Date:	Mon, 19 Jan 2009 09:05:28 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Steven Whitehouse <swhiteho@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, cluster-devel@...hat.com
Subject: Re: mmotm 2009-01-14-20-31 uploaded (gfs2)

Steven Whitehouse wrote:
> Hi,
> 
> On Fri, 2009-01-16 at 09:35 -0800, Andrew Morton wrote:
>> On Fri, 16 Jan 2009 09:06:23 -0800 Randy Dunlap <randy.dunlap@...cle.com> wrote:
>>
>>>>>> which is not ideal, but I don't see any easy way to avoid the #ifdef,
>>>>>>
>>>>> Take a look in fs.h:
>>>>>
>>>>> #define generic_setlease(a, b, c) ({ -EINVAL; })
>>>>>
>>>>> If that wasn't a stupid macro, your code would have compiled and ran
>>>>> just as intended.
>>>>>
>>>> There doesn't seem to be an easy answer though. If I #define it to NULL,
>>>> that upsets other parts of the code that rely on that macro, and if I
>>>> turn it into a inline function which returns -EINVAL, then presumably I
>>>> can't take its address for my file_operations.
>>> No, gcc will allow &inline_func and out-of-line it if it is needed (AFAIK;
>>> I've seen a few cases of that).
>>>
>> yup.  It measn that we'll get a separate private copy of the
>> generic_setlease() code in each compilation unit which takes its
>> address, but I don't think that would kill us.
>>
>> The prevention is of course to put the stub function in a core kernel
>> .c file and export it to modules.
>>
> Having looked into this in a bit more detail now, it seems that this
> particular function (generic_setlease) is one of a number appearing in
> fs.h which are replaced by macros in the case that CONFIG_FILE_LOCKING
> is not set.
> 
> So rather than just do the one function, it seemed to make sense to me
> to make them all the same. So this uses inline functions as originally
> proposed. If you'd prefer that we don't inline them and instead have a
> fs/no-locks.c or something like that with stub functions in it, then I"m
> happy to revise the patch accordingly.

Acked-by/Tested-by: Randy Dunlap <randy.dunlap@...cle.com>

> This patch passes my compile tests, modulo a small change that I need to
> make in GFS2 to suppress a warning (not attached). That seems to be
> related to yet another set of macros which appear only with
> CONFIG_FILE_LOCKING not set. Maybe I should update those to be inline
> functions as well....

You mean these?  Probably should update them as well.

#else /* !CONFIG_FILE_LOCKING */
#define locks_mandatory_locked(a) ({ 0; })
#define locks_mandatory_area(a, b, c, d, e) ({ 0; })
#define __mandatory_lock(a) ({ 0; })
#define mandatory_lock(a) ({ 0; })
#define locks_verify_locked(a) ({ 0; })
#define locks_verify_truncate(a, b, c) ({ 0; })
#define break_lease(a, b) ({ 0; })
#endif /* CONFIG_FILE_LOCKING */



Thanks.

