Date: Sat, 16 Jan 2021 00:32:39 GMT From: Kirk McKusick <mckusick@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 79a5c790bdf0 - main - Eliminate a locking panic when cleaning up UFS snapshots after a disk failure. Message-ID: <202101160032.10G0WdCv005456@gitrepo.freebsd.org>
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The branch main has been updated by mckusick: URL: https://cgit.FreeBSD.org/src/commit/?id=79a5c790bdf08cb925693add4699f3e785c12bc6 commit 79a5c790bdf08cb925693add4699f3e785c12bc6 Author: Kirk McKusick <mckusick@FreeBSD.org> AuthorDate: 2021-01-16 00:33:00 +0000 Commit: Kirk McKusick <mckusick@FreeBSD.org> CommitDate: 2021-01-16 00:36:42 +0000 Eliminate a locking panic when cleaning up UFS snapshots after a disk failure. Each vnode has an embedded lock that controls access to its contents. However vnodes describing a UFS snapshot all share a single snapshot lock to coordinate their access and update. As part of mounting a UFS filesystem with snapshots, each of the vnodes describing a snapshot has its individual lock replaced with the snapshot lock. When the filesystem is unmounted the vnode's original lock is returned replacing the snapshot lock. When a disk fails while the UFS filesystem it contains is still mounted (for example when a thumb drive is removed) UFS forcibly unmounts the filesystem. The loss of the drive causes the GEOM subsystem to orphan the provider, but the consumer remains until the filesystem has finished with the unmount. Information describing the snapshot locks was being prematurely cleared during the orphaning causing the return of the snapshot vnode's original locks to fail. The fix is to not clear the needed information prematurely. Sponsored by: Netflix --- sys/kern/kern_conf.c | 1 - sys/ufs/ffs/ffs_vfsops.c | 1 + 2 files changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c index c38bbdb29f5f..5211422199bb 100644 --- a/sys/kern/kern_conf.c +++ b/sys/kern/kern_conf.c @@ -1172,7 +1172,6 @@ destroy_devl(struct cdev *dev) dev->si_drv1 = 0; dev->si_drv2 = 0; - bzero(&dev->__si_u, sizeof(dev->__si_u)); if (!(dev->si_flags & SI_ALIAS)) { /* Remove from cdevsw list */ diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c index 52b9b860f817..415bb4614c1a 100644 --- a/sys/ufs/ffs/ffs_vfsops.c +++ b/sys/ufs/ffs/ffs_vfsops.c @@ -1035,6 +1035,7 @@ ffs_mountfs(odevvp, mp, td) VOP_UNLOCK(odevvp); KASSERT(devvp->v_type == VCHR, ("reclaimed devvp")); dev = devvp->v_rdev; + KASSERT(dev->si_snapdata == NULL, ("non-NULL snapshot data")); if (atomic_cmpset_acq_ptr((uintptr_t *)&dev->si_mountpt, 0, (uintptr_t)mp) == 0) { mntfs_freevp(devvp);
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