/* $NetBSD: uvm_aobj.c,v 1.128 2019/07/28 05:28:53 msaitoh Exp $ */ /* * Copyright (c) 1998 Chuck Silvers, Charles D. Cranor and * Washington University. * All rights reserved. * * 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. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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: uvm_aobj.c,v 1.1.2.5 1998/02/06 05:14:38 chs Exp */ /* * uvm_aobj.c: anonymous memory uvm_object pager * * author: Chuck Silvers * started: Jan-1998 * * - design mostly from Chuck Cranor */ #include __KERNEL_RCSID(0, "$NetBSD: uvm_aobj.c,v 1.128 2019/07/28 05:28:53 msaitoh Exp $"); #ifdef _KERNEL_OPT #include "opt_uvmhist.h" #endif #include #include #include #include #include #include #include /* * An anonymous UVM object (aobj) manages anonymous-memory. In addition to * keeping the list of resident pages, it may also keep a list of allocated * swap blocks. Depending on the size of the object, this list is either * stored in an array (small objects) or in a hash table (large objects). * * Lock order * * uao_list_lock -> * uvm_object::vmobjlock */ /* * Note: for hash tables, we break the address space of the aobj into blocks * of UAO_SWHASH_CLUSTER_SIZE pages, which shall be a power of two. */ #define UAO_SWHASH_CLUSTER_SHIFT 4 #define UAO_SWHASH_CLUSTER_SIZE (1 << UAO_SWHASH_CLUSTER_SHIFT) /* Get the "tag" for this page index. */ #define UAO_SWHASH_ELT_TAG(idx) ((idx) >> UAO_SWHASH_CLUSTER_SHIFT) #define UAO_SWHASH_ELT_PAGESLOT_IDX(idx) \ ((idx) & (UAO_SWHASH_CLUSTER_SIZE - 1)) /* Given an ELT and a page index, find the swap slot. */ #define UAO_SWHASH_ELT_PAGESLOT(elt, idx) \ ((elt)->slots[UAO_SWHASH_ELT_PAGESLOT_IDX(idx)]) /* Given an ELT, return its pageidx base. */ #define UAO_SWHASH_ELT_PAGEIDX_BASE(ELT) \ ((elt)->tag << UAO_SWHASH_CLUSTER_SHIFT) /* The hash function. */ #define UAO_SWHASH_HASH(aobj, idx) \ (&(aobj)->u_swhash[(((idx) >> UAO_SWHASH_CLUSTER_SHIFT) \ & (aobj)->u_swhashmask)]) /* * The threshold which determines whether we will use an array or a * hash table to store the list of allocated swap blocks. */ #define UAO_SWHASH_THRESHOLD (UAO_SWHASH_CLUSTER_SIZE * 4) #define UAO_USES_SWHASH(aobj) \ ((aobj)->u_pages > UAO_SWHASH_THRESHOLD) /* The number of buckets in a hash, with an upper bound. */ #define UAO_SWHASH_MAXBUCKETS 256 #define UAO_SWHASH_BUCKETS(aobj) \ (MIN((aobj)->u_pages >> UAO_SWHASH_CLUSTER_SHIFT, UAO_SWHASH_MAXBUCKETS)) /* * uao_swhash_elt: when a hash table is being used, this structure defines * the format of an entry in the bucket list. */ struct uao_swhash_elt { LIST_ENTRY(uao_swhash_elt) list; /* the hash list */ voff_t tag; /* our 'tag' */ int count; /* our number of active slots */ int slots[UAO_SWHASH_CLUSTER_SIZE]; /* the slots */ }; /* * uao_swhash: the swap hash table structure */ LIST_HEAD(uao_swhash, uao_swhash_elt); /* * uao_swhash_elt_pool: pool of uao_swhash_elt structures. * Note: pages for this pool must not come from a pageable kernel map. */ static struct pool uao_swhash_elt_pool __cacheline_aligned; /* * uvm_aobj: the actual anon-backed uvm_object * * => the uvm_object is at the top of the structure, this allows * (struct uvm_aobj *) == (struct uvm_object *) * => only one of u_swslots and u_swhash is used in any given aobj */ struct uvm_aobj { struct uvm_object u_obj; /* has: lock, pgops, memq, #pages, #refs */ pgoff_t u_pages; /* number of pages in entire object */ int u_flags; /* the flags (see uvm_aobj.h) */ int *u_swslots; /* array of offset->swapslot mappings */ /* * hashtable of offset->swapslot mappings * (u_swhash is an array of bucket heads) */ struct uao_swhash *u_swhash; u_long u_swhashmask; /* mask for hashtable */ LIST_ENTRY(uvm_aobj) u_list; /* global list of aobjs */ int u_freelist; /* freelist to allocate pages from */ }; static void uao_free(struct uvm_aobj *); static int uao_get(struct uvm_object *, voff_t, struct vm_page **, int *, int, vm_prot_t, int, int); static int uao_put(struct uvm_object *, voff_t, voff_t, int); #if defined(VMSWAP) static struct