4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 only,
8 * as published by the Free Software Foundation.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License version 2 for more details (a copy is included
14 * in the LICENSE file that accompanied this code).
16 * You should have received a copy of the GNU General Public License
17 * version 2 along with this program; If not, see
18 * http://www.gnu.org/licenses/gpl-2.0.html
23 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
24 * Use is subject to license terms.
26 * Copyright (c) 2011, 2017, Intel Corporation.
29 * This file is part of Lustre, http://www.lustre.org/
30 * Lustre is a trademark of Sun Microsystems, Inc.
32 * lustre/lustre/llite/rw26.c
34 * Lustre Lite I/O page cache routines for the 2.5/2.6 kernel version
37 #include <linux/buffer_head.h>
38 #include <linux/errno.h>
40 #include <linux/kernel.h>
42 #include <linux/mpage.h>
43 #include <linux/pagemap.h>
44 #include <linux/string.h>
45 #include <linux/unistd.h>
46 #include <linux/writeback.h>
49 #include <linux/migrate.h>
50 #elif defined(HAVE_MIGRATE_MODE_H)
51 #include <linux/migrate_mode.h>
54 #define DEBUG_SUBSYSTEM S_LLITE
56 #include "llite_internal.h"
57 #include <lustre_compat.h>
60 * Implements Linux VM address_space::invalidatepage() method. This method is
61 * called when the page is truncate from a file, either as a result of
62 * explicit truncate, or when inode is removed from memory (as a result of
63 * final iput(), umount, or memory pressure induced icache shrinking).
65 * [0, offset] bytes of the page remain valid (this is for a case of not-page
66 * aligned truncate). Lustre leaves partially truncated page in the cache,
67 * relying on struct inode::i_size to limit further accesses.
69 static void ll_invalidatepage(struct page *vmpage,
70 #ifdef HAVE_INVALIDATE_RANGE
71 unsigned int offset, unsigned int length
80 struct cl_object *obj;
82 LASSERT(PageLocked(vmpage));
83 LASSERT(!PageWriteback(vmpage));
86 * It is safe to not check anything in invalidatepage/releasepage
87 * below because they are run with page locked and all our io is
88 * happening with locked page too
90 #ifdef HAVE_INVALIDATE_RANGE
91 if (offset == 0 && length == PAGE_SIZE) {
95 /* See the comment in ll_releasepage() */
96 env = cl_env_percpu_get();
97 LASSERT(!IS_ERR(env));
99 inode = vmpage->mapping->host;
100 obj = ll_i2info(inode)->lli_clob;
102 page = cl_vmpage_page(vmpage, obj);
104 cl_page_delete(env, page);
105 cl_page_put(env, page);
108 LASSERT(vmpage->private == 0);
110 cl_env_percpu_put(env);
114 #ifdef HAVE_RELEASEPAGE_WITH_INT
115 #define RELEASEPAGE_ARG_TYPE int
117 #define RELEASEPAGE_ARG_TYPE gfp_t
119 static int ll_releasepage(struct page *vmpage, RELEASEPAGE_ARG_TYPE gfp_mask)
122 struct cl_object *obj;
123 struct cl_page *page;
124 struct address_space *mapping;
127 LASSERT(PageLocked(vmpage));
128 if (PageWriteback(vmpage) || PageDirty(vmpage))
131 mapping = vmpage->mapping;
135 obj = ll_i2info(mapping->host)->lli_clob;
139 /* 1 for caller, 1 for cl_page and 1 for page cache */
140 if (page_count(vmpage) > 3)
143 page = cl_vmpage_page(vmpage, obj);
147 env = cl_env_percpu_get();
148 LASSERT(!IS_ERR(env));
150 if (!cl_page_in_use(page)) {
152 cl_page_delete(env, page);
155 /* To use percpu env array, the call path can not be rescheduled;
156 * otherwise percpu array will be messed if ll_releaspage() called
157 * again on the same CPU.
159 * If this page holds the last refc of cl_object, the following
160 * call path may cause reschedule:
161 * cl_page_put -> cl_page_free -> cl_object_put ->
162 * lu_object_put -> lu_object_free -> lov_delete_raid0.
