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, 52 insertions, 0 deletions

diff --git a/drivers/target/Kconfig b/drivers/target/Kconfig
new file mode 100644
index 000000000..92641d391
--- /dev/null
+++ b/drivers/target/Kconfig
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menuconfig TARGET_CORE
+	tristate "Generic Target Core Mod (TCM) and ConfigFS Infrastructure"
+	depends on BLOCK
+	select CONFIGFS_FS
+	select CRC_T10DIF
+	select SCSI_COMMON
+	select SGL_ALLOC
+	default n
+	help
+	Say Y or M here to enable the TCM Storage Engine and ConfigFS enabled
+	control path for target_core_mod.  This includes built-in TCM RAMDISK
+	subsystem logic for virtual LUN 0 access
+
+if TARGET_CORE
+
+config TCM_IBLOCK
+	tristate "TCM/IBLOCK Subsystem Plugin for Linux/BLOCK"
+	select BLK_DEV_INTEGRITY
+	help
+	Say Y here to enable the TCM/IBLOCK subsystem plugin for non-buffered
+	access to Linux/Block devices using BIO
+
+config TCM_FILEIO
+	tristate "TCM/FILEIO Subsystem Plugin for Linux/VFS"
+	help
+	Say Y here to enable the TCM/FILEIO subsystem plugin for buffered
+	access to Linux/VFS struct file or struct block_device
+
+config TCM_PSCSI
+	tristate "TCM/pSCSI Subsystem Plugin for Linux/SCSI"
+	depends on SCSI
+	help
+	Say Y here to enable the TCM/pSCSI subsystem plugin for non-buffered
+	passthrough access to Linux/SCSI device
+
+config TCM_USER2
+	tristate "TCM/USER Subsystem Plugin for Linux"
+	depends on UIO && NET
+	help
+	Say Y here to enable the TCM/USER subsystem plugin for a userspace
+	process to handle requests. This is version 2 of the ABI; version 1
+	is obsolete.
+
+source "drivers/target/loopback/Kconfig"
+source "drivers/target/tcm_fc/Kconfig"
+source "drivers/target/iscsi/Kconfig"
+source "drivers/target/sbp/Kconfig"
+source "drivers/target/tcm_remote/Kconfig"
+
+endif