Messages in this thread Patch in this message | | | Date | Fri, 9 Oct 2015 09:24:50 +1100 | From | Dave Chinner <> | Subject | Re: [PATCH] xfs: clarify lock ordering comment |
| |
On Thu, Oct 08, 2015 at 03:58:01PM -0600, Ross Zwisler wrote: > Replace "i_mmap_lock" with "mmap_lock" in the lock ordering comment above > xfs_filemap_page_mkwrite(). The lock in question is actually the > XFS_MMAPLOCK_SHARED rw_semaphore (no leading "i"), and this comment is
struct xfs_inode { .... mrlock_t i_mmaplock; /* inode mmap IO lock */ ....
> easily confused with the "i_mmap_lock_[read|write]" functions that operate > on struct address_space->i_mmap_rwsem. This clarification is especially > important because address_space->i_mmap_rwsem is taken down in the DAX > code as part of this fault path. > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> > --- > fs/xfs/xfs_file.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index f429662..b190033 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -1477,7 +1477,7 @@ xfs_file_llseek( > * > * mmap_sem (MM) > * sb_start_pagefault(vfs, freeze) > - * i_mmap_lock (XFS - truncate serialisation) > + * mmap_lock (XFS - truncate serialisation)
As per above, the XFS lock is "i_mmaplock"...
The lock names are annotated with the subsystem the lock belongs to to avoid this confusion. Along with the lock ordering (inside sb_start_pagefault) this should indicate that it's not the "i_mmap_lock (MM - vma serialisation)" lock... ;)
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
| |