164 * However, the kernel can't get rid of this inode until all pages have
165 * been cleaned up. Now that we hold page lock here, it's pretty safe
166 * that we won't get into object delete path.
168 LASSERT(cl_object_refc(obj) > 1);
169 cl_page_put(env, page);
171 cl_env_percpu_put(env);
175 #define MAX_DIRECTIO_SIZE 2*1024*1024*1024UL
178 ll_direct_IO_seg(const struct lu_env *env, struct cl_io *io, int rw,
179 struct inode *inode, size_t size, loff_t file_offset,
180 struct page **pages, int page_count)
183 struct cl_2queue *queue;
184 struct cl_object *obj = io->ci_obj;
187 size_t page_size = cl_page_size(obj);
188 size_t orig_size = size;
193 queue = &io->ci_queue;
194 cl_2queue_init(queue);
195 for (i = 0; i < page_count; i++) {
196 LASSERT(!(file_offset & (page_size - 1)));
197 clp = cl_page_find(env, obj, cl_index(obj, file_offset),
198 pages[i], CPT_TRANSIENT);
204 rc = cl_page_own(env, io, clp);
206 LASSERT(clp->cp_state == CPS_FREEING);
207 cl_page_put(env, clp);
213 /* check the page type: if the page is a host page, then do
216 if (clp->cp_type == CPT_CACHEABLE) {
217 struct page *vmpage = cl_page_vmpage(clp);
218 struct page *src_page;
219 struct page *dst_page;
223 src_page = (rw == WRITE) ? pages[i] : vmpage;
224 dst_page = (rw == WRITE) ? vmpage : pages[i];
226 src = ll_kmap_atomic(src_page, KM_USER0);
227 dst = ll_kmap_atomic(dst_page, KM_USER1);
228 memcpy(dst, src, min(page_size, size));
229 ll_kunmap_atomic(dst, KM_USER1);
230 ll_kunmap_atomic(src, KM_USER0);
232 /* make sure page will be added to the transfer by
233 * cl_io_submit()->...->vvp_page_prep_write().
236 set_page_dirty(vmpage);
239 /* do not issue the page for read, since it
240 * may reread a ra page which has NOT uptodate
243 cl_page_disown(env, io, clp);
249 cl_2queue_add(queue, clp);
252 * Set page clip to tell transfer formation engine
253 * that page has to be sent even if it is beyond KMS.
255 cl_page_clip(env, clp, 0, min(size, page_size));
260 /* drop the reference count for cl_page_find */
261 cl_page_put(env, clp);
263 file_offset += page_size;
266 if (rc == 0 && io_pages) {
267 rc = cl_io_submit_sync(env, io,
268 rw == READ ? CRT_READ : CRT_WRITE,
274 cl_2queue_discard(env, io, queue);
275 cl_2queue_disown(env, io, queue);
276 cl_2queue_fini(env, queue);
280 /* ll_free_user_pages - tear down page struct array
281 * @pages: array of page struct pointers underlying target buffer */
282 static void ll_free_user_pages(struct page **pages, int npages, int do_dirty)
286 for (i = 0; i < npages; i++) {
287 if (pages[i] == NULL)
290 set_page_dirty_lock(pages[i]);
294 #if defined(HAVE_DIRECTIO_ITER) || defined(HAVE_IOV_ITER_RW)
297 OBD_FREE_LARGE(pages, npages * sizeof(*pages));
301 #ifdef KMALLOC_MAX_SIZE
302 #define MAX_MALLOC KMALLOC_MAX_SIZE
304 #define MAX_MALLOC (128 * 1024)
307 /* This is the maximum size of a single O_DIRECT request, based on the
308 * kmalloc limit. We need to fit all of the brw_page structs, each one
309 * representing PAGE_SIZE worth of user data, into a single buffer, and
310 * then truncate this to be a full-sized RPC. For 4kB PAGE_SIZE this is
311 * up to 22MB for 128kB kmalloc and up to 682MB for 4MB kmalloc. */
312 #define MAX_DIO_SIZE ((MAX_MALLOC / sizeof(struct brw_page) * PAGE_SIZE) & \
