From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 13 May 2003 16:20:38 -0700 From: William Lee Irwin III Subject: Re: Race between vmtruncate and mapped areas? Message-ID: <20030513232038.GB8978@holomorphy.com> References: <154080000.1052858685@baldur.austin.ibm.com> <3EC15C6D.1040403@kolumbus.fi> <199610000.1052864784@baldur.austin.ibm.com> <20030513224929.GX8978@holomorphy.com> <220550000.1052866808@baldur.austin.ibm.com> <20030513231139.GZ8978@holomorphy.com> <247390000.1052867776@baldur.austin.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <247390000.1052867776@baldur.austin.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: Mika Penttil? , Linux Memory Management , Linux Kernel List-ID: On Tuesday, May 13, 2003 16:11:39 -0700 William Lee Irwin III wrote: >> Okay, what's stopping filemap_nopage() from fetching the page from >> pagecache after one of the mm->mmap_sem's is dropped but before >> truncate_inode_pages() removes the page? The fault path is only locked >> out for one mm during one part of the operation. I can see taking >> ->i_sem in do_no_page() fixing it, but not ->mmap_sem in vmtruncate() >> (but of course that's _far_ too heavy-handed to merge at all). On Tue, May 13, 2003 at 06:16:16PM -0500, Dave McCracken wrote: > mmap_sem is held for read across the entire fault, so by the time > vmtruncate_list() can call zap_page_range() the page has been instantiated > in the page table and will get removed. That's not quite the answer, inode->i_size is. The mmap_sem works because then ->i_size can't be sampled by filemap_nopage() before the pagetable wiping operation starts. -- wli -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org