To simplify crash recovery and reduce performance impact, backing_ids
are not persisted across daemon restarts. After crash recovery, this
may lead to resource leaks if backing file resources are not properly
cleaned up.

Add FUSE_DEV_IOC_BACKING_CLOSE_ALL ioctl to release all backing_ids
and put backing files. When the FUSE daemon restarts, it can use this
ioctl to cleanup all backing file resources.

Signed-off-by: Chunsheng Luo <luochunsheng@ustc.edu>
---
 fs/fuse/backing.c         | 19 +++++++++++++++++++
 fs/fuse/dev.c             | 16 ++++++++++++++++
 fs/fuse/fuse_i.h          |  1 +
 include/uapi/linux/fuse.h |  1 +
 4 files changed, 37 insertions(+)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index 4afda419dd14..e93d797a2cde 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -166,6 +166,25 @@ int fuse_backing_close(struct fuse_conn *fc, int backing_id)
 	return err;
 }
 
+static int fuse_backing_close_one(int id, void *p, void *data)
+{
+	struct fuse_conn *fc = data;
+
+	fuse_backing_close(fc, id);
+
+	return 0;
+}
+
+int fuse_backing_close_all(struct fuse_conn *fc)
+{
+	if (!fc->passthrough || !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	idr_for_each(&fc->backing_files_map, fuse_backing_close_one, fc);
+
+	return 0;
+}
+
 struct fuse_backing *fuse_backing_lookup(struct fuse_conn *fc, int backing_id)
 {
 	struct fuse_backing *fb;
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6d59cbc877c6..f05d55302598 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2654,6 +2654,19 @@ static long fuse_dev_ioctl_backing_close(struct file *file, __u32 __user *argp)
 	return fuse_backing_close(fud->fc, backing_id);
 }
 
+static long fuse_dev_ioctl_backing_close_all(struct file *file)
+{
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (IS_ERR(fud))
+		return PTR_ERR(fud);
+
+	if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
+		return -EOPNOTSUPP;
+
+	return fuse_backing_close_all(fud->fc);
+}
+
 static long fuse_dev_ioctl_sync_init(struct file *file)
 {
 	int err = -EINVAL;
@@ -2682,6 +2695,9 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 	case FUSE_DEV_IOC_BACKING_CLOSE:
 		return fuse_dev_ioctl_backing_close(file, argp);
 
+	case FUSE_DEV_IOC_BACKING_CLOSE_ALL:
+		return fuse_dev_ioctl_backing_close_all(file);
+
 	case FUSE_DEV_IOC_SYNC_INIT:
 		return fuse_dev_ioctl_sync_init(file);
 
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 7f16049387d1..33e91a5d3765 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1573,6 +1573,7 @@ void fuse_backing_files_init(struct fuse_conn *fc);
 void fuse_backing_files_free(struct fuse_conn *fc);
 int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map);
 int fuse_backing_close(struct fuse_conn *fc, int backing_id);
+int fuse_backing_close_all(struct fuse_conn *fc);
 
 /* passthrough.c */
 static inline struct fuse_backing *fuse_inode_backing(struct fuse_inode *fi)
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index c13e1f9a2f12..e4ff28a4ff40 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -1139,6 +1139,7 @@ struct fuse_backing_map {
 					     struct fuse_backing_map)
 #define FUSE_DEV_IOC_BACKING_CLOSE	_IOW(FUSE_DEV_IOC_MAGIC, 2, uint32_t)
 #define FUSE_DEV_IOC_SYNC_INIT		_IO(FUSE_DEV_IOC_MAGIC, 3)
+#define FUSE_DEV_IOC_BACKING_CLOSE_ALL	_IO(FUSE_DEV_IOC_MAGIC, 4)
 
 struct fuse_lseek_in {
 	uint64_t	fh;
-- 
2.43.0

To simplify crash recovery and reduce performance impact, backing_ids
are not persisted across daemon restarts. However, when the daemon
restarts and another process open the same FUSE file and assigning it
the same backing file (with the same inode) will also cause the
fuse_inode_uncached_io_start() function to fail due to a mismatch in
the fb pointer.

So Relax the validation in fuse_inode_uncached_io_start() to compare
backing inodes instead of fuse_backing pointers.

Signed-off-by: Chunsheng Luo <luochunsheng@ustc.edu>
---
 fs/fuse/iomode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/iomode.c b/fs/fuse/iomode.c
index 3728933188f3..ca7619958b0d 100644
--- a/fs/fuse/iomode.c
+++ b/fs/fuse/iomode.c
@@ -90,7 +90,7 @@ int fuse_inode_uncached_io_start(struct fuse_inode *fi, struct fuse_backing *fb)
 	spin_lock(&fi->lock);
 	/* deny conflicting backing files on same fuse inode */
 	oldfb = fuse_inode_backing(fi);
-	if (fb && oldfb && oldfb != fb) {
+	if (fb && oldfb && file_inode(oldfb->file) != file_inode(fb->file)) {
 		err = -EBUSY;
 		goto unlock;
 	}
-- 
2.43.0