From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63FC5C3A5A6 for ; Thu, 19 Sep 2019 22:24:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C2E921924 for ; Thu, 19 Sep 2019 22:24:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="HRWd40WC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407219AbfISWYi (ORCPT ); Thu, 19 Sep 2019 18:24:38 -0400 Received: from mail-pl1-f202.google.com ([209.85.214.202]:50991 "EHLO mail-pl1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407218AbfISWYh (ORCPT ); Thu, 19 Sep 2019 18:24:37 -0400 Received: by mail-pl1-f202.google.com with SMTP id x7so3063159plr.17 for ; Thu, 19 Sep 2019 15:24:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=ZaSw360C7R9ABa3P7kf32xECvn5Wcc6BLiRVTROxdnA=; b=HRWd40WCmmtbyzFz9AcjHdk0MS70paekhXr7POjPADm2pwWRjrHf29ExqH3v7uu8jf 1Wt1uvgBfjnGDhMSLok/6qIxi4FxdtQ8Jprq1Nm04aBPf3lFzYDoFv6/XvQRZ+37NDDd zJYSOo1qDvhoeRtJH8CzQMV/CoFQJVBtz4Py4Vo6kue94F9h9MdhCTNVGJzfkg0BR2at KKZbKwigL9QHH85/9sdFnWo8aBsUGAnDEy8E0f1kmX4GHlXhm3Anvrs+r+k9vnvotP88 Vkki5suEBBK7B/AdUtJwoh3KsikEDsFbhPvwX4sc8eSkDI1Jo10lK1Hn60zymk/1k0M0 FFYQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=ZaSw360C7R9ABa3P7kf32xECvn5Wcc6BLiRVTROxdnA=; b=VZvzScf6mRR+YGdFYF7GvdlXI9lKtJb43IKn6xk/lb+6gasZKpwZ72LO5vl/+9SKXU ncZDcGFCViiHW+iYZgHajIB1UURRhjbfrCIBDRdVryUF3JS/YezTfE5xkdvLZ1YbT1tP pB24bqioISgA5Nc1AJZsXSpcZX/5FICkSkI3nojImsPaO/8jC6RgQakr71I/DXGyxsL+ xotSkFEExJnkQrk2Yr419/ThzKYm5PjjFmG5JvVqrZETxH58TXBGR0wbb7u1rdYXcYeG uWyzCD/TKRpc/QZVF0KjA/ZJ0TEFOcsGOx3pyGZ8V1cVv6/j0CVoT3/1GQZD7TvKXXc4 lUJw== X-Gm-Message-State: APjAAAUQuj8jEGHn9WJgCS7cRCWaa6aIupdZoKCpCRoc8A5qY6iuaD25 bZUIunfoMteeEQ5AUf5Bhlr4asrfFiKKbcsuIQ== X-Google-Smtp-Source: APXvYqwfc8yxLwCZc6wKvz9fWNFVKZPE8eWAhu53muWyqbtMwjq/N34SeqSjZ3hkbi1FcjXbLOWy7lsh3snYf+QZPg== X-Received: by 2002:a63:e812:: with SMTP id s18mr10992828pgh.291.1568931875693; Thu, 19 Sep 2019 15:24:35 -0700 (PDT) Date: Thu, 19 Sep 2019 15:24:18 -0700 In-Reply-To: <20190919222421.27408-1-almasrymina@google.com> Message-Id: <20190919222421.27408-5-almasrymina@google.com> Mime-Version: 1.0 References: <20190919222421.27408-1-almasrymina@google.com> X-Mailer: git-send-email 2.23.0.351.gc4317032e6-goog Subject: [PATCH v5 4/7] hugetlb: disable region_add file_region coalescing From: Mina Almasry To: mike.kravetz@oracle.com Cc: shuah@kernel.org, almasrymina@google.com, rientjes@google.com, shakeelb@google.com, gthelen@google.com, akpm@linux-foundation.org, khalid.aziz@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, mkoutny@suse.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org A follow up patch in this series adds hugetlb cgroup uncharge info the file_region entries in resv->regions. The cgroup uncharge info may differ for different regions, so they can no longer be coalesced at region_add time. So, disable region coalescing in region_add in this patch. Behavior change: Say a resv_map exists like this [0->1], [2->3], and [5->6]. Then a region_chg/add call comes in region_chg/add(f=0, t=5). Old code would generate resv->regions: [0->5], [5->6]. New code would generate resv->regions: [0->1], [1->2], [2->3], [3->5], [5->6]. Special care needs to be taken to handle the resv->adds_in_progress variable correctly. In the past, only 1 region would be added for every region_chg and region_add call. But now, each call may add multiple regions, so we can no longer increment adds_in_progress by 1 in region_chg, or decrement adds_in_progress by 1 after region_add or region_abort. Instead, region_chg calls add_reservation_in_range() to count the number of regions needed and allocates those, and that info is passed to region_add and region_abort to decrement adds_in_progress correctly. Signed-off-by: Mina Almasry --- mm/hugetlb.c | 273 +++++++++++++++++++++++++++++---------------------- 1 file changed, 158 insertions(+), 115 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bac1cbdd027c..d03b048084a3 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -244,6 +244,12 @@ struct file_region { long to; }; +/* Helper that removes a struct