[Devel] [PATCH 1/2] fuse: add a new async operation to unmap regions

[Andrei Vagin]

The fuse interface allows to run any operation asynchronously, because
the kernel redirect all operations to an user daemon and then waits an
answer.

In ploop, we want to handle discard requests via fallocate and
a simplest way to do this is to run fallocate(FALLOC_FL_PUNCH_HOLE)
asynchronously like the write command.

This patch adds a new async command IOCB_CMD_UNMAP_ITER, which sends
fallocate(FALLOC_FL_PUNCH_HOLE) to a fuse user daemon.

Signed-off-by: Andrei Vagin <avagin at openvz.org>
---
 fs/aio.c                     |  1 +
 fs/fuse/file.c               | 63 ++++++++++++++++++++++++++++++++++++++------
 fs/fuse/fuse_i.h             |  3 +++
 include/uapi/linux/aio_abi.h |  1 +
 4 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 3a6a9b0..cdc7558 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1492,6 +1492,7 @@ rw_common:
 		ret = aio_read_iter(req);
 		break;
 
+	case IOCB_CMD_UNMAP_ITER:
 	case IOCB_CMD_WRITE_ITER:
 		ret = aio_write_iter(req);
 		break;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 877c41f..83ea9da 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -920,6 +920,19 @@ static void fuse_aio_complete_req(struct fuse_conn *fc, struct fuse_req *req)
 	if (!req->bvec)
 		fuse_release_user_pages(req, !io->write);
 
+	if (req->in.h.opcode == FUSE_FALLOCATE) {
+		if (req->out.h.error)
+			printk("fuse_aio_complete_req: request (fallocate fh=0x%llx "
+			       "offset=%lld length=%lld mode=%x) completed with err=%d\n",
+			       req->misc.fallocate.in.fh,
+			       req->misc.fallocate.in.offset,
+			       req->misc.fallocate.in.length,
+			       req->misc.fallocate.in.mode,
+			       req->out.h.error);
+		fuse_aio_complete(io, req->out.h.error, -1);
+		return;
+	}
+
 	if (io->write) {
 		if (req->misc.write.in.size != req->misc.write.out.size)
 			pos = req->misc.write.in.offset - io->offset +
@@ -1322,6 +1335,33 @@ static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
 	req->out.args[0].value = outarg;
 }
 
+static size_t fuse_send_unmap(struct fuse_req *req, struct fuse_io_priv *io,
+			      loff_t pos, size_t count, fl_owner_t owner)
+{
+	struct file *file = io->file;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+	struct fuse_fallocate_in *inarg = &req->misc.fallocate.in;
+
+	inarg->fh = ff->fh;
+	inarg->offset = pos;
+	inarg->length = count;
+	inarg->mode = FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE;
+	req->in.h.opcode = FUSE_FALLOCATE;
+	req->in.h.nodeid = ff->nodeid;
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(struct fuse_fallocate_in);
+	req->in.args[0].value = inarg;
+
+	fuse_account_request(fc, count);
+
+	if (io->async)
+		return fuse_async_req_send(fc, req, count, io);
+
+	fuse_request_send(fc, req);
+	return count;
+}
+
 static size_t fuse_send_write(struct fuse_req *req, struct fuse_io_priv *io,
 			      loff_t pos, size_t count, fl_owner_t owner)
 {
@@ -3455,7 +3495,7 @@ static ssize_t fuse_direct_IO_bvec(int rw, struct kiocb *iocb,
 			req->bvec = bvec;
 		}
 
-		if (filled + bvec->bv_len <= nmax) {
+		if (bvec_len && filled + bvec->bv_len <= nmax) {
 			filled += bvec->bv_len;
 			req->num_bvecs++;
 			bvec++;
@@ -3465,14 +3505,21 @@ static ssize_t fuse_direct_IO_bvec(int rw, struct kiocb *iocb,
 				continue;
 		}
 
-		BUG_ON(!filled);
 
-		if (rw == WRITE)
-			nres = fuse_send_write(req, io, pos,
-					filled, NULL);
-		else
-			nres = fuse_send_read(req, io, pos,
-					filled, NULL);
+		if (iocb->ki_opcode == IOCB_CMD_UNMAP_ITER) {
+			req->in.argbvec = 0;
+			nres = fuse_send_unmap(req, io, pos,
+					iocb->ki_nbytes, NULL);
+			filled = nres;
+		} else {
+			BUG_ON(!filled);
+			if (rw == WRITE)
+				nres = fuse_send_write(req, io, pos,
+						filled, NULL);
+			else
+				nres = fuse_send_read(req, io, pos,
+						filled, NULL);
+		}
 
 		BUG_ON(nres != filled);
 		fuse_put_request(fc, req);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 2da4520..b2edcf9 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -364,6 +364,9 @@ struct fuse_req {
 			struct fuse_write_in in;
 			struct fuse_write_out out;
 		} write;
+		struct {
+			struct fuse_fallocate_in in;
+		} fallocate;
 		struct fuse_notify_retrieve_in retrieve_in;
 		struct fuse_lk_in lk_in;
 	} misc;
diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index 22ce4bd..ea2c346 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h
@@ -46,6 +46,7 @@ enum {
 	IOCB_CMD_PWRITEV = 8,
 	IOCB_CMD_READ_ITER = 9,
 	IOCB_CMD_WRITE_ITER = 10,
+	IOCB_CMD_UNMAP_ITER = 11,
 };
 
 /*
-- 
1.8.3.1