From 06b534773d5a7dbfc9d0cf04fa6770a14c77d67d Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Sat, 4 May 2013 00:11:23 +0200
Subject: [PATCH] --- yaml --- r: 372728 b: refs/heads/master c:
 5ae98f1589e076e4b314fc54ae2beac58842ddc2 h: refs/heads/master v: v3

---
 [refs]                   | 2 +-
 trunk/include/linux/fs.h | 7 +++++++
 trunk/kernel/acct.c      | 7 ++++++-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index b25f95828ee7..3c9a5bf28a73 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 9dcc26cf67fb7db7613290e62eeed6c4276c75ce
+refs/heads/master: 5ae98f1589e076e4b314fc54ae2beac58842ddc2
diff --git a/trunk/include/linux/fs.h b/trunk/include/linux/fs.h
index e8cd6b839675..b5a24ba83b6f 100644
--- a/trunk/include/linux/fs.h
+++ b/trunk/include/linux/fs.h
@@ -2227,6 +2227,13 @@ static inline void file_start_write(struct file *file)
 	__sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, true);
 }
 
+static inline bool file_start_write_trylock(struct file *file)
+{
+	if (!S_ISREG(file_inode(file)->i_mode))
+		return true;
+	return __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, false);
+}
+
 static inline void file_end_write(struct file *file)
 {
 	if (!S_ISREG(file_inode(file)->i_mode))
diff --git a/trunk/kernel/acct.c b/trunk/kernel/acct.c
index 85389fe2abd0..8d6e145138bb 100644
--- a/trunk/kernel/acct.c
+++ b/trunk/kernel/acct.c
@@ -539,11 +539,16 @@ static void do_acct_process(struct bsd_acct_struct *acct,
 	ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
 	ac.ac_swaps = encode_comp_t(0);
 
+	/*
+	 * Get freeze protection. If the fs is frozen, just skip the write
+	 * as we could deadlock the system otherwise.
+	 */
+	if (!file_start_write_trylock(file))
+		goto out;
 	/*
 	 * Kernel segment override to datasegment and write it
 	 * to the accounting file.
 	 */
-	file_start_write(file);
 	fs = get_fs();
 	set_fs(KERNEL_DS);
 	/*