From c2d7543851849a6923680cdd7e1047ed1a84a1c5 Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Tue, 31 Mar 2009 15:23:46 -0700 Subject: 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 Cc: Takashi Sato Signed-off-by: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/fs.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/fs.h b/include/linux/fs.h index 87e7bfc5ebd..61211ad823f 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1878,6 +1878,7 @@ extern struct block_device *open_by_devnum(dev_t, fmode_t); extern void invalidate_bdev(struct block_device *); extern int sync_blockdev(struct block_device *bdev); extern struct super_block *freeze_bdev(struct block_device *); +extern void emergency_thaw_all(void); extern int thaw_bdev(struct block_device *bdev, struct super_block *sb); extern int fsync_bdev(struct block_device *); extern int fsync_super(struct super_block *); -- cgit v1.2.3