fuse: support clients that don't implement 'open'
open/release operations require userspace transitions to keep track
of the open count and to perform any FS-specific setup. However,
for some purely read-only FSs which don't need to perform any setup
at open/release time, we can avoid the performance overhead of
calling into userspace for open/release calls.
This patch adds the necessary support to the fuse kernel modules to prevent
open/release operations from hitting in userspace. When the client returns
ENOSYS, we avoid sending the subsequent release to userspace, and also
remember this so that future opens also don't trigger a userspace
operation.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index d53af8f..74f6ca5 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -127,7 +127,15 @@
if (atomic_dec_and_test(&ff->count)) {
struct fuse_req *req = ff->reserved_req;
- if (sync) {
+ if (ff->fc->no_open) {
+ /*
+ * Drop the release request when client does not
+ * implement 'open'
+ */
+ req->background = 0;
+ path_put(&req->misc.release.path);
+ fuse_put_request(ff->fc, req);
+ } else if (sync) {
req->background = 0;
fuse_request_send(ff->fc, req);
path_put(&req->misc.release.path);
@@ -144,27 +152,36 @@
int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
bool isdir)
{
- struct fuse_open_out outarg;
struct fuse_file *ff;
- int err;
int opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
ff = fuse_file_alloc(fc);
if (!ff)
return -ENOMEM;
- err = fuse_send_open(fc, nodeid, file, opcode, &outarg);
- if (err) {
- fuse_file_free(ff);
- return err;
+ ff->fh = 0;
+ ff->open_flags = FOPEN_KEEP_CACHE; /* Default for no-open */
+ if (!fc->no_open || isdir) {
+ struct fuse_open_out outarg;
+ int err;
+
+ err = fuse_send_open(fc, nodeid, file, opcode, &outarg);
+ if (!err) {
+ ff->fh = outarg.fh;
+ ff->open_flags = outarg.open_flags;
+
+ } else if (err != -ENOSYS || isdir) {
+ fuse_file_free(ff);
+ return err;
+ } else {
+ fc->no_open = 1;
+ }
}
if (isdir)
- outarg.open_flags &= ~FOPEN_DIRECT_IO;
+ ff->open_flags &= ~FOPEN_DIRECT_IO;
- ff->fh = outarg.fh;
ff->nodeid = nodeid;
- ff->open_flags = outarg.open_flags;
file->private_data = fuse_file_get(ff);
return 0;