netfs: Fix undifferentiation of DIO reads from unbuffered reads

On cifs, "DIO reads" (specified by O_DIRECT) need to be differentiated from
"unbuffered reads" (specified by cache=none in the mount parameters).  The
difference is flagged in the protocol and the server may behave
differently: Windows Server will, for example, mandate that DIO reads are
block aligned.

Fix this by adding a NETFS_UNBUFFERED_READ to differentiate this from
NETFS_DIO_READ, parallelling the write differentiation that already exists.
cifs will then do the right thing.

Fixes: 016dc8516aec ("netfs: Implement unbuffered/DIO read support")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/3444961.1747987072@warthog.procyon.org.uk
Reviewed-by: "Paulo Alcantara (Red Hat)" <pc@manguebit.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
cc: Steve French <sfrench@samba.org>
cc: netfs@lists.linux.dev
cc: v9fs@lists.linux.dev
cc: linux-afs@lists.infradead.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

5 files changed, 10 insertions, 3 deletions

diff --git a/fs/netfs/direct_read.c b/fs/netfs/direct_read.c
index e72c8b69b147..a05e13472baf 100644
--- a/fs/netfs/direct_read.c
+++ b/fs/netfs/direct_read.c
@@ -185,7 +185,8 @@ ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *i
 
 	rreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp,
 				   iocb->ki_pos, orig_count,
-				   NETFS_DIO_READ);
+				   iocb->ki_flags & IOCB_DIRECT ?
+				   NETFS_DIO_READ : NETFS_UNBUFFERED_READ);
 	if (IS_ERR(rreq))
 		return PTR_ERR(rreq);
 
diff --git a/fs/netfs/main.c b/fs/netfs/main.c
index 4e3e62040831..7ade92aee45a 100644
--- a/fs/netfs/main.c
+++ b/fs/netfs/main.c
@@ -39,6 +39,7 @@ static const char *netfs_origins[nr__netfs_io_origin] = {
 	[NETFS_READ_GAPS]		= "RG",
 	[NETFS_READ_SINGLE]		= "R1",
 	[NETFS_READ_FOR_WRITE]		= "RW",
+	[NETFS_UNBUFFERED_READ]		= "UR",
 	[NETFS_DIO_READ]		= "DR",
 	[NETFS_WRITEBACK]		= "WB",
 	[NETFS_WRITEBACK_SINGLE]	= "W1",
diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 77e7f7c79d27..43b67a28a8fa 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -461,6 +461,7 @@ all_collected:
 		case NETFS_DIO_READ:
 		case NETFS_DIO_WRITE:
 		case NETFS_READ_SINGLE:
+		case NETFS_UNBUFFERED_READ:
 		case NETFS_UNBUFFERED_WRITE:
 			break;
 		default:
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index f603f107ba1d..e8c99738b5bb 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -59,6 +59,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
 	    origin == NETFS_READ_GAPS ||
 	    origin == NETFS_READ_SINGLE ||
 	    origin == NETFS_READ_FOR_WRITE ||
+	    origin == NETFS_UNBUFFERED_READ ||
 	    origin == NETFS_DIO_READ) {
 		INIT_WORK(&rreq->work, netfs_read_collection_worker);
 		rreq->io_streams[0].avail = true;
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index 31d00e30a59c..96ee18af28ef 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -340,7 +340,8 @@ static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
 {
 	unsigned int i;
 
-	if (rreq->origin == NETFS_DIO_READ) {
+	if (rreq->origin == NETFS_UNBUFFERED_READ ||
+	    rreq->origin == NETFS_DIO_READ) {
 		for (i = 0; i < rreq->direct_bv_count; i++) {
 			flush_dcache_page(rreq->direct_bv[i].bv_page);
 			// TODO: cifs marks pages in the destination buffer
@@ -358,7 +359,8 @@ static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
 	}
 	if (rreq->netfs_ops->done)
 		rreq->netfs_ops->done(rreq);
-	if (rreq->origin == NETFS_DIO_READ)
+	if (rreq->origin == NETFS_UNBUFFERED_READ ||
+	    rreq->origin == NETFS_DIO_READ)
 		inode_dio_end(rreq->inode);
 }
 
@@ -414,6 +416,7 @@ bool netfs_read_collection(struct netfs_io_request *rreq)
 	//netfs_rreq_is_still_valid(rreq);
 
 	switch (rreq->origin) {
+	case NETFS_UNBUFFERED_READ:
 	case NETFS_DIO_READ:
 	case NETFS_READ_GAPS:
 		netfs_rreq_assess_dio(rreq);