On 22.12.2019 20:47, Andrew Doran wrote: > Module Name: src > Committed By: ad > Date: Sun Dec 22 19:47:35 UTC 2019 > > Modified Files: > src/external/cddl/osnet/dist/uts/common/fs/zfs: zfs_ctldir.c > src/sys/kern: vfs_mount.c vfs_subr.c vfs_syscalls.c > src/sys/miscfs/genfs: genfs_vfsops.c > src/sys/nfs: nfs_export.c > src/sys/sys: mount.h vnode.h vnode_impl.h > src/sys/ufs/lfs: ulfs_vfsops.c > src/sys/ufs/ufs: ufs_vfsops.c ufs_wapbl.c > > Log Message: > Make mntvnode_lock per-mount, and address false sharing of struct mount. >
This change broke kUBSan syzbot. The sanitizer is now very noisy as struct mount requires 64 byte alignment. http://netbsd.org/~kamil/kubsan/mount-alignment.txt > diff -u src/sys/sys/mount.h:1.234 src/sys/sys/mount.h:1.235 > --- src/sys/sys/mount.h:1.234 Tue Jan 1 10:06:54 2019 > +++ src/sys/sys/mount.h Sun Dec 22 19:47:34 2019 > @@ -1,4 +1,4 @@ > -/* $NetBSD: mount.h,v 1.234 2019/01/01 10:06:54 hannken Exp $ */ > +/* $NetBSD: mount.h,v 1.235 2019/12/22 19:47:34 ad Exp $ */ > > /* > * Copyright (c) 1989, 1991, 1993 > @@ -133,29 +133,38 @@ struct vattr; > * array of operations and an instance record. > */ > struct mount { > - TAILQ_HEAD(, vnode_impl) mnt_vnodelist; /* list of vnodes this mount */ > + /* > + * Mostly stable data. > + */ > + kmutex_t *mnt_vnodelock; /* lock on mnt_vnodelist */ > struct vfsops *mnt_op; /* operations on fs */ > struct vnode *mnt_vnodecovered; /* vnode we mounted on */ > struct mount *mnt_lower; /* fs mounted on */ > - int mnt_synclist_slot; /* synclist slot index */ > void *mnt_transinfo; /* for FS-internal use */ > void *mnt_data; /* private data */ > - kmutex_t mnt_renamelock; /* per-fs rename lock */ > - int mnt_refcnt; /* ref count on this structure > */ > + kmutex_t *mnt_renamelock; /* per-fs rename lock */ > int mnt_flag; /* flags */ > int mnt_iflag; /* internal flags */ > int mnt_fs_bshift; /* offset shift for lblkno */ > int mnt_dev_bshift; /* shift for device sectors */ > - struct statvfs mnt_stat; /* cache of filesystem stats */ > specificdata_reference > mnt_specdataref; /* subsystem specific data */ > - kmutex_t mnt_updating; /* to serialize updates */ > + kmutex_t *mnt_updating; /* to serialize updates */ > const struct wapbl_ops > *mnt_wapbl_op; /* logging ops */ > struct wapbl *mnt_wapbl; /* log info */ > struct wapbl_replay > *mnt_wapbl_replay; /* replay support XXX: what? */ > uint64_t mnt_gen; > + > + /* > + * Volatile data: pad to keep away from the stable items. > + */ > + int mnt_refcnt /* ref count on this structure > */ > + __aligned(COHERENCY_UNIT); > + int mnt_synclist_slot; /* synclist slot index */ > + TAILQ_HEAD(, vnode_impl) mnt_vnodelist; /* list of vnodes this mount */ > + struct statvfs mnt_stat; /* cache of filesystem stats */ > }; > > #endif /* defined(_KERNEL) || defined(__EXPOSE_MOUNT) */ >
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