uao_swhash_elt *uao_find_swhash_elt (struct uvm_aobj *, int, bool); static bool uao_pagein(struct uvm_aobj *, int, int); static bool uao_pagein_page(struct uvm_aobj *, int); #endif /* defined(VMSWAP) */ static struct vm_page *uao_pagealloc(struct uvm_object *, voff_t, int); /* * aobj_pager * * note that some functions (e.g. put) are handled elsewhere */ const struct uvm_pagerops aobj_pager = { .pgo_reference = uao_reference, .pgo_detach = uao_detach, .pgo_get = uao_get, .pgo_put = uao_put, }; /* * uao_list: global list of active aobjs, locked by uao_list_lock */ static LIST_HEAD(aobjlist, uvm_aobj) uao_list __cacheline_aligned; static kmutex_t uao_list_lock __cacheline_aligned; /* * hash table/array related functions */ #if defined(VMSWAP) /* * uao_find_swhash_elt: find (or create) a hash table entry for a page * offset. * * => the object should be locked by the caller */ static struct uao_swhash_elt * uao_find_swhash_elt(struct uvm_aobj *aobj, int pageidx, bool create) { struct uao_swhash *swhash; struct uao_swhash_elt *elt; voff_t page_tag; swhash = UAO_SWHASH_HASH(aobj, pageidx); page_tag = UAO_SWHASH_ELT_TAG(pageidx); /* * now search the bucket for the requested tag */ LIST_FOREACH(elt, swhash, list) { if (elt->tag == page_tag) { return elt; } } if (!create) { return NULL; } /* * allocate a new entry for the bucket and init/insert it in */ elt = pool_get(&uao_swhash_elt_pool, PR_NOWAIT); if (elt == NULL) { return NULL; } LIST_INSERT_HEAD(swhash, elt, list); elt->tag = page_tag; elt->count = 0; memset(elt->slots, 0, sizeof(elt->slots)); return elt; } /* * uao_find_swslot: find the swap slot number for an aobj/pageidx * * => object must be locked by caller */ int uao_find_swslot(struct uvm_object *uobj, int pageidx) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; struct uao_swhash_elt *elt; /* * if noswap flag is set, then we never return a slot */ if (aobj->u_flags & UAO_FLAG_NOSWAP) return 0; /* * if hashing, look in hash table. */ if (UAO_USES_SWHASH(aobj)) { elt = uao_find_swhash_elt(aobj, pageidx, false); return elt ? UAO_SWHASH_ELT_PAGESLOT(elt, pageidx) : 0; } /* * otherwise, look in the array */ return aobj->u_swslots[pageidx]; } /* * uao_set_swslot: set the swap slot for a page in an aobj. * * => setting a slot to zero frees the slot * => object must be locked by caller * => we return the old slot number, or -1 if we failed to allocate * memory to record the new slot number */ int uao_set_swslot(struct uvm_object *uobj, int pageidx, int slot) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; struct uao_swhash_elt *elt; int oldslot; UVMHIST_FUNC("uao_set_swslot"); UVMHIST_CALLED(pdhist); UVMHIST_LOG(pdhist, "aobj %#jx pageidx %jd slot %jd", (uintptr_t)aobj, pageidx, slot, 0); KASSERT(mutex_owned(uobj->vmobjlock) || uobj->uo_refs == 0); /* * if noswap flag is set, then we can't set a non-zero slot. */ if (aobj->u_flags & UAO_FLAG_NOSWAP) { KASSERTMSG(slot == 0, "uao_set_swslot: no swap object"); return 0; } /* * are we using a hash table? if so, add it in the hash. */ if (UAO_USES_SWHASH(aobj)) { /* * Avoid allocating an entry just to free it again if * the page had not swap slot in the first place, and * we are freeing. */ elt = uao_find_swhash_elt(aobj, pageidx, slot != 0); if (elt == NULL) { return slot ? -1 : 0; } oldslot = UAO_SWHASH_ELT_PAGESLOT(elt, pageidx); UAO_SWHASH_ELT_PAGESLOT(elt, pageidx) = slot; /* * now adjust the elt's reference counter and free it if we've * dropped it to zero. */ if (slot) { if (oldslot == 0) elt->count++; } else { if (oldslot) elt->count--; if (elt->count == 0) { LIST_REMOVE(elt, list); pool_put(&uao_swhash_elt_pool, elt); } } } else { /* we are using an array */ oldslot = aobj->u_swslots[pageidx]; aobj->u_swslots[pageidx] = slot; } return oldslot; } #endif /* defined(VMSWAP) */ /* * end of hash/array functions */ /* * uao_free: free all resources held by an aobj, and then free the aobj * * => the aobj should be dead */ static void uao_free(struct uvm_aobj *aobj) { struct uvm_object *uobj = &aobj->u_obj; KASSERT(mutex_owned(uobj->vmobjlock)); uao_dropswap_range(uobj, 0, 0); mutex_exit(uobj->vmobjlock); #if defined(VMSWAP) if (UAO_USES_SWHASH(aobj)) { /* * free the hash table itself. */ hashdone(aobj->u_swhash, HASH_LIST, aobj->u_swhashmask); } else { /* * free the array itsself. */ kmem_free(aobj->u_swslots, aobj->u_pages * sizeof(int)); } #endif /* defined(VMSWAP) */ /* * finally free the aobj itself */ uvm_obj_destroy(uobj, true); kmem_free(aobj, sizeof(struct uvm_aobj)); } /* * pager functions */ /* * uao_create: create an aobj of the given size and return its uvm_object. * * => for normal use, flags are always zero * => for the kernel object, the flags are: * UAO_FLAG_KERNOBJ - allocate the kernel object (can only happen once) * UAO_FLAG_KERNSWAP - enable swapping of kernel object (" ") */ struct uvm_object * uao_create(voff_t size, int flags) { static struct uvm_aobj kernel_object_store; static kmutex_t kernel_object_lock; static int kobj_alloced __diagused = 0; pgoff_t pages = round_page((uint64_t)size) >> PAGE_SHIFT; struct uvm_aobj *aobj; int refs; /* * Allocate a new aobj, unless kernel object is requested. */ if (flags & UAO_FLAG_KERNOBJ) { KASSERT(!kobj_alloced); aobj = &kernel_object_store; aobj->u_pages = pages; aobj->u_flags = UAO_FLAG_NOSWAP; refs = UVM_OBJ_KERN; kobj_alloced = UAO_FLAG_KERNOBJ; } else if (flags & UAO_FLAG_KERNSWAP) { KASSERT(kobj_alloced == UAO_FLAG_KERNOBJ); aobj = &kernel_object_store; kobj_alloced = UAO_FLAG_KERNSWAP; refs = 0xdeadbeaf; /* XXX: gcc */ } else { aobj = kmem_alloc(sizeof(struct uvm_aobj), KM_SLEEP); aobj->u_pages = pages; aobj->u_flags = 0; refs = 1; } /* * no freelist by default */ aobj->u_freelist = VM_NFREELIST; /* * allocate hash/array if necessary * * note: in the KERNSWAP case no need to worry about locking since * we are still booting we should be the only thread around. */ if (flags == 0 || (flags & UAO_FLAG_KERNSWAP) != 0) { #if defined(VMSWAP) const int kernswap = (flags & UAO_FLAG_KERNSWAP) != 0; /* allocate hash table or array depending on object size */ if (UAO_USES_SWHASH(aobj)) { aobj->u_swhash = hashinit(UAO_SWHASH_BUCKETS(aobj), HASH_LIST, kernswap ? false : true, &aobj->u_swhashmask); if (aobj->u_swhash == NULL) panic("uao_create: hashinit swhash failed"); } else { aobj->u_swslots = kmem_zalloc(pages * sizeof(int), kernswap ? KM_NOSLEEP : KM_SLEEP); if (aobj->u_swslots == NULL) panic("uao_create: swslots allocation failed"); } #endif /* defined(VMSWAP) */ if (flags) { aobj->u_flags &= ~UAO_FLAG_NOSWAP; /* clear noswap */ return &aobj->u_obj; } } /* * Initialise UVM object. */ const bool kernobj = (flags & UAO_FLAG_KERNOBJ) != 0; uvm_obj_init(&aobj->u_obj, &aobj_pager, !kernobj, refs); if (__predict_false(kernobj)) { /* Initialisation only once, for UAO_FLAG_KERNOBJ. */ mutex_init(&kernel_object_lock, MUTEX_DEFAULT, IPL_NONE); uvm_obj_setlock(&aobj->u_obj, &kernel_object_lock); } /* * now that aobj is ready, add it to the global list */ mutex_enter(&uao_list_lock); LIST_INSERT_HEAD(&uao_list, aobj, u_list); mutex_exit(&uao_list_lock); return(&aobj->u_obj); } /* * uao_set_pgfl: allocate pages only from the specified freelist. * * => must be called before any pages are allocated for the object. * => reset by setting it to VM_NFREELIST, meaning any freelist. */ void uao_set_pgfl(struct uvm_object *uobj, int freelist) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; KASSERTMSG((0 <= freelist), "invalid freelist %d", freelist); KASSERTMSG((freelist <= VM_NFREELIST), "invalid freelist %d", freelist); aobj->u_freelist = freelist; } /* * uao_pagealloc: allocate a page for aobj. */ static inline struct vm_page * uao_pagealloc(struct uvm_object *uobj, voff_t offset, int flags) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; if (__predict_true(aobj->u_freelist == VM_NFREELIST)) return uvm_pagealloc(uobj, offset, NULL, flags); else return uvm_pagealloc_strat(uobj, offset, NULL, flags, UVM_PGA_STRAT_ONLY, aobj->u_freelist); } /* * uao_init: set up aobj pager subsystem * * => called at boot time from