Author: mjg Date: Mon Sep 16 21:32:21 2019 New Revision: 352425 URL: https://svnweb.freebsd.org/changeset/base/352425
Log: vfs: manage mnt_lockref with atomics See r352424. Reviewed by: kib, jeff Tested by: pho Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21574 Modified: head/sys/kern/vfs_subr.c Modified: head/sys/kern/vfs_subr.c ============================================================================== --- head/sys/kern/vfs_subr.c Mon Sep 16 21:31:02 2019 (r352424) +++ head/sys/kern/vfs_subr.c Mon Sep 16 21:32:21 2019 (r352425) @@ -641,6 +641,18 @@ vfs_busy(struct mount *mp, int flags) MPASS((flags & ~MBF_MASK) == 0); CTR3(KTR_VFS, "%s: mp %p with flags %d", __func__, mp, flags); + if (vfs_op_thread_enter(mp)) { + MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0); + MPASS((mp->mnt_kern_flag & MNTK_UNMOUNT) == 0); + MPASS((mp->mnt_kern_flag & MNTK_REFEXPIRE) == 0); + MNT_REF_UNLOCKED(mp); + atomic_add_int(&mp->mnt_lockref, 1); + vfs_op_thread_exit(mp); + if (flags & MBF_MNTLSTLOCK) + mtx_unlock(&mountlist_mtx); + return (0); + } + MNT_ILOCK(mp); MNT_REF(mp); /* @@ -673,7 +685,7 @@ vfs_busy(struct mount *mp, int flags) } if (flags & MBF_MNTLSTLOCK) mtx_unlock(&mountlist_mtx); - mp->mnt_lockref++; + atomic_add_int(&mp->mnt_lockref, 1); MNT_IUNLOCK(mp); return (0); } @@ -684,13 +696,24 @@ vfs_busy(struct mount *mp, int flags) void vfs_unbusy(struct mount *mp) { + int c; CTR2(KTR_VFS, "%s: mp %p", __func__, mp); + + if (vfs_op_thread_enter(mp)) { + MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0); + c = atomic_fetchadd_int(&mp->mnt_lockref, -1) - 1; + KASSERT(c >= 0, ("%s: negative mnt_lockref %d\n", __func__, c)); + MNT_REL_UNLOCKED(mp); + vfs_op_thread_exit(mp); + return; + } + MNT_ILOCK(mp); MNT_REL(mp); - KASSERT(mp->mnt_lockref > 0, ("negative mnt_lockref")); - mp->mnt_lockref--; - if (mp->mnt_lockref == 0 && (mp->mnt_kern_flag & MNTK_DRAINING) != 0) { + c = atomic_fetchadd_int(&mp->mnt_lockref, -1) - 1; + KASSERT(c >= 0, ("%s: negative mnt_lockref %d\n", __func__, c)); + if (c == 0 && (mp->mnt_kern_flag & MNTK_DRAINING) != 0) { MPASS(mp->mnt_kern_flag & MNTK_UNMOUNT); CTR1(KTR_VFS, "%s: waking up waiters", __func__); mp->mnt_kern_flag &= ~MNTK_DRAINING; _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
