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, 65 insertions, 0 deletions

diff --git a/drivers/tty/vt/Makefile b/drivers/tty/vt/Makefile
new file mode 100644
index 000000000..ae746dcde
--- /dev/null
+++ b/drivers/tty/vt/Makefile
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# This file contains the font map for the default (hardware) font
+#
+FONTMAPFILE = cp437.uni
+
+obj-$(CONFIG_VT)			+= vt_ioctl.o vc_screen.o \
+					   selection.o keyboard.o \
+					   vt.o defkeymap.o
+obj-$(CONFIG_CONSOLE_TRANSLATIONS)	+= consolemap.o consolemap_deftbl.o \
+					   ucs.o
+
+# Files generated that shall be removed upon make clean
+clean-files :=	consolemap_deftbl.c defkeymap.c \
+		ucs_width_table.h ucs_recompose_table.h ucs_fallback_table.h
+
+hostprogs += conmakehash
+
+quiet_cmd_conmk = CONMK   $@
+      cmd_conmk = $(obj)/conmakehash $< > $@
+
+$(obj)/consolemap_deftbl.c: $(src)/$(FONTMAPFILE) $(obj)/conmakehash
+	$(call cmd,conmk)
+
+$(obj)/defkeymap.o:  $(obj)/defkeymap.c
+
+# Uncomment if you're changing the keymap and have an appropriate
+# loadkeys version for the map. By default, we'll use the shipped
+# versions.
+# GENERATE_KEYMAP := 1
+
+ifdef GENERATE_KEYMAP
+
+$(obj)/defkeymap.c: $(obj)/%.c: $(src)/%.map
+	loadkeys --mktable --unicode $< > $@
+
+endif
+
+$(obj)/ucs.o:	$(src)/ucs.c $(obj)/ucs_width_table.h \
+		$(obj)/ucs_recompose_table.h $(obj)/ucs_fallback_table.h
+
+# You may uncomment one of those to have the UCS tables be regenerated
+# during the build process. By default the _shipped versions are used.
+#
+#GENERATE_UCS_TABLES := 1
+#GENERATE_UCS_TABLES := 2  # invokes gen_ucs_recompose_table.py with --full
+
+ifdef GENERATE_UCS_TABLES
+
+$(obj)/ucs_width_table.h: $(src)/gen_ucs_width_table.py
+	$(PYTHON3) $< -o $@
+
+ifeq ($(GENERATE_UCS_TABLES),2)
+gen_recomp_arg := --full
+else
+gen_recomp_arg :=
+endif
+
+$(obj)/ucs_recompose_table.h: $(src)/gen_ucs_recompose_table.py
+	$(PYTHON3) $< -o $@ $(gen_recomp_arg)
+
+$(obj)/ucs_fallback_table.h: $(src)/gen_ucs_fallback_table.py
+	$(PYTHON3) $< -o $@
+
+endif