uvm_pager_init() */ void uao_init(void) { static int uao_initialized; if (uao_initialized) return; uao_initialized = true; LIST_INIT(&uao_list); mutex_init(&uao_list_lock, MUTEX_DEFAULT, IPL_NONE); pool_init(&uao_swhash_elt_pool, sizeof(struct uao_swhash_elt), 0, 0, 0, "uaoeltpl", NULL, IPL_VM); } /* * uao_reference: hold a reference to an anonymous UVM object. */ void uao_reference(struct uvm_object *uobj) { /* Kernel object is persistent. */ if (UVM_OBJ_IS_KERN_OBJECT(uobj)) { return; } atomic_inc_uint(&uobj->uo_refs); } /* * uao_detach: drop a reference to an anonymous UVM object. */ void uao_detach(struct uvm_object *uobj) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; struct vm_page *pg; UVMHIST_FUNC("uao_detach"); UVMHIST_CALLED(maphist); /* * Detaching from kernel object is a NOP. */ if (UVM_OBJ_IS_KERN_OBJECT(uobj)) return; /* * Drop the reference. If it was the last one, destroy the object. */ KASSERT(uobj->uo_refs > 0); UVMHIST_LOG(maphist," (uobj=0x%#jx) ref=%jd", (uintptr_t)uobj, uobj->uo_refs, 0, 0); if (atomic_dec_uint_nv(&uobj->uo_refs) > 0) { UVMHIST_LOG(maphist, "<- done (rc>0)", 0,0,0,0); return; } /* * Remove the aobj from the global list. */ mutex_enter(&uao_list_lock); LIST_REMOVE(aobj, u_list); mutex_exit(&uao_list_lock); /* * Free all the pages left in the aobj. For each page, when the * page is no longer busy (and thus after any disk I/O that it is * involved in is complete), release any swap resources and free * the page itself. */ mutex_enter(uobj->vmobjlock); mutex_enter(&uvm_pageqlock); while ((pg = TAILQ_FIRST(&uobj->memq)) != NULL) { pmap_page_protect(pg, VM_PROT_NONE); if (pg->flags & PG_BUSY) { pg->flags |= PG_WANTED; mutex_exit(&uvm_pageqlock); UVM_UNLOCK_AND_WAIT(pg, uobj->vmobjlock, false, "uao_det", 0); mutex_enter(uobj->vmobjlock); mutex_enter(&uvm_pageqlock); continue; } uao_dropswap(&aobj->u_obj, pg->offset >> PAGE_SHIFT); uvm_pagefree(pg); } mutex_exit(&uvm_pageqlock); /* * Finally, free the anonymous UVM object itself. */ uao_free(aobj); } /* * uao_put: flush pages out of a uvm object * * => object should be locked by caller. we may _unlock_ the object * if (and only if) we need to clean a page (PGO_CLEANIT). * XXXJRT Currently, however, we don't. In the case of cleaning * XXXJRT a page, we simply just deactivate it. Should probably * XXXJRT handle this better, in the future (although "flushing" * XXXJRT anonymous memory isn't terribly important). * => if PGO_CLEANIT is not set, then we will neither unlock the object * or block. * => if PGO_ALLPAGE is set, then all pages in the object are valid targets * for flushing. * => NOTE: we rely on the fact that the object's memq is a TAILQ and * that new pages are inserted on the tail end of the list. thus, * we can make a complete pass through the object in one go by starting * at the head and working towards the tail (new pages are put in * front of us). * => NOTE: we are allowed to lock the page queues, so the caller * must not be holding the lock on them [e.g. pagedaemon had * better not call us with the queues locked] * => we return 0 unless we encountered some sort of I/O error * XXXJRT currently never happens, as we never directly initiate * XXXJRT I/O * * note on page traversal: * we can traverse the pages in an object either by going down the * linked list in "uobj->memq", or we can go over the address range * by page doing hash table lookups for each address. depending * on how many pages are in the object it may be cheaper to do one * or the other. we set "by_list" to true if we are using memq. * if the cost of a hash lookup was equal to the cost of the list * traversal we could compare the number of pages in the start->stop * range to the total number of pages in the object. however, it * seems that a hash table lookup is more expensive than the linked * list traversal, so we multiply the number of pages in the * start->stop range by a penalty which we define below. */ static int uao_put(struct uvm_object *uobj, voff_t start, voff_t stop, int