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, 58 insertions, 0 deletions

diff --git a/include/crypto/internal/engine.h b/include/crypto/internal/engine.h
new file mode 100644
index 000000000..6a1d27880
--- /dev/null
+++ b/include/crypto/internal/engine.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Crypto engine API
+ *
+ * Copyright (c) 2016 Baolin Wang <baolin.wang@linaro.org>
+ * Copyright (c) 2023 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+#ifndef _CRYPTO_INTERNAL_ENGINE_H
+#define _CRYPTO_INTERNAL_ENGINE_H
+
+#include <crypto/algapi.h>
+#include <crypto/engine.h>
+#include <linux/kthread.h>
+#include <linux/spinlock_types.h>
+#include <linux/types.h>
+
+#define ENGINE_NAME_LEN	30
+
+struct device;
+
+/*
+ * struct crypto_engine - crypto hardware engine
+ * @name: the engine name
+ * @busy: request pump is busy
+ * @running: the engine is on working
+ * @retry_support: indication that the hardware allows re-execution
+ * of a failed backlog request
+ * crypto-engine, in head position to keep order
+ * @rt: whether this queue is set to run as a realtime task
+ * @list: link with the global crypto engine list
+ * @queue_lock: spinlock to synchronise access to request queue
+ * @queue: the crypto queue of the engine
+ * @kworker: kthread worker struct for request pump
+ * @pump_requests: work struct for scheduling work to the request pump
+ * @priv_data: the engine private data
+ * @cur_req: the current request which is on processing
+ */
+struct crypto_engine {
+	char			name[ENGINE_NAME_LEN];
+	bool			busy;
+	bool			running;
+
+	bool			retry_support;
+	bool			rt;
+
+	struct list_head	list;
+	spinlock_t		queue_lock;
+	struct crypto_queue	queue __guarded_by(&queue_lock);
+	struct device		*dev;
+
+	struct kthread_worker           *kworker;
+	struct kthread_work             pump_requests;
+
+	void				*priv_data;
+	struct crypto_async_request	*cur_req;
+};
+
+#endif