Patch "ovl: fix failure to fsync lower dir" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

ovl: fix failure to fsync lower dir

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ovl-fix-failure-to-fsync-lower-dir.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Amir Goldstein <[email protected]>
Date: Wed, 8 Nov 2017 09:39:46 +0200
Subject: ovl: fix failure to fsync lower dir
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From: Amir Goldstein <[email protected]>

commit d796e77f1dd541fe34481af2eee6454688d13982 upstream.

As a writable mount, it is not expected for overlayfs to return EINVAL/EROFS for fsync, even if dir/file is not changed.

This commit fixes the case of fsync of directory, which is easier to address, because overlayfs already implements fsync file operation for directories.

The problem reported by Raphael is that new PostgreSQL 10.0 with a database in overlayfs where lower layer in squashfs fails to start. The failure is due to fsync error, when PostgreSQL does fsync on all existing db directories on startup and a specific directory exists lower layer with no changes.

---
 fs/overlayfs/readdir.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -769,10 +769,14 @@ static int ovl_dir_fsync(struct file *fi
 	struct dentry *dentry = file->f_path.dentry;
 	struct file *realfile = od->realfile;
 
+	/* Nothing to sync for lower */
+	if (!OVL_TYPE_UPPER(ovl_path_type(dentry)))
+		return 0;
+
 	/*
 	 * Need to check if we started out being a lower dir, but got copied up
 	 */
-	if (!od->is_upper && OVL_TYPE_UPPER(ovl_path_type(dentry))) {
+	if (!od->is_upper) {
 		struct inode *inode = file_inode(file);
 
 		realfile = READ_ONCE(od->upperfile);

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/ovl-take-mnt_want_write-for-removing-impure-xattr.patch queue-4.15/ovl-take-mnt_want_write-for-work-index-dir-setup.patch queue-4.15/ovl-hash-directory-inodes-for-fsnotify.patch queue-4.15/ovl-force-r-o-mount-when-index-dir-creation-fails.patch queue-4.15/ovl-fix-failure-to-fsync-lower-dir.patch