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, 36 insertions, 0 deletions

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
new file mode 100644
index 000000000..435710f64
--- /dev/null
+++ b/drivers/base/Makefile
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for the Linux device tree
+
+obj-y			:= component.o core.o bus.o dd.o syscore.o \
+			   driver.o class.o platform.o \
+			   cpu.o firmware.o init.o map.o devres.o \
+			   attribute_container.o transport_class.o \
+			   topology.o container.o property.o cacheinfo.o \
+			   swnode.o faux.o
+obj-$(CONFIG_AUXILIARY_BUS) += auxiliary.o
+obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
+obj-y			+= power/
+obj-$(CONFIG_ISA_BUS_API)	+= isa.o
+obj-y				+= firmware_loader/
+obj-$(CONFIG_NUMA)	+= node.o
+obj-$(CONFIG_MEMORY_HOTPLUG) += memory.o
+ifeq ($(CONFIG_SYSFS),y)
+obj-$(CONFIG_MODULES)	+= module.o
+obj-$(CONFIG_AUXILIARY_BUS) += auxiliary_sysfs.o
+endif
+obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
+obj-$(CONFIG_REGMAP)	+= regmap/
+obj-$(CONFIG_SOC_BUS) += soc.o
+obj-$(CONFIG_PINCTRL) += pinctrl.o
+obj-$(CONFIG_DEV_COREDUMP) += devcoredump.o
+obj-$(CONFIG_GENERIC_MSI_IRQ) += platform-msi.o
+obj-$(CONFIG_GENERIC_ARCH_TOPOLOGY) += arch_topology.o
+obj-$(CONFIG_ACPI) += physical_location.o
+
+obj-y			+= test/
+
+ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
+
+# define_trace.h needs to know how to find our header
+CFLAGS_trace.o		:= -I$(src)
+obj-$(CONFIG_TRACING)	+= trace.o