/* $NetBSD: layer_subr.c,v 1.15 2003/08/07 16:32:36 agc Exp $ */ /* * Copyright (c) 1999 National Aeronautics & Space Administration * All rights reserved. * * This software was written by William Studenmund of the * Numerical Aerospace Simulation Facility, NASA Ames Research Center. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the National Aeronautics & Space Administration * nor the names of its contributors may be used to endorse or promote * products derived from this software without specific prior written * permission. * * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB- * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /* * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software donated to Berkeley by * Jan-Simon Pendry. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 */ #include __KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.15 2003/08/07 16:32:36 agc Exp $"); #include #include #include #include #include #include #include #include #include #include #include #define NLAYERNODECACHE 16 /* * layer cache: * Each cache entry holds a reference to the lower vnode * along with a pointer to the alias vnode. When an * entry is added the lower vnode is VREF'd. When the * alias is removed the lower vnode is vrele'd. */ /* * Initialise cache headers */ void layerfs_init() { #ifdef LAYERFS_DIAGNOSTIC printf("layerfs_init\n"); /* printed during system boot */ #endif } /* * Free global resources of layerfs. */ void layerfs_done() { #ifdef LAYERFS_DIAGNOSTIC printf("layerfs_done\n"); /* printed on layerfs detach */ #endif } /* * Return a locked, VREF'ed alias for lower vnode if already exists, else 0. */ struct vnode * layer_node_find(mp, lowervp) struct mount *mp; struct vnode *lowervp; { struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); struct layer_node_hashhead *hd; struct layer_node *a; struct vnode *vp; /* * Find hash base, and then search the (two-way) linked * list looking for a layer_node structure which is referencing * the lower vnode. If found, the increment the layer_node * reference count (but NOT the lower vnode's VREF counter) * and return the vnode locked. */ hd = LAYER_NHASH(lmp, lowervp); loop: simple_lock(&lmp->layerm_hashlock); for (a = hd->lh_first; a != 0; a = a->layer_hash.le_next) { if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) { vp = LAYERTOV(a); simple_unlock(&lmp->layerm_hashlock); /* * We must be careful here as the fact the lower * vnode is locked will imply vp is locked unless * someone has decided to start vclean'ing either * vp or lowervp. * * So we try for an exclusive, recursive lock * on the upper vnode. If it fails, vcleaning * is in progress (so when we try again, we'll * fail). If it succeeds, we now have double * locked the bottom node. So we do an explicit * VOP_UNLOCK on it to keep the counts right. Note * that we will end up with the upper node and * the lower node locked once. */ if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE)) { printf ("layer_node_find: vget failed.\n"); goto loop; }; VOP_UNLOCK(lowervp, 0); return (vp); } } simple_unlock(&lmp->layerm_hashlock); return NULL; } /* * Make a new layer_node node. * Vp is the alias vnode, lowervp is the lower vnode. * Maintain a reference to lowervp. */ int layer_node_alloc(mp, lowervp, vpp) struct mount *mp; struct vnode *lowervp; struct vnode **vpp; { struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); struct layer_node_hashhead *hd; struct layer_node *xp; struct vnode *vp, *nvp; int error; extern int (**dead_vnodeop_p) __P((void *)); if ((error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp)) != 0) return (error); vp->v_type = lowervp->v_type; vp->v_flag |= VLAYER; xp = malloc(lmp->layerm_size, M_TEMP, M_WAITOK); if (vp->v_type == VBLK || vp->v_type == VCHR) { MALLOC(vp->v_specinfo, struct specinfo *, sizeof(struct specinfo), M_VNODE, M_WAITOK); vp->v_hashchain = NULL; vp->v_rdev = lowervp->v_rdev; } vp->v_data = xp; xp->layer_vnode = vp; xp->layer_lowervp = lowervp; xp->layer_flags = 0; /* * Before we insert our new node onto the hash chains, * check to see if someone else has beaten us to it. * (We could have slept in MALLOC.) */ if ((nvp = layer_node_find(mp, lowervp)) != NULL) { *vpp = nvp; /* free the substructures we've allocated. */ FREE(xp, M_TEMP); if (vp->v_type == VBLK || vp->v_type == VCHR) FREE(vp->v_specinfo, M_VNODE); vp->v_type = VBAD; /* node is discarded */ vp->v_op = dead_vnodeop_p; /* so ops will still work */ vrele(vp); /* get rid of it. */ return (0); } simple_lock(&lmp->layerm_hashlock); /* * Now lock the new node. We rely on the fact that we were passed * a locked vnode. If the lower node is exporting a struct lock * (v_vnlock != NULL) then we just set the upper v_vnlock to the * lower one, and both are now locked. If the lower node is exporting * NULL, then we copy that up and manually lock the upper node. * * LAYERFS_UPPERLOCK already has the test, so we use it after copying * up the v_vnlock from below. */ vp->v_vnlock = lowervp->v_vnlock; LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); if (error) { /* * How did we get a locking error? The node just came off * of the free list, and we're the only routine which * knows it's there... */ vp->v_vnlock = &vp->v_lock; *vpp = NULL; /* free the substructures we've allocated. */ FREE(xp, M_TEMP); if (vp->v_type == VBLK || vp->v_type == VCHR) FREE(vp->v_specinfo, M_VNODE); vp->v_type = VBAD; /* node is discarded */ vp->v_op = dead_vnodeop_p; /* so ops will still work */ vrele(vp); /* get rid of it. */ return (error); } /* * NetBSD used to do an inlined checkalias here. We do not, as * we never flag device nodes as being aliased. The lowervp * node will, when appropriate, be flaged as an alias. */ *vpp = vp; VREF(lowervp); /* Take into account reference held in layer_node */ hd = LAYER_NHASH(lmp, lowervp); LIST_INSERT_HEAD(hd, xp, layer_hash); uvm_vnp_setsize(vp, 0); simple_unlock(&lmp->layerm_hashlock); return (0); } /* * Try to find an existing layer_node vnode refering * to it, otherwise make a new layer_node vnode which * contains a reference to the lower vnode. * * >>> we assume that the lower node is already locked upon entry, so we * propagate the lock state to upper node << */ int layer_node_create(mp, lowervp, newvpp) struct mount *mp; struct vnode *lowervp; struct vnode **newvpp; { struct vnode *aliasvp; struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); if ((aliasvp = layer_node_find(mp, lowervp)) != NULL) { /* * layer_node_find has taken another reference * to the alias vnode and moved the lock holding to * aliasvp */ #ifdef LAYERFS_DIAGNOSTIC vprint("layer_node_create: exists", aliasvp); #endif } else { int error; /* * Get new vnode. */ #ifdef LAYERFS_DIAGNOSTIC printf("layer_node_create: create new alias vnode\n"); #endif /* * Make new vnode reference the layer_node. */ if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) return error; /* * aliasvp is already VREF'd by getnewvnode() */ } /* * Now that we have VREF'd the upper vnode, release the reference * to the lower node. The existance of the layer_node retains one * reference to the lower node. */ vrele(lowervp); #ifdef DIAGNOSTIC if (lowervp->v_usecount < 1) { /* Should never happen... */ vprint("layer_node_create: alias", aliasvp); vprint("layer_node_create: lower", lowervp); panic("layer_node_create: lower has 0 usecount."); }; #endif #ifdef LAYERFS_DIAGNOSTIC vprint("layer_node_create: alias", aliasvp); #endif *newvpp = aliasvp; return (0); } struct vnode * layer_checkvp(vp, fil, lno) struct vnode *vp; char *fil; int lno; { struct layer_node *a = VTOLAYER(vp); #ifdef notyet /* * Can't do this check because vop_reclaim runs * with a funny vop vector. * * WRS - no it doesnt... */ if (vp->v_op != layer_vnodeop_p) { printf ("layer_checkvp: on non-layer-node\n"); #ifdef notyet while (layer_checkvp_barrier) /*WAIT*/ ; #endif panic("layer_checkvp"); }; #endif if (a->layer_lowervp == NULL) { /* Should never happen */ int i; u_long *p; printf("vp = %p, ZERO ptr\n", vp); for (p = (u_long *) a, i = 0; i < 8; i++) printf(" %lx", p[i]); printf("\n"); /* wait for debugger */ panic("layer_checkvp"); } if (a->layer_lowervp->v_usecount < 1) { int i; u_long *p; printf("vp = %p, unref'ed lowervp\n", vp); for (p = (u_long *) a, i = 0; i < 8; i++) printf(" %lx", p[i]); printf("\n"); /* wait for debugger */ panic ("layer with unref'ed lowervp"); }; #ifdef notnow printf("layer %p/%d -> %p/%d [%s, %d]\n", LAYERTOV(a), LAYERTOV(a)->v_usecount, a->layer_lowervp, a->layer_lowervp->v_usecount, fil, lno); #endif return a->layer_lowervp; }