> Steve.
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 6022f44..392c18a 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1057,34 +1057,147 @@ extern int lease_modify(struct file_lock **, int);
>  extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
>  extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
>  #else /* !CONFIG_FILE_LOCKING */
> -#define fcntl_getlk(a, b) ({ -EINVAL; })
> -#define fcntl_setlk(a, b, c, d) ({ -EACCES; })
> +static inline int fcntl_getlk(struct file *file, struct flock __user *user)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int fcntl_setlk(unsigned int fd, struct file *file,
> +			      unsigned int cmd, struct flock __user *user)
> +{
> +	return -EACCES;
> +}
> +
>  #if BITS_PER_LONG == 32
> -#define fcntl_getlk64(a, b) ({ -EINVAL; })
> -#define fcntl_setlk64(a, b, c, d) ({ -EACCES; })
> +static inline int fcntl_getlk64(struct file *file, struct flock64 __user *user)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int fcntl_setlk64(unsigned int fd, struct file *file,
> +				unsigned int cmd, struct flock64 __user *user)
> +{
> +	return -EACCES;
> +}
>  #endif
> -#define fcntl_setlease(a, b, c) ({ 0; })
> -#define fcntl_getlease(a) ({ 0; })
> -#define locks_init_lock(a) ({ })
> -#define __locks_copy_lock(a, b) ({ })
> -#define locks_copy_lock(a, b) ({ })
> -#define locks_remove_posix(a, b) ({ })
> -#define locks_remove_flock(a) ({ })
> -#define posix_test_lock(a, b) ({ 0; })
> -#define posix_lock_file(a, b, c) ({ -ENOLCK; })
> -#define posix_lock_file_wait(a, b) ({ -ENOLCK; })
> -#define posix_unblock_lock(a, b) (-ENOENT)
> -#define vfs_test_lock(a, b) ({ 0; })
> -#define vfs_lock_file(a, b, c, d) (-ENOLCK)
> -#define vfs_cancel_lock(a, b) ({ 0; })
> -#define flock_lock_file_wait(a, b) ({ -ENOLCK; })
> -#define __break_lease(a, b) ({ 0; })
> -#define lease_get_mtime(a, b) ({ })
> -#define generic_setlease(a, b, c) ({ -EINVAL; })
> -#define vfs_setlease(a, b, c) ({ -EINVAL; })
> -#define lease_modify(a, b) ({ -EINVAL; })
> -#define lock_may_read(a, b, c) ({ 1; })
> -#define lock_may_write(a, b, c) ({ 1; })
> +static inline int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
> +{
> +	return 0;
> +}
> +
> +static inline int fcntl_getlease(struct file *filp)
> +{
> +	return 0;
> +}
> +
> +static inline void locks_init_lock(struct file_lock *fl)
> +{
> +	return;
> +}
> +
> +static inline void __locks_copy_lock(struct file_lock *new, struct file_lock *fl)
> +{
> +	return;
> +}
> +
> +static inline void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
> +{
> +	return;
> +}
> +
> +static inline void locks_remove_posix(struct file *filp, fl_owner_t owner)
> +{
> +	return;
> +}
> +
> +static inline void locks_remove_flock(struct file *filp)
> +{
> +	return;
> +}
> +
> +static inline void posix_test_lock(struct file *filp, struct file_lock *fl)
> +{
> +	return;
> +}
> +
> +static inline int posix_lock_file(struct file *filp, struct file_lock *fl,
> +				  struct file_lock *conflock)
> +{
> +	return -ENOLCK;
> +}
> +
> +static inline int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
> +{
> +	return -ENOLCK;
> +}
> +
> +static inline int posix_unblock_lock(struct file *filp,
> +				     struct file_lock *waiter)
> +{
> +	return -ENOENT;
> +}
> +
> +static inline int vfs_test_lock(struct file *filp, struct file_lock *fl)
> +{
> +	return 0;
> +}
> +
> +static inline int vfs_lock_file(struct file *filp, unsigned int cmd,
> +				struct file_lock *fl, struct file_lock *conf)
> +{
> +	return -ENOLCK;
> +}
> +
> +static inline int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
> +{
> +	return 0;
> +}
> +
> +static inline int flock_lock_file_wait(struct file *filp,
> +				       struct file_lock *request)
> +{
> +	return -ENOLCK;
> +}
> +
> +static inline int __break_lease(struct inode *inode, unsigned int mode)
> +{
> +	return 0;
> +}
> +
> +static inline void lease_get_mtime(struct inode *inode, struct timespec *time)
> +{
> +	return;
> +}
> +
> +static inline int generic_setlease(struct file *filp, long arg,
> +				    struct file_lock **flp)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int vfs_setlease(struct file *filp, long arg,
> +			       struct file_lock **lease)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int lease_modify(struct file_lock **before, int arg)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int lock_may_read(struct inode *inode, loff_t start,
> +				unsigned long len)
> +{
> +	return 1;
> +}
> +
> +static inline int lock_may_write(struct inode *inode, loff_t start,
> +				 unsigned long len)
> +{
> +	return 1;
> +}
> +
>  #endif /* !CONFIG_FILE_LOCKING */
>  
>  
> 
> 


-- 
~Randy
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