Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754665AbZAGX5T (ORCPT ); Wed, 7 Jan 2009 18:57:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751665AbZAGX5L (ORCPT ); Wed, 7 Jan 2009 18:57:11 -0500 Received: from smtp-out.google.com ([216.239.45.13]:50614 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751594AbZAGX5J (ORCPT ); Wed, 7 Jan 2009 18:57:09 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding: x-gmailtapped-by:x-gmailtapped; b=gow52/s/51k+SyK052lezrcJLgt6lwFK2Y/4EuIBMWnPERMTGgiG6by/aAEHi7aIk mQkz/+kHjVD2InoISnveQ== MIME-Version: 1.0 In-Reply-To: <4576.1230006925@turing-police.cc.vt.edu> References: <4576.1230006925@turing-police.cc.vt.edu> Date: Wed, 7 Jan 2009 15:57:02 -0800 Message-ID: <604427e00901071557o33d93e8fh995bea170b78f338@mail.gmail.com> Subject: Re: 28-rc9-mmotm1219 page_fault-retry-with-nopage_retry.patch hoses xmms From: Ying Han To: Valdis.Kletnieks@vt.edu Cc: Andrew Morton , linux-kernel@vger.kernel.org, Mike Waychison , Rohit Seth Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-GMailtapped-By: 172.28.16.146 X-GMailtapped: yinghan Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7371 Lines: 250 Hi Valdis: I made a fix for the patch and i tested with xmms on ubuntu8.10. Please give a try with it. thanks diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9e268b6..f4bbd9b 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -593,6 +593,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigne unsigned long flags; int sig; #endif + unsigned int retry_flag = FAULT_FLAG_RETRY; tsk = current; mm = tsk->mm; @@ -690,6 +691,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigne down_read(&mm->mmap_sem); } +retry: vma = find_vma(mm, address); if (!vma) goto bad_area; @@ -716,6 +718,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigne good_area: si_code = SEGV_ACCERR; write = 0; + write |= retry_flag; switch (error_code & (PF_PROT|PF_WRITE)) { default: /* 3: write, present */ /* fall through */ @@ -744,6 +747,21 @@ good_area: goto do_sigbus; BUG(); } + + /* + * Here we retry fault once and switch to synchronous mode. The + * main reason is to prevent us from the cases of starvation. + * The retry logic open a starvation hole in which case pages might + * be removed or changed after the retry. + */ + if (fault & VM_FAULT_RETRY) { + if (write & FAULT_FLAG_RETRY) { + retry_flag &= ~FAULT_FLAG_RETRY; + goto retry; + } + BUG(); + } + if (fault & VM_FAULT_MAJOR) tsk->maj_flt++; else diff --git a/include/linux/mm.h b/include/linux/mm.h index 4a3d28c..be770f9 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -144,6 +144,7 @@ extern pgprot_t protection_map[16]; #define FAULT_FLAG_WRITE 0x01 /* Fault was a write access */ #define FAULT_FLAG_NONLINEAR 0x02 /* Fault was via a nonlinear mapping */ +#define FAULT_FLAG_RETRY 0x04 /* Retry major fault */ /* * This interface is used by x86 PAT code to identify a pfn mapping that is @@ -707,6 +708,7 @@ static inline int page_mapped(struct page *page) #define VM_FAULT_MINOR 0 /* For backwards compat. Remove me quickly. */ +#define VM_FAULT_RETRY 0x0010 #define VM_FAULT_OOM 0x0001 #define VM_FAULT_SIGBUS 0x0002 #define VM_FAULT_MAJOR 0x0004 diff --git a/mm/filemap.c b/mm/filemap.c index 2f55a1e..aed5a3f 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -714,6 +714,58 @@ repeat: EXPORT_SYMBOL(find_lock_page); /** + * find_lock_page_retry - locate, pin and lock a pagecache page + * @mapping: the address_space to search + * @offset: the page index + * @vma: vma in which the fault was taken + * @ppage: zero if page not present, otherwise point to the page in pagecache + * @retry: 1 indicate caller tolerate a retry. + * + * If retry flag is on, and page is already locked by someone else, return + * a hint of retry. + * + * Return *ppage==NULL if page is not in pagecache. Otherwise return *ppage + * points to the page in the pagecache with ret=VM_FAULT_RETRY indicate a + * hint to caller for retry, or ret=0 which means page