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, 188 insertions, 0 deletions

diff --git a/usr/include/Makefile b/usr/include/Makefile
new file mode 100644
index 000000000..ee69dd9d9
--- /dev/null
+++ b/usr/include/Makefile
@@ -0,0 +1,188 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+# Unlike the kernel space, exported headers are written in standard C.
+#  - Forbid C++ style comments
+#  - Use '__inline__', '__asm__' instead of 'inline', 'asm'
+#
+# -std=c90 (equivalent to -ansi) catches the violation of those.
+# We cannot go as far as adding -Wpedantic since it emits too many warnings.
+UAPI_CFLAGS := -std=c90 -Werror=implicit-function-declaration
+UAPI_ARCH := $(or $(HEADER_ARCH),$(SRCARCH))
+
+override c_flags = $(KBUILD_USERCFLAGS) $(UAPI_CFLAGS) -Wp,-MMD,$(depfile)
+cxx_flags = $(filter-out -Wmissing-prototypes -Wstrict-prototypes -std=%, $(KBUILD_USERCFLAGS)) -std=c++98
+
+# The following are excluded for now because they fail to build.
+#
+# Do not add a new header to the blacklist without legitimate reason.
+# Please consider to fix the header first.
+#
+# Sorted alphabetically.
+no-header-test += asm/ucontext.h
+no-header-test += drm/vmwgfx_drm.h
+no-header-test += linux/am437x-vpfe.h
+no-header-test += linux/coda.h
+no-header-test += linux/cyclades.h
+no-header-test += linux/errqueue.h
+no-header-test += linux/hdlc/ioctl.h
+no-header-test += linux/ivtv.h
+no-header-test += linux/matroxfb.h
+no-header-test += linux/omap3isp.h
+no-header-test += linux/omapfb.h
+no-header-test += linux/patchkey.h
+no-header-test += linux/phonet.h
+no-header-test += linux/sctp.h
+no-header-test += linux/sysctl.h
+no-header-test += linux/usb/audio.h
+no-header-test += linux/v4l2-mediabus.h
+no-header-test += linux/v4l2-subdev.h
+no-header-test += linux/videodev2.h
+no-header-test += linux/vm_sockets.h
+no-header-test += sound/asequencer.h
+no-header-test += sound/asoc.h
+no-header-test += sound/asound.h
+no-header-test += sound/compress_offload.h
+no-header-test += sound/emu10k1.h
+no-header-test += sound/sfnt_info.h
+no-header-test += xen/evtchn.h
+no-header-test += xen/gntdev.h
+no-header-test += xen/privcmd.h
+
+# More headers are broken in some architectures
+
+ifneq ($(filter arc openrisc xtensa nios2, $(UAPI_ARCH)),)
+no-header-test += linux/bpf_perf_event.h
+endif
+
+ifeq ($(UAPI_ARCH),sparc)
+no-header-test += asm/uctx.h
+no-header-test += asm/fbio.h
+endif
+
+# asm-generic/*.h is used by asm/*.h, and should not be included directly
+no-header-test += asm-generic/%
+
+# The following are not compatible with C++.
+#
+# Do not add a new header to the list without legitimate reason.
+# Please consider to fix the header first.
+#
+# Sorted alphabetically.
+no-header-test-cxx += linux/auto_dev-ioctl.h
+no-header-test-cxx += linux/map_to_14segment.h
+no-header-test-cxx += linux/map_to_7segment.h
+no-header-test-cxx += linux/netfilter/xt_sctp.h
+no-header-test-cxx += linux/target_core_user.h
+no-header-test-cxx += linux/vhost.h
+no-header-test-cxx += linux/vhost_types.h
+no-header-test-cxx += linux/virtio_net.h
+no-header-test-cxx += linux/virtio_ring.h
+no-header-test-cxx += scsi/fc/fc_els.h
+
+ifeq ($(UAPI_ARCH),x86)
+no-header-test-cxx += asm/elf.h
+endif
+
+# The following are using libc header and types.
+#
+# Do not add a new header to the list without legitimate reason.
+# Please consider to fix the header first.
+#
+# Sorted alphabetically.