313 ~(DT_MAX_BRW_SIZE - 1))
315 #ifndef HAVE_IOV_ITER_RW
316 # define iov_iter_rw(iter) rw
319 #if defined(HAVE_DIRECTIO_ITER) || defined(HAVE_IOV_ITER_RW)
322 # ifndef HAVE_IOV_ITER_RW
325 struct kiocb *iocb, struct iov_iter *iter
326 # ifndef HAVE_DIRECTIO_2ARGS
331 #ifdef HAVE_DIRECTIO_2ARGS
332 loff_t file_offset = iocb->ki_pos;
334 struct ll_cl_context *lcc;
335 const struct lu_env *env;
337 struct file *file = iocb->ki_filp;
338 struct inode *inode = file->f_mapping->host;
339 ssize_t count = iov_iter_count(iter);
340 ssize_t tot_bytes = 0, result = 0;
341 size_t size = MAX_DIO_SIZE;
343 /* Check EOF by ourselves */
344 if (iov_iter_rw(iter) == READ && file_offset >= i_size_read(inode))
346 /* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
347 if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
350 CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), "
351 "offset=%lld=%llx, pages %zd (max %lu)\n",
352 PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
353 file_offset, file_offset, count >> PAGE_SHIFT,
354 MAX_DIO_SIZE >> PAGE_SHIFT);
356 /* Check that all user buffers are aligned as well */
357 if (iov_iter_alignment(iter) & ~PAGE_MASK)
360 lcc = ll_cl_find(file);
365 LASSERT(!IS_ERR(env));
369 /* 0. Need locking between buffered and direct access. and race with
370 * size changing by concurrent truncates and writes.
371 * 1. Need inode mutex to operate transient pages.
373 if (iov_iter_rw(iter) == READ)
376 while (iov_iter_count(iter)) {
380 count = min_t(size_t, iov_iter_count(iter), size);
381 if (iov_iter_rw(iter) == READ) {
382 if (file_offset >= i_size_read(inode))
385 if (file_offset + count > i_size_read(inode))
386 count = i_size_read(inode) - file_offset;
389 result = iov_iter_get_pages_alloc(iter, &pages, count, &offs);
390 if (likely(result > 0)) {
391 int n = DIV_ROUND_UP(result + offs, PAGE_SIZE);
393 result = ll_direct_IO_seg(env, io, iov_iter_rw(iter),
394 inode, result, file_offset,
396 ll_free_user_pages(pages, n,
397 iov_iter_rw(iter) == READ);
400 if (unlikely(result <= 0)) {
401 /* If we can't allocate a large enough buffer
402 * for the request, shrink it to a smaller
403 * PAGE_SIZE multiple and try again.
404 * We should always be able to kmalloc for a
405 * page worth of page pointers = 4MB on i386. */
406 if (result == -ENOMEM &&
407 size > (PAGE_SIZE / sizeof(*pages)) *
409 size = ((((size / 2) - 1) |
410 ~PAGE_MASK) + 1) & PAGE_MASK;
411 CDEBUG(D_VFSTRACE, "DIO size now %zu\n",
419 iov_iter_advance(iter, result);
421 file_offset += result;
424 if (iov_iter_rw(iter) == READ)
428 struct vvp_io *vio = vvp_env_io(env);
430 /* no commit async for direct IO */
431 vio->u.write.vui_written += tot_bytes;
434 return tot_bytes ? : result;
436 #else /* !HAVE_DIRECTIO_ITER && !HAVE_IOV_ITER_RW */
438 static inline int ll_get_user_pages(int rw, unsigned long user_addr,
439 size_t size, struct page ***pages,
442 int result = -ENOMEM;
444 /* set an arbitrary limit to prevent arithmetic overflow */
445 if (size > MAX_DIRECTIO_SIZE) {
450 *max_pages = (user_addr + size + PAGE_SIZE - 1) >>
452 *max_pages -= user_addr >> PAGE_SHIFT;
454 OBD_ALLOC_LARGE(*pages, *max_pages * sizeof(**pages));
456 down_read(¤t->mm->mmap_sem);
457 result = get_user_pages(current, current->mm, user_addr,