flags) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; struct vm_page *pg, *nextpg, curmp, endmp; bool by_list; voff_t curoff; UVMHIST_FUNC("uao_put"); UVMHIST_CALLED(maphist); KASSERT(mutex_owned(uobj->vmobjlock)); curoff = 0; if (flags & PGO_ALLPAGES) { start = 0; stop = aobj->u_pages << PAGE_SHIFT; by_list = true; /* always go by the list */ } else { start = trunc_page(start); if (stop == 0) { stop = aobj->u_pages << PAGE_SHIFT; } else { stop = round_page(stop); } if (stop > (uint64_t)(aobj->u_pages << PAGE_SHIFT)) { printf("uao_put: strange, got an out of range " "flush 0x%jx > 0x%jx (fixed)\n", (uintmax_t)stop, (uintmax_t)(aobj->u_pages << PAGE_SHIFT)); stop = aobj->u_pages << PAGE_SHIFT; } by_list = (uobj->uo_npages <= ((stop - start) >> PAGE_SHIFT) * UVM_PAGE_TREE_PENALTY); } UVMHIST_LOG(maphist, " flush start=0x%jx, stop=0x%jx, by_list=%jd, flags=0x%jx", start, stop, by_list, flags); /* * Don't need to do any work here if we're not freeing * or deactivating pages. */ if ((flags & (PGO_DEACTIVATE|PGO_FREE)) == 0) { mutex_exit(uobj->vmobjlock); return 0; } /* * Initialize the marker pages. See the comment in * genfs_putpages() also. */ curmp.flags = PG_MARKER; endmp.flags = PG_MARKER; /* * now do it. note: we must update nextpg in the body of loop or we * will get stuck. we need to use nextpg if we'll traverse the list * because we may free "pg" before doing the next loop. */ if (by_list) { TAILQ_INSERT_TAIL(&uobj->memq, &endmp, listq.queue); nextpg = TAILQ_FIRST(&uobj->memq); } else { curoff = start; nextpg = NULL; /* Quell compiler warning */ } /* locked: uobj */ for (;;) { if (by_list) { pg = nextpg; if (pg == &endmp) break; nextpg = TAILQ_NEXT(pg, listq.queue); if (pg->flags & PG_MARKER) continue; if (pg->offset < start || pg->offset >= stop) continue; } else { if (curoff < stop) { pg = uvm_pagelookup(uobj, curoff); curoff += PAGE_SIZE; } else break; if (pg == NULL) continue; } /* * wait and try again if the page is busy. */ if (pg->flags & PG_BUSY) { if (by_list) { TAILQ_INSERT_BEFORE(pg, &curmp, listq.queue); } pg->flags |= PG_WANTED; UVM_UNLOCK_AND_WAIT(pg, uobj->vmobjlock, 0, "uao_put", 0); mutex_enter(uobj->vmobjlock); if (by_list) { nextpg = TAILQ_NEXT(&curmp, listq.queue); TAILQ_REMOVE(&uobj->memq, &curmp, listq.queue); } else curoff -= PAGE_SIZE; continue; } switch (flags & (PGO_CLEANIT|PGO_FREE|PGO_DEACTIVATE)) { /* * XXX In these first 3 cases, we always just * XXX deactivate the page. We may want to * XXX handle the different cases more specifically * XXX in the future. */ case PGO_CLEANIT|PGO_FREE: case PGO_CLEANIT|PGO_DEACTIVATE: case PGO_DEACTIVATE: deactivate_it: mutex_enter(&uvm_pageqlock); /* skip the page if it's wired */ if (pg->wire_count == 0) { uvm_pagedeactivate(pg); } mutex_exit(&uvm_pageqlock); break; case PGO_FREE: /* * If there are multiple references to * the object, just deactivate the page. */ if (uobj->uo_refs > 1) goto deactivate_it; /* * free the swap slot and the page. */ pmap_page_protect(pg, VM_PROT_NONE); /* * freeing swapslot here is not strictly necessary. * however, leaving it here doesn't save much * because we need to update swap accounting anyway. */ uao_dropswap(uobj, pg->offset >> PAGE_SHIFT); mutex_enter(&uvm_pageqlock); uvm_pagefree(pg); mutex_exit(&uvm_pageqlock); break; default: panic("%s: impossible", __func__); } } if (by_list) { TAILQ_REMOVE(&uobj->memq, &endmp, listq.queue); } mutex_exit(uobj->vmobjlock); return 0; } /* * uao_get: fetch me a page * * we have three cases: * 1: page is resident -> just return the page. * 2: page is zero-fill -> allocate a new page and zero it. * 3: page is swapped out -> fetch the page from swap. * * cases 1 and 2 can be handled with PGO_LOCKED, case 3 cannot. * so, if the "center" page hits case 3 (or any page, with PGO_ALLPAGES), * then we will need to return EBUSY. * * => prefer map unlocked (not required) * => object must be locked! we will _unlock_ it before starting any I/O. * => flags: PGO_ALLPAGES: get all of the pages * PGO_LOCKED: fault data structures are locked * => NOTE: