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, 93 insertions, 0 deletions

diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
new file mode 100644
index 000000000..3c76a5bf6
--- /dev/null
+++ b/drivers/base/regmap/Kconfig
@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: GPL-2.0
+# Generic register map support.  There are no user servicable options here,
+# this is an API intended to be used by other kernel subsystems.  These
+# subsystems should select the appropriate symbols.
+
+config REGMAP
+	bool
+	default y if (REGMAP_I2C || REGMAP_SLIMBUS || REGMAP_SPI || REGMAP_SPMI || REGMAP_W1 || REGMAP_AC97 || REGMAP_MMIO || REGMAP_IRQ || REGMAP_SOUNDWIRE || REGMAP_SOUNDWIRE_MBQ || REGMAP_SCCB || REGMAP_I3C || REGMAP_SPI_AVMM || REGMAP_MDIO || REGMAP_FSI)
+	help
+	  Enable support for the Register Map (regmap) access API.
+
+	  Usually, this option is automatically selected when needed.
+	  However, you may want to enable it manually for running the regmap
+	  KUnit tests.
+
+	  If unsure, say N.
+
+config REGMAP_KUNIT
+	tristate "KUnit tests for regmap"
+	depends on KUNIT && REGMAP
+	default KUNIT_ALL_TESTS
+	select REGMAP_RAM
+
+config REGMAP_BUILD
+	bool "Enable regmap build"
+	depends on KUNIT
+	select REGMAP
+	help
+	  This option exists purely to allow the regmap KUnit tests to
+	  be enabled without having to enable some driver that uses
+	  regmap due to unfortunate issues with how KUnit tests are
+	  normally enabled.
+
+config REGMAP_AC97
+	tristate
+
+config REGMAP_I2C
+	tristate
+	depends on I2C
+
+config REGMAP_SLIMBUS
+	tristate
+	depends on SLIMBUS
+
+config REGMAP_SPI
+	tristate
+	depends on SPI
+
+config REGMAP_SPMI
+	tristate
+	depends on SPMI
+
+config REGMAP_W1
+	tristate
+	depends on W1
+
+config REGMAP_MDIO
+	tristate
+	depends on PHYLIB
+
+config REGMAP_MMIO
+	tristate
+
+config REGMAP_IRQ
+	bool
+	select IRQ_DOMAIN
+
+config REGMAP_RAM
+	tristate
+
+config REGMAP_SOUNDWIRE
+	tristate
+	depends on SOUNDWIRE
+
+config REGMAP_SOUNDWIRE_MBQ
+	tristate
+	depends on SOUNDWIRE
+
+config REGMAP_SCCB
+	tristate
+	depends on I2C
+
+config REGMAP_I3C
+	tristate
+	depends on I3C
+
+config REGMAP_SPI_AVMM
+	tristate
+	depends on SPI
+
+config REGMAP_FSI
+	tristate
+	depends on FSI