Patch "ovl: take mnt_want_write() for removing impure xattr" 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: take mnt_want_write() for removing impure xattr

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-take-mnt_want_write-for-removing-impure-xattr.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, 3 Jan 2018 18:54:42 +0200
Subject: ovl: take mnt_want_write() for removing impure xattr

From: Amir Goldstein <[email protected]>

commit a5a927a7c82e28ea76599dee4019c41e372c911f upstream.

The optimization in ovl_cache_get_impure() that tries to remove an unneeded "impure" xattr needs to take mnt_want_write() on upper fs.

---
 fs/overlayfs/readdir.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

@@ -593,8 +593,15 @@ static struct ovl_dir_cache *ovl_cache_g
 		return ERR_PTR(res);
 	}
 	if (list_empty(&cache->entries)) {
-		/* Good oportunity to get rid of an unnecessary "impure" flag */
-		ovl_do_removexattr(ovl_dentry_upper(dentry), OVL_XATTR_IMPURE);
+		/*
+		 * A good opportunity to get rid of an unneeded "impure" flag.
+		 * Removing the "impure" xattr is best effort.
+		 */
+		if (!ovl_want_write(dentry)) {
+			ovl_do_removexattr(ovl_dentry_upper(dentry),
+					   OVL_XATTR_IMPURE);
+			ovl_drop_write(dentry);
+		}
 		ovl_clear_flag(OVL_IMPURE, d_inode(dentry));
 		kfree(cache);
 		return NULL;

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