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authorEric Sandeen <sandeen@redhat.com>2009-04-01 02:23:46 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-01 19:59:17 +0400
commitc2d7543851849a6923680cdd7e1047ed1a84a1c5 (patch)
treebf3038819d4be83a1d1e64d7b95bbb3d9d908544 /fs/buffer.c
parent55a63998b8967615a15e2211ba0ff3a84a565824 (diff)
downloadlinux-c2d7543851849a6923680cdd7e1047ed1a84a1c5.tar.xz
filesystem freeze: allow SysRq emergency thaw to thaw frozen filesystems
Now that the filesystem freeze operation has been elevated to the VFS, and is just an ioctl away, some sort of safety net for unintentionally frozen root filesystems may be in order. The timeout thaw originally proposed did not get merged, but perhaps something like this would be useful in emergencies. For example, freeze /path/to/mountpoint may freeze your root filesystem if you forgot that you had that unmounted. I chose 'j' as the last remaining character other than 'h' which is sort of reserved for help (because help is generated on any unknown character). I've tested this on a non-root fs with multiple (nested) freezers, as well as on a system rendered unresponsive due to a frozen root fs. [randy.dunlap@oracle.com: emergency thaw only if CONFIG_BLOCK enabled] Signed-off-by: Eric Sandeen <sandeen@redhat.com> Cc: Takashi Sato <t-sato@yk.jp.nec.com> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/buffer.c')
-rw-r--r--fs/buffer.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index c77b848c3d43..f5f8b15a6e40 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -547,6 +547,39 @@ repeat:
return err;
}
+void do_thaw_all(unsigned long unused)
+{
+ struct super_block *sb;
+ char b[BDEVNAME_SIZE];
+
+ spin_lock(&sb_lock);
+restart:
+ list_for_each_entry(sb, &super_blocks, s_list) {
+ sb->s_count++;
+ spin_unlock(&sb_lock);
+ down_read(&sb->s_umount);
+ while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
+ printk(KERN_WARNING "Emergency Thaw on %s\n",
+ bdevname(sb->s_bdev, b));
+ up_read(&sb->s_umount);
+ spin_lock(&sb_lock);
+ if (__put_super_and_need_restart(sb))
+ goto restart;
+ }
+ spin_unlock(&sb_lock);
+ printk(KERN_WARNING "Emergency Thaw complete\n");
+}
+
+/**
+ * emergency_thaw_all -- forcibly thaw every frozen filesystem
+ *
+ * Used for emergency unfreeze of all filesystems via SysRq
+ */
+void emergency_thaw_all(void)
+{
+ pdflush_operation(do_thaw_all, 0);
+}
+
/**
* sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
* @mapping: the mapping which wants those buffers written