request for 4.14-stable: e8d4bfe3a715 ("ovl: Sync upper dirty data when syncing overlayfs")

request for 4.14-stable: e8d4bfe3a715 ("ovl: Sync upper dirty data when syncing overlayfs")

[Sudip Mukherjee]

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Hi Greg,

This was missing in 4.14-stable. Please apply to your queue.

--
Regards
Sudip

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>From 2ebe080a6236a3ff63f6fa0656ad2988e27e8e77 Mon Sep 17 00:00:00 2001
From: Chengguang Xu <cgxu@mykernel.net>
Date: Wed, 29 Nov 2017 10:01:32 +0800
Subject: [PATCH] ovl: Sync upper dirty data when syncing overlayfs

commit e8d4bfe3a71537284a90561f77c85dea6c154369 upstream

When executing filesystem sync or umount on overlayfs,
dirty data does not get synced as expected on upper filesystem.
This patch fixes sync filesystem method to keep data consistency
for overlayfs.

Signed-off-by: Chengguang Xu <cgxu@mykernel.net>
Fixes: e593b2bf513d ("ovl: properly implement sync_filesystem()")
Cc: <stable@vger.kernel.org> #4.11
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 fs/overlayfs/super.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index b8f8d666e8d4..ba20393d60ef 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -232,6 +232,7 @@ static void ovl_put_super(struct super_block *sb)
 	kfree(ufs);
 }
 
+/* Sync real dirty inodes in upper filesystem (if it exists) */
 static int ovl_sync_fs(struct super_block *sb, int wait)
 {
 	struct ovl_fs *ufs = sb->s_fs_info;
@@ -240,14 +241,24 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
 
 	if (!ufs->upper_mnt)
 		return 0;
-	upper_sb = ufs->upper_mnt->mnt_sb;
-	if (!upper_sb->s_op->sync_fs)
+
+	/*
+	 * If this is a sync(2) call or an emergency sync, all the super blocks
+	 * will be iterated, including upper_sb, so no need to do anything.
+	 *
+	 * If this is a syncfs(2) call, then we do need to call
+	 * sync_filesystem() on upper_sb, but enough if we do it when being
+	 * called with wait == 1.
+	 */
+	if (!wait)
 		return 0;
 
-	/* real inodes have already been synced by sync_filesystem(ovl_sb) */
+	upper_sb = ufs->upper_mnt->mnt_sb;
+
 	down_read(&upper_sb->s_umount);
-	ret = upper_sb->s_op->sync_fs(upper_sb, wait);
+	ret = sync_filesystem(upper_sb);
 	up_read(&upper_sb->s_umount);
+
 	return ret;
 }
 
-- 
2.11.0

Re: request for 4.14-stable: e8d4bfe3a715 ("ovl: Sync upper dirty data when syncing overlayfs")

[Greg Kroah-Hartman]

On Sun, Jul 29, 2018 at 06:50:04PM +0100, Sudip Mukherjee wrote:
> Hi Greg,
> 
> This was missing in 4.14-stable. Please apply to your queue.

Now applied, thanks.

greg k-h