From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate1.de.ibm.com (8.13.6/8.13.6) with ESMTP id k3OCYtMH074430 for ; Mon, 24 Apr 2006 12:34:55 GMT Received: from d12av02.megacenter.de.ibm.com (d12av02.megacenter.de.ibm.com [9.149.165.228]) by d12nrmr1607.megacenter.de.ibm.com (8.12.10/NCO/VER6.8) with ESMTP id k3OCa0Gv123304 for ; Mon, 24 Apr 2006 14:36:00 +0200 Received: from d12av02.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av02.megacenter.de.ibm.com (8.12.11/8.13.3) with ESMTP id k3OCYtKw006033 for ; Mon, 24 Apr 2006 14:34:55 +0200 Date: Mon, 24 Apr 2006 14:34:59 +0200 From: Martin Schwidefsky Subject: [patch 4/8] Page host virtual assist: mlocked pages. Message-ID: <20060424123459.GE15817@skybase> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org From: Martin Schwidefsky From: Hubertus Franke From: Himanshu Raj Return-Path: To: linux-mm@kvack.org, akpm@osdl.org, frankeh@watson.ibm.com, rhim@cc.gatech.edu List-ID: [patch 4/8] Page host virtual assist: mlocked pages. Add code to get mlock() working with page host virtual assist. The problem with mlock is that locked pages may not be removed from page cache. That means they need to be stable. page_hva_make_volatile needs a way to check if a page has been locked. To avoid traversing vma lists - which would hurt performance a lot - a field is added in the struct address space. This bit is set in mlock_fixup if a vma gets mlocked. The bit never gets removed - once a file had an mlocked vma all future pages added to it will stay stable. To complete the picture make_pages_present has to check for the host page state besides making the pages present in the linux page table. This is done by a call to get_user_pages with a pages parameter. Since the VM_LOCKED bit of the vma will be set prior to the call to get_user_pages an additional check is needed in the try_to_unmap_one function. If get_user_pages finds a discarded page it needs to get removed from the page cache and all page tables dispite the fact that VM_LOCKED is set. After get_user_pages is back the pages are stable. The references to the pages can be returned immediatly, the pages will stay in stable because the mlocked bit is not set for the mapping. Signed-off-by: Martin Schwidefsky --- include/linux/fs.h | 1 + mm/memory.c | 25 +++++++++++++++++++++++++ mm/mlock.c | 2 ++ mm/page_hva.c | 5 ++++- mm/rmap.c | 3 ++- 5 files changed, 34 insertions(+), 2 deletions(-) diff -urpN linux-2.6/include/linux/fs.h linux-2.6-patched/include/linux/fs.h --- linux-2.6/include/linux/fs.h 2006-04-24 12:51:20.000000000 +0200 +++ linux-2.6-patched/include/linux/fs.h 2006-04-24 12:51:28.000000000 +0200 @@ -394,6 +394,7 @@ struct address_space { spinlock_t private_lock; /* for use by the address_space */ struct list_head private_list; /* ditto */ struct address_space *assoc_mapping; /* ditto */ + unsigned int mlocked; /* set if VM_LOCKED vmas present */ } __attribute__((aligned(sizeof(long)))); /* * On most architectures that alignment is already the case; but diff -urpN linux-2.6/mm/memory.c linux-2.6-patched/mm/memory.c --- linux-2.6/mm/memory.c 2006-04-24 12:51:28.000000000 +0200 +++ linux-2.6-patched/mm/memory.c 2006-04-24 12:51:28.000000000 +0200 @@ -2403,6 +2403,31 @@ int make_pages_present(unsigned long add BUG_ON(addr >= end); BUG_ON(end > vma->vm_end); len = (end+PAGE_SIZE-1)/PAGE_SIZE-addr/PAGE_SIZE; + + if (page_hva_enabled() && (vma->vm_flags & VM_LOCKED)) { + int rlen = len; + ret = 0; + while (rlen > 0) { + struct page *page_refs[32]; + int chunk, cret, i; + + chunk = rlen < 32 ? rlen : 32; + cret = get_user_pages(current, current->mm, addr, + chunk, write, 0, + page_refs, NULL); + if (cret > 0) { + for (i = 0; i < cret; i++) + page_cache_release(page_refs[i]); + ret += cret; + } + if (cret < chunk) + return ret ? : cret; + addr += 32*PAGE_SIZE; + rlen -= 32; + } + return ret == len ? 0 : -1; + } + ret = get_user_pages(current, current->mm, addr, len, write, 0, NULL, NULL); if (ret < 0) diff -urpN linux-2.6/mm/mlock.c linux-2.6-patched/mm/mlock.c --- linux-2.6/mm/mlock.c 2006-03-20 06:53:29.000000000 +0100 +++ linux-2.6-patched/mm/mlock.c 2006-04-24 12:51:28.000000000 +0200 @@ -60,6 +60,8 @@ success: */ pages = (end - start) >> PAGE_SHIFT; if (newflags & VM_LOCKED) { + if (vma->vm_file && vma->vm_file->f_mapping) + vma->vm_file->f_mapping->mlocked = 1; pages = -pages; if (!(newflags & VM_IO)) ret = make_pages_present(start, end); diff -urpN linux-2.6/mm/page_hva.c linux-2.6-patched/mm/page_hva.c --- linux-2.6/mm/page_hva.c 2006-04-24 12:51:28.000000000 +0200 +++ linux-2.6-patched/mm/page_hva.c 2006-04-24 12:51:28.000000000 +0200 @@ -27,6 +27,8 @@ */ static inline int __page_hva_discardable(struct page *page,unsigned int offset) { + struct address_space *mapping; + /* * There are several conditions that prevent a page from becoming * volatile. The first check is for the page bits. @@ -41,7 +43,8 @@ static inline int __page_hva_discardable * it volatile. It will be freed soon. If the mapping ever had * locked pages all pages of the mapping will stay stable. */ - if (!page_mapping(page)) + mapping = page_mapping(page); + if (!mapping || mapping->mlocked) return 0; /* diff -urpN linux-2.6/mm/rmap.c linux-2.6-patched/mm/rmap.c --- linux-2.6/mm/rmap.c 2006-04-24 12:51:28.000000000 +0200 +++ linux-2.6-patched/mm/rmap.c 2006-04-24 12:51:28.000000000 +0200 @@ -559,7 +559,8 @@ static int try_to_unmap_one(struct page * If it's recently referenced (perhaps page_referenced * skipped over this mm) then we should reactivate it. */ - if ((vma->vm_flags & VM_LOCKED) || + if (((vma->vm_flags & VM_LOCKED) && + !unlikely(page_hva_enabled() && PageDiscarded(page))) || (ptep_clear_flush_young(vma, address, pte) && !migration)) { ret = SWAP_FAIL; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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