linux-kernel - [PATCH 2/2] nilfs2: use inode_set_flags() in nilfs_set_inode

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Date:	Wed,  8 Apr 2015 23:49:45 +0900
From:	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-nilfs@...r.kernel.org,
	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	"Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 2/2] nilfs2: use inode_set_flags() in nilfs_set_inode_flags()

Use inode_set_flags() to atomically set i_flags instead of clearing
out the S_IMMUTABLE, S_APPEND, etc. flags and then setting them from
the FS_IMMUTABLE_FL, FS_APPEND_FL flags to avoid a race where an
immutable file has the immutable flag cleared for a brief window of
time.

This is a similar fix to commit 5f16f3225b06 ("ext4: atomically set
inode->i_flags in ext4_set_inode_flags()").

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
Cc: "Theodore Ts'o" <tytso@....edu>
---
 fs/nilfs2/inode.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 0c28ccb..72c7fbf 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -443,19 +443,20 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
 void nilfs_set_inode_flags(struct inode *inode)
 {
 	unsigned int flags = NILFS_I(inode)->i_flags;
+	unsigned int new_fl = 0;
 
-	inode->i_flags &= ~(S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME |
-			    S_DIRSYNC);
 	if (flags & FS_SYNC_FL)
-		inode->i_flags |= S_SYNC;
+		new_fl |= S_SYNC;
 	if (flags & FS_APPEND_FL)
-		inode->i_flags |= S_APPEND;
+		new_fl |= S_APPEND;
 	if (flags & FS_IMMUTABLE_FL)
-		inode->i_flags |= S_IMMUTABLE;
+		new_fl |= S_IMMUTABLE;
 	if (flags & FS_NOATIME_FL)
-		inode->i_flags |= S_NOATIME;
+		new_fl |= S_NOATIME;
 	if (flags & FS_DIRSYNC_FL)
-		inode->i_flags |= S_DIRSYNC;
+		new_fl |= S_DIRSYNC;
+	inode_set_flags(inode, new_fl, S_SYNC | S_APPEND | S_IMMUTABLE |
+			S_NOATIME | S_DIRSYNC);
 }
 
 int nilfs_read_inode_common(struct inode *inode,
-- 
1.8.3.1

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