From: Simon Wilkinson <sxw@inf.ed.ac.uk>
Date: Fri, 23 Apr 2010 14:07:58 +0000 (+0100)
Subject: Linux: Don't roll our own llseek
X-Git-Tag: openafs-devel-1_5_75~377
X-Git-Url: https://git.michaelhowe.org/gitweb/?a=commitdiff_plain;h=20d08fb0ec7190bac622e9ac8a17f97b7feef1cb;p=packages%2Fo%2Fopenafs.git

Linux: Don't roll our own llseek

llseek is a little more complex than just setting the pos field of
the file structure.

Where vfs_llseek is available to us (it has been since 2.6.8) use that
directly. If vfs_llseek isn't available, then use either the
filesystem's llseek method, or default_llseek (available since 2.6.0),
to ensure we get the proper locking.

Change-Id: I26bcbff984c7164be1724eee7a46cbe6e02bc510
Reviewed-on: http://gerrit.openafs.org/1816
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
---

diff --git a/acinclude.m4 b/acinclude.m4
index 80cb33ad2..14f10e837 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -815,6 +815,7 @@ case $AFS_SYSNAME in *_linux* | *_umlinux*)
 		 LINUX_HAVE_SPLICE_DIRECT_TO_ACTOR
 		 LINUX_HAVE_PAGE_OFFSET
 		 LINUX_HAVE_ZERO_USER_SEGMENTS
+		 LINUX_HAVE_VFS_LLSEEK
                  LINUX_STRUCT_TASK_HAS_CRED
 		 LINUX_STRUCT_PROC_DIR_ENTRY_HAS_OWNER
 		 LINUX_HAVE_KMEM_CACHE_T
diff --git a/src/afs/LINUX/osi_compat.h b/src/afs/LINUX/osi_compat.h
index 0b52019cf..e507e6b45 100644
--- a/src/afs/LINUX/osi_compat.h
+++ b/src/afs/LINUX/osi_compat.h
@@ -230,3 +230,12 @@ zero_user_segments(struct page *pp, unsigned int from1, unsigned int to1,
 }
 #endif
 
+#ifndef HAVE_VFS_LLSEEK
+static inline loff_t
+vfs_llseek(struct file *filp, loff_t offset, int origin) {
+    if (filp->f_op->llseek)
+	return filp->f_op->llseek(filp, offset, origin);
+    return default_llseek(filp, offset, origin);
+}
+#endif
+
diff --git a/src/afs/LINUX/osi_file.c b/src/afs/LINUX/osi_file.c
index f5e21d563..8b2151ac1 100644
--- a/src/afs/LINUX/osi_file.c
+++ b/src/afs/LINUX/osi_file.c
@@ -387,13 +387,10 @@ osi_rdwr(struct osi_file *osifile, uio_t * uiop, int rw)
 	TO_USER_SPACE();
 
     /* seek to the desired position. Return -1 on error. */
-    if (filp->f_op->llseek) {
-	if (filp->f_op->llseek(filp, (loff_t) uiop->uio_offset, 0) != uiop->uio_offset) {
-	    code = -1;
-	    goto out;
-	}
-    } else
-	filp->f_pos = uiop->uio_offset;
+    if (vfs_llseek(filp, (loff_t) uiop->uio_offset, 0) != uiop->uio_offset) {
+	code = -1;
+	goto out;
+    }
 
     while (code == 0 && uiop->uio_resid > 0 && uiop->uio_iovcnt > 0) {
 	iov = uiop->uio_iov;
diff --git a/src/cf/linux-test4.m4 b/src/cf/linux-test4.m4
index 14cf9a6be..8d0a00fce 100644
--- a/src/cf/linux-test4.m4
+++ b/src/cf/linux-test4.m4
@@ -1257,3 +1257,16 @@ AC_DEFUN([LINUX_HAVE_PAGE_OFFSET], [
     AC_DEFINE([HAVE_PAGE_OFFSET], 1, [define if your kernel has the page_offset function])
   fi])
 
+AC_DEFUN([LINUX_HAVE_VFS_LLSEEK], [
+  AC_MSG_CHECKING([for vfs_llseek])
+  AC_CACHE_VAL([ac_cv_linux_have_vfs_llseek], [
+    AC_TRY_KBUILD(
+[#include <linux/fs.h>],
+[vfs_llseek(NULL, 0, 0);],
+      ac_cv_linux_have_vfs_llseek=yes,
+      ac_cv_linux_have_vfs_llseek=no)])
+  AC_MSG_RESULT($ac_cv_linux_have_vfs_llseek)
+  if test "x$ac_cv_linux_have_vfs_llseek" = "xyes"; then
+    AC_DEFINE([HAVE_VFS_LLSEEK], 1, [define if your kernel has the vfs_llseek function])
+  fi])
+