/* $NetBSD: layer_subr.c,v 1.31 2010/07/21 17:52:12 hannken 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 1.31 2010/07/21 17:52:12 hannken Exp $"); #include #include #include #include #include #include #include #include #include #include #include #include #ifdef LAYERFS_DIAGNOSTIC int layerfs_debug = 1; #endif /* * 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. */ void layerfs_init(void) { /* Nothing. */ } void layerfs_done(void) { /* Nothing. */ } /* * layer_node_find: find and return alias for lower vnode or NULL. * * => Return alias vnode locked and referenced. if already exists. * => The layermp's hashlock must be held on entry, we will unlock on success. */ struct vnode * layer_node_find(struct mount *mp, struct vnode *lowervp) { struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); struct layer_node_hashhead *hd; struct layer_node *a; struct vnode *vp; int error; /* * Find hash bucket and search the (two-way) linked list looking * for a layerfs node structure which is referencing the lower vnode. * If found, the increment the layer_node reference count, but NOT * the lower vnode's reference counter. Return vnode locked. */ KASSERT(mutex_owned(&lmp->layerm_hashlock)); hd = LAYER_NHASH(lmp, lowervp); loop: LIST_FOREACH(a, hd, layer_hash) { if (a->layer_lowervp != lowervp) { continue; } vp = LAYERTOV(a); if (vp->v_mount != mp) { continue; } mutex_enter(&vp->v_interlock); /* * If we find a node being cleaned out, then ignore it and * continue. A thread trying to clean out the extant layer * vnode needs to acquire the shared lock (i.e. the lower * vnode's lock), which our caller already holds. To allow * the cleaning to succeed the current thread must make * progress. So, for a brief time more than one vnode in a * layered file system may refer to a single vnode in the * lower file system. */ if ((vp->v_iflag & VI_XLOCK) != 0) { mutex_exit(&vp->v_interlock); continue; } mutex_exit(&lmp->layerm_hashlock); /* * We must not let vget() try to lock the layer vp, since * the lower vp is already locked and locking the layer vp * will involve locking the lower vp. */ error = vget(vp, LK_NOWAIT); if (error) { kpause("layerfs", false, 1, NULL); mutex_enter(&lmp->layerm_hashlock); goto loop; } return vp; } return NULL; } /* * layer_node_alloc: make a new layerfs vnode. * * => vp is the alias vnode, lowervp is the lower vnode. * => We will hold a reference to lowervp. */ int layer_node_alloc(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)(void *); error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp); if (error) { return error; } vp->v_type = lowervp->v_type; mutex_enter(&vp->v_interlock); vp->v_iflag |= VI_LAYER; mutex_exit(&vp->v_interlock); xp = kmem_alloc(lmp->layerm_size, KM_SLEEP); if (xp == NULL) { ungetnewvnode(vp); return ENOMEM; } if (vp->v_type == VBLK || vp->v_type == VCHR) { spec_node_init(vp, lowervp->v_rdev); } vp->v_data = xp; vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) | (lowervp->v_vflag & VV_MPSAFE); xp->layer_vnode = vp; xp->layer_lowervp = lowervp; xp->layer_flags = 0; /* * Before inserting the node into the hash, check if other thread * did not race with us. If so - return that node, destroy ours. */ mutex_enter(&lmp->layerm_hashlock); if ((nvp = layer_node_find(mp, lowervp)) != NULL) { /* Free the structures we have created. */ if (vp->v_type == VBLK || vp->v_type == VCHR) spec_node_destroy(vp); vp->v_type = VBAD; /* node is discarded */ vp->v_op = dead_vnodeop_p; /* so ops will still work */ vrele(vp); /* get rid of it. */ kmem_free(xp, lmp->layerm_size); *vpp = nvp; return 0; } /* * Insert the new node into the hash. * Add a reference to the lower node. */ vref(lowervp); hd = LAYER_NHASH(lmp, lowervp); LIST_INSERT_HEAD(hd, xp, layer_hash); uvm_vnp_setsize(vp, 0); mutex_exit(&lmp->layerm_hashlock); *vpp = vp; return 0; } /* * layer_node_create: try to find an existing layerfs vnode refering to it, * otherwise make a new vnode which contains a reference to the lower vnode. * * => Caller should lock the lower node. */ int layer_node_create(struct mount *mp, struct vnode *lowervp, struct vnode **nvpp) { struct vnode *aliasvp; struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); KASSERT(VOP_ISLOCKED(lowervp)); mutex_enter(&lmp->layerm_hashlock); aliasvp = layer_node_find(mp, lowervp); if (aliasvp != NULL) { /* * Note: layer_node_find() has taken another reference to * the alias vnode and moved the lock holding to aliasvp. */ #ifdef LAYERFS_DIAGNOSTIC if (layerfs_debug) vprint("layer_node_create: exists", aliasvp); #endif } else { int error; mutex_exit(&lmp->layerm_hashlock); /* * Get a new vnode. Make it to reference the layer_node. * Note: aliasvp will be return with the reference held. */ error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp); if (error) return error; #ifdef LAYERFS_DIAGNOSTIC if (layerfs_debug) printf("layer_node_create: create new alias vnode\n"); #endif } /* * Now that we acquired a reference on the upper vnode, release one * on the lower node. The existence of the layer_node retains one * reference to the lower node. */ vrele(lowervp); KASSERT(lowervp->v_usecount > 0); #ifdef LAYERFS_DIAGNOSTIC if (layerfs_debug) vprint("layer_node_create: alias", aliasvp); #endif *nvpp = aliasvp; return 0; } #ifdef LAYERFS_DIAGNOSTIC struct vnode * layer_checkvp(struct vnode *vp, const 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; } #endif