[RFC PATCH v2 4/9] fuse: handle stale inode connection in fuse_queue_forget

[Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>]

We don't want to send FUSE_FORGET request to the new
fuse daemon if inode was lookuped by the old fuse daemon
because it can confuse and break userspace (libfuse).

For now, just add a new argument to fuse_queue_forget and
handle it. Adjust all callers to match the old behaviour.

Cc: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Amir Goldstein <amir73il@xxxxxxxxx>
Cc: Stéphane Graber <stgraber@xxxxxxxxxx>
Cc: Seth Forshee <sforshee@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxx>
Cc: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx>
Cc: Bernd Schubert <bschubert@xxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: criu@xxxxxxxxxx
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
---
 fs/fuse/dev.c    | 4 ++--
 fs/fuse/dir.c    | 8 ++++----
 fs/fuse/fuse_i.h | 2 +-
 fs/fuse/inode.c  | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index eb4f88e3dc97..2e7cd60b685e 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -234,7 +234,7 @@ __releases(fiq->lock)
 }
 
 void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
-		       u64 nodeid, u64 nlookup)
+		       u64 nodeid, u64 nlookup, bool stale_inode_conn)
 {
 	struct fuse_iqueue *fiq = &fc->iq;
 
@@ -242,7 +242,7 @@ void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
 	forget->forget_one.nlookup = nlookup;
 
 	spin_lock(&fiq->lock);
-	if (fiq->connected) {
+	if (fiq->connected && likely(!stale_inode_conn)) {
 		fiq->forget_list_tail->next = forget;
 		fiq->forget_list_tail = forget;
 		fiq->ops->wake_forget_and_unlock(fiq);
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 5a4a7155cf1c..7e308a655191 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -250,7 +250,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 			if (outarg.nodeid != get_node_id(inode) ||
 			    (bool) IS_AUTOMOUNT(inode) != (bool) (outarg.attr.flags & FUSE_ATTR_SUBMOUNT)) {
 				fuse_queue_forget(fm->fc, forget,
-						  outarg.nodeid, 1);
+						  outarg.nodeid, 1, false);
 				goto invalid;
 			}
 			spin_lock(&fi->lock);
@@ -403,7 +403,7 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name
 			   attr_version);
 	err = -ENOMEM;
 	if (!*inode) {
-		fuse_queue_forget(fm->fc, forget, outarg->nodeid, 1);
+		fuse_queue_forget(fm->fc, forget, outarg->nodeid, 1, false);
 		goto out;
 	}
 	err = 0;
@@ -690,7 +690,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 	if (!inode) {
 		flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
 		fuse_sync_release(NULL, ff, flags);
-		fuse_queue_forget(fm->fc, forget, outentry.nodeid, 1);
+		fuse_queue_forget(fm->fc, forget, outentry.nodeid, 1, false);
 		err = -ENOMEM;
 		goto out_err;
 	}
@@ -815,7 +815,7 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
 	inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
 			  &outarg.attr, entry_attr_timeout(&outarg), 0);
 	if (!inode) {
-		fuse_queue_forget(fm->fc, forget, outarg.nodeid, 1);
+		fuse_queue_forget(fm->fc, forget, outarg.nodeid, 1, false);
 		return -ENOMEM;
 	}
 	kfree(forget);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 8d4276d7ab1e..be5d5d3fe6f5 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1008,7 +1008,7 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name
  * Send FORGET command
  */
 void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
-		       u64 nodeid, u64 nlookup);
+		       u64 nodeid, u64 nlookup, bool stale_inode_conn);
 
 struct fuse_forget_link *fuse_alloc_forget(void);
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 009fe5bbb855..e5ad5d4c215a 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -124,7 +124,7 @@ static void fuse_evict_inode(struct inode *inode)
 			fuse_dax_inode_cleanup(inode);
 		if (fi->nlookup) {
 			fuse_queue_forget(fc, fi->forget, fi->nodeid,
-					  fi->nlookup);
+					  fi->nlookup, false);
 			fi->forget = NULL;
 		}
 	}
-- 
2.34.1