On Thu, Feb 20, 2020 at 04:41:30PM -0800, ira.weiny@xxxxxxxxx wrote: > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > XFS requires the use of the aops of an inode to quiesced prior to > changing it to/from the DAX aops vector. > > Take the aops write lock while changing DAX state. > > We define a new XFS_DAX_EXCL lock type to carry the lock through to > transaction completion. > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > --- > Changes from v3: > Change locking function names to reflect changes in previous > patches. > > Changes from V2: > Change name of patch (WAS: fs/xfs: Add lock/unlock state to xfs) > Remove the xfs specific lock and move to the vfs layer. > We still use XFS_LOCK_DAX_EXCL to be able to pass this > flag through to the transaction code. But we no longer > have a lock specific to xfs. This removes a lot of code > from the XFS layer, preps us for using this in ext4, and > is actually more straight forward now that all the > locking requirements are better known. > > Fix locking order comment > Rework for new 'state' names > (Other comments on the previous patch are not applicable with > new patch as much of the code was removed in favor of the vfs > level lock) > --- > fs/xfs/xfs_inode.c | 22 ++++++++++++++++++++-- > fs/xfs/xfs_inode.h | 7 +++++-- > 2 files changed, 25 insertions(+), 4 deletions(-) > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > index 35df324875db..5b014c428f0f 100644 > --- a/fs/xfs/xfs_inode.c > +++ b/fs/xfs/xfs_inode.c > @@ -142,12 +142,12 @@ xfs_ilock_attr_map_shared( > * > * Basic locking order: > * > - * i_rwsem -> i_mmap_lock -> page_lock -> i_ilock > + * s_dax_sem -> i_rwsem -> i_mmap_lock -> page_lock -> i_ilock > * > * mmap_sem locking order: > * > * i_rwsem -> page lock -> mmap_sem > - * mmap_sem -> i_mmap_lock -> page_lock > + * s_dax_sem -> mmap_sem -> i_mmap_lock -> page_lock > * > * The difference in mmap_sem locking order mean that we cannot hold the > * i_mmap_lock over syscall based read(2)/write(2) based IO. These IO paths can > @@ -182,6 +182,9 @@ xfs_ilock( > (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)); > ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0); > > + if (lock_flags & XFS_DAX_EXCL) > + inode_aops_down_write(VFS_I(ip)); I largely don't see the point of adding this to xfs_ilock/iunlock. It's only got one caller, so I don't see much point in adding it to an interface that has over a hundred other call sites that don't need or use this lock. just open code it where it is needed in the ioctl code. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
