On Wed, Oct 14, 2020 at 11:04:31PM +0200, Pavel Reichl wrote:
>
>
> On 10/12/20 6:03 PM, Brian Foster wrote:
> > On Fri, Oct 09, 2020 at 09:55:12PM +0200, Pavel Reichl wrote:
> >> Refactor xfs_isilocked() to use newly introduced __xfs_rwsem_islocked().
> >> __xfs_rwsem_islocked() is a helper function which encapsulates checking
> >> state of rw_semaphores hold by inode.
> >>
> >> Signed-off-by: Pavel Reichl <preichl@xxxxxxxxxx>
> >> Suggested-by: Dave Chinner <dchinner@xxxxxxxxxx>
> >> Suggested-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> >> Suggested-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >> ---
> >> fs/xfs/xfs_inode.c | 48 ++++++++++++++++++++++++++++++++++++++--------
> >> fs/xfs/xfs_inode.h | 21 +++++++++++++-------
> >> 2 files changed, 54 insertions(+), 15 deletions(-)
> >>
> >> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> >> index c06129cffba9..7c1ceb4df4ec 100644
> >> --- a/fs/xfs/xfs_inode.c
> >> +++ b/fs/xfs/xfs_inode.c
> >> @@ -345,9 +345,43 @@ xfs_ilock_demote(
> >> }
> >>
> >> #if defined(DEBUG) || defined(XFS_WARN)
> >> -int
> >> +static inline bool
> >> +__xfs_rwsem_islocked(
> >> + struct rw_semaphore *rwsem,
> >> + int lock_flags)
> >> +{
> >> + int arg;
> >> +
> >> + if (!debug_locks)
> >> + return rwsem_is_locked(rwsem);
> >> +
> >> + if (lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
> >> + /*
> >> + * The caller could be asking if we have (shared | excl)
> >> + * access to the lock. Ask lockdep if the rwsem is
> >> + * locked either for read or write access.
> >> + *
> >> + * The caller could also be asking if we have only
> >> + * shared access to the lock. Holding a rwsem
> >> + * write-locked implies read access as well, so the
> >> + * request to lockdep is the same for this case.
> >> + */
> >> + arg = -1;
> >> + } else {
> >> + /*
> >> + * The caller is asking if we have only exclusive access
> >> + * to the lock. Ask lockdep if the rwsem is locked for
> >> + * write access.
> >> + */
> >> + arg = 0;
> >> + }
> ...
> >
> > Also, I find the pattern of shifting in the caller slightly confusing,
> > particularly with the 'lock_flags' name being passed down through the
> > caller. Any reason we couldn't pass the shift value as a parameter and
> > do the shift at the top of the function so the logic is clear and in one
> > place?
> >
>
> Hi Brian, is following change what you had in mind? Thanks!
>
Yep, pretty much. I find shifted_lock_flags to be a little verbose as a
name. I'd be fine with just doing something like 'lock_flags >>= shift'
near the top of the function, but that's more of a personal nit. I also
like Christoph's suggestion to avoid the arg variable (along with the
comment update suggested in the discussion with Darrick).
Brian
>
> >> @@ -349,14 +349,16 @@ xfs_ilock_demote(
> static inline bool
> __xfs_rwsem_islocked(
> struct rw_semaphore *rwsem,
> - int lock_flags)
> + int lock_flags,
> + int shift)
> {
> int arg;
> + const int shifted_lock_flags = lock_flags >> shift;
>
> if (!debug_locks)
> return rwsem_is_locked(rwsem);
>
> - if (lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
> + if (shifted_lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
> /*
> * The caller could be asking if we have (shared | excl)
> * access to the lock. Ask lockdep if the rwsem is
> @@ -387,20 +389,20 @@ xfs_isilocked(
> {
> if (lock_flags & (XFS_ILOCK_EXCL | XFS_ILOCK_SHARED)) {
> ASSERT(!(lock_flags & ~(XFS_ILOCK_EXCL | XFS_ILOCK_SHARED)));
> - return __xfs_rwsem_islocked(&ip->i_lock,
> - (lock_flags >> XFS_ILOCK_FLAG_SHIFT));
> + return __xfs_rwsem_islocked(&ip->i_lock, lock_flags,
> + XFS_ILOCK_FLAG_SHIFT);
> }
>
> if (lock_flags & (XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED)) {
> ASSERT(!(lock_flags &
> ~(XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED)));
> - return __xfs_rwsem_islocked(&ip->i_mmaplock,
> - (lock_flags >> XFS_MMAPLOCK_FLAG_SHIFT));
> + return __xfs_rwsem_islocked(&ip->i_mmaplock, lock_flags,
> + XFS_MMAPLOCK_FLAG_SHIFT);
> }
>
> if (lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) {
> - return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem,
> - (lock_flags >> XFS_IOLOCK_FLAG_SHIFT));
> + return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem, lock_flags,
> + XFS_IOLOCK_FLAG_SHIFT);
> }
>
> ASSERT(0);
>
