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, 48 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-s3c.h b/drivers/rtc/rtc-s3c.h
new file mode 100644
index 000000000..11d7a1255
--- /dev/null
+++ b/drivers/rtc/rtc-s3c.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2003 Simtec Electronics <linux@simtec.co.uk>
+ *		      http://www.simtec.co.uk/products/SWLINUX/
+ *
+ * S3C2410 Internal RTC register definition
+*/
+
+#ifndef __ASM_ARCH_REGS_RTC_H
+#define __ASM_ARCH_REGS_RTC_H __FILE__
+
+#define S3C2410_RTCREG(x) (x)
+#define S3C2410_INTP		S3C2410_RTCREG(0x30)
+#define S3C2410_INTP_ALM	(1 << 1)
+#define S3C2410_INTP_TIC	(1 << 0)
+
+#define S3C2410_RTCCON		S3C2410_RTCREG(0x40)
+#define S3C2410_RTCCON_RTCEN	(1 << 0)
+#define S3C2410_RTCCON_CNTSEL	(1 << 2)
+#define S3C2410_RTCCON_CLKRST	(1 << 3)
+#define S3C2443_RTCCON_TICSEL	(1 << 4)
+#define S3C64XX_RTCCON_TICEN	(1 << 8)
+
+#define S3C2410_RTCALM		S3C2410_RTCREG(0x50)
+#define S3C2410_RTCALM_ALMEN	(1 << 6)
+#define S3C2410_RTCALM_YEAREN	(1 << 5)
+#define S3C2410_RTCALM_MONEN	(1 << 4)
+#define S3C2410_RTCALM_DAYEN	(1 << 3)
+#define S3C2410_RTCALM_HOUREN	(1 << 2)
+#define S3C2410_RTCALM_MINEN	(1 << 1)
+#define S3C2410_RTCALM_SECEN	(1 << 0)
+
+#define S3C2410_ALMSEC		S3C2410_RTCREG(0x54)
+#define S3C2410_ALMMIN		S3C2410_RTCREG(0x58)
+#define S3C2410_ALMHOUR		S3C2410_RTCREG(0x5c)
+
+#define S3C2410_ALMDATE		S3C2410_RTCREG(0x60)
+#define S3C2410_ALMMON		S3C2410_RTCREG(0x64)
+#define S3C2410_ALMYEAR		S3C2410_RTCREG(0x68)
+
+#define S3C2410_RTCSEC		S3C2410_RTCREG(0x70)
+#define S3C2410_RTCMIN		S3C2410_RTCREG(0x74)
+#define S3C2410_RTCHOUR		S3C2410_RTCREG(0x78)
+#define S3C2410_RTCDATE		S3C2410_RTCREG(0x7c)
+#define S3C2410_RTCMON		S3C2410_RTCREG(0x84)
+#define S3C2410_RTCYEAR		S3C2410_RTCREG(0x88)
+
+#endif /* __ASM_ARCH_REGS_RTC_H */