xfs: add ->pfn_mkwrite support for DAX

->pfn_mkwrite support is needed so that when a page with allocated
backing store takes a write fault we can check that the fault has
not raced with a truncate and is pointing to a region beyond the
current end of file.

This also allows us to update the timestamp on the inode, too, which
fixes a generic/080 failure.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 9c8eef7c57b45fc7757894bdc6c8a16ce4474fbe..f429662d7d42b359165a35c63974f6f878cd86d1 100644 (file)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1572,11 +1572,46 @@ xfs_filemap_pmd_fault(
        return ret;
 }
 
+/*
+ * 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.
+ */
+static int
+xfs_filemap_pfn_mkwrite(
+       struct vm_area_struct   *vma,
+       struct vm_fault         *vmf)
+{
+
+       struct inode            *inode = file_inode(vma->vm_file);
+       struct xfs_inode        *ip = XFS_I(inode);
+       int                     ret = VM_FAULT_NOPAGE;
+       loff_t                  size;
+
+       trace_xfs_filemap_pfn_mkwrite(ip);
+
+       sb_start_pagefault(inode->i_sb);
+       file_update_time(vma->vm_file);
+
+       /* check if the faulting page hasn't raced with truncate */
+       xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
+       size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+       if (vmf->pgoff >= size)
+               ret = VM_FAULT_SIGBUS;
+       xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
+       sb_end_pagefault(inode->i_sb);
+       return ret;
+
+}
+
 static const struct vm_operations_struct xfs_file_vm_ops = {
        .fault          = xfs_filemap_fault,
        .pmd_fault      = xfs_filemap_pmd_fault,
        .map_pages      = filemap_map_pages,
        .page_mkwrite   = xfs_filemap_page_mkwrite,
+       .pfn_mkwrite    = xfs_filemap_pfn_mkwrite,
 };
 
 STATIC int

diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 5ed36b1e04c1af6103122450e33aa8e1f2546c1b..c53beda675d6297490f62fc814e9fdb4ae209a29 100644 (file)
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -689,6 +689,7 @@ DEFINE_INODE_EVENT(xfs_inode_free_eofblocks_invalid);
 DEFINE_INODE_EVENT(xfs_filemap_fault);
 DEFINE_INODE_EVENT(xfs_filemap_pmd_fault);
 DEFINE_INODE_EVENT(xfs_filemap_page_mkwrite);
+DEFINE_INODE_EVENT(xfs_filemap_pfn_mkwrite);
 
 DECLARE_EVENT_CLASS(xfs_iref_class,
        TP_PROTO(struct xfs_inode *ip, unsigned long caller_ip),