[Devel] [PATCH] ovl: do not generate duplicate fsnotify events for "fake" path

[Valeriy Vdovin]

From: Amir Goldstein <amir73il at gmail.com>

Overlayfs "fake" path is used for stacked file operations on underlying
files.  Operations on files with "fake" path must not generate fsnotify
events with path data, because those events have already been generated at
overlayfs layer and because the reported event->fd for fanotify marks on
underlying inode/filesystem will have the wrong path (the overlayfs path).

Link: https://lore.kernel.org/linux-fsdevel/20190423065024.12695-1-jencce.kernel@gmail.com/
Reported-by: Murphy Zhou <jencce.kernel at gmail.com>
Fixes: d1d04ef8572b ("ovl: stack file ops")
Signed-off-by: Amir Goldstein <amir73il at gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi at redhat.com>

(cherry-picked from d989903058a83e8536cc7aadf9256a47d5c173fe)
https://jira.sw.ru/browse/PSBM-102737

Signed-off-by: Valeriy Vdovin <valeriy.vdovin at virtuozzo.com>
---
 fs/overlayfs/file.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 84dd957..6f6eb63 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -29,10 +29,11 @@ static struct file *ovl_open_realfile(const struct file *file,
 	struct inode *inode = file_inode(file);
 	struct file *realfile;
 	const struct cred *old_cred;
+	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
 
 	old_cred = ovl_override_creds(inode->i_sb);
-	realfile = open_with_fake_path(&file->f_path, file->f_flags | O_NOATIME,
-				       realinode, current_cred());
+	realfile = open_with_fake_path(&file->f_path, flags, realinode,
+				       current_cred());
 	revert_creds(old_cred);
 
 	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
@@ -50,7 +51,7 @@ static int ovl_change_flags(struct file *file, unsigned int flags)
 	int err;
 
 	/* No atime modificaton on underlying */
-	flags |= O_NOATIME;
+	flags |= O_NOATIME | FMODE_NONOTIFY;
 
 	/* If some flag changed that cannot be changed then something's amiss */
 	if (WARN_ON((file->f_flags ^ flags) & ~OVL_SETFL_MASK))
-- 
1.8.3.1