+uses-libc += linux/a.out.h
+uses-libc += linux/atmbr2684.h
+uses-libc += linux/auto_dev-ioctl.h
+uses-libc += linux/auto_fs.h
+uses-libc += linux/auto_fs4.h
+uses-libc += linux/btrfs_tree.h
+uses-libc += linux/cec-funcs.h
+uses-libc += linux/cec.h
+uses-libc += linux/dvb/dmx.h
+uses-libc += linux/dvb/video.h
+uses-libc += linux/ethtool.h
+uses-libc += linux/ethtool_netlink.h
+uses-libc += linux/fuse.h
+uses-libc += linux/gsmmux.h
+uses-libc += linux/icmp.h
+uses-libc += linux/idxd.h
+uses-libc += linux/if.h
+uses-libc += linux/if_arp.h
+uses-libc += linux/if_bonding.h
+uses-libc += linux/if_pppox.h
+uses-libc += linux/if_tunnel.h
+uses-libc += linux/input.h
+uses-libc += linux/ip6_tunnel.h
+uses-libc += linux/joystick.h
+uses-libc += linux/llc.h
+uses-libc += linux/mctp.h
+uses-libc += linux/mdio.h
+uses-libc += linux/mii.h
+uses-libc += linux/mptcp.h
+uses-libc += linux/netdevice.h
+uses-libc += linux/netfilter/xt_RATEEST.h
+uses-libc += linux/netfilter/xt_hashlimit.h
+uses-libc += linux/netfilter/xt_physdev.h
+uses-libc += linux/netfilter/xt_rateest.h
+uses-libc += linux/netfilter_arp/arp_tables.h
+uses-libc += linux/netfilter_arp/arpt_mangle.h
+uses-libc += linux/netfilter_bridge.h
+uses-libc += linux/netfilter_bridge/ebtables.h
+uses-libc += linux/netfilter_ipv4.h
+uses-libc += linux/netfilter_ipv4/ip_tables.h
+uses-libc += linux/netfilter_ipv6.h
+uses-libc += linux/netfilter_ipv6/ip6_tables.h
+uses-libc += linux/route.h
+uses-libc += linux/shm.h
+uses-libc += linux/soundcard.h
+uses-libc += linux/string.h
+uses-libc += linux/tipc_config.h
+uses-libc += linux/uhid.h
+uses-libc += linux/uinput.h
+uses-libc += linux/vhost.h
+uses-libc += linux/vhost_types.h
+uses-libc += linux/virtio_ring.h
+uses-libc += linux/wireless.h
+uses-libc += regulator/regulator.h
+uses-libc += scsi/fc/fc_els.h
+
+ifeq ($(UAPI_ARCH),hexagon)
+uses-libc += asm/sigcontext.h
+endif
+
+ifeq ($(UAPI_ARCH),nios2)
+uses-libc += asm/ptrace.h
+endif
+
+ifeq ($(UAPI_ARCH),s390)
+uses-libc += asm/chpid.h
+uses-libc += asm/chsc.h
+endif
+
+always-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))
+
+# $(cc-option) forces '-x c' which breaks '-x c++' detection.
+cc-can-compile-cxx := $(call try-run,$(CC) $(CLANG_FLAGS) -c -x c++ /dev/null -o "$$TMP", 1)
+
+target-libc = $(filter $(uses-libc), $*.h)
+target-can-compile = $(filter-out $(no-header-test), $*.h)
+target-can-compile-cxx = $(and $(cc-can-compile-cxx), $(target-can-compile), $(filter-out $(no-header-test-cxx), $*.h))
+
+hdrtest-flags = -fsyntax-only -Werror \
+		-nostdinc -I $(obj) $(if $(target-libc), -I $(srctree)/usr/dummy-include)
+
+# Include the header twice to detect missing include guard.
+quiet_cmd_hdrtest = HDRTEST $<
+      cmd_hdrtest = \
+		$(CC) $(c_flags) $(hdrtest-flags) -x c /dev/null \
+			$(if $(target-can-compile), -include $< -include $<); \
+		$(if $(target-can-compile-cxx), \
+			$(CC) $(cxx_flags) $(hdrtest-flags) -x c++ /dev/null -include $<;) \
+		$(PERL) $(src)/headers_check.pl $(obj) $<; \
+		touch $@
+
+$(obj)/%.hdrtest: $(obj)/%.h $(src)/headers_check.pl FORCE
+	$(call if_changed_dep,hdrtest)
+
+# Since GNU Make 4.3, $(patsubst $(obj)/%/,%,$(wildcard $(obj)/*/)) works.
+# To support older Make versions, use a somewhat tedious way.
+clean-files += $(filter-out Makefile headers_check.pl, $(notdir $(wildcard $(obj)/*)))