Jan Kara 296291cdd1 mm: make sendfile(2) killable
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 <jack@suse.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-10-23 17:55:10 +09:00
..
2015-09-10 13:29:01 -07:00
2015-10-23 17:55:10 +09:00
2015-06-24 17:49:45 -07:00
2015-09-11 16:42:39 -07:00
2015-04-15 16:35:18 -07:00
2015-09-11 16:42:39 -07:00
2015-10-16 11:42:28 -07:00
2015-09-08 14:35:59 -07:00
2015-10-16 11:42:28 -07:00
2015-09-08 15:35:28 -07:00
2015-10-01 21:42:35 -04:00
2015-02-11 17:06:02 -08:00
2015-09-10 13:29:01 -07:00
2015-09-10 13:29:01 -07:00
2015-09-10 13:29:01 -07:00
2015-09-08 15:35:28 -07:00
2015-09-10 13:29:01 -07:00
2015-09-08 15:35:28 -07:00
2015-09-10 13:29:01 -07:00
2015-09-08 15:35:28 -07:00