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, 175 insertions, 0 deletions

diff --git a/drivers/net/phy/swphy.c b/drivers/net/phy/swphy.c
new file mode 100644
index 000000000..59f1ba4d4
--- /dev/null
+++ b/drivers/net/phy/swphy.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Software PHY emulation
+ *
+ * Code taken from fixed_phy.c by Russell King.
+ *
+ * Author: Vitaly Bordug <vbordug@ru.mvista.com>
+ *         Anton Vorontsov <avorontsov@ru.mvista.com>
+ *
+ * Copyright (c) 2006-2007 MontaVista Software, Inc.
+ */
+#include <linux/export.h>
+#include <linux/mii.h>
+#include <linux/phy.h>
+#include <linux/phy_fixed.h>
+
+#include "swphy.h"
+
+#define MII_REGS_NUM 29
+
+struct swmii_regs {
+	u16 bmsr;
+	u16 lpa;
+	u16 lpagb;
+	u16 estat;
+};
+
+enum {
+	SWMII_SPEED_10 = 0,
+	SWMII_SPEED_100,
+	SWMII_SPEED_1000,
+	SWMII_DUPLEX_HALF = 0,
+	SWMII_DUPLEX_FULL,
+};
+
+/*
+ * These two tables get bitwise-anded together to produce the final result.
+ * This means the speed table must contain both duplex settings, and the
+ * duplex table must contain all speed settings.
+ */
+static const struct swmii_regs speed[] = {
+	[SWMII_SPEED_10] = {
+		.lpa   = LPA_10FULL | LPA_10HALF,
+	},
+	[SWMII_SPEED_100] = {
+		.bmsr  = BMSR_100FULL | BMSR_100HALF,
+		.lpa   = LPA_100FULL | LPA_100HALF,
+	},
+	[SWMII_SPEED_1000] = {
+		.bmsr  = BMSR_ESTATEN,
+		.lpagb = LPA_1000FULL | LPA_1000HALF,
+		.estat = ESTATUS_1000_TFULL | ESTATUS_1000_THALF,
+	},
+};
+
+static const struct swmii_regs duplex[] = {
+	[SWMII_DUPLEX_HALF] = {
+		.bmsr  = BMSR_ESTATEN | BMSR_100HALF,
+		.lpa   = LPA_10HALF | LPA_100HALF,
+		.lpagb = LPA_1000HALF,
+		.estat = ESTATUS_1000_THALF,
+	},
+	[SWMII_DUPLEX_FULL] = {
+		.bmsr  = BMSR_ESTATEN | BMSR_100FULL,
+		.lpa   = LPA_10FULL | LPA_100FULL,
+		.lpagb = LPA_1000FULL,
+		.estat = ESTATUS_1000_TFULL,
+	},
+};
+
+static int swphy_decode_speed(int speed)
+{
+	switch (speed) {
+	case 1000:
+		return SWMII_SPEED_1000;
+	case 100:
+		return SWMII_SPEED_100;
+	case 10:
+		return SWMII_SPEED_10;
+	default:
+		return -EINVAL;
+	}
+}
+
+/**
+ * swphy_validate_state - validate the software phy status
+ * @state: software phy status
+ *
+ * This checks that we can represent the state stored in @state can be
+ * represented in the emulated MII registers.  Returns 0 if it can,
+ * otherwise returns -EINVAL.
+ */
+int swphy_validate_state(const struct fixed_phy_status *state)
+{
+	int err;
+
+	if (state->link) {
+		err = swphy_decode_speed(state->speed);
+		if (err < 0) {
+			pr_warn("swphy: unknown speed\n");
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(swphy_validate_state);
+
+/**
+ * swphy_read_reg - return a MII register from the fixed phy state
+ * @reg: MII register
+ * @state: fixed phy status
+ *
+ * Return the MII @reg register generated from the fixed phy state @state.
+ */
+int swphy_read_reg(int reg, const struct fixed_phy_status *state)
+{
+	int speed_index, duplex_index;
+	u16 bmsr = BMSR_ANEGCAPABLE;
+	u16 estat = 0;
+	u16 lpagb = 0;
+	u16 lpa = 0;
+
+	if (reg > MII_REGS_NUM)
+		return -1;
+
+	speed_index = swphy_decode_speed(state->speed);
+	if (WARN_ON(speed_index < 0))
+		return 0;
+
+	duplex_index = state->duplex ? SWMII_DUPLEX_FULL : SWMII_DUPLEX_HALF;
+
+	bmsr |= speed[speed_index].bmsr & duplex[duplex_index].bmsr;
+	estat |= speed[speed_index].estat & duplex[duplex_index].estat;
+
+	if (state->link) {
+		bmsr |= BMSR_LSTATUS | BMSR_ANEGCOMPLETE;
+
+		lpa   |= speed[speed_index].lpa   & duplex[duplex_index].lpa;
+		lpagb |= speed[speed_index].lpagb & duplex[duplex_index].lpagb;
+
+		if (state->pause)
+			lpa |= LPA_PAUSE_CAP;
+
+		if (state->asym_pause)
+			lpa |= LPA_PAUSE_ASYM;
+	}
+
+	switch (reg) {
+	case MII_BMCR:
+		return BMCR_ANENABLE;
+	case MII_BMSR:
+		return bmsr;
+	case MII_PHYSID1:
+	case MII_PHYSID2:
+		return 0;
+	case MII_LPA:
+		return lpa;
+	case MII_STAT1000:
+		return lpagb;
+	case MII_ESTATUS:
+		return estat;
+
+	/*
+	 * We do not support emulating Clause 45 over Clause 22 register
+	 * reads.  Return an error instead of bogus data.
+	 */
+	case MII_MMD_CTRL:
+	case MII_MMD_DATA:
+		return -1;
+
+	default:
+		return 0xffff;
+	}
+}
+EXPORT_SYMBOL_GPL(swphy_read_reg);