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-rw-r--r--Documentation/sysrq.txt5
-rw-r--r--drivers/char/sysrq.c19
-rw-r--r--fs/buffer.c33
-rw-r--r--include/linux/fs.h1
4 files changed, 57 insertions, 1 deletions
diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt
index 9e592c718af..afa2946892d 100644
--- a/Documentation/sysrq.txt
+++ b/Documentation/sysrq.txt
@@ -81,6 +81,8 @@ On all - write a character to /proc/sysrq-trigger. e.g.:
'i' - Send a SIGKILL to all processes, except for init.
+'j' - Forcibly "Just thaw it" - filesystems frozen by the FIFREEZE ioctl.
+
'k' - Secure Access Key (SAK) Kills all programs on the current virtual
console. NOTE: See important comments below in SAK section.
@@ -160,6 +162,9 @@ t'E'rm and k'I'll are useful if you have some sort of runaway process you
are unable to kill any other way, especially if it's spawning other
processes.
+"'J'ust thaw it" is useful if your system becomes unresponsive due to a frozen
+(probably root) filesystem via the FIFREEZE ioctl.
+
* Sometimes SysRq seems to get 'stuck' after using it, what can I do?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
That happens to me, also. I've found that tapping shift, alt, and control
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 33a9351c896..5afe7316c72 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 */
diff --git a/fs/buffer.c b/fs/buffer.c
index c77b848c3d4..f5f8b15a6e4 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
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 *);