[PATCH AUTOSEL 5.4 059/266] scsi: vhost: Notify TCM about the maximum sg entries supported per command

[PATCH AUTOSEL 5.4 059/266] scsi: vhost: Notify TCM about the maximum sg entries supported per command

[Sasha Levin]

From: Sudhakar Panneerselvam <sudhakar.panneerselvam@oracle.com>

[ Upstream commit 5ae6a6a915033bfee79e76e0c374d4f927909edc ]

vhost-scsi pre-allocates the maximum sg entries per command and if a
command requires more than VHOST_SCSI_PREALLOC_SGLS entries, then that
command is failed by it. This patch lets vhost communicate the max sg limit
when it registers vhost_scsi_ops with TCM. With this change, TCM would
report the max sg entries through "Block Limits" VPD page which will be
typically queried by the SCSI initiator during device discovery. By knowing
this limit, the initiator could ensure the maximum transfer length is less
than or equal to what is reported by vhost-scsi.

Link: https://lore.kernel.org/r/1590166317-953-1-git-send-email-sudhakar.panneerselvam@oracle.com
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Sudhakar Panneerselvam <sudhakar.panneerselvam@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/vhost/scsi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index a9caf1bc3c3e..88ce114790d7 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -2290,6 +2290,7 @@ static struct configfs_attribute *vhost_scsi_wwn_attrs[] = {
 static const struct target_core_fabric_ops vhost_scsi_ops = {
 	.module				= THIS_MODULE,
 	.fabric_name			= "vhost",
+	.max_data_sg_nents		= VHOST_SCSI_PREALLOC_SGLS,
 	.tpg_get_wwn			= vhost_scsi_get_fabric_wwn,
 	.tpg_get_tag			= vhost_scsi_get_tpgt,
 	.tpg_check_demo_mode		= vhost_scsi_check_true,
-- 
2.25.1

[PATCH AUTOSEL 5.4 096/266] virtiofs: schedule blocking async replies in separate worker

[Sasha Levin]

From: Vivek Goyal <vgoyal@redhat.com>

[ Upstream commit bb737bbe48bea9854455cb61ea1dc06e92ce586c ]

In virtiofs (unlike in regular fuse) processing of async replies is
serialized.  This can result in a deadlock in rare corner cases when
there's a circular dependency between the completion of two or more async
replies.

Such a deadlock can be reproduced with xfstests:generic/503 if TEST_DIR ==
SCRATCH_MNT (which is a misconfiguration):

 - Process A is waiting for page lock in worker thread context and blocked
   (virtio_fs_requests_done_work()).
 - Process B is holding page lock and waiting for pending writes to
   finish (fuse_wait_on_page_writeback()).
 - Write requests are waiting in virtqueue and can't complete because
   worker thread is blocked on page lock (process A).

Fix this by creating a unique work_struct for each async reply that can
block (O_DIRECT read).

Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem")
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/fuse/file.c      |   1 +
 fs/fuse/fuse_i.h    |   1 +
 fs/fuse/virtio_fs.c | 106 +++++++++++++++++++++++++++++---------------
 3 files changed, 73 insertions(+), 35 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 3dd37a998ea9..713d55a61890 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -712,6 +712,7 @@ static ssize_t fuse_async_req_send(struct fuse_conn *fc,
 	spin_unlock(&io->lock);
 
 	ia->ap.args.end = fuse_aio_complete_req;
+	ia->ap.args.may_block = io->should_dirty;
 	err = fuse_simple_background(fc, &ia->ap.args, GFP_KERNEL);
 	if (err)
 		fuse_aio_complete_req(fc, &ia->ap.args, err);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index ca344bf71404..d7cde216fc87 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -249,6 +249,7 @@ struct fuse_args {
 	bool out_argvar:1;
 	bool page_zeroing:1;
 	bool page_replace:1;
+	bool may_block:1;
 	struct fuse_in_arg in_args[3];
 	struct fuse_arg out_args[2];
 	void (*end)(struct fuse_conn *fc, struct fuse_args *args, int error);
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index a5c86048b96e..7505f8102762 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -55,6 +55,12 @@ struct virtio_fs_forget {
 	struct list_head list;
 };
 
+struct virtio_fs_req_work {
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq;
+	struct work_struct done_work;
+};
+
 static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
 				 struct fuse_req *req, bool in_flight);
 
