Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 187 insertions, 0 deletions

diff --git a/drivers/md/dm-cache-policy.h b/drivers/md/dm-cache-policy.h
new file mode 100644
index 000000000..a1eedcc42
--- /dev/null
+++ b/drivers/md/dm-cache-policy.h
@@ -0,0 +1,187 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2012 Red Hat. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_CACHE_POLICY_H
+#define DM_CACHE_POLICY_H
+
+#include "dm-cache-block-types.h"
+
+#include <linux/device-mapper.h>
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The cache policy makes the important decisions about which blocks get to
+ * live on the faster cache device.
+ */
+enum policy_operation {
+	POLICY_PROMOTE,
+	POLICY_DEMOTE,
+	POLICY_WRITEBACK
+};
+
+/*
+ * This is the instruction passed back to the core target.
+ */
+struct policy_work {
+	enum policy_operation op;
+	dm_oblock_t oblock;
+	dm_cblock_t cblock;
+};
+
+/*
+ * The cache policy object.  It is envisaged that this structure will be
+ * embedded in a bigger, policy specific structure (ie. use container_of()).
+ */
+struct dm_cache_policy {
+	/*
+	 * Destroys this object.
+	 */
+	void (*destroy)(struct dm_cache_policy *p);
+
+	/*
+	 * Find the location of a block.
+	 *
+	 * Must not block.
+	 *
+	 * Returns 0 if in cache (cblock will be set), -ENOENT if not, < 0 for
+	 * other errors (-EWOULDBLOCK would be typical).  data_dir should be
+	 * READ or WRITE. fast_copy should be set if migrating this block would
+	 * be 'cheap' somehow (eg, discarded data). background_queued will be set
+	 * if a migration has just been queued.
+	 */
+	int (*lookup)(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock,
+		      int data_dir, bool fast_copy, bool *background_queued);
+
+	/*
+	 * Sometimes the core target can optimise a migration, eg, the
+	 * block may be discarded, or the bio may cover an entire block.
+	 * In order to optimise it needs the migration immediately though
+	 * so it knows to do something different with the bio.
+	 *
+	 * This method is optional (policy-internal will fallback to using
+	 * lookup).
+	 */
+	int (*lookup_with_work)(struct dm_cache_policy *p,
+				dm_oblock_t oblock, dm_cblock_t *cblock,
+				int data_dir, bool fast_copy,
+				struct policy_work **work);
+
+	/*
+	 * Retrieves background work.  Returns -ENODATA when there's no
+	 * background work.
+	 */
+	int (*get_background_work)(struct dm_cache_policy *p, bool idle,
+				   struct policy_work **result);
+
+	/*
+	 * You must pass in the same work pointer that you were given, not
+	 * a copy.
+	 */
+	void (*complete_background_work)(struct dm_cache_policy *p,
+					 struct policy_work *work,
+					 bool success);
+
+	void (*set_dirty)(struct dm_cache_policy *p, dm_cblock_t cblock);
+	void (*clear_dirty)(struct dm_cache_policy *p, dm_cblock_t cblock);
+
+	/*
+	 * Called when a cache target is first created.  Used to load a
+	 * mapping from the metadata device into the policy.
+	 */
+	int (*load_mapping)(struct dm_cache_policy *p, dm_oblock_t oblock,
+			    dm_cblock_t cblock, bool dirty,
+			    uint32_t hint, bool hint_valid);
+
+	/*
+	 * Drops the mapping, irrespective of whether it's clean or dirty.
+	 * Returns -ENODATA if cblock is not mapped.
+	 */
+	int (*invalidate_mapping)(struct dm_cache_policy *p, dm_cblock_t cblock);
+
+	/*
+	 * Gets the hint for a given cblock.  Called in a single threaded
+	 * context.  So no locking required.
+	 */
+	uint32_t (*get_hint)(struct dm_cache_policy *p, dm_cblock_t cblock);
+
+	/*
+	 * How full is the cache?
+	 */
+	dm_cblock_t (*residency)(struct dm_cache_policy *p);
+
+	/*
+	 * Because of where we sit in the block layer, we can be asked to
+	 * map a lot of little bios that are all in the same block (no
+	 * queue merging has occurred).  To stop the policy being fooled by
+	 * these, the core target sends regular tick() calls to the policy.
+	 * The policy should only count an entry as hit once per tick.
+	 *
+	 * This method is optional.
+	 */
+	void (*tick)(struct dm_cache_policy *p, bool can_block);
+
+	/*
+	 * Configuration.
+	 */
+	int (*emit_config_values)(struct dm_cache_policy *p, char *result,
+				  unsigned int maxlen, ssize_t *sz_ptr);
+	int (*set_config_value)(struct dm_cache_policy *p,
+				const char *key, const char *value);
+
+	void (*allow_migrations)(struct dm_cache_policy *p, bool allow);
+
+	/*
+	 * Book keeping ptr for the policy register, not for general use.
+	 */
+	void *private;
+};
+
+/*----------------------------------------------------------------*/
+
+/*
+ * We maintain a little register of the different policy types.
+ */
+#define CACHE_POLICY_NAME_SIZE 16
+#define CACHE_POLICY_VERSION_SIZE 3
+
+struct dm_cache_policy_type {
+	/* For use by the register code only. */
+	struct list_head list;
+
+	/*
+	 * Policy writers should fill in these fields.  The name field is
+	 * what gets passed on the target line to select your policy.
+	 */
+	char name[CACHE_POLICY_NAME_SIZE];
+	unsigned int version[CACHE_POLICY_VERSION_SIZE];
+
+	/*
+	 * For use by an alias dm_cache_policy_type to point to the
+	 * real dm_cache_policy_type.
+	 */
+	struct dm_cache_policy_type *real;
+
+	/*
+	 * Policies may store a hint for each cache block.
+	 * Currently the size of this hint must be 0 or 4 bytes but we
+	 * expect to relax this in future.
+	 */
+	size_t hint_size;
+
+	struct module *owner;
+	struct dm_cache_policy *(*create)(dm_cblock_t cache_size,
+					  sector_t origin_size,
+					  sector_t block_size);
+};
+
+int dm_cache_policy_register(struct dm_cache_policy_type *type);
+void dm_cache_policy_unregister(struct dm_cache_policy_type *type);
+
+/*----------------------------------------------------------------*/
+
+#endif	/* DM_CACHE_POLICY_H */