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, 82 insertions, 0 deletions

diff --git a/scripts/as-version.sh b/scripts/as-version.sh
new file mode 100755
index 000000000..af7174761
--- /dev/null
+++ b/scripts/as-version.sh
@@ -0,0 +1,82 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Print the assembler name and its version in a 5 or 6-digit form.
+# Also, perform the minimum version check.
+# (If it is the integrated assembler, return 0 as the version, and
+# skip the version check.)
+
+set -e
+
+# Convert the version string x.y.z to a canonical 5 or 6-digit form.
+get_canonical_version()
+{
+	IFS=.
+	set -- $1
+
+	# If the 2nd or 3rd field is missing, fill it with a zero.
+	#
+	# The 4th field, if present, is ignored.
+	# This occurs in development snapshots as in 2.35.1.20201116
+	echo $((10000 * $1 + 100 * ${2:-0} + ${3:-0}))
+}
+
+# Clang fails to handle -Wa,--version unless -fno-integrated-as is given.
+# We check -fintegrated-as, expecting it is explicitly passed in for the
+# integrated assembler case.
+check_integrated_as()
+{
+	while [ $# -gt 0 ]; do
+		if [ "$1" = -fintegrated-as ]; then
+			# For the integrated assembler, we do not check the
+			# version here. It is the same as the clang version, and
+			# it has been already checked by scripts/cc-version.sh.
+			echo LLVM 0
+			exit 0
+		fi
+		shift
+	done
+}
+
+check_integrated_as "$@"
+
+orig_args="$@"
+
+# Get the first line of the --version output.
+IFS='
+'
+set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler-with-cpp /dev/null -o /dev/null 2>/dev/null)
+
+# Split the line on spaces.
+IFS=' '
+set -- $1
+
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
+if [ "$1" = GNU -a "$2" = assembler ]; then
+	shift $(($# - 1))
+	version=$1
+	min_version=$($min_tool_version binutils)
+	name=GNU
+else
+	echo "$orig_args: unknown assembler invoked" >&2
+	exit 1
+fi
+
+# Some distributions append a package release number, as in 2.34-4.fc32
+# Trim the hyphen and any characters that follow.
+version=${version%-*}
+
+cversion=$(get_canonical_version $version)
+min_cversion=$(get_canonical_version $min_version)
+
+if [ "$cversion" -lt "$min_cversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** Assembler is too old."
+	echo >&2 "***   Your $name assembler version:    $version"
+	echo >&2 "***   Minimum $name assembler version: $min_version"
+	echo >&2 "***"
+	exit 1
+fi
+
+echo $name $cversion