458 *max_pages, (rw == READ), 0, *pages,
460 up_read(¤t->mm->mmap_sem);
461 if (unlikely(result <= 0))
462 OBD_FREE_LARGE(*pages, *max_pages * sizeof(**pages));
469 ll_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
470 loff_t file_offset, unsigned long nr_segs)
472 struct ll_cl_context *lcc;
473 const struct lu_env *env;
475 struct file *file = iocb->ki_filp;
476 struct inode *inode = file->f_mapping->host;
477 ssize_t count = iov_length(iov, nr_segs);
478 ssize_t tot_bytes = 0, result = 0;
479 unsigned long seg = 0;
480 size_t size = MAX_DIO_SIZE;
483 /* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
484 if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
487 CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), "
488 "offset=%lld=%llx, pages %zd (max %lu)\n",
489 PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
490 file_offset, file_offset, count >> PAGE_SHIFT,
491 MAX_DIO_SIZE >> PAGE_SHIFT);
493 /* Check that all user buffers are aligned as well */
494 for (seg = 0; seg < nr_segs; seg++) {
495 if (((unsigned long)iov[seg].iov_base & ~PAGE_MASK) ||
496 (iov[seg].iov_len & ~PAGE_MASK))
500 lcc = ll_cl_find(file);
505 LASSERT(!IS_ERR(env));
509 for (seg = 0; seg < nr_segs; seg++) {
510 size_t iov_left = iov[seg].iov_len;
511 unsigned long user_addr = (unsigned long)iov[seg].iov_base;
514 if (file_offset >= i_size_read(inode))
516 if (file_offset + iov_left > i_size_read(inode))
517 iov_left = i_size_read(inode) - file_offset;
520 while (iov_left > 0) {
522 int page_count, max_pages = 0;
525 bytes = min(size, iov_left);
526 page_count = ll_get_user_pages(rw, user_addr, bytes,
528 if (likely(page_count > 0)) {
529 if (unlikely(page_count < max_pages))
530 bytes = page_count << PAGE_SHIFT;
531 result = ll_direct_IO_seg(env, io, rw, inode,
534 ll_free_user_pages(pages, max_pages, rw==READ);
535 } else if (page_count == 0) {
536 GOTO(out, result = -EFAULT);
540 if (unlikely(result <= 0)) {
541 /* If we can't allocate a large enough buffer
542 * for the request, shrink it to a smaller
543 * PAGE_SIZE multiple and try again.
544 * We should always be able to kmalloc for a
545 * page worth of page pointers = 4MB on i386. */
546 if (result == -ENOMEM &&
547 size > (PAGE_SIZE / sizeof(*pages)) *
549 size = ((((size / 2) - 1) |
552 CDEBUG(D_VFSTRACE, "DIO size now %zu\n",
561 file_offset += result;
568 struct vvp_io *vio = vvp_env_io(env);
570 /* no commit async for direct IO */
571 vio->u.write.vui_written += tot_bytes;
574 RETURN(tot_bytes ? tot_bytes : result);
576 #endif /* HAVE_DIRECTIO_ITER || HAVE_IOV_ITER_RW */
579 * Prepare partially written-to page for a write.
580 * @pg is owned when passed in and disowned when it returns non-zero result to
583 static int ll_prepare_partial_page(const struct lu_env *env, struct cl_io *io,
584 struct cl_page *pg, struct file *file)
586 struct cl_attr *attr = vvp_env_thread_attr(env);
587 struct cl_object *obj = io->ci_obj;
588 struct vvp_page *vpg = cl_object_page_slice(obj, pg);
589 loff_t offset = cl_offset(obj, vvp_index(vpg));
593 cl_object_attr_lock(obj);
594 result = cl_object_attr_get(env, obj, attr);
595 cl_object_attr_unlock(obj);
597 cl_page_disown(env, io, pg);
602 * If are writing to a new page, no need to read old data.
