Any process attempting to write to a frozen filesystem uninterruptibly and
unkillably waits for the filesystem to be thawed. This wait is of unbounded
length. Ignore such waits in the hung_task detector.
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
---
diff -urNp linux-3.6.1-orig/fs/super.c linux-3.6.1/fs/super.c
--- linux-3.6.1-orig/fs/super.c 2012-10-01 08:47:46.000000000 +0900
+++ linux-3.6.1/fs/super.c 2012-10-12 18:01:56.881255168 +0900
@@ -46,6 +46,13 @@ static char *sb_writers_name[SB_FREEZE_L
"sb_internal",
};
+static inline void wait_thaw(struct super_block *sb, int level)
+{
+ current->flags |= PF_FSFROZEN;
+ wait_event(sb->s_writers.wait_unfrozen, sb->s_writers.frozen < level);
+ current->flags &= ~ PF_FSFROZEN;
+}
+
/*
* One thing we have to be careful of with a per-sb shrinker is that we don't
* drop the last active reference to the superblock from within the shrinker.
@@ -663,8 +670,7 @@ struct super_block *get_super_thawed(str
if (!s || s->s_writers.frozen == SB_UNFROZEN)
return s;
up_read(&s->s_umount);
- wait_event(s->s_writers.wait_unfrozen,
- s->s_writers.frozen == SB_UNFROZEN);
+ wait_thaw(s, SB_FREEZE_WRITE);
put_super(s);
}
}
@@ -1227,8 +1233,7 @@ retry:
if (unlikely(sb->s_writers.frozen >= level)) {
if (!wait)
return 0;
- wait_event(sb->s_writers.wait_unfrozen,
- sb->s_writers.frozen < level);
+ wait_thaw(sb, level);
}
#ifdef CONFIG_LOCKDEP
diff -urNp linux-3.6.1-orig/include/linux/sched.h linux-3.6.1/include/linux/sched.h
--- linux-3.6.1-orig/include/linux/sched.h 2012-10-01 08:47:46.000000000 +0900
+++ linux-3.6.1/include/linux/sched.h 2012-10-12 17:46:48.909249791 +0900
@@ -1803,6 +1803,7 @@ extern void thread_group_times(struct ta
#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
#define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezable */
+#define PF_FSFROZEN 0x80000000 /* Waiting filesystem thaw */
/*
* Only the _current_ task can read/write to tsk->flags, but other
diff -urNp linux-3.6.1-orig/kernel/hung_task.c linux-3.6.1/kernel/hung_task.c
--- linux-3.6.1-orig/kernel/hung_task.c 2012-10-01 08:47:46.000000000 +0900
+++ linux-3.6.1/kernel/hung_task.c 2012-10-12 18:04:02.465256245 +0900
@@ -73,10 +73,11 @@ static void check_hung_task(struct task_
unsigned long switch_count = t->nvcsw + t->nivcsw;
/*
- * Ensure the task is not frozen.
- * Also, skip vfork and any other user process that freezer should skip.
+ * Ensure the task is not frozen or waiting for a filesystem to be
+ * thawed to proceed with a write. Also, skip vfork and any other user
+ * process that freezer should skip.
*/
- if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP)))
+ if (unlikely(t->flags & (PF_FROZEN | PF_FSFROZEN | PF_FREEZER_SKIP)))
return;
/*
--
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