Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964970AbVKGVjG (ORCPT ); Mon, 7 Nov 2005 16:39:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965164AbVKGVjF (ORCPT ); Mon, 7 Nov 2005 16:39:05 -0500 Received: from e6.ny.us.ibm.com ([32.97.182.146]:12260 "EHLO e6.ny.us.ibm.com") by vger.kernel.org with ESMTP id S964970AbVKGVjD (ORCPT ); Mon, 7 Nov 2005 16:39:03 -0500 Subject: [RFC 1/2] Hugetlb fault fixes and reorg From: Adam Litke To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, David Gibson , hugh@veritas.com, rohit.seth@intel.com, "Chen, Kenneth W" , akpm@osdl.org In-Reply-To: <1131397841.25133.90.camel@localhost.localdomain> References: <1131397841.25133.90.camel@localhost.localdomain> Content-Type: text/plain Organization: IBM Date: Mon, 07 Nov 2005 15:38:16 -0600 Message-Id: <1131399496.25133.103.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.4.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4627 Lines: 174 [RFC] Cleanup / small fixes to hugetlb fault handling (Patch originally from David Gibson ) Initial Post: Tue. 25 Oct 2005 On Thu, 2005-10-27 at 16:37 +1000, 'David Gibson' wrote: > This patch makes some slight tweaks / cleanups to the fault handling > path for huge pages in -mm. My main motivation is to make it simpler > to fit COW in, but along the way it addresses a few minor problems > with the existing code: > > - The check against i_size was duplicated: once in > find_lock_huge_page() and again in hugetlb_fault() after taking the > page_table_lock. We only really need the locked one, so remove the > other. > > - find_lock_huge_page() isn't a great name, since it does extra things > not analagous to find_lock_page(). Rename it > find_or_alloc_huge_page() which is closer to the mark. > > Signed-off-by: David Gibson Acked-by: Adam Litke --- hugetlb.c | 77 +++++++++++++++++++++++++++++++++++++------------------------- 1 files changed, 46 insertions(+), 31 deletions(-) diff -upN reference/mm/hugetlb.c current/mm/hugetlb.c --- reference/mm/hugetlb.c +++ current/mm/hugetlb.c @@ -339,30 +339,24 @@ void unmap_hugepage_range(struct vm_area flush_tlb_range(vma, start, end); } -static struct page *find_lock_huge_page(struct address_space *mapping, - unsigned long idx) +static struct page *find_or_alloc_huge_page(struct address_space *mapping, + unsigned long idx) { struct page *page; int err; - struct inode *inode = mapping->host; - unsigned long size; retry: page = find_lock_page(mapping, idx); if (page) - goto out; - - /* Check to make sure the mapping hasn't been truncated */ - size = i_size_read(inode) >> HPAGE_SHIFT; - if (idx >= size) - goto out; + return page; if (hugetlb_get_quota(mapping)) - goto out; + return NULL; + page = alloc_huge_page(); if (!page) { hugetlb_put_quota(mapping); - goto out; + return NULL; } err = add_to_page_cache(page, mapping, idx, GFP_KERNEL); @@ -373,50 +367,49 @@ retry: goto retry; page = NULL; } -out: + return page; } -int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long address, int write_access) +int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *ptep) { - int ret = VM_FAULT_SIGBUS; + int ret; unsigned long idx; unsigned long size; - pte_t *pte; struct page *page; struct address_space *mapping; - pte = huge_pte_alloc(mm, address); - if (!pte) - goto out; - mapping = vma->vm_file->f_mapping; idx = ((address - vma->vm_start) >> HPAGE_SHIFT) + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT)); - /* - * Use page lock to guard against racing truncation - * before we get page_table_lock. - */ - page = find_lock_huge_page(mapping, idx); + /* This returns a locked page, which keeps us safe in the + * event of a race with truncate() */ + page = find_or_alloc_huge_page(mapping, idx); if (!page) - goto out; + return VM_FAULT_SIGBUS; spin_lock(&mm->page_table_lock); + + ret = VM_FAULT_SIGBUS; + size = i_size_read(mapping->host) >> HPAGE_SHIFT; if (idx >= size) goto backout; ret = VM_FAULT_MINOR; - if (!pte_none(*pte)) + + if (!pte_none(*ptep)) + /* oops, someone instantiated this PTE before us */ goto backout; add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE); - set_huge_pte_at(mm, address, pte, make_huge_pte(vma, page)); + set_huge_pte_at(mm, address, ptep, make_huge_pte(vma, page)); + spin_unlock(&mm->page_table_lock); unlock_page(page); -out: + return ret; backout: @@ -424,7 +417,29 @@ backout: hugetlb_put_quota(mapping); unlock_page(page); put_page(page); - goto out; + + return ret; +} + +int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, int write_access) +{ + pte_t *ptep; + pte_t entry; + + ptep = huge_pte_alloc(mm, address); + if (! ptep) + return VM_FAULT_OOM; + + entry = *ptep; + + if (pte_none(entry)) + return hugetlb_no_page(mm, vma, address, ptep); + + /* we could get here if another thread instantiated the pte + * before the test above */ + + return VM_FAULT_MINOR; } int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, -- Adam Litke - (agl at us.ibm.com) IBM Linux Technology Center - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/