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From: Mike Snitzer <snitzer@kernel.org>
To: linux-nfs@vger.kernel.org
Cc: Jeff Layton <jlayton@kernel.org>,
	Chuck Lever <chuck.lever@oracle.com>,
	Trond Myklebust <trondmy@hammerspace.com>,
	snitzer@hammerspace.com
Subject: [for-6.11 PATCH 16/29] NFS: Don't call filesystem read() routines directly
Date: Fri,  7 Jun 2024 10:26:33 -0400
Message-ID: <20240607142646.20924-17-snitzer@kernel.org>
In-Reply-To: <20240607142646.20924-1-snitzer@kernel.org>
References: <20240607142646.20924-1-snitzer@kernel.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

In order to avoid issues with stack overflow, just call the read
routines from a workqueue job.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
 fs/nfs/localio.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index 2c6811b20dcf..d997f0a96627 100644
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -465,21 +465,38 @@ nfs_local_read_aio_complete(struct kiocb *kiocb, long ret)
 	nfs_local_pgio_complete(iocb);
 }
 
-static int
-nfs_do_local_read(struct nfs_pgio_header *hdr, struct file *filp,
-		const struct rpc_call_ops *call_ops)
+static void nfs_local_call_read(struct work_struct *work)
 {
-	struct nfs_local_kiocb *iocb;
+	struct nfs_local_io_args *args =
+		container_of(work, struct nfs_local_io_args, work);
+	struct nfs_local_kiocb *iocb = args->iocb;
+	struct file *filp = iocb->kiocb.ki_filp;
 	struct iov_iter iter;
 	ssize_t status;
 
+	nfs_local_iter_init(&iter, iocb, READ);
+
+	status = filp->f_op->read_iter(&iocb->kiocb, &iter);
+	if (status != -EIOCBQUEUED) {
+		nfs_local_read_done(iocb, status);
+		nfs_local_pgio_release(iocb);
+	}
+	complete(args->done);
+}
+
+static int nfs_do_local_read(struct nfs_pgio_header *hdr, struct file *filp,
+			     const struct rpc_call_ops *call_ops)
+{
+	struct nfs_local_io_args args;
+	DECLARE_COMPLETION_ONSTACK(done);
+	struct nfs_local_kiocb *iocb;
+
 	dprintk("%s: vfs_read count=%u pos=%llu\n",
 		__func__, hdr->args.count, hdr->args.offset);
 
 	iocb = nfs_local_iocb_alloc(hdr, filp, GFP_KERNEL);
 	if (iocb == NULL)
 		return -ENOMEM;
-	nfs_local_iter_init(&iter, iocb, READ);
 
 	nfs_local_pgio_init(hdr, call_ops);
 	hdr->res.eof = false;
@@ -489,11 +506,13 @@ nfs_do_local_read(struct nfs_pgio_header *hdr, struct file *filp,
 		iocb->kiocb.ki_complete = nfs_local_read_aio_complete;
 	}
 
-	status = filp->f_op->read_iter(&iocb->kiocb, &iter);
-	if (status != -EIOCBQUEUED) {
-		nfs_local_read_done(iocb, status);
-		nfs_local_pgio_release(iocb);
-	}
+	args.iocb = iocb;
+	args.done = &done;
+	INIT_WORK_ONSTACK(&args.work, nfs_local_call_read);
+
+	queue_work(nfsiod_workqueue, &args.work);
+	wait_for_completion(&done);
+	destroy_work_on_stack(&args.work);
 	return 0;
 }
 
-- 
2.44.0