[PATCH v2 12/17] md/raid5-cache: Move struct r5l_log definition to raid5-log.h

[Logan Gunthorpe <logang@deltatee.com>]

Move struct r5l_log definition to raid5-log.h. While this reduces
encapsulation, it is necessary for the definition of r5l_log to be
public so that rcu_access_pointer() can be used on conf-log in the
next patch.

rcu_access_pointer(p) doesn't technically dereference the log pointer
however, it does use typeof(*p) and some older GCC versions (anything
earlier than gcc-10) will wrongly try to dereference the structure:

    include/linux/rcupdate.h:384:9: error: dereferencing pointer to
                 incomplete type ‘struct r5l_log’

      typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \
           ^

    include/linux/rcupdate.h:495:31: note: in expansion of
                  macro ‘__rcu_access_pointer’

       #define rcu_access_pointer(p) __rcu_access_pointer((p),
       __UNIQUE_ID(rcu), __rcu)

To prevent this, simply provide the definition where
rcu_access_pointer() may be used.

Reported-by: Donald Buczek <buczek@molgen.mpg.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/md/raid5-cache.c | 75 ----------------------------------------
 drivers/md/raid5-log.h   | 75 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 75 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index a3c4d43d6deb..6349cfaae2c8 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -79,81 +79,6 @@ static char *r5c_journal_mode_str[] = {"write-through",
  *	- return IO for pending writes
  */
 
-struct r5l_log {
-	struct md_rdev *rdev;
-
-	u32 uuid_checksum;
-
-	sector_t device_size;		/* log device size, round to
-					 * BLOCK_SECTORS */
-	sector_t max_free_space;	/* reclaim run if free space is at
-					 * this size */
-
-	sector_t last_checkpoint;	/* log tail. where recovery scan
-					 * starts from */
-	u64 last_cp_seq;		/* log tail sequence */
-
-	sector_t log_start;		/* log head. where new data appends */
-	u64 seq;			/* log head sequence */
-
-	sector_t next_checkpoint;
-
-	struct mutex io_mutex;
-	struct r5l_io_unit *current_io;	/* current io_unit accepting new data */
-
-	spinlock_t io_list_lock;
-	struct list_head running_ios;	/* io_units which are still running,
-					 * and have not yet been completely
-					 * written to the log */
-	struct list_head io_end_ios;	/* io_units which have been completely
-					 * written to the log but not yet written
-					 * to the RAID */
-	struct list_head flushing_ios;	/* io_units which are waiting for log
-					 * cache flush */
-	struct list_head finished_ios;	/* io_units which settle down in log disk */
-	struct bio flush_bio;
-
-	struct list_head no_mem_stripes;   /* pending stripes, -ENOMEM */
-
-	struct kmem_cache *io_kc;
-	mempool_t io_pool;
-	struct bio_set bs;
-	mempool_t meta_pool;
-
-	struct md_thread *reclaim_thread;
-	unsigned long reclaim_target;	/* number of space that need to be
-					 * reclaimed.  if it's 0, reclaim spaces
-					 * used by io_units which are in
-					 * IO_UNIT_STRIPE_END state (eg, reclaim
-					 * dones't wait for specific io_unit
-					 * switching to IO_UNIT_STRIPE_END
-					 * state) */
-	wait_queue_head_t iounit_wait;
-
-	struct list_head no_space_stripes; /* pending stripes, log has no space */
-	spinlock_t no_space_stripes_lock;
-
-	bool need_cache_flush;
-
-	/* for r5c_cache */
-	enum r5c_journal_mode r5c_journal_mode;
-
-	/* all stripes in r5cache, in the order of seq at sh->log_start */
-	struct list_head stripe_in_journal_list;
-
-	spinlock_t stripe_in_journal_lock;
-	atomic_t stripe_in_journal_count;
-
-	/* to submit async io_units, to fulfill ordering of flush */
-	struct work_struct deferred_io_work;
-	/* to disable write back during in degraded mode */
-	struct work_struct disable_writeback_work;
-
-	/* to for chunk_aligned_read in writeback mode, details below */
-	spinlock_t tree_lock;
-	struct radix_tree_root big_stripe_tree;
-};
-
 /*
  * Enable chunk_aligned_read() with write back cache.
  *
diff --git a/drivers/md/raid5-log.h b/drivers/md/raid5-log.h
index 1c184fe20939..5948c41f1f2e 100644
--- a/drivers/md/raid5-log.h
+++ b/drivers/md/raid5-log.h
@@ -2,6 +2,81 @@
 #ifndef _RAID5_LOG_H
 #define _RAID5_LOG_H
 
+struct r5l_log {
+	struct md_rdev *rdev;
+
+	u32 uuid_checksum;
+
+	sector_t device_size;		/* log device size, round to
+					 * BLOCK_SECTORS */
+	sector_t max_free_space;	/* reclaim run if free space is at
+					 * this size */
+
+	sector_t last_checkpoint;	/* log tail. where recovery scan
+					 * starts from */
+	u64 last_cp_seq;		/* log tail sequence */
+
+	sector_t log_start;		/* log head. where new data appends */
+	u64 seq;			/* log head sequence */
+
+	sector_t next_checkpoint;
+
+	struct mutex io_mutex;
+	struct r5l_io_unit *current_io;	/* current io_unit accepting new data */
+
+	spinlock_t io_list_lock;
+	struct list_head running_ios;	/* io_units which are still running,
+					 * and have not yet been completely
+					 * written to the log */
+	struct list_head io_end_ios;	/* io_units which have been completely
+					 * written to the log but not yet written
+					 * to the RAID */
+	struct list_head flushing_ios;	/* io_units which are waiting for log
+					 * cache flush */
+	struct list_head finished_ios;	/* io_units which settle down in log disk */
+	struct bio flush_bio;
+
+	struct list_head no_mem_stripes;   /* pending stripes, -ENOMEM */
+
+	struct kmem_cache *io_kc;
+	mempool_t io_pool;
+	struct bio_set bs;
+	mempool_t meta_pool;
+
+	struct md_thread *reclaim_thread;
+	unsigned long reclaim_target;	/* number of space that need to be
+					 * reclaimed.  if it's 0, reclaim spaces
+					 * used by io_units which are in
+					 * IO_UNIT_STRIPE_END state (eg, reclaim
+					 * dones't wait for specific io_unit
+					 * switching to IO_UNIT_STRIPE_END
+					 * state) */
+	wait_queue_head_t iounit_wait;
+
+	struct list_head no_space_stripes; /* pending stripes, log has no space */
+	spinlock_t no_space_stripes_lock;
+
+	bool need_cache_flush;
+
+	/* for r5c_cache */
+	enum r5c_journal_mode r5c_journal_mode;
+
+	/* all stripes in r5cache, in the order of seq at sh->log_start */
+	struct list_head stripe_in_journal_list;
+
+	spinlock_t stripe_in_journal_lock;
+	atomic_t stripe_in_journal_count;
+
+	/* to submit async io_units, to fulfill ordering of flush */
+	struct work_struct deferred_io_work;
+	/* to disable write back during in degraded mode */
+	struct work_struct disable_writeback_work;
+
+	/* to for chunk_aligned_read in writeback mode, details below */
+	spinlock_t tree_lock;
+	struct radix_tree_root big_stripe_tree;
+};
+
 int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev);
 void r5l_exit_log(struct r5conf *conf);
 int r5l_write_stripe(struct r5conf *conf, struct stripe_head *head_sh);
-- 
2.30.2