Author: mjg
Date: Wed Nov 20 12:07:54 2019
New Revision: 354892
URL: https://svnweb.freebsd.org/changeset/base/354892
Log:
vfs: perform a more racy check in vfs_notify_upper
Locking mp does not buy anything interms of correctness and only contributes
to
contention.
Modified:
head/sys/kern/vfs_subr.c
Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c Wed Nov 20 12:06:29 2019 (r354891)
+++ head/sys/kern/vfs_subr.c Wed Nov 20 12:07:54 2019 (r354892)
@@ -3526,11 +3526,9 @@ vfs_notify_upper(struct vnode *vp, int event)
mp = vp->v_mount;
if (mp == NULL)
return;
-
- MNT_ILOCK(mp);
if (TAILQ_EMPTY(&mp->mnt_uppers))
- goto unlock;
- MNT_IUNLOCK(mp);
+ return;
+
mmp = malloc(sizeof(struct mount), M_TEMP, M_WAITOK | M_ZERO);
mmp->mnt_op = &vgonel_vfsops;
mmp->mnt_kern_flag |= MNTK_MARKER;
@@ -3564,7 +3562,6 @@ vfs_notify_upper(struct vnode *vp, int event)
mp->mnt_kern_flag &= ~MNTK_VGONE_WAITER;
wakeup(&mp->mnt_uppers);
}
-unlock:
MNT_IUNLOCK(mp);
}
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