603 * The extent locking will have updated the KMS, and for our
604 * purposes here we can treat it like i_size.
606 if (attr->cat_kms <= offset) {
607 char *kaddr = ll_kmap_atomic(vpg->vpg_page, KM_USER0);
609 memset(kaddr, 0, cl_page_size(obj));
610 ll_kunmap_atomic(kaddr, KM_USER0);
611 GOTO(out, result = 0);
614 if (vpg->vpg_defer_uptodate) {
615 vpg->vpg_ra_used = 1;
616 GOTO(out, result = 0);
619 result = ll_io_read_page(env, io, pg, file);
623 /* ll_io_read_page() disowns the page */
624 result = cl_page_own(env, io, pg);
626 if (!PageUptodate(cl_page_vmpage(pg))) {
627 cl_page_disown(env, io, pg);
630 } else if (result == -ENOENT) {
631 /* page was truncated */
640 static int ll_tiny_write_begin(struct page *vmpage)
642 /* Page must be present, up to date, dirty, and not in writeback. */
643 if (!vmpage || !PageUptodate(vmpage) || !PageDirty(vmpage) ||
644 PageWriteback(vmpage))
650 static int ll_write_begin(struct file *file, struct address_space *mapping,
651 loff_t pos, unsigned len, unsigned flags,
652 struct page **pagep, void **fsdata)
654 struct ll_cl_context *lcc = NULL;
655 const struct lu_env *env = NULL;
656 struct cl_io *io = NULL;
657 struct cl_page *page = NULL;
659 struct cl_object *clob = ll_i2info(mapping->host)->lli_clob;
660 pgoff_t index = pos >> PAGE_SHIFT;
661 struct page *vmpage = NULL;
662 unsigned from = pos & (PAGE_SIZE - 1);
663 unsigned to = from + len;
667 CDEBUG(D_PAGE, "Writing %lu of %d to %d bytes\n", index, from, len);
669 lcc = ll_cl_find(file);
671 vmpage = grab_cache_page_nowait(mapping, index);
672 result = ll_tiny_write_begin(vmpage);
679 if (file->f_flags & O_DIRECT && io->ci_designated_mirror > 0) {
680 /* direct IO failed because it couldn't clean up cached pages,
681 * this causes a problem for mirror write because the cached
682 * page may belong to another mirror, which will result in
683 * problem submitting the I/O. */
684 GOTO(out, result = -EBUSY);
688 /* To avoid deadlock, try to lock page first. */
689 vmpage = grab_cache_page_nowait(mapping, index);
691 if (unlikely(vmpage == NULL ||
692 PageDirty(vmpage) || PageWriteback(vmpage))) {
693 struct vvp_io *vio = vvp_env_io(env);
694 struct cl_page_list *plist = &vio->u.write.vui_queue;
696 /* if the page is already in dirty cache, we have to commit
697 * the pages right now; otherwise, it may cause deadlock
698 * because it holds page lock of a dirty page and request for
699 * more grants. It's okay for the dirty page to be the first
700 * one in commit page list, though. */
701 if (vmpage != NULL && plist->pl_nr > 0) {
707 /* commit pages and then wait for page lock */
708 result = vvp_io_write_commit(env, io);
712 if (vmpage == NULL) {
713 vmpage = grab_cache_page_write_begin(mapping, index,
716 GOTO(out, result = -ENOMEM);
720 page = cl_page_find(env, clob, vmpage->index, vmpage, CPT_CACHEABLE);
722 GOTO(out, result = PTR_ERR(page));
724 lcc->lcc_page = page;
725 lu_ref_add(&page->cp_reference, "cl_io", io);
727 cl_page_assume(env, io, page);
728 if (!PageUptodate(vmpage)) {
730 * We're completely overwriting an existing page,
731 * so _don't_ set it up to date until commit_write
733 if (from == 0 && to == PAGE_SIZE) {
734 CL_PAGE_HEADER(D_PAGE, env, page, "full page write\n");
735 POISON_PAGE(vmpage, 0x11);
737 /* TODO: can be optimized at OSC layer to check if it
738 * is a lockless IO. In that case, it's not necessary
739 * to read the data. */
740 result = ll_prepare_partial_page(env, io, page, file);
742 /* vmpage should have been unlocked */
746 if (result == -EAGAIN)
755 if (vmpage != NULL) {
759 /* On tiny_write failure, page and io are always null. */
760 if (!IS_ERR_OR_NULL(page)) {
761 lu_ref_del(&page->cp_reference, "cl_io", io);
762 cl_page_put(env, page);
765 io->ci_result = result;
773 static int ll_tiny_write_end(struct file *file, struct address_space *mapping,
774 loff_t pos, unsigned int len, unsigned int copied,
777 struct cl_page *clpage = (struct cl_page *) vmpage->private;
778 loff_t kms = pos+copied;
779 loff_t to = kms & (PAGE_SIZE-1) ? kms & (PAGE_SIZE-1) : PAGE_SIZE;
781 struct lu_env *env = cl_env_get(&refcheck);
791 /* This page is dirty in cache, so it should have a cl_page pointer
792 * set in vmpage->private.
