Commit 7678ac50 authored by Andrew Gallagher's avatar Andrew Gallagher Committed by Miklos Szeredi
Browse files

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: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent 451418fc

fs/fuse/file.c

+27 −10
Original line number Diff line number Diff line
@@ -127,7 +127,15 @@ static void fuse_file_put(struct fuse_file *ff, bool sync) 
	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 @@ static void fuse_file_put(struct fuse_file *ff, bool sync) 
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;



	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) {

		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;

fs/fuse/fuse_i.h

+3 −0
Original line number Diff line number Diff line
@@ -485,6 +485,9 @@ struct fuse_conn { 
	 * and hence races in setting them will not cause malfunction

	 */



	/** Is open/release not implemented by fs? */

	unsigned no_open:1;



	/** Is fsync not implemented by fs? */

	unsigned no_fsync:1;

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