Commit 84759c6d authored by Kent Overstreet's avatar Kent Overstreet
Browse files

Revert "rw_semaphore: remove up/down_read_non_owner" 



This reverts commit 11b80f45.

Bcache needs rw semaphores for cache coherency in writeback mode -
writes have to take a read lock on a per cache device rw sem, and
release it when the bio completes.

But since this is for bios it's naturally not in the context of the
process that originally took the lock.

Signed-off-by: default avatarKent Overstreet <koverstreet@google.com>
CC: Christoph Hellwig <hch@infradead.org>
CC: David Howells <dhowells@redhat.com>
parent a937536b

include/linux/rwsem.h

+10 −0
Original line number Diff line number Diff line
@@ -133,10 +133,20 @@ do { \ 
	_down_write_nest_lock(sem, &(nest_lock)->dep_map);	\

} while (0);



/*

 * Take/release a lock when not the owner will release it.

 *

 * [ This API should be avoided as much as possible - the

 *   proper abstraction for this case is completions. ]

 */

extern void down_read_non_owner(struct rw_semaphore *sem);

extern void up_read_non_owner(struct rw_semaphore *sem);

#else

# define down_read_nested(sem, subclass)		down_read(sem)

# define down_write_nest_lock(sem, nest_lock)	down_write(sem)

# define down_write_nested(sem, subclass)	down_write(sem)

# define down_read_non_owner(sem)		down_read(sem)

# define up_read_non_owner(sem)			up_read(sem)

#endif



#endif /* _LINUX_RWSEM_H */

kernel/rwsem.c

+16 −0
Original line number Diff line number Diff line
@@ -126,6 +126,15 @@ void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) 


EXPORT_SYMBOL(_down_write_nest_lock);



void down_read_non_owner(struct rw_semaphore *sem)

{

	might_sleep();



	__down_read(sem);

}



EXPORT_SYMBOL(down_read_non_owner);



void down_write_nested(struct rw_semaphore *sem, int subclass)

{

	might_sleep();
@@ -136,6 +145,13 @@ void down_write_nested(struct rw_semaphore *sem, int subclass) 


EXPORT_SYMBOL(down_write_nested);



void up_read_non_owner(struct rw_semaphore *sem)

{

	__up_read(sem);

}



EXPORT_SYMBOL(up_read_non_owner);



#endif

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