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, 29 insertions, 0 deletions

diff --git a/drivers/usb/image/Kconfig b/drivers/usb/image/Kconfig
new file mode 100644
index 000000000..a65c638e7
--- /dev/null
+++ b/drivers/usb/image/Kconfig
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# USB Imaging devices configuration
+#
+comment "USB Imaging devices"
+
+config USB_MDC800
+	tristate "USB Mustek MDC800 Digital Camera support"
+	help
+	  Say Y here if you want to connect this type of still camera to
+	  your computer's USB port. This driver can be used with gphoto 0.4.3
+	  and higher (look at <http://www.gphoto.org/>).
+	  To use it create a device node with "mknod /dev/mustek c 180 32" and
+	  configure it in your software.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mdc800.
+
+config USB_MICROTEK
+	tristate "Microtek X6USB scanner support"
+	depends on SCSI
+	help
+	  Say Y here if you want support for the Microtek X6USB and
+	  possibly the Phantom 336CX, Phantom C6 and ScanMaker V6U(S)L.
+	  Support for anything but the X6 is experimental.
+	  Please report failures and successes.
+	  The scanner will appear as a scsi generic device to the rest
+	  of the system. Scsi support is required.
+	  This driver can be compiled as a module, called microtek.