sb))
> goto restart;
> }
> }
> spin_unlock(&sb_lock);
>
> }
>
> That isn't quite sufficient to use for get_super(), but I think it
> could be made so.
>
> Ditto user_get_super().
>
> Ditto do_emergency_remount()
>
> But that's a separate little project for someone. For the purposes of
> this patch I guess you could do yet another copy-n-paste.

Ok, thanks. Sorry for dragging this out through 5 revisions :(

-Eric


\
 
 \ /
  Last update: 2009-02-03 23:09    [from the cache]
©2003-2011 Jasper Spaans