f2fs: do not use mutex lock in atomic context

Fix below warning coming because of using mutex lock in atomic context.

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:98
in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh
Preemption disabled at: __radix_tree_preload+0x28/0x130
Call trace:
 dump_backtrace+0x0/0x2b4
 show_stack+0x20/0x28
 dump_stack+0xa8/0xe0
 ___might_sleep+0x144/0x194
 __might_sleep+0x58/0x8c
 mutex_lock+0x2c/0x48
 f2fs_trace_pid+0x88/0x14c
 f2fs_set_node_page_dirty+0xd0/0x184

Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with
spin_lock() acquired.
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/trace.c

@@ -14,7 +14,7 @@
 #include "trace.h"
 
 static RADIX_TREE(pids, GFP_ATOMIC);
-static struct mutex pids_lock;
+static spinlock_t pids_lock;
 static struct last_io_info last_io;
 
 static inline void __print_last_io(void)
@@ -58,23 +58,29 @@ void f2fs_trace_pid(struct page *page)
 
 	set_page_private(page, (unsigned long)pid);
 
+retry:
 	if (radix_tree_preload(GFP_NOFS))
 		return;
 
-	mutex_lock(&pids_lock);
+	spin_lock(&pids_lock);
 	p = radix_tree_lookup(&pids, pid);
 	if (p == current)
 		goto out;
 	if (p)
 		radix_tree_delete(&pids, pid);
 
-	f2fs_radix_tree_insert(&pids, pid, current);
+	if (radix_tree_insert(&pids, pid, current)) {
+		spin_unlock(&pids_lock);
+		radix_tree_preload_end();
+		cond_resched();
+		goto retry;
+	}
 
 	trace_printk("%3x:%3x %4x %-16s\n",
 			MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
 			pid, current->comm);
 out:
-	mutex_unlock(&pids_lock);
+	spin_unlock(&pids_lock);
 	radix_tree_preload_end();
 }
 
@@ -119,7 +125,7 @@ void f2fs_trace_ios(struct f2fs_io_info *fio, int flush)
 
 void f2fs_build_trace_ios(void)
 {
-	mutex_init(&pids_lock);
+	spin_lock_init(&pids_lock);
 }
 
 #define PIDVEC_SIZE	128
@@ -147,7 +153,7 @@ void f2fs_destroy_trace_ios(void)
 	pid_t next_pid = 0;
 	unsigned int found;
 
-	mutex_lock(&pids_lock);
+	spin_lock(&pids_lock);
 	while ((found = gang_lookup_pids(pid, next_pid, PIDVEC_SIZE))) {
 		unsigned idx;
 
@@ -155,5 +161,5 @@ void f2fs_destroy_trace_ios(void)
 		for (idx = 0; idx < found; idx++)
 			radix_tree_delete(&pids, pid[idx]);
 	}
-	mutex_unlock(&pids_lock);
+	spin_unlock(&pids_lock);
 }