794 LASSERT(clpage != NULL);
799 /* Update the underlying size information in the OSC/LOV objects this
802 cl_page_touch(env, clpage, to);
805 cl_env_put(env, &refcheck);
808 /* Must return page unlocked. */
814 static int ll_write_end(struct file *file, struct address_space *mapping,
815 loff_t pos, unsigned len, unsigned copied,
816 struct page *vmpage, void *fsdata)
818 struct ll_cl_context *lcc = fsdata;
819 const struct lu_env *env;
822 struct cl_page *page;
823 unsigned from = pos & (PAGE_SIZE - 1);
830 CDEBUG(D_VFSTRACE, "pos %llu, len %u, copied %u\n", pos, len, copied);
833 result = ll_tiny_write_end(file, mapping, pos, len, copied,
838 LASSERT(lcc != NULL);
840 page = lcc->lcc_page;
842 vio = vvp_env_io(env);
844 LASSERT(cl_page_is_owned(page, io));
846 struct cl_page_list *plist = &vio->u.write.vui_queue;
848 lcc->lcc_page = NULL; /* page will be queued */
850 /* Add it into write queue */
851 cl_page_list_add(plist, page);
852 if (plist->pl_nr == 1) /* first page */
853 vio->u.write.vui_from = from;
856 vio->u.write.vui_to = from + copied;
858 /* To address the deadlock in balance_dirty_pages() where
859 * this dirty page may be written back in the same thread. */
860 if (PageDirty(vmpage))
863 /* We may have one full RPC, commit it soon */
864 if (plist->pl_nr >= PTLRPC_MAX_BRW_PAGES)
867 CL_PAGE_DEBUG(D_PAGE, env, page,
868 "queued page: %d.\n", plist->pl_nr);
870 cl_page_disown(env, io, page);
872 lcc->lcc_page = NULL;
873 lu_ref_del(&page->cp_reference, "cl_io", io);
874 cl_page_put(env, page);
876 /* page list is not contiguous now, commit it now */
879 if (unplug || io->u.ci_rw.rw_sync)
880 result = vvp_io_write_commit(env, io);
883 io->ci_result = result;
887 RETURN(result >= 0 ? copied : result);
890 #ifdef CONFIG_MIGRATION
891 static int ll_migratepage(struct address_space *mapping,
892 struct page *newpage, struct page *page
893 #ifdef HAVE_MIGRATEPAGE_4ARGS
894 , enum migrate_mode mode
898 /* Always fail page migration until we have a proper implementation */
903 const struct address_space_operations ll_aops = {
904 .readpage = ll_readpage,
905 .direct_IO = ll_direct_IO,
906 .writepage = ll_writepage,
907 .writepages = ll_writepages,
908 .set_page_dirty = __set_page_dirty_nobuffers,
909 .write_begin = ll_write_begin,
910 .write_end = ll_write_end,
911 .invalidatepage = ll_invalidatepage,
912 .releasepage = (void *)ll_releasepage,
913 #ifdef CONFIG_MIGRATION
914 .migratepage = ll_migratepage,