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, 69 insertions, 0 deletions

diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
new file mode 100644
index 000000000..2bc00c67d
--- /dev/null
+++ b/include/asm-generic/Kbuild
@@ -0,0 +1,69 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# asm headers that all architectures except um should have
+# (This file is not included when SRCARCH=um since UML borrows several
+# asm headers from the host architecture.)
+
+mandatory-y += atomic.h
+mandatory-y += archrandom.h
+mandatory-y += barrier.h
+mandatory-y += bitops.h
+mandatory-y += bug.h
+mandatory-y += cacheflush.h
+mandatory-y += cfi.h
+mandatory-y += checksum.h
+mandatory-y += compat.h
+mandatory-y += current.h
+mandatory-y += delay.h
+mandatory-y += device.h
+mandatory-y += div64.h
+mandatory-y += dma-mapping.h
+mandatory-y += dma.h
+mandatory-y += emergency-restart.h
+mandatory-y += exec.h
+mandatory-y += ftrace.h
+mandatory-y += futex.h
+mandatory-y += hardirq.h
+mandatory-y += hw_irq.h
+mandatory-y += io.h
+mandatory-y += irq.h
+mandatory-y += irq_regs.h
+mandatory-y += irq_work.h
+mandatory-y += kdebug.h
+mandatory-y += kmap_size.h
+mandatory-y += kprobes.h
+mandatory-y += kvm_types.h
+mandatory-y += linkage.h
+mandatory-y += local.h
+mandatory-y += local64.h
+mandatory-y += mmiowb.h
+mandatory-y += mmu.h
+mandatory-y += mmu_context.h
+mandatory-y += module.h
+mandatory-y += module.lds.h
+mandatory-y += msi.h
+mandatory-y += pci.h
+mandatory-y += percpu.h
+mandatory-y += percpu_types.h
+mandatory-y += pgalloc.h
+mandatory-y += preempt.h
+mandatory-y += rqspinlock.h
+mandatory-y += runtime-const.h
+mandatory-y += rwonce.h
+mandatory-y += sections.h
+mandatory-y += serial.h
+mandatory-y += shmparam.h
+mandatory-y += simd.h
+mandatory-y += softirq_stack.h
+mandatory-y += switch_to.h
+mandatory-y += timex.h
+mandatory-y += tlbflush.h
+mandatory-y += topology.h
+mandatory-y += trace_clock.h
+mandatory-y += uaccess.h
+mandatory-y += unwind_user.h
+mandatory-y += vdso/clocksource.h
+mandatory-y += vermagic.h
+mandatory-y += vga.h
+mandatory-y += video.h
+mandatory-y += word-at-a-time.h