[PATCH v14 12/12] fuse: implement passthrough for readdir

[Amir Goldstein <amir73il@xxxxxxxxx>]

Same as for regular file read, when dir is open with FOPEN_PASSTHROUGH,
passthrough readdir to backing directory.

FOPEN_CACHE_DIR is ignored with passthrough readdir and it does not
populated children inode cache as READDIRPLUS does.

Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
 fs/fuse/file.c        |  3 +++
 fs/fuse/fuse_i.h      |  1 +
 fs/fuse/passthrough.c | 25 ++++++++++++++++++++++++-
 fs/fuse/readdir.c     | 12 +++++++++++-
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index bae1137426a9..a8ebd25765c6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -148,6 +148,9 @@ struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
 			ff->fh = outargp->fh;
 			ff->open_flags = outargp->open_flags;
 
+			/* Readdir cache not used for passthrough */
+			if (ff->open_flags & FOPEN_PASSTHROUGH)
+				ff->open_flags &= ~FOPEN_CACHE_DIR;
 		} else if (err != -ENOSYS) {
 			fuse_file_free(ff);
 			return ERR_PTR(err);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 6fee4c33678f..822226fe96bf 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1404,5 +1404,6 @@ ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
 				      struct file *out, loff_t *ppos,
 				      size_t len, unsigned int flags);
 ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma);
+int fuse_passthrough_readdir(struct file *file, struct dir_context *ctx);
 
 #endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index a05280ceba83..828f26597b16 100644
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -164,6 +164,28 @@ ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma)
 	return backing_file_mmap(backing_file, vma, &ctx);
 }
 
+int fuse_passthrough_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+	struct file *backing_file = fuse_file_passthrough(ff);
+	const struct cred *old_cred;
+	bool locked;
+	int ret;
+
+	pr_debug("%s: backing_file=0x%p, pos=%lld\n", __func__,
+		 backing_file, ctx->pos);
+
+	locked = fuse_lock_inode(inode);
+	old_cred = override_creds(ff->cred);
+	ret = iterate_dir(backing_file, ctx);
+	revert_creds(old_cred);
+	fuse_file_accessed(file);
+	fuse_unlock_inode(inode, locked);
+
+	return ret;
+}
+
 struct fuse_backing *fuse_backing_get(struct fuse_backing *fb)
 {
 	if (fb && refcount_inc_not_zero(&fb->count))
@@ -257,7 +279,8 @@ int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map)
 		goto out;
 
 	res = -EOPNOTSUPP;
-	if (!file->f_op->read_iter || !file->f_op->write_iter)
+	if (!file->f_op->iterate_shared &&
+	    !(file->f_op->read_iter && file->f_op->write_iter))
 		goto out_fput;
 
 	backing_sb = file_inode(file)->i_sb;
diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index 9e6d587b3e67..e59c072ca29c 100644
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -327,7 +327,7 @@ static int parse_dirplusfile(char *buf, size_t nbytes, struct file *file,
 	return 0;
 }
 
-static int fuse_readdir_uncached(struct file *file, struct dir_context *ctx)
+static int fuse_do_readdir(struct file *file, struct dir_context *ctx)
 {
 	int plus;
 	ssize_t res;
@@ -581,6 +581,16 @@ static int fuse_readdir_cached(struct file *file, struct dir_context *ctx)
 	return res == FOUND_SOME ? 0 : UNCACHED;
 }
 
+static int fuse_readdir_uncached(struct file *file, struct dir_context *ctx)
+{
+	struct fuse_file *ff = file->private_data;
+
+	if (fuse_file_passthrough(ff))
+		return fuse_passthrough_readdir(file, ctx);
+	else
+		return fuse_do_readdir(file, ctx);
+}
+
 int fuse_readdir(struct file *file, struct dir_context *ctx)
 {
 	struct fuse_file *ff = file->private_data;
-- 
2.34.1