is succefully + * locked. + */ +unsigned find_lock_page_retry(struct address_space *mapping, pgoff_t offset, + struct vm_area_struct *vma, struct page **ppage, + int retry) +{ + unsigned int ret = 0; + struct page *page; + +repeat: + page = find_get_page(mapping, offset); + if (page) { + if (!retry) + lock_page(page); + else { + if (!trylock_page(page)) { + struct mm_struct *mm = vma->vm_mm; + + up_read(&mm->mmap_sem); + wait_on_page_locked(page); + down_read(&mm->mmap_sem); + + page_cache_release(page); + return VM_FAULT_RETRY; + } + } + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + page_cache_release(page); + goto repeat; + } + VM_BUG_ON(page->index != offset); + } + *ppage = page; + return ret; +} +EXPORT_SYMBOL(find_lock_page_retry); + +/** * find_or_create_page - locate or add a pagecache page * @mapping: the page's address_space * @index: the page's index into the mapping @@ -1452,6 +1504,8 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_ pgoff_t size; int did_readaround = 0; int ret = 0; + int retry_flag = vmf->flags & FAULT_FLAG_RETRY; + int retry_ret; size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (vmf->pgoff >= size) @@ -1466,6 +1520,8 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_ */ retry_find: page = find_lock_page(mapping, vmf->pgoff); + +retry_find_nopage: /* * For sequential accesses, we use the generic readahead logic. */ @@ -1473,9 +1529,12 @@ retry_find: if (!page) { page_cache_sync_readahead(mapping, ra, file, vmf->pgoff, 1); - page = find_lock_page(mapping, vmf->pgoff); + retry_ret = find_lock_page_retry(mapping, vmf->pgoff, + vma, &page, retry_flag); if (!page) goto no_cached_page; + if (retry_ret == VM_FAULT_RETRY) + return retry_ret; } if (PageReadahead(page)) { page_cache_async_readahead(mapping, ra, file, page, @@ -1512,14 +1571,18 @@ retry_find: start = vmf->pgoff - ra_pages / 2; do_page_cache_readahead(mapping, file, start, ra_pages); } - page = find_lock_page(mapping, vmf->pgoff); + retry_ret = find_lock_page_retry(mapping, vmf->pgoff, + vma, &page, retry_flag); if (!page) goto no_cached_page; + if (retry_ret == VM_FAULT_RETRY) + return retry_ret; } if (!did_readaround) ra->mmap_miss--; +retry_page_update: /* * We have a locked page in the page cache, now we need to check * that it's up-to-date. If not, it is going to be due to an error. @@ -1554,8 +1617,23 @@ no_cached_page: * In the unlikely event that someone removed it in the * meantime, we'll just come back here and read it again. */ - if (error >= 0) - goto retry_find; + if (error >= 0) { + /* + * If caller cannot tolerate a retry in the ->fault path + * go back to check the page again. + */ + if (!retry_flag) + goto retry_find; + + retry_ret = find_lock_page_retry(mapping, vmf->pgoff, + vma, &page, retry_flag); + if (!page) + goto retry_find_nopage; + else if (retry_ret == VM_FAULT_RETRY) + return retry_ret; + else + goto retry_page_update; + } /* * An error return from page_cache_read can result if the diff --git a/mm/memory.c b/mm/memory.c index 3f8fa06..534ba1d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2572,6 +2572,13 @@ static int __do_fault(struct mm_struct *mm, struct vm_a vmf.page = NULL; ret = vma->vm_ops->fault(vma, &vmf); + + /* page may be available, but we have to restart the process + * because mmap_sem was dropped during the ->fault + */ + if (ret & VM_FAULT_RETRY) + return ret; + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) return ret; @@ -2713,8 +2720,10 @@ static int do_linear_fault(struct mm_struct *mm, struct { pgoff_t pgoff = (((address & PAGE_MASK) - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; - unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0); + int write = write_access & ~FAULT_FLAG_RETRY; + unsigned int flags = (write ? FAULT_FLAG_WRITE : 0); + flags |= (write_access & FAULT_FLAG_RETRY); pte_unmap(page_table); return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); } -- 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/