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, 35 insertions, 0 deletions

diff --git a/drivers/tee/tee_private.h b/drivers/tee/tee_private.h
new file mode 100644
index 000000000..6bde688bf
--- /dev/null
+++ b/drivers/tee/tee_private.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2015-2016, Linaro Limited
+ */
+#ifndef TEE_PRIVATE_H
+#define TEE_PRIVATE_H
+
+#include <linux/cdev.h>
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/kref.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+/* extra references appended to shm object for registered shared memory */
+struct tee_shm_dmabuf_ref {
+	struct tee_shm shm;
+	size_t offset;
+	struct dma_buf *dmabuf;
+	struct tee_shm *parent_shm;
+};
+
+int tee_shm_get_fd(struct tee_shm *shm);
+
+struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
+struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
+					  unsigned long addr, size_t length);
+
+int tee_heap_update_from_dma_buf(struct tee_device *teedev,
+				 struct dma_buf *dmabuf, size_t *offset,
+				 struct tee_shm *shm,
+				 struct tee_shm **parent_shm);
+
+#endif /*TEE_PRIVATE_H*/