offset is the offset of pps[0], _NOT_ pps[centeridx] * => NOTE: caller must check for released pages!! */ static int uao_get(struct uvm_object *uobj, voff_t offset, struct vm_page **pps, int *npagesp, int centeridx, vm_prot_t access_type, int advice, int flags) { voff_t current_offset; struct vm_page *ptmp = NULL; /* Quell compiler warning */ int lcv, gotpages, maxpages, swslot, pageidx; bool done; UVMHIST_FUNC("uao_get"); UVMHIST_CALLED(pdhist); UVMHIST_LOG(pdhist, "aobj=%#jx offset=%jd, flags=%jd", (uintptr_t)uobj, offset, flags,0); /* * get number of pages */ maxpages = *npagesp; /* * step 1: handled the case where fault data structures are locked. */ if (flags & PGO_LOCKED) { /* * step 1a: get pages that are already resident. only do * this if the data structures are locked (i.e. the first * time through). */ done = true; /* be optimistic */ gotpages = 0; /* # of pages we got so far */ for (lcv = 0, current_offset = offset ; lcv < maxpages ; lcv++, current_offset += PAGE_SIZE) { /* do we care about this page? if not, skip it */ if (pps[lcv] == PGO_DONTCARE) continue; ptmp = uvm_pagelookup(uobj, current_offset); /* * if page is new, attempt to allocate the page, * zero-fill'd. */ if (ptmp == NULL && uao_find_swslot(uobj, current_offset >> PAGE_SHIFT) == 0) { ptmp = uao_pagealloc(uobj, current_offset, UVM_FLAG_COLORMATCH|UVM_PGA_ZERO); if (ptmp) { /* new page */ ptmp->flags &= ~(PG_FAKE); ptmp->pqflags |= PQ_AOBJ; goto gotpage; } } /* * to be useful must get a non-busy page */ if (ptmp == NULL || (ptmp->flags & PG_BUSY) != 0) { if (lcv == centeridx || (flags & PGO_ALLPAGES) != 0) /* need to do a wait or I/O! */ done = false; continue; } /* * useful page: busy/lock it and plug it in our * result array */ /* caller must un-busy this page */ ptmp->flags |= PG_BUSY; UVM_PAGE_OWN(ptmp, "uao_get1"); gotpage: pps[lcv] = ptmp; gotpages++; } /* * step 1b: now we've either done everything needed or we * to unlock and do some waiting or I/O. */ UVMHIST_LOG(pdhist, "<- done (done=%jd)", done, 0,0,0); *npagesp = gotpages; if (done) return 0; else return EBUSY; } /* * step 2: get non-resident or busy pages. * object is locked. data structures are unlocked. */ if ((flags & PGO_SYNCIO) == 0) { goto done; } for (lcv = 0, current_offset = offset ; lcv < maxpages ; lcv++, current_offset += PAGE_SIZE) { /* * - skip over pages we've already gotten or don't want * - skip over pages we don't _have_ to get */ if (pps[lcv] != NULL || (lcv != centeridx && (flags & PGO_ALLPAGES) == 0)) continue; pageidx = current_offset >> PAGE_SHIFT; /* * we have yet to locate the current page (pps[lcv]). we * first look for a page that is already at the current offset. * if we find a page, we check to see if it is busy or * released. if that is the case, then we sleep on the page * until it is no longer busy or released and repeat the lookup. * if the page we found is neither busy nor released, then we * busy it (so we own it) and plug it into pps[lcv]. this * 'break's the following while loop and indicates we are * ready to move on to the next page in the "lcv" loop above. * * if we exit the while loop with pps[lcv] still set to NULL, * then it means that we allocated a new busy/fake/clean page * ptmp in the object and we need to do I/O to fill in the data. */ /* top of "pps" while loop */ while (pps[lcv] == NULL) { /* look for a resident page */ ptmp = uvm_pagelookup(uobj, current_offset); /* not resident? allocate one now (if we can) */ if (ptmp == NULL) { ptmp = uao_pagealloc(uobj, current_offset, 0); /* out of RAM? */ if (ptmp == NULL) { mutex_exit(uobj->vmobjlock); UVMHIST_LOG(pdhist, "sleeping, ptmp == NULL\n",0,0,0,0); uvm_wait("uao_getpage"); mutex_enter(uobj->vmobjlock); continue; } /* * safe with PQ's unlocked: because we just * alloc'd the page */ ptmp->pqflags |= PQ_AOBJ; /* * got new page ready for I/O. break pps while * loop. pps[lcv] is still NULL. */ break; } /* page is there, see if we need to wait on it */ if ((ptmp->flags & PG_BUSY) != 0) { ptmp->flags |= PG_WANTED; UVMHIST_LOG(pdhist, "sleeping, ptmp->flags 