| Message ID | 1450312575-2690-1-git-send-email-kamal@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/fs/splice.c b/fs/splice.c index f345d53..4eef647 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -871,6 +871,13 @@ EXPORT_SYMBOL(splice_from_pipe_feed); */ int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) { + /* + * Check for signal early to make process killable when there are + * always buffers available + */ + if (signal_pending(current)) + return -ERESTARTSYS; + while (!pipe->nrbufs) { if (!pipe->writers) return 0;
This is a note to let you know that I have just added a patch titled vfs: Make sendfile(2) killable even better to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11-ckt32. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 2dc2063c53071cdc167044c2015e78e49579c254 Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@suse.cz> Date: Mon, 23 Nov 2015 13:09:50 +0100 Subject: vfs: Make sendfile(2) killable even better commit c725bfce7968009756ed2836a8cd7ba4dc163011 upstream. Commit 296291cdd162 (mm: make sendfile(2) killable) fixed an issue where sendfile(2) was doing a lot of tiny writes into a filesystem and thus was unkillable for a long time. However sendfile(2) can be (mis)used to issue lots of writes into arbitrary file descriptor such as evenfd or similar special file descriptors which never hit the standard filesystem write path and thus are still unkillable. E.g. the following example from Dmitry burns CPU for ~16s on my test system without possibility to be killed: int r1 = eventfd(0, 0); int r2 = memfd_create("", 0); unsigned long n = 1<<30; fallocate(r2, 0, 0, n); sendfile(r1, r2, 0, n); There are actually quite a few tests for pending signals in sendfile code however we data to write is always available none of them seems to trigger. So fix the problem by adding a test for pending signal into splice_from_pipe_next() also before the loop waiting for pipe buffers to be available. This should fix all the lockup issues with sendfile of the do-ton-of-tiny-writes nature. Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- fs/splice.c | 7 +++++++ 1 file changed, 7 insertions(+) -- 1.9.1