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
"dax_sem"? I thought this was now called i_aops_sem?
> *
> * 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)
And similarly, I think this should be XFS_OPSLOCK_EXCL...
--D
> + inode_aops_down_write(VFS_I(ip));
> +
> if (lock_flags & XFS_IOLOCK_EXCL) {
> down_write_nested(&VFS_I(ip)->i_rwsem,
> XFS_IOLOCK_DEP(lock_flags));
> @@ -224,6 +227,8 @@ xfs_ilock_nowait(
> * You can't set both SHARED and EXCL for the same lock,
> * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
> * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
> + *
> + * XFS_DAX_* is not allowed
> */
> ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
> (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
> @@ -232,6 +237,7 @@ xfs_ilock_nowait(
> ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
> (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
> ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
> + ASSERT((lock_flags & XFS_DAX_EXCL) == 0);
>
> if (lock_flags & XFS_IOLOCK_EXCL) {
> if (!down_write_trylock(&VFS_I(ip)->i_rwsem))
> @@ -318,6 +324,9 @@ xfs_iunlock(
> else if (lock_flags & XFS_ILOCK_SHARED)
> mrunlock_shared(&ip->i_lock);
>
> + if (lock_flags & XFS_DAX_EXCL)
> + inode_aops_up_write(VFS_I(ip));
> +
> trace_xfs_iunlock(ip, lock_flags, _RET_IP_);
> }
>
> @@ -333,6 +342,8 @@ xfs_ilock_demote(
> ASSERT(lock_flags & (XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL));
> ASSERT((lock_flags &
> ~(XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);
> + /* XFS_DAX_* is not allowed */
> + ASSERT((lock_flags & XFS_DAX_EXCL) == 0);
>
> if (lock_flags & XFS_ILOCK_EXCL)
> mrdemote(&ip->i_lock);
> @@ -465,6 +476,9 @@ xfs_lock_inodes(
> ASSERT(!(lock_mode & XFS_ILOCK_EXCL) ||
> inodes <= XFS_ILOCK_MAX_SUBCLASS + 1);
>
> + /* XFS_DAX_* is not allowed */
> + ASSERT((lock_mode & XFS_DAX_EXCL) == 0);
> +
> if (lock_mode & XFS_IOLOCK_EXCL) {
> ASSERT(!(lock_mode & (XFS_MMAPLOCK_EXCL | XFS_ILOCK_EXCL)));
> } else if (lock_mode & XFS_MMAPLOCK_EXCL)
> @@ -566,6 +580,10 @@ xfs_lock_two_inodes(
> ASSERT(!(ip0_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) ||
> !(ip1_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
>
> + /* XFS_DAX_* is not allowed */
> + ASSERT((ip0_mode & XFS_DAX_EXCL) == 0);
> + ASSERT((ip1_mode & XFS_DAX_EXCL) == 0);
> +
> ASSERT(ip0->i_ino != ip1->i_ino);
>
> if (ip0->i_ino > ip1->i_ino) {
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index 492e53992fa9..25fe20740bf7 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -278,10 +278,12 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
> #define XFS_ILOCK_SHARED (1<<3)
> #define XFS_MMAPLOCK_EXCL (1<<4)
> #define XFS_MMAPLOCK_SHARED (1<<5)
> +#define XFS_DAX_EXCL (1<<6)
>
> #define XFS_LOCK_MASK (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED \
> | XFS_ILOCK_EXCL | XFS_ILOCK_SHARED \
> - | XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED)
> + | XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED \
> + | XFS_DAX_EXCL)
>
> #define XFS_LOCK_FLAGS \
> { XFS_IOLOCK_EXCL, "IOLOCK_EXCL" }, \
> @@ -289,7 +291,8 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
> { XFS_ILOCK_EXCL, "ILOCK_EXCL" }, \
> { XFS_ILOCK_SHARED, "ILOCK_SHARED" }, \
> { XFS_MMAPLOCK_EXCL, "MMAPLOCK_EXCL" }, \
> - { XFS_MMAPLOCK_SHARED, "MMAPLOCK_SHARED" }
> + { XFS_MMAPLOCK_SHARED, "MMAPLOCK_SHARED" }, \
> + { XFS_DAX_EXCL, "DAX_EXCL" }
>
>
> /*
> --
> 2.21.0
>
