From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50365 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030447AbbKFAkp (ORCPT ); Thu, 5 Nov 2015 19:40:45 -0500 Subject: Patch "mm: make sendfile(2) killable" has been added to the 4.2-stable tree To: jack@suse.com, akpm@linux-foundation.org, dvyukov@google.com, gregkh@linuxfoundation.org, torvalds@linux-foundation.org, viro@ZenIV.linux.org.uk Cc: , From: Date: Thu, 05 Nov 2015 16:40:44 -0800 Message-ID: <144677044417427@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mm: make sendfile(2) killable to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-make-sendfile-2-killable.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 296291cdd1629c308114504b850dc343eabc2782 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 22 Oct 2015 13:32:21 -0700 Subject: mm: make sendfile(2) killable From: Jan Kara commit 296291cdd1629c308114504b850dc343eabc2782 upstream. Currently a simple program below issues a sendfile(2) system call which takes about 62 days to complete in my test KVM instance. int fd; off_t off = 0; fd = open("file", O_RDWR | O_TRUNC | O_SYNC | O_CREAT, 0644); ftruncate(fd, 2); lseek(fd, 0, SEEK_END); sendfile(fd, fd, &off, 0xfffffff); Now you should not ask kernel to do a stupid stuff like copying 256MB in 2-byte chunks and call fsync(2) after each chunk but if you do, sysadmin should have a way to stop you. We actually do have a check for fatal_signal_pending() in generic_perform_write() which triggers in this path however because we always succeed in writing something before the check is done, we return value > 0 from generic_perform_write() and thus the information about signal gets lost. Fix the problem by doing the signal check before writing anything. That way generic_perform_write() returns -EINTR, the error gets propagated up and the sendfile loop terminates early. Signed-off-by: Jan Kara Reported-by: Dmitry Vyukov Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2488,6 +2488,11 @@ again: break; } + if (fatal_signal_pending(current)) { + status = -EINTR; + break; + } + status = a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); if (unlikely(status < 0)) @@ -2525,10 +2530,6 @@ again: written += copied; balance_dirty_pages_ratelimited(mapping); - if (fatal_signal_pending(current)) { - status = -EINTR; - break; - } } while (iov_iter_count(i)); return written ? written : status; Patches currently in stable-queue which might be from jack@suse.com are queue-4.2/mm-make-sendfile-2-killable.patch