Date: Wed, 1 Nov 2023 08:40:39 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 0c5cd045bfb8 - main - vfs: remove majority of stale commentary about free list Message-ID: <202311010840.3A18ed2m023650@gitrepo.freebsd.org>
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The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=0c5cd045bfb847428a8a5e0e91e6fc3cf27a17c2 commit 0c5cd045bfb847428a8a5e0e91e6fc3cf27a17c2 Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2023-11-01 08:28:28 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2023-11-01 08:39:05 +0000 vfs: remove majority of stale commentary about free list There is no "free list" for a long time now. While here slightly tidy up affected comments in other ways. Note that the "free vnode" term is a misnomer at best and will also need to get sorted out. --- sys/kern/vfs_subr.c | 47 +++++++++++++++++------------------------------ 1 file changed, 17 insertions(+), 30 deletions(-) diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c index 881e9452a6db..b12b257ce340 100644 --- a/sys/kern/vfs_subr.c +++ b/sys/kern/vfs_subr.c @@ -1224,7 +1224,7 @@ restart: * If it's been deconstructed already, it's still * referenced, or it exceeds the trigger, skip it. * Also skip free vnodes. We are trying to make space - * to expand the free list, not reduce it. + * for more free vnodes, not reduce their count. */ if (vp->v_usecount > 0 || vp->v_holdcnt == 0 || (!reclaim_nc_src && !LIST_EMPTY(&vp->v_cache_src))) @@ -1319,7 +1319,7 @@ SYSCTL_INT(_vfs_vnode_vnlru, OID_AUTO, max_free_per_call, CTLFLAG_RW, "limit on vnode free requests per call to the vnlru_free routine"); /* - * Attempt to reduce the free list by the requested amount. + * Attempt to recycle requested amount of free vnodes. */ static int vnlru_free_impl(int count, struct vfsops *mnt_op, struct vnode *mvp, bool isvnlru) @@ -1761,7 +1761,7 @@ vnlru_proc(void) /* * If numvnodes is too large (due to desiredvnodes being * adjusted using its sysctl, or emergency growth), first - * try to reduce it by discarding from the free list. + * try to reduce it by discarding free vnodes. */ if (rnumvnodes > desiredvnodes + 10) { vnlru_free_locked_vnlru(rnumvnodes - desiredvnodes); @@ -1772,7 +1772,7 @@ vnlru_proc(void) * Sleep if the vnode cache is in a good state. This is * when it is not over-full and has space for about a 4% * or 9% expansion (by growing its size or inexcessively - * reducing its free list). Otherwise, try to reclaim + * reducing free vnode count). Otherwise, try to reclaim * space for a 10% expansion. */ if (vstir && force == 0) { @@ -1858,10 +1858,7 @@ SYSINIT(vnlru, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, */ /* - * Try to recycle a freed vnode. We abort if anyone picks up a reference - * before we actually vgone(). This function must be called with the vnode - * held to prevent the vnode from being returned to the free list midway - * through vgone(). + * Try to recycle a freed vnode. */ static int vtryrecycle(struct vnode *vp, bool isvnlru) @@ -1976,14 +1973,10 @@ vn_alloc_hard(struct mount *mp, u_long rnumvnodes, bool bumped) } /* - * Grow the vnode cache if it will not be above its target max - * after growing. Otherwise, if the free list is nonempty, try - * to reclaim 1 item from it before growing the cache (possibly - * above its target max if the reclamation failed or is delayed). - * Otherwise, wait for some space. In all cases, schedule - * vnlru_proc() if we are getting short of space. The watermarks - * should be chosen so that we never wait or even reclaim from - * the free list to below its target minimum. + * Grow the vnode cache if it will not be above its target max after + * growing. Otherwise, if there is at least one free vnode, try to + * reclaim 1 item from it before growing the cache (possibly above its + * target max if the reclamation failed or is delayed). */ if (vnlru_free_locked_direct(1) > 0) goto alloc; @@ -2038,7 +2031,7 @@ vn_free(struct vnode *vp) } /* - * Return the next vnode from the free list. + * Allocate a new vnode. */ int getnewvnode(const char *tag, struct mount *mp, struct vop_vector *vops, @@ -3221,16 +3214,10 @@ v_init_counters(struct vnode *vp) } /* - * Grab a particular vnode from the free list, increment its - * reference count and lock it. VIRF_DOOMED is set if the vnode - * is being destroyed. Only callers who specify LK_RETRY will - * see doomed vnodes. If inactive processing was delayed in - * vput try to do it here. - * - * usecount is manipulated using atomics without holding any locks. + * Get a usecount on a vnode. * - * holdcnt can be manipulated using atomics without holding any locks, - * except when transitioning 1<->0, in which case the interlock is held. + * vget and vget_finish may fail to lock the vnode if they lose a race against + * it being doomed. LK_RETRY can be passed in flags to lock it anyway. * * Consumers which don't guarantee liveness of the vnode can use SMR to * try to get a reference. Note this operation can fail since the vnode @@ -3882,9 +3869,9 @@ vdbatch_dequeue(struct vnode *vp) } /* - * Drop the hold count of the vnode. If this is the last reference to - * the vnode we place it on the free list unless it has been vgone'd - * (marked VIRF_DOOMED) in which case we will free it. + * Drop the hold count of the vnode. + * + * It will only get freed if this is the last hold *and* it has been vgone'd. * * Because the vnode vm object keeps a hold reference on the vnode if * there is at least one resident non-cached page, the vnode cannot @@ -4200,7 +4187,7 @@ loop: } /* - * Recycle an unused vnode to the front of the free list. + * Recycle an unused vnode. */ int vrecycle(struct vnode *vp)
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