Date: Tue, 15 Mar 2022 21:15:34 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: aa49e413a866 - stable/13 - vfs: [1/2] fix stalls in vnode reclaim by not requeieing from vnlru Message-ID: <202203152115.22FLFY9d018615@gitrepo.freebsd.org>
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The branch stable/13 has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=aa49e413a8661c4a855fa798094c8ae19b9fe6c9 commit aa49e413a8661c4a855fa798094c8ae19b9fe6c9 Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2022-03-07 10:33:59 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2022-03-15 21:12:43 +0000 vfs: [1/2] fix stalls in vnode reclaim by not requeieing from vnlru Reported by: pho (cherry picked from commit c35ec1efdcb2978bc3b6a0098c2b412be8d33e39) --- sys/kern/vfs_subr.c | 55 +++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 45 insertions(+), 10 deletions(-) diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c index a7a432d31a55..5c5faf455f2b 100644 --- a/sys/kern/vfs_subr.c +++ b/sys/kern/vfs_subr.c @@ -113,6 +113,8 @@ static void vn_seqc_init(struct vnode *); static void vn_seqc_write_end_free(struct vnode *vp); static void vgonel(struct vnode *); static bool vhold_recycle_free(struct vnode *); +static void vdropl_recycle(struct vnode *vp); +static void vdrop_recycle(struct vnode *vp); static void vfs_knllock(void *arg); static void vfs_knlunlock(void *arg); static void vfs_knl_assert_lock(void *arg, int what); @@ -1203,11 +1205,11 @@ restart: mtx_unlock(&vnode_list_mtx); if (vn_start_write(vp, &mp, V_NOWAIT) != 0) { - vdrop(vp); + vdrop_recycle(vp); goto next_iter_unlocked; } if (VOP_LOCK(vp, LK_EXCLUSIVE|LK_NOWAIT) != 0) { - vdrop(vp); + vdrop_recycle(vp); vn_finished_write(mp); goto next_iter_unlocked; } @@ -1218,14 +1220,14 @@ restart: (vp->v_object != NULL && vp->v_object->handle == vp && vp->v_object->resident_page_count > trigger)) { VOP_UNLOCK(vp); - vdropl(vp); + vdropl_recycle(vp); vn_finished_write(mp); goto next_iter_unlocked; } counter_u64_add(recycles_count, 1); vgonel(vp); VOP_UNLOCK(vp); - vdropl(vp); + vdropl_recycle(vp); vn_finished_write(mp); done++; next_iter_unlocked: @@ -1636,7 +1638,7 @@ vtryrecycle(struct vnode *vp) CTR2(KTR_VFS, "%s: impossible to recycle, vp %p lock is already held", __func__, vp); - vdrop(vp); + vdrop_recycle(vp); return (EWOULDBLOCK); } /* @@ -1647,7 +1649,7 @@ vtryrecycle(struct vnode *vp) CTR2(KTR_VFS, "%s: impossible to recycle, cannot start the write for %p", __func__, vp); - vdrop(vp); + vdrop_recycle(vp); return (EBUSY); } /* @@ -1659,7 +1661,7 @@ vtryrecycle(struct vnode *vp) VI_LOCK(vp); if (vp->v_usecount) { VOP_UNLOCK(vp); - vdropl(vp); + vdropl_recycle(vp); vn_finished_write(vnmp); CTR2(KTR_VFS, "%s: impossible to recycle, %p is already referenced", @@ -1671,7 +1673,7 @@ vtryrecycle(struct vnode *vp) vgonel(vp); } VOP_UNLOCK(vp); - vdropl(vp); + vdropl_recycle(vp); vn_finished_write(vnmp); return (0); } @@ -3624,8 +3626,8 @@ vdrop(struct vnode *vp) vdropl(vp); } -void -vdropl(struct vnode *vp) +static void __always_inline +vdropl_impl(struct vnode *vp, bool enqueue) { ASSERT_VI_LOCKED(vp, __func__); @@ -3653,6 +3655,39 @@ vdropl(struct vnode *vp) vdbatch_enqueue(vp); } +void +vdropl(struct vnode *vp) +{ + + vdropl_impl(vp, true); +} + +/* + * vdrop a vnode when recycling + * + * This is a special case routine only to be used when recycling, differs from + * regular vdrop by not requeieing the vnode on LRU. + * + * Consider a case where vtryrecycle continuously fails with all vnodes (due to + * e.g., frozen writes on the filesystem), filling the batch and causing it to + * be requeued. Then vnlru will end up revisiting the same vnodes. This is a + * loop which can last for as long as writes are frozen. + */ +static void +vdropl_recycle(struct vnode *vp) +{ + + vdropl_impl(vp, false); +} + +static void +vdrop_recycle(struct vnode *vp) +{ + + VI_LOCK(vp); + vdropl_recycle(vp); +} + /* * Call VOP_INACTIVE on the vnode and manage the DOINGINACT and OWEINACT * flags. DOINGINACT prevents us from recursing in calls to vinactive.
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