Date: Wed, 20 Nov 2019 12:07:54 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r354892 - head/sys/kern Message-ID: <201911201207.xAKC7s4J022079@repo.freebsd.org>
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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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