xfs: fallback to vmalloc for large buffers in xfs_compat_attrlist_by_handle

Shamelessly copied from dchinner's:
ad650f5b xfs: fallback to vmalloc for large buffers in xfs_attrmulti_attr_get
    
xfsdump uses a large buffer for extended attributes, which has a
kmalloc'd shadow buffer in the kernel. This can fail after the
system has been running for some time as it is a high order
allocation. Add a fallback to vmalloc so that it doesn't require
contiguous memory and so won't randomly fail while xfsdump is
running.

This was done for xfs_attrlist_by_handle but
xfs_compat_attrlist_by_handle (the 32-bit version) needs the same
attention.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_ioctl32.c

@@ -373,9 +373,12 @@ xfs_compat_attrlist_by_handle(
 		return PTR_ERR(dentry);
 
 	error = -ENOMEM;
-	kbuf = kmalloc(al_hreq.buflen, GFP_KERNEL);
+	kbuf = kmem_zalloc(al_hreq.buflen, KM_SLEEP | KM_MAYFAIL);
+	if (!kbuf) {
+		kbuf = kmem_zalloc_large(al_hreq.buflen);
 		if (!kbuf)
 			goto out_dput;
+	}
 
 	cursor = (attrlist_cursor_kern_t *)&al_hreq.pos;
 	error = -xfs_attr_list(XFS_I(dentry->d_inode), kbuf, al_hreq.buflen,
@@ -387,7 +390,10 @@ xfs_compat_attrlist_by_handle(
 		error = -EFAULT;
 
  out_kfree:
-	kfree(kbuf);
+	if (is_vmalloc_addr(kbuf))
+		kmem_free_large(kbuf);
+	else
+		kmem_free(kbuf);
  out_dput:
 	dput(dentry);
 	return error;