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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 /drivers/char/sysrq.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 'drivers/char/sysrq.c')
-rw-r--r--drivers/char/sysrq.c19
1 files changed, 18 insertions, 1 deletions
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 33a9351c896d..5afe7316c72e 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -346,6 +346,19 @@ static struct sysrq_key_op sysrq_moom_op = {
.enable_mask = SYSRQ_ENABLE_SIGNAL,
};
+#ifdef CONFIG_BLOCK
+static void sysrq_handle_thaw(int key, struct tty_struct *tty)
+{
+ emergency_thaw_all();
+}
+static struct sysrq_key_op sysrq_thaw_op = {
+ .handler = sysrq_handle_thaw,
+ .help_msg = "thaw-filesystems(J)",
+ .action_msg = "Emergency Thaw of all frozen filesystems",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
+};
+#endif
+
static void sysrq_handle_kill(int key, struct tty_struct *tty)
{
send_sig_all(SIGKILL);
@@ -396,9 +409,13 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
&sysrq_moom_op, /* f */
/* g: May be registered by ppc for kgdb */
NULL, /* g */
- NULL, /* h */
+ NULL, /* h - reserved for help */
&sysrq_kill_op, /* i */
+#ifdef CONFIG_BLOCK
+ &sysrq_thaw_op, /* j */
+#else
NULL, /* j */
+#endif
&sysrq_SAK_op, /* k */
#ifdef CONFIG_SMP
&sysrq_showallcpus_op, /* l */