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, 167 insertions, 0 deletions

diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
new file mode 100644
index 000000000..9ba45e5b3
--- /dev/null
+++ b/scripts/Makefile.modinst
@@ -0,0 +1,167 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Installing modules
+# ==========================================================================
+
+PHONY := __modinst
+__modinst:
+
+include $(objtree)/include/config/auto.conf
+include $(srctree)/scripts/Kbuild.include
+
+install-y :=
+
+ifeq ($(KBUILD_EXTMOD)$(sign-only),)
+
+# remove the old directory and symlink
+$(shell rm -fr $(MODLIB)/kernel $(MODLIB)/build)
+
+install-$(CONFIG_MODULES) += $(addprefix $(MODLIB)/, build modules.order)
+
+$(MODLIB)/build: FORCE
+	$(call cmd,symlink)
+
+quiet_cmd_symlink = SYMLINK $@
+      cmd_symlink = ln -s $(CURDIR) $@
+
+$(MODLIB)/modules.order: modules.order FORCE
+	$(call cmd,install_modorder)
+
+quiet_cmd_install_modorder = INSTALL $@
+      cmd_install_modorder = sed 's:^\(.*\)\.o$$:kernel/\1.ko:' $< > $@
+
+# Install modules.builtin(.modinfo,.ranges) even when CONFIG_MODULES is disabled.
+install-y += $(addprefix $(MODLIB)/, modules.builtin modules.builtin.modinfo)
+
+install-$(CONFIG_BUILTIN_MODULE_RANGES) += $(MODLIB)/modules.builtin.ranges
+
+$(addprefix $(MODLIB)/, modules.builtin modules.builtin.modinfo modules.builtin.ranges): $(MODLIB)/%: % FORCE
+	$(call cmd,install)
+
+endif
+
+modules := $(call read-file, modules.order)
+
+ifeq ($(KBUILD_EXTMOD),)
+dst := $(MODLIB)/kernel
+else
+INSTALL_MOD_DIR ?= updates
+dst := $(MODLIB)/$(INSTALL_MOD_DIR)
+endif
+
+$(foreach x, % :, $(if $(findstring $x, $(dst)), \
+	$(error module installation path cannot contain '$x')))
+
+suffix-y				:=
+ifdef CONFIG_MODULE_COMPRESS_ALL
+suffix-$(CONFIG_MODULE_COMPRESS_GZIP)	:= .gz
+suffix-$(CONFIG_MODULE_COMPRESS_XZ)	:= .xz
+suffix-$(CONFIG_MODULE_COMPRESS_ZSTD)	:= .zst
+endif
+
+modules := $(patsubst %.o, $(dst)/%.ko$(suffix-y), $(modules))
+install-$(CONFIG_MODULES) += $(modules)
+
+__modinst: $(install-y)
+	@:
+
+#
+# Installation
+#
+quiet_cmd_install = INSTALL $@
+      cmd_install = cp $< $@
+
+# Strip
+#
+# INSTALL_MOD_STRIP, if defined, will cause modules to be stripped after they
+# are installed. If INSTALL_MOD_STRIP is '1', then the default option
+# --strip-debug will be used. Otherwise, INSTALL_MOD_STRIP value will be used
+# as the options to the strip command.
+ifdef INSTALL_MOD_STRIP
+
+ifeq ($(INSTALL_MOD_STRIP),1)
+strip-option := --strip-debug
+else
+strip-option := $(INSTALL_MOD_STRIP)
+endif
+
+quiet_cmd_strip = STRIP   $@
+      cmd_strip = $(STRIP) $(strip-option) $@
+
+else
+
+quiet_cmd_strip =
+      cmd_strip = :
+
+endif
+
+#
+# Signing
+# Don't stop modules_install even if we can't sign external modules.
+#
+ifeq ($(filter pkcs11:%, $(CONFIG_MODULE_SIG_KEY)),)
+sig-key := $(if $(wildcard $(CONFIG_MODULE_SIG_KEY)),,$(objtree)/)$(CONFIG_MODULE_SIG_KEY)
+else
+sig-key := $(CONFIG_MODULE_SIG_KEY)
+endif
+quiet_cmd_sign = SIGN    $@
+      cmd_sign = $(objtree)/scripts/sign-file $(CONFIG_MODULE_SIG_HASH) "$(sig-key)" $(objtree)/certs/signing_key.x509 $@ \
+                 $(if $(KBUILD_EXTMOD),|| true)
+
+ifeq ($(sign-only),)
+
+# During modules_install, modules are signed only when CONFIG_MODULE_SIG_ALL=y.
+ifndef CONFIG_MODULE_SIG_ALL
+quiet_cmd_sign :=
+      cmd_sign := :
+endif
+
+# Create necessary directories
+$(foreach dir, $(sort $(dir $(install-y))), $(shell mkdir -p $(dir)))
+
+$(dst)/%.ko: %.ko FORCE
+	$(call cmd,install)
+	$(call cmd,strip)
+	$(call cmd,sign)
+
+ifdef CONFIG_MODULES
+__modinst: depmod
+
+PHONY += depmod
+depmod: $(install-y)
+	$(call cmd,depmod)
+
+quiet_cmd_depmod = DEPMOD  $(MODLIB)
+      cmd_depmod = $(srctree)/scripts/depmod.sh $(KERNELRELEASE)
+endif
+
+else
+
+$(dst)/%.ko: FORCE
+	$(call cmd,sign)
+
+endif
+
+#
+# Compression
+#
+quiet_cmd_gzip = GZIP    $@
+      cmd_gzip = $(KGZIP) -n -f $<
+quiet_cmd_xz = XZ      $@
+      cmd_xz = $(XZ) --check=crc32 --lzma2=dict=1MiB -f $<
+quiet_cmd_zstd = ZSTD    $@
+      cmd_zstd = $(ZSTD) --rm -f -q $<
+
+$(dst)/%.ko.gz: $(dst)/%.ko FORCE
+	$(call cmd,gzip)
+
+$(dst)/%.ko.xz: $(dst)/%.ko FORCE
+	$(call cmd,xz)
+
+$(dst)/%.ko.zst: $(dst)/%.ko FORCE
+	$(call cmd,zstd)
+
+PHONY += FORCE
+FORCE:
+
+.PHONY: $(PHONY)