0x%jx\n", ptmp->flags,0,0,0); UVM_UNLOCK_AND_WAIT(ptmp, uobj->vmobjlock, false, "uao_get", 0); mutex_enter(uobj->vmobjlock); continue; } /* * if we get here then the page has become resident and * unbusy between steps 1 and 2. we busy it now (so we * own it) and set pps[lcv] (so that we exit the while * loop). */ /* we own it, caller must un-busy */ ptmp->flags |= PG_BUSY; UVM_PAGE_OWN(ptmp, "uao_get2"); pps[lcv] = ptmp; } /* * if we own the valid page at the correct offset, pps[lcv] will * point to it. nothing more to do except go to the next page. */ if (pps[lcv]) continue; /* next lcv */ /* * we have a "fake/busy/clean" page that we just allocated. * do the needed "i/o", either reading from swap or zeroing. */ swslot = uao_find_swslot(uobj, pageidx); /* * just zero the page if there's nothing in swap. */ if (swslot == 0) { /* * page hasn't existed before, just zero it. */ uvm_pagezero(ptmp); } else { #if defined(VMSWAP) int error; UVMHIST_LOG(pdhist, "pagein from swslot %jd", swslot, 0,0,0); /* * page in the swapped-out page. * unlock object for i/o, relock when done. */ mutex_exit(uobj->vmobjlock); error = uvm_swap_get(ptmp, swslot, PGO_SYNCIO); mutex_enter(uobj->vmobjlock); /* * I/O done. check for errors. */ if (error != 0) { UVMHIST_LOG(pdhist, "<- done (error=%jd)", error,0,0,0); if (ptmp->flags & PG_WANTED) wakeup(ptmp); /* * remove the swap slot from the aobj * and mark the aobj as having no real slot. * don't free the swap slot, thus preventing * it from being used again. */ swslot = uao_set_swslot(uobj, pageidx, SWSLOT_BAD); if (swslot > 0) { uvm_swap_markbad(swslot, 1); } mutex_enter(&uvm_pageqlock); uvm_pagefree(ptmp); mutex_exit(&uvm_pageqlock); mutex_exit(uobj->vmobjlock); return error; } #else /* defined(VMSWAP) */ panic("%s: pagein", __func__); #endif /* defined(VMSWAP) */ } if ((access_type & VM_PROT_WRITE) == 0) { ptmp->flags |= PG_CLEAN; pmap_clear_modify(ptmp); } /* * we got the page! clear the fake flag (indicates valid * data now in page) and plug into our result array. note * that page is still busy. * * it is the callers job to: * => check if the page is released * => unbusy the page * => activate the page */ ptmp->flags &= ~PG_FAKE; pps[lcv] = ptmp; } /* * finally, unlock object and return. */ done: mutex_exit(uobj->vmobjlock); UVMHIST_LOG(pdhist, "<- done (OK)",0,0,0,0); return 0; } #if defined(VMSWAP) /* * uao_dropswap: release any swap resources from this aobj page. * * => aobj must be locked or have a reference count of 0. */ void uao_dropswap(struct uvm_object *uobj, int pageidx) { int slot; slot = uao_set_swslot(uobj, pageidx, 0); if (slot) { uvm_swap_free(slot, 1); } } /* * page in every page in every aobj that is paged-out to a range of swslots. * * => nothing should be locked. * => returns true if pagein was aborted due to lack of memory. */ bool uao_swap_off(int startslot, int endslot) { struct uvm_aobj *aobj; /* * Walk the list of all anonymous UVM objects. Grab the first. */ mutex_enter(&uao_list_lock); if ((aobj = LIST_FIRST(&uao_list)) == NULL) { mutex_exit(&uao_list_lock); return false; } uao_reference(&aobj->u_obj); do { struct uvm_aobj *nextaobj; bool rv; /* * Prefetch the next object and immediately hold a reference * on it, so neither the current nor the next entry could * disappear while we are iterating. */ if ((nextaobj = LIST_NEXT(aobj, u_list)) != NULL) { uao_reference(&nextaobj->u_obj); } mutex_exit(&uao_list_lock); /* * Page in all pages in the swap slot range. */ mutex_enter(aobj->u_obj.vmobjlock); rv = uao_pagein(aobj, startslot, endslot); mutex_exit(aobj->u_obj.vmobjlock); /* Drop the reference of the current object. */ uao_detach(&aobj->u_obj); if (rv) { if (nextaobj) { uao_detach(&nextaobj->u_obj); } return rv; } aobj = nextaobj; mutex_enter(&uao_list_lock); } while (aobj); mutex_exit(&uao_list_lock); return false; } /* * page in any pages from aobj in the given range. * * => aobj must be locked and is returned locked. * => returns true if pagein was aborted due to lack of memory. */ static bool uao_pagein(struct uvm_aobj *aobj, int startslot, int endslot) { bool rv; if (UAO_USES_SWHASH(aobj)) { struct uao_swhash_elt *elt; int buck; restart: for (buck = aobj->u_swhashmask; buck >= 0; buck--) { for (elt = LIST_FIRST(&aobj->u_swhash[buck]); elt != NULL; elt = LIST_NEXT(elt, list)) { int i; for (i = 0; i < UAO_SWHASH_CLUSTER_SIZE; i++) { int slot = elt->slots[i]; /* * if the slot isn't in range, skip it. */ if (slot < startslot || slot >= endslot) { continue; } /* * process the page, * the start over on this object * since the swhash elt * may have been freed. */ rv = uao_pagein_page(aobj, UAO_SWHASH_ELT_PAGEIDX_BASE(elt) + i); if (rv) { return rv; } goto restart; } } } } else { int i; for (i = 0; i < aobj->u_pages; i++) { int slot = aobj->u_swslots[i]; /* * if the slot isn't in range, skip it */ if (slot < startslot || slot >= endslot) { continue; } /* * process the page. */ rv = uao_pagein_page(aobj, i); if (rv) { return rv; } } } return false; } /* * uao_pagein_page: page in a single page from an anonymous UVM object. * * => Returns true if pagein was aborted due to lack of memory. * => Object must be locked and is returned locked. */ static bool uao_pagein_page(struct uvm_aobj *aobj, int pageidx) { struct uvm_object *uobj = &aobj->u_obj; struct vm_page *pg; int rv, npages; pg = NULL; npages = 1; KASSERT(mutex_owned(uobj->vmobjlock)); rv = uao_get(uobj, (voff_t)pageidx << PAGE_SHIFT, &pg, &npages, 0, VM_PROT_READ | VM_PROT_WRITE, 0, PGO_SYNCIO); /* * relock and finish up. */ mutex_enter(uobj->vmobjlock); switch (rv) { case 0: break; case EIO: case ERESTART: /* * nothing more to do on errors. * ERESTART can only mean that the anon was freed, * so again there's nothing to do. */ return false; default: return true; } /* * ok, we've got the page now. * mark it as dirty, clear its swslot and un-busy it. */ uao_dropswap(&aobj->u_obj, pageidx); /* * make sure it's on a page queue. */ mutex_enter(&uvm_pageqlock); if (pg->wire_count == 0) uvm_pageenqueue(pg); mutex_exit(&uvm_pageqlock); if (pg->flags & PG_WANTED) { wakeup(pg); } pg->flags &= ~(PG_WANTED|PG_BUSY|PG_CLEAN|PG_FAKE); UVM_PAGE_OWN(pg, NULL); return false; } /* * uao_dropswap_range: drop swapslots in the range. * * => aobj must be locked and is returned locked. * => start is inclusive. end is exclusive. */ void uao_dropswap_range(struct uvm_object *uobj, voff_t start, voff_t end) { struct uvm_aobj *aobj = (struct uvm_aobj *)uobj; int swpgonlydelta = 0; KASSERT(mutex_owned(uobj->vmobjlock)); if (end == 0) { end = INT64_MAX; } if (UAO_USES_SWHASH(aobj)) { int i, hashbuckets = aobj->u_swhashmask + 1; voff_t taghi; voff_t taglo; taglo = UAO_SWHASH_ELT_TAG(start); taghi = UAO_SWHASH_ELT_TAG(end); for (i = 0; i < hashbuckets; i++) { struct uao_swhash_elt *elt, *next; for (elt = LIST_FIRST(&aobj->u_swhash[i]); elt != NULL; elt = next) { int startidx, endidx; int j; next = LIST_NEXT(elt, list); if (elt->tag < taglo || taghi < elt->tag) { continue; } if (elt->tag == taglo) { startidx = UAO_SWHASH_ELT_PAGESLOT_IDX(start); } else { startidx = 0; } if (elt->tag == taghi) { endidx = UAO_SWHASH_ELT_PAGESLOT_IDX(end); } else { endidx = UAO_SWHASH_CLUSTER_SIZE; } for (j = startidx; j < endidx; j++) { int slot = elt->slots[j]; KASSERT(uvm_pagelookup(&aobj->u_obj, (UAO_SWHASH_ELT_PAGEIDX_BASE(elt) + j) << PAGE_SHIFT) == NULL); if (slot > 0) { uvm_swap_free(slot, 1); swpgonlydelta++; KASSERT(elt->count > 0); elt->slots[j] = 0; elt->count--; } } if (elt->count == 0) { LIST_REMOVE(elt, list); pool_put(&uao_swhash_elt_pool, elt); } } } } else { int i; if (aobj->u_pages < end) { end = aobj->u_pages; } for (i = start; i < end; i++) { int slot = aobj->u_swslots[i]; if (slot > 0) { uvm_swap_free(slot, 1); swpgonlydelta++; } } } /* * adjust the counter of pages only in swap for all * the swap slots we've freed. */ if (swpgonlydelta > 0) { mutex_enter(&uvm_swap_data_lock); KASSERT(uvmexp.swpgonly >= swpgonlydelta); uvmexp.swpgonly -= swpgonlydelta; mutex_exit(&uvm_swap_data_lock); } } #endif /* defined(VMSWAP) */