file_region from the resv_map cache and returns + * it for use. + */ +static struct file_region * +get_file_region_entry_from_cache(struct resv_map *resv, long from, long to); + /* Must be called with resv->lock held. Calling this with count_only == true * will count the number of pages to be added but will not modify the linked * list. @@ -251,51 +257,61 @@ struct file_region { static long add_reservation_in_range(struct resv_map *resv, long f, long t, bool count_only) { - long chg = 0; + long add = 0; struct list_head *head = &resv->regions; + long last_accounted_offset = f; struct file_region *rg = NULL, *trg = NULL, *nrg = NULL; - /* Locate the region we are before or in. */ - list_for_each_entry (rg, head, link) - if (f <= rg->to) - break; - - /* Round our left edge to the current segment if it encloses us. */ - if (f > rg->from) - f = rg->from; - - chg = t - f; + /* In this loop, we essentially handle an entry for the range + * last_accounted_offset -> rg->from, at every iteration, with some + * bounds checking. + */ + list_for_each_entry_safe(rg, trg, head, link) { + /* Skip irrelevant regions that start before our range. */ + if (rg->from < f) { + /* If this region ends after the last accounted offset, + * then we need to update last_accounted_offset. + */ + if (rg->to > last_accounted_offset) + last_accounted_offset = rg->to; + continue; + } - /* Check for and consume any regions we now overlap with. */ - nrg = rg; - list_for_each_entry_safe (rg, trg, rg->link.prev, link) { - if (&rg->link == head) - break; + /* When we find a region that starts beyond our range, we've + * finished. + */ if (rg->from > t) break; - /* We overlap with this area, if it extends further than - * us then we must extend ourselves. Account for its - * existing reservation. + /* Add an entry for last_accounted_offset -> rg->from, and + * update last_accounted_offset. */ - if (rg->to > t) { - chg += rg->to - t; - t = rg->to; + if (rg->from > last_accounted_offset) { + add += rg->from - last_accounted_offset; + if (!count_only) { + nrg = get_file_region_entry_from_cache( + resv, last_accounted_offset, rg->from); + list_add(&nrg->link, rg->link.prev); + } } - chg -= rg->to - rg->from; - if (!count_only && rg != nrg) { - list_del(&rg->link); - kfree(rg); - } + last_accounted_offset = rg->to; } - if (!count_only) { - nrg->from = f; - nrg->to = t; + /* Handle the case where our range extends beyond + * last_accounted_offset. + */ + if (last_accounted_offset < t) { + add += t - last_accounted_offset; + if (!count_only) { + nrg = get_file_region_entry_from_cache( + resv, last_accounted_offset, t); + list_add(&nrg->link, rg->link.prev); + } + last_accounted_offset = t; } - return chg; + return add; } /* @@ -305,46 +321,24 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t, * must exist in the cache due to the previous call to region_chg with * the same range. * + * regions_needed is the out value provided by a previous + * call to region_chg. + * * Return the number of new huge pages added to the map. This * number is greater than or equal to zero. */ -static long region_add(struct resv_map *resv, long f, long t) +static long region_add(struct resv_map *resv, long f, long t, + long regions_needed) { - struct list_head *head = &resv->regions; - struct file_region *rg, *nrg; long add = 0; spin_lock(&resv->lock); - /* Locate the region we are either in or before. */ - list_for_each_entry(rg, head, link) - if (f <= rg->to) - break; - /* - * If no region exists which can be expanded to include the - * specified range, pull a region descriptor from the cache - * and use it for this range. - */ - if (&rg->link == head || t < rg->from) { - VM_BUG_ON(resv->region_cache_count <= 0); - - resv->region_cache_count--; - nrg = list_first_entry(&resv->region_cache, struct file_region, - link); - list_del(&nrg->link); - - nrg->from = f; - nrg->to = t; - list_add(&nrg->link, rg->link.prev); - - add += t - f; - goto out_locked; - } + VM_BUG_ON(resv->region_cache_count < regions_needed); add = add_reservation_in_range(resv, f, t, false); + resv->adds_in_progress -= regions_needed; -out_locked: - resv->adds_in_progress--; spin_unlock(&resv->lock); VM_BUG_ON(add < 0); return add; @@ -361,42 +355,55 @@ static long region_add(struct resv_map *resv, long f, long t) * as a placeholder, so that the subsequent region_add * call will have all the regions it needs and will not fail. * + * out_regions_needed is the number of regions added to the + * resv->region_cache_count. This value needs to be provided to a follow up + * call to region_add or region_abort for proper accounting. + * * Returns the number of huge pages that need to be added to the existing * reservation map for the range [f, t). This number is greater or equal to * zero. -ENOMEM is returned if a new file_region structure or cache entry * is needed and can not be allocated. */ -static long region_chg(struct resv_map *resv, long f, long t) +static long region_chg(struct resv_map *resv, long f, long t, + long *out_regions_needed) { + struct file_region *trg = NULL; long chg = 0; + /* Allocate the maximum number of regions we're going to need for this + * reservation. The maximum number of regions we're going to need is + * (t - f) / 2 + 1, which corresponds to a region with alternating + * reserved and unreserved pages. + */ + *out_regions_needed = (t - f) / 2 + 1; +retry: spin_lock(&resv->lock); -retry_locked: - resv->adds_in_progress++; + + /* Count how many hugepages in this range are NOT respresented. */ + chg = add_reservation_in_range(resv, f, t, true); /* * Check for sufficient descriptors in the cache to accommodate * the number of in progress add operations. */ - if (resv->adds_in_progress > resv->region_cache_count) { - struct file_region *trg; - - VM_BUG_ON(resv->adds_in_progress - resv->region_cache_count > 1); + if (resv->region_cache_count < *out_regions_needed) { /* Must drop lock to allocate a new descriptor. */ - resv->adds_in_progress--; spin_unlock(&resv->lock); - trg = kmalloc(sizeof(*trg), GFP_KERNEL); - if (!trg) - return -ENOMEM; + while (resv->region_cache_count < *out_regions_needed + 1) { + trg = kmalloc(sizeof(*trg), GFP_KERNEL); + if (!trg) + return -ENOMEM; - spin_lock(&resv->lock); - list_add(&trg->link, &resv->region_cache); - resv->region_cache_count++; - goto retry_locked; + spin_lock(&resv->lock); + list_add(&trg->link, &resv->region_cache); + resv->region_cache_count++; + spin_unlock(&resv->lock); + } + goto retry; } - chg = add_reservation_in_range(resv, f, t, true); + resv->adds_in_progress += *out_regions_needed; spin_unlock(&resv->lock); return chg; @@ -407,17 +414,19 @@ static long region_chg(struct resv_map *resv, long f, long t) * of the resv_map keeps track of the operations in progress between * calls to region_chg and region_add. Operations are sometimes * aborted after the call to region_chg. In such cases, region_abort - * is called to decrement the adds_in_progress counter. + * is called to decrement the adds_in_progress counter. regions_needed + * is the value returned by the region_chg call, it is used to decrement + * the adds_in_progress counter. * * NOTE: The range arguments [f, t) are not needed or used in this * routine. They are kept to make reading the calling code easier as * arguments will match the associated region_chg call. */ -static void region_abort(struct resv_map *resv, long f, long t) +static void region_abort(struct resv_map *resv, long f, long t, + long regions_needed) { spin_lock(&resv->lock); - VM_BUG_ON(!resv->region_cache_count); - resv->adds_in_progress--; + resv->adds_in_progress -= regions_needed; spin_unlock(&resv->lock); } @@ -1866,9 +1875,10 @@ enum vma_resv_mode { VMA_END_RESV, VMA_ADD_RESV, }; -static long __vma_reservation_common(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr, - enum vma_resv_mode mode) +static long +__vma_reservation_common(struct hstate *h, struct vm_area_struct *vma, + unsigned long addr, enum vma_resv_mode mode, + long *out_regions_needed, long in_regions_needed) { struct resv_map *resv; pgoff_t idx; @@ -1881,20 +1891,24 @@ static long __vma_reservation_common(struct hstate *h, idx = vma_hugecache_offset(h, vma, addr); switch (mode) { case VMA_NEEDS_RESV: - ret = region_chg(resv, idx, idx + 1); + VM_BUG_ON(!out_regions_needed); + ret = region_chg(resv, idx, idx + 1, out_regions_needed); break; case VMA_COMMIT_RESV: - ret = region_add(resv, idx, idx + 1); + VM_BUG_ON(in_regions_needed == -1); + ret = region_add(resv, idx, idx + 1, in_regions_needed); break; case VMA_END_RESV: - region_abort(resv, idx, idx + 1); + VM_BUG_ON(in_regions_needed == -1); + region_abort(resv, idx, idx + 1, in_regions_needed); ret = 0; break; case VMA_ADD_RESV: + VM_BUG_ON(in_regions_needed == -1); if (vma->vm_flags & VM_MAYSHARE) - ret = region_add(resv, idx, idx + 1); + ret = region_add(resv, idx, idx + 1, in_regions_needed); else { - region_abort(resv, idx, idx + 1); + region_abort(resv, idx, idx + 1, in_regions_needed); ret = region_del(resv, idx, idx + 1); } break; @@ -1927,28 +1941,32 @@ static long __vma_reservation_common(struct hstate *h, return ret < 0 ? ret : 0; } -static long vma_needs_reservation(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr) +static long vma_needs_reservation(struct hstate *h, struct vm_area_struct *vma, + unsigned long addr, long *out_regions_needed) { - return __vma_reservation_common(h, vma, addr, VMA_NEEDS_RESV); + return __vma_reservation_common(h, vma, addr, VMA_NEEDS_RESV, + out_regions_needed, -1); } -static long vma_commit_reservation(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr) +static long vma_commit_reservation(struct hstate *h, struct vm_area_struct *vma, + unsigned long addr, long regions_needed) { - return __vma_reservation_common(h, vma, addr, VMA_COMMIT_RESV); + return __vma_reservation_common(h, vma, addr, VMA_COMMIT_RESV, NULL, + regions_needed); } -static void vma_end_reservation(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr) +static void vma_end_reservation(struct hstate *h, struct vm_area_struct *vma, + unsigned long addr, long regions_needed) { - (void)__vma_reservation_common(h, vma, addr, VMA_END_RESV); + (void)__vma_reservation_common(h, vma, addr, VMA_END_RESV, NULL, + regions_needed); } -static long vma_add_reservation(struct hstate *h, - struct vm_area_struct *vma, unsigned long addr) +static long vma_add_reservation(struct hstate *h, struct vm_area_struct *vma, + unsigned long addr, long regions_needed) { - return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV); + return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV, NULL, + regions_needed); } /* @@ -1966,8 +1984,10 @@ static void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma, unsigned long address, struct page *page) { + long regions_needed = 0; if (unlikely(PagePrivate(page))) { - long rc = vma_needs_reservation(h, vma, address); + long rc = + vma_needs_reservation(h, vma, address, ®ions_needed); if (unlikely(rc < 0)) { /* @@ -1983,7 +2003,8 @@ static void restore_reserve_on_error(struct hstate *h, */ ClearPagePrivate(page); } else if (rc) { - rc = vma_add_reservation(h, vma, address); + rc = vma_add_reservation(h, vma, address, + regions_needed); if (unlikely(rc < 0)) /* * See above comment about rare out of @@ -1991,7 +2012,7 @@ static void restore_reserve_on_error(struct hstate *h, */ ClearPagePrivate(page); } else - vma_end_reservation(h, vma, address); + vma_end_reservation(h, vma, address, regions_needed); } } @@ -2005,6 +2026,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, long gbl_chg; int ret, idx; struct hugetlb_cgroup *h_cg; + long regions_needed = 0; idx = hstate_index(h); /* @@ -2012,7 +2034,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, * has a reservation for the page to be allocated. A return * code of zero indicates a reservation exists (no change). */ - map_chg = gbl_chg = vma_needs_reservation(h, vma, addr); + map_chg = gbl_chg = + vma_needs_reservation(h, vma, addr, ®ions_needed); if (map_chg < 0) return ERR_PTR(-ENOMEM); @@ -2026,7 +2049,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, if (map_chg || avoid_reserve) { gbl_chg = hugepage_subpool_get_pages(spool, 1); if (gbl_chg < 0) { - vma_end_reservation(h, vma, addr); + vma_end_reservation(h, vma, addr, regions_needed); return ERR_PTR(-ENOSPC); } @@ -2072,7 +2095,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, set_page_private(page, (unsigned long)spool); - map_commit = vma_commit_reservation(h, vma, addr); + map_commit = vma_commit_reservation(h, vma, addr, regions_needed); if (unlikely(map_chg > map_commit)) { /* * The page was added to the reservation map between @@ -2096,7 +2119,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, out_subpool_put: if (map_chg || avoid_reserve) hugepage_subpool_put_pages(spool, 1); - vma_end_reservation(h, vma, addr); + vma_end_reservation(h, vma, addr, regions_needed); return ERR_PTR(-ENOSPC); } @@ -3780,6 +3803,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, spinlock_t *ptl; unsigned long haddr = address & huge_page_mask(h); bool new_page = false; + long regions_needed = 0; /* * Currently, we are forced to kill the process in the event the @@ -3897,12 +3921,12 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, * the spinlock. */ if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) { - if (vma_needs_reservation(h, vma, haddr) < 0) { + if (vma_needs_reservation(h, vma, haddr, ®ions_needed) < 0) { ret = VM_FAULT_OOM; goto backout_unlocked; } /* Just decrements count, does not deallocate */ - vma_end_reservation(h, vma, haddr); + vma_end_reservation(h, vma, haddr, regions_needed); } ptl = huge_pte_lock(h, mm, ptep); @@ -3992,6 +4016,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, struct address_space *mapping; int need_wait_lock = 0; unsigned long haddr = address & huge_page_mask(h); + long regions_needed = 0; ptep = huge_pte_offset(mm, haddr, huge_page_size(h)); if (ptep) { @@ -4046,12 +4071,12 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, * consumed. */ if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) { - if (vma_needs_reservation(h, vma, haddr) < 0) { + if (vma_needs_reservation(h, vma, haddr, ®ions_needed) < 0) { ret = VM_FAULT_OOM; goto out_mutex; } /* Just decrements count, does not deallocate */ - vma_end_reservation(h, vma, haddr); + vma_end_reservation(h, vma, haddr, regions_needed); if (!(vma->vm_flags & VM_MAYSHARE)) pagecache_page = hugetlbfs_pagecache_page(h, @@ -4514,7 +4539,7 @@ int hugetlb_reserve_pages(struct inode *inode, struct hugepage_subpool *spool = subpool_inode(inode); struct resv_map *resv_map; struct hugetlb_cgroup *h_cg; - long gbl_reserve; + long gbl_reserve, regions_needed = 0; /* This should never happen */ if (from > to) { @@ -4544,7 +4569,7 @@ int hugetlb_reserve_pages(struct inode *inode, */ resv_map = inode_resv_map(inode); - chg = region_chg(resv_map, from, to); + chg = region_chg(resv_map, from, to, ®ions_needed); } else { /* Private mapping. */ @@ -4614,7 +4639,7 @@ int hugetlb_reserve_pages(struct inode *inode, * else has to be done for private mappings here */ if (!vma || vma->vm_flags & VM_MAYSHARE) { - long add = region_add(resv_map, from, to); + long add = region_add(resv_map, from, to, regions_needed); if (unlikely(chg > add)) { /* @@ -4636,7 +4661,7 @@ int hugetlb_reserve_pages(struct inode *inode, if (!vma || vma->vm_flags & VM_MAYSHARE) /* Don't call region_abort if region_chg failed */ if (chg >= 0) - region_abort(resv_map, from, to); + region_abort(resv_map, from, to, regions_needed); if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) kref_put(&resv_map->refs, resv_map_release); return ret; @@ -5060,3 +5085,21 @@ void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason) spin_unlock(&hugetlb_lock); } } + +static struct file_region * +get_file_region_entry_from_cache(struct resv_map *resv, long from, long to) +{ + struct file_region *nrg = NULL; + + VM_BUG_ON(resv->region_cache_count <= 0); + + resv->region_cache_count--; + nrg = list_first_entry(&resv->region_cache, struct file_region, link); + VM_BUG_ON(!nrg); + list_del(&nrg->link); + + nrg->from = from; + nrg->to = to; + + return nrg; +} -- 2.23.0.351.gc4317032e6-goog