netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/usb/usbip/Makefile b/drivers/usb/usbip/Makefile
new file mode 100644
index 000000000..f4c8f3840
--- /dev/null
+++ b/drivers/usb/usbip/Makefile
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+ccflags-$(CONFIG_USBIP_DEBUG) := -DDEBUG
+
+obj-$(CONFIG_USBIP_CORE) += usbip-core.o
+usbip-core-y := usbip_common.o usbip_event.o
+
+obj-$(CONFIG_USBIP_VHCI_HCD) += vhci-hcd.o
+vhci-hcd-y := vhci_sysfs.o vhci_tx.o vhci_rx.o vhci_hcd.o
+
+obj-$(CONFIG_USBIP_HOST) += usbip-host.o
+usbip-host-y := stub_dev.o stub_main.o stub_rx.o stub_tx.o
+
+obj-$(CONFIG_USBIP_VUDC) += usbip-vudc.o
+usbip-vudc-y := vudc_dev.o vudc_sysfs.o vudc_tx.o vudc_rx.o vudc_transfer.o vudc_main.o