@@ -443,19 +449,67 @@ static void copy_args_from_argbuf(struct fuse_args *args, struct fuse_req *req)
 }
 
 /* Work function for request completion */
+static void virtio_fs_request_complete(struct fuse_req *req,
+				       struct virtio_fs_vq *fsvq)
+{
+	struct fuse_pqueue *fpq = &fsvq->fud->pq;
+	struct fuse_conn *fc = fsvq->fud->fc;
+	struct fuse_args *args;
+	struct fuse_args_pages *ap;
+	unsigned int len, i, thislen;
+	struct page *page;
+
+	/*
+	 * TODO verify that server properly follows FUSE protocol
+	 * (oh.uniq, oh.len)
+	 */
+	args = req->args;
+	copy_args_from_argbuf(args, req);
+
+	if (args->out_pages && args->page_zeroing) {
+		len = args->out_args[args->out_numargs - 1].size;
+		ap = container_of(args, typeof(*ap), args);
+		for (i = 0; i < ap->num_pages; i++) {
+			thislen = ap->descs[i].length;
+			if (len < thislen) {
+				WARN_ON(ap->descs[i].offset);
+				page = ap->pages[i];
+				zero_user_segment(page, len, thislen);
+				len = 0;
+			} else {
+				len -= thislen;
+			}
+		}
+	}
+
+	spin_lock(&fpq->lock);
+	clear_bit(FR_SENT, &req->flags);
+	spin_unlock(&fpq->lock);
+
+	fuse_request_end(fc, req);
+	spin_lock(&fsvq->lock);
+	dec_in_flight_req(fsvq);
+	spin_unlock(&fsvq->lock);
+}
+
+static void virtio_fs_complete_req_work(struct work_struct *work)
+{
+	struct virtio_fs_req_work *w =
+		container_of(work, typeof(*w), done_work);
+
+	virtio_fs_request_complete(w->req, w->fsvq);
+	kfree(w);
+}
+
 static void virtio_fs_requests_done_work(struct work_struct *work)
 {
 	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
 						 done_work);
 	struct fuse_pqueue *fpq = &fsvq->fud->pq;
-	struct fuse_conn *fc = fsvq->fud->fc;
 	struct virtqueue *vq = fsvq->vq;
 	struct fuse_req *req;
-	struct fuse_args_pages *ap;
 	struct fuse_req *next;
-	struct fuse_args *args;
-	unsigned int len, i, thislen;
-	struct page *page;
+	unsigned int len;
 	LIST_HEAD(reqs);
 
 	/* Collect completed requests off the virtqueue */
@@ -473,38 +527,20 @@ static void virtio_fs_requests_done_work(struct work_struct *work)
 
 	/* End requests */
 	list_for_each_entry_safe(req, next, &reqs, list) {
-		/*
-		 * TODO verify that server properly follows FUSE protocol
-		 * (oh.uniq, oh.len)
-		 */
-		args = req->args;
-		copy_args_from_argbuf(args, req);
-
-		if (args->out_pages && args->page_zeroing) {
-			len = args->out_args[args->out_numargs - 1].size;
-			ap = container_of(args, typeof(*ap), args);
-			for (i = 0; i < ap->num_pages; i++) {
-				thislen = ap->descs[i].length;
-				if (len < thislen) {
-					WARN_ON(ap->descs[i].offset);
-					page = ap->pages[i];
-					zero_user_segment(page, len, thislen);
-					len = 0;
-				} else {
-					len -= thislen;
-				}
-			}
-		}
-
-		spin_lock(&fpq->lock);
-		clear_bit(FR_SENT, &req->flags);
 		list_del_init(&req->list);
-		spin_unlock(&fpq->lock);
 
-		fuse_request_end(fc, req);
-		spin_lock(&fsvq->lock);
-		dec_in_flight_req(fsvq);
-		spin_unlock(&fsvq->lock);
+		/* blocking async request completes in a worker context */
+		if (req->args->may_block) {
+			struct virtio_fs_req_work *w;
+
+			w = kzalloc(sizeof(*w), GFP_NOFS | __GFP_NOFAIL);
+			INIT_WORK(&w->done_work, virtio_fs_complete_req_work);
+			w->fsvq = fsvq;
+			w->req = req;
+			schedule_work(&w->done_work);
+		} else {
+			virtio_fs_request_complete(req, fsvq);
+		}
 	}
 }
 
-- 
2.25.1