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, 118 insertions, 0 deletions

diff --git a/drivers/md/dm-ima.h b/drivers/md/dm-ima.h
new file mode 100644
index 000000000..0ec013d15
--- /dev/null
+++ b/drivers/md/dm-ima.h
@@ -0,0 +1,118 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Microsoft Corporation
+ *
+ * Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
+ *
+ * Header file for device mapper IMA measurements.
+ */
+
+#ifndef DM_IMA_H
+#define DM_IMA_H
+
+#define DM_IMA_MEASUREMENT_BUF_LEN	4096
+#define DM_IMA_DEVICE_BUF_LEN		1024
+#define DM_IMA_TARGET_METADATA_BUF_LEN	128
+#define DM_IMA_TARGET_DATA_BUF_LEN	2048
+#define DM_IMA_DEVICE_CAPACITY_BUF_LEN	128
+
+#define __dm_ima_stringify(s) #s
+#define __dm_ima_str(s) __dm_ima_stringify(s)
+
+#define DM_IMA_VERSION_STR "dm_version="	\
+	__dm_ima_str(DM_VERSION_MAJOR) "."	\
+	__dm_ima_str(DM_VERSION_MINOR) "."	\
+	__dm_ima_str(DM_VERSION_PATCHLEVEL) ";"
+
+enum dm_ima_table_op {
+	DM_IMA_TABLE_SAVE,
+	DM_IMA_TABLE_RESTORE,
+};
+
+#ifdef CONFIG_IMA
+
+struct dm_ima_device_table_metadata {
+	/*
+	 * Contains data specific to the device which is common across
+	 * all the targets in the table (e.g. name, uuid, major, minor, etc).
+	 * The values are stored in comma separated list of key1=val1,key2=val2;
+	 * pairs delimited by a semicolon at the end of the list.
+	 */
+	char *device_metadata;
+	unsigned int device_metadata_len;
+	unsigned int num_targets;
+	sector_t capacity;
+
+	/*
+	 * Contains the sha256 hashes of the IMA measurements of the target
+	 * attributes' key-value pairs from the active/inactive tables.
+	 */
+	char *hash;
+	unsigned int hash_len;
+};
+
+struct dm_ima_context {
+	struct dm_ima_device_table_metadata table;
+	unsigned int update_idx;
+	char dev_name[DM_NAME_LEN*2];
+	char dev_uuid[DM_UUID_LEN*2];
+};
+
+/*
+ * This structure contains device metadata, and table hash for
+ * active and inactive tables for ima measurements.
+ */
+struct dm_ima_measurements {
+	unsigned int update_idx;
+	unsigned int measure_idx;
+	struct wait_queue_head ima_wq;
+	spinlock_t ima_lock;
+	struct dm_ima_device_table_metadata active_table;
+	struct dm_ima_device_table_metadata inactive_table;
+};
+
+void dm_ima_init(struct mapped_device *md);
+void dm_ima_alloc_context(struct dm_ima_context **context, bool noio);
+void dm_ima_free_context(struct dm_ima_context *context);
+void dm_ima_context_table_op(struct mapped_device *md,
+			     struct dm_ima_context *context,
+			     enum dm_ima_table_op op);
+void dm_ima_measure_on_table_load(struct dm_table *table,
+				  struct dm_ima_context *context);
+void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap,
+				     struct dm_ima_context *context);
+void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all,
+				     struct dm_ima_context *context,
+				     unsigned int idx);
+void dm_ima_measure_on_table_clear(struct mapped_device *md,
+				   struct dm_ima_context *context);
+void dm_ima_measure_on_device_rename(struct mapped_device *md,
+				     struct dm_ima_context *context);
+
+#else
+
+struct dm_ima_context;
+
+static inline void dm_ima_init(struct mapped_device *md) {}
+static inline void dm_ima_alloc_context(struct dm_ima_context **context, bool noio) {}
+static inline void dm_ima_free_context(struct dm_ima_context *context) {}
+static inline void dm_ima_context_table_op(struct mapped_device *md,
+					   struct dm_ima_context *context,
+					   enum dm_ima_table_op op) {}
+static inline void dm_ima_measure_on_table_load(struct dm_table *table,
+						struct dm_ima_context *context) {}
+static inline void dm_ima_measure_on_device_resume(struct mapped_device *md,
+						   bool swap,
+						   struct dm_ima_context *context) {}
+static inline void dm_ima_measure_on_device_remove(struct mapped_device *md,
+						   bool remove_all,
+						   struct dm_ima_context *context,
+						   unsigned int idx) {}
+static inline void dm_ima_measure_on_table_clear(struct mapped_device *md,
+						 struct dm_ima_context *context) {}
+static inline void dm_ima_measure_on_device_rename(struct mapped_device *md,
+						   struct dm_ima_context *context) {}
+
+#endif /* CONFIG_IMA */
+
+#endif /* DM_IMA_H */