Messages in this thread Patch in this message |  | | | Date | Tue, 3 Feb 2009 14:01:35 -0800 | | From | Andrew Morton <> | | Subject | Re: [PATCH V4] Allow SysRq emergency thaw to thaw frozen filesystems |
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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>
--- 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.
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.
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