kernel - Refactor VMSC_ONEPASS

* Refactor the VMSC_ONEPASS flag to only iterate the current number
  of vnodes associated with a mount point, instead of 2x the vnodes.
  This makes 'sync' a bit more consistent in the face of heavy filesystem
  activity.

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index a940273..7f1be20 100644 (file)
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -1005,7 +1005,7 @@ vmntvnodescan(
        struct vmntvnodescan_info info;
        struct vnode *vp;
        int r = 0;
-       int maxcount = 1000000;
+       int maxcount = mp->mnt_nvnodelistsize * 2;
        int stopcount = 0;
        int count = 0;
 
@@ -1018,13 +1018,15 @@ vmntvnodescan(
         * so this isn't perfect.  Create a slop factor of 2x.
         */
        if (flags & VMSC_ONEPASS)
-               stopcount = mp->mnt_nvnodelistsize * 2;
+               stopcount = mp->mnt_nvnodelistsize;
 
        info.vp = TAILQ_FIRST(&mp->mnt_nvnodelist);
        TAILQ_INSERT_TAIL(&mntvnodescan_list, &info, entry);
        while ((vp = info.vp) != NULL) {
-               if (--maxcount == 0)
-                       panic("maxcount reached during vmntvnodescan");
+               if (--maxcount == 0) {
+                       kprintf("Warning: excessive fssync iteration\n");
+                       maxcount = mp->mnt_nvnodelistsize * 2;
+               }
 
                /*
                 * Skip if visible but not ready, or special (e.g.