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, 162 insertions, 0 deletions

diff --git a/lib/crc/mips/crc32.h b/lib/crc/mips/crc32.h
new file mode 100644
index 000000000..3100354a0
--- /dev/null
+++ b/lib/crc/mips/crc32.h
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * crc32-mips.c - CRC32 and CRC32C using optional MIPSr6 instructions
+ *
+ * Module based on arm64/crypto/crc32-arm.c
+ *
+ * Copyright (C) 2014 Linaro Ltd <yazen.ghannam@linaro.org>
+ * Copyright (C) 2018 MIPS Tech, LLC
+ */
+
+#include <linux/cpufeature.h>
+#include <asm/mipsregs.h>
+#include <linux/unaligned.h>
+
+#ifndef TOOLCHAIN_SUPPORTS_CRC
+#define _ASM_SET_CRC(OP, SZ, TYPE)					  \
+_ASM_MACRO_3R(OP, rt, rs, rt2,						  \
+	".ifnc	\\rt, \\rt2\n\t"					  \
+	".error	\"invalid operands \\\"" #OP " \\rt,\\rs,\\rt2\\\"\"\n\t" \
+	".endif\n\t"							  \
+	_ASM_INSN_IF_MIPS(0x7c00000f | (__rt << 16) | (__rs << 21) |	  \
+			  ((SZ) <<  6) | ((TYPE) << 8))			  \
+	_ASM_INSN32_IF_MM(0x00000030 | (__rs << 16) | (__rt << 21) |	  \
+			  ((SZ) << 14) | ((TYPE) << 3)))
+#define _ASM_UNSET_CRC(op, SZ, TYPE) ".purgem " #op "\n\t"
+#else /* !TOOLCHAIN_SUPPORTS_CRC */
+#define _ASM_SET_CRC(op, SZ, TYPE) ".set\tcrc\n\t"
+#define _ASM_UNSET_CRC(op, SZ, TYPE)
+#endif
+
+#define __CRC32(crc, value, op, SZ, TYPE)		\
+do {							\
+	__asm__ __volatile__(				\
+		".set	push\n\t"			\
+		_ASM_SET_CRC(op, SZ, TYPE)		\
+		#op "	%0, %1, %0\n\t"			\
+		_ASM_UNSET_CRC(op, SZ, TYPE)		\
+		".set	pop"				\
+		: "+r" (crc)				\
+		: "r" (value));				\
+} while (0)
+
+#define _CRC32_crc32b(crc, value)	__CRC32(crc, value, crc32b, 0, 0)
+#define _CRC32_crc32h(crc, value)	__CRC32(crc, value, crc32h, 1, 0)
+#define _CRC32_crc32w(crc, value)	__CRC32(crc, value, crc32w, 2, 0)
+#define _CRC32_crc32d(crc, value)	__CRC32(crc, value, crc32d, 3, 0)
+#define _CRC32_crc32cb(crc, value)	__CRC32(crc, value, crc32cb, 0, 1)
+#define _CRC32_crc32ch(crc, value)	__CRC32(crc, value, crc32ch, 1, 1)
+#define _CRC32_crc32cw(crc, value)	__CRC32(crc, value, crc32cw, 2, 1)
+#define _CRC32_crc32cd(crc, value)	__CRC32(crc, value, crc32cd, 3, 1)
+
+#define _CRC32(crc, value, size, op) \
+	_CRC32_##op##size(crc, value)
+
+#define CRC32(crc, value, size) \
+	_CRC32(crc, value, size, crc32)
+
+#define CRC32C(crc, value, size) \
+	_CRC32(crc, value, size, crc32c)
+
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_crc32);
+
+static inline u32 crc32_le_arch(u32 crc, const u8 *p, size_t len)
+{
+	if (!static_branch_likely(&have_crc32))
+		return crc32_le_base(crc, p, len);
+
+	if (IS_ENABLED(CONFIG_64BIT)) {
+		for (; len >= sizeof(u64); p += sizeof(u64), len -= sizeof(u64)) {
+			u64 value = get_unaligned_le64(p);
+
+			CRC32(crc, value, d);
+		}
+
+		if (len & sizeof(u32)) {
+			u32 value = get_unaligned_le32(p);
+
+			CRC32(crc, value, w);
+			p += sizeof(u32);
+		}
+	} else {
+		for (; len >= sizeof(u32); len -= sizeof(u32)) {
+			u32 value = get_unaligned_le32(p);
+
+			CRC32(crc, value, w);
+			p += sizeof(u32);
+		}
+	}
+
+	if (len & sizeof(u16)) {
+		u16 value = get_unaligned_le16(p);
+
+		CRC32(crc, value, h);
+		p += sizeof(u16);
+	}
+
+	if (len & sizeof(u8)) {
+		u8 value = *p++;
+
+		CRC32(crc, value, b);
+	}
+
+	return crc;
+}
+
+static inline u32 crc32c_arch(u32 crc, const u8 *p, size_t len)
+{
+	if (!static_branch_likely(&have_crc32))
+		return crc32c_base(crc, p, len);
+
+	if (IS_ENABLED(CONFIG_64BIT)) {
+		for (; len >= sizeof(u64); p += sizeof(u64), len -= sizeof(u64)) {
+			u64 value = get_unaligned_le64(p);
+
+			CRC32C(crc, value, d);
+		}
+
+		if (len & sizeof(u32)) {
+			u32 value = get_unaligned_le32(p);
+
+			CRC32C(crc, value, w);
+			p += sizeof(u32);
+		}
+	} else {
+		for (; len >= sizeof(u32); len -= sizeof(u32)) {
+			u32 value = get_unaligned_le32(p);
+
+			CRC32C(crc, value, w);
+			p += sizeof(u32);
+		}
+	}
+
+	if (len & sizeof(u16)) {
+		u16 value = get_unaligned_le16(p);
+
+		CRC32C(crc, value, h);
+		p += sizeof(u16);
+	}
+
+	if (len & sizeof(u8)) {
+		u8 value = *p++;
+
+		CRC32C(crc, value, b);
+	}
+	return crc;
+}
+
+#define crc32_be_arch crc32_be_base /* not implemented on this arch */
+
+#define crc32_mod_init_arch crc32_mod_init_arch
+static void crc32_mod_init_arch(void)
+{
+	if (cpu_have_feature(cpu_feature(MIPS_CRC32)))
+		static_branch_enable(&have_crc32);
+}
+
+static inline u32 crc32_optimizations_arch(void)
+{
+	if (static_key_enabled(&have_crc32))
+		return CRC32_LE_OPTIMIZATION | CRC32C_OPTIMIZATION;
+	return 0;
+}