LU-506 kernel: FC15 - vfsmount.mnt_count doesn't use atomic_t

vfsmount.mnt_count use pre-cpu variable instead of atomic_t.

Change-Id: I5eba5a67839719e03d0b44be6312b452bf4dcb98
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1845
Tested-by: Hudson
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>

diff --git a/lustre/autoconf/lustre-core.m4 b/lustre/autoconf/lustre-core.m4
index 043d1db..45b127e 100644 (file)
--- a/lustre/autoconf/lustre-core.m4
+++ b/lustre/autoconf/lustre-core.m4
@@ -2105,6 +2105,26 @@ AC_DEFINE(HAVE_BLKDEV_GET_BY_DEV, 1,
 ])
 
 #
+# 2.6.38 vfsmount.mnt_count doesn't use atomic_t
+#
+AC_DEFUN([LC_ATOMIC_MNT_COUNT],
+[AC_MSG_CHECKING([if vfsmount.mnt_count is atomic_t])
+LB_LINUX_TRY_COMPILE([
+        #include <asm/atomic.h>
+        #include <linux/fs.h>
+        #include <linux/mount.h>
+],[
+        ((struct vfsmount *)0)->mnt_count = ((atomic_t) { 0 });
+],[
+        AC_DEFINE(HAVE_ATOMIC_MNT_COUNT, 1,
+                [vfsmount.mnt_count is atomic_t])
+        AC_MSG_RESULT([yes])
+],[
+        AC_MSG_RESULT([no])
+])
+])
+
+#
 # 2.6.39 remove unplug_fn from request_queue.
 #
 AC_DEFUN([LC_REQUEST_QUEUE_UNPLUG_FN],
@@ -2301,6 +2321,7 @@ AC_DEFUN([LC_PROG_LINUX],
          LC_SBOPS_EVICT_INODE
 
          # 2.6.38
+         LC_ATOMIC_MNT_COUNT
          LC_BLKDEV_GET_BY_DEV
          LC_GENERIC_PERMISSION
 

diff --git a/lustre/include/linux/lustre_compat25.h b/lustre/include/linux/lustre_compat25.h
index 8324e20..f44b7b0 100644 (file)
--- a/lustre/include/linux/lustre_compat25.h
+++ b/lustre/include/linux/lustre_compat25.h
@@ -401,6 +401,26 @@ ll_kern_mount(const char *fstype, int flags, const char *name, void *data)
 #define ll_kern_mount(fstype, flags, name, data) do_kern_mount((fstype), (flags), (name), (data))
 #endif
 
+#ifndef HAVE_ATOMIC_MNT_COUNT
+static inline unsigned int mnt_get_count(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+        unsigned int count = 0;
+        int cpu;
+
+        for_each_possible_cpu(cpu) {
+                count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
+        }
+
+        return count;
+#else
+        return mnt->mnt_count;
+#endif
+}
+#else
+# define mnt_get_count(mnt)      cfs_atomic_read(&mnt->mnt_count)
+#endif
+
 #ifdef HAVE_STATFS_DENTRY_PARAM
 #define ll_do_statfs(sb, sfs) (sb)->s_op->statfs((sb)->s_root, (sfs))
 #else

diff --git a/lustre/obdclass/obd_mount.c b/lustre/obdclass/obd_mount.c
index 39fe240..5618337 100644 (file)
--- a/lustre/obdclass/obd_mount.c
+++ b/lustre/obdclass/obd_mount.c
@@ -123,7 +123,7 @@ static int server_register_mount(const char *name, struct super_block *sb,
         cfs_up(&lustre_mount_info_lock);
 
         CDEBUG(D_MOUNT, "reg_mnt %p from %s, vfscount=%d\n",
-               lmi->lmi_mnt, name, cfs_atomic_read(&lmi->lmi_mnt->mnt_count));
+               lmi->lmi_mnt, name, mnt_get_count(lmi->lmi_mnt));
 
         RETURN(0);
 }
@@ -143,7 +143,7 @@ static int server_deregister_mount(const char *name)
         }
 
         CDEBUG(D_MOUNT, "dereg_mnt %p from %s, vfscount=%d\n",
-               lmi->lmi_mnt, name, cfs_atomic_read(&lmi->lmi_mnt->mnt_count));
+               lmi->lmi_mnt, name, mnt_get_count(lmi->lmi_mnt));
 
         OBD_FREE(lmi->lmi_name, strlen(lmi->lmi_name) + 1);
         cfs_list_del(&lmi->lmi_list_chain);
@@ -175,7 +175,7 @@ struct lustre_mount_info *server_get_mount(const char *name)
 
         CDEBUG(D_MOUNT, "get_mnt %p from %s, refs=%d, vfscount=%d\n",
                lmi->lmi_mnt, name, cfs_atomic_read(&lsi->lsi_mounts),
-               cfs_atomic_read(&lmi->lmi_mnt->mnt_count));
+               mnt_get_count(lmi->lmi_mnt));
 
         RETURN(lmi);
 }
@@ -217,7 +217,7 @@ int server_put_mount(const char *name, struct vfsmount *mnt)
 {
         struct lustre_mount_info *lmi;
         struct lustre_sb_info *lsi;
-        int count = atomic_read(&mnt->mnt_count) - 1;
+        int count = mnt_get_count(mnt) - 1;
         ENTRY;
 
         /* This might be the last one, can't deref after this */
@@ -1520,25 +1520,25 @@ static void server_wait_finished(struct vfsmount *mnt)
 
        cfs_waitq_init(&waitq);
 
-       while (atomic_read(&mnt->mnt_count) > 1) {
+       while (mnt_get_count(mnt) > 1) {
                if (waited && (waited % 30 == 0))
                        LCONSOLE_WARN("Mount still busy with %d refs after "
                                       "%d secs.\n",
-                                      atomic_read(&mnt->mnt_count),
+                                      mnt_get_count(mnt),
                                       waited);
                /* Cannot use l_event_wait() for an interruptible sleep. */
                waited += 3;
                blocked = cfs_block_sigsinv(sigmask(SIGKILL));
                cfs_waitq_wait_event_interruptible_timeout(
                        waitq,
-                       (atomic_read(&mnt->mnt_count) == 1),
+                       (mnt_get_count(mnt) == 1),
                        cfs_time_seconds(3),
                        rc);
                cfs_block_sigs(blocked);
                if (rc < 0) {
                        LCONSOLE_EMERG("Danger: interrupted umount %s with "
                                       "%d refs!\n", mnt->mnt_devname,
-                                      atomic_read(&mnt->mnt_count));
+                                      mnt_get_count(mnt));
                        break;
                }