[PATCH v2 11/11] xfs: add support for DAX fsync/msync

[Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>]

To properly support the new DAX fsync/msync infrastructure filesystems
need to call dax_pfn_mkwrite() so that DAX can properly track when a user
write faults on a previously cleaned address.  They also need to call
dax_fsync() in the filesystem fsync() path.  This dax_fsync() call uses
addresses retrieved from get_block() so it needs to be ordered with
respect to truncate.  This is accomplished by using the same locking that
was set up for DAX page faults.

Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
---
 fs/xfs/xfs_file.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 39743ef..2b490a1 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -209,7 +209,8 @@ xfs_file_fsync(
        loff_t                  end,
        int                     datasync)
 {
-       struct inode            *inode = file->f_mapping->host;
+       struct address_space    *mapping = file->f_mapping;
+       struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        int                     error = 0;
@@ -218,7 +219,13 @@ xfs_file_fsync(
 
        trace_xfs_file_fsync(ip);
 
-       error = filemap_write_and_wait_range(inode->i_mapping, start, end);
+       if (dax_mapping(mapping)) {
+               xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
+               dax_fsync(mapping, start, end);
+               xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
+       }
+
+       error = filemap_write_and_wait_range(mapping, start, end);
        if (error)
                return error;
 
@@ -1603,9 +1610,8 @@ xfs_filemap_pmd_fault(
 /*
  * pfn_mkwrite was originally inteneded to ensure we capture time stamp
  * updates on write faults. In reality, it's need to serialise against
- * truncate similar to page_mkwrite. Hence we open-code dax_pfn_mkwrite()
- * here and cycle the XFS_MMAPLOCK_SHARED to ensure we serialise the fault
- * barrier in place.
+ * truncate similar to page_mkwrite. Hence we cycle the XFS_MMAPLOCK_SHARED
+ * to ensure we serialise the fault barrier in place.
  */
 static int
 xfs_filemap_pfn_mkwrite(
@@ -1628,6 +1634,8 @@ xfs_filemap_pfn_mkwrite(
        size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
        if (vmf->pgoff >= size)
                ret = VM_FAULT_SIGBUS;
+       else if (IS_DAX(inode))
+               ret = dax_pfn_mkwrite(vma, vmf);
        xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
        sb_end_pagefault(inode->i_sb);
        return ret;
-- 
2.1.0