From: Oleg Nesterov Date: Tue, 30 Apr 2013 22:28:15 +0000 (-0700) Subject: coredump: introduce dump_interrupted() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=528f827ee0bb508af5c9466562f474675540473e;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git coredump: introduce dump_interrupted() By discussion with Mandeep. Change dump_write(), dump_seek() and do_coredump() to check signal_pending() and abort if it is true. dump_seek() does this only before f_op->llseek(), otherwise it relies on dump_write(). We need this change to ensure that the coredump won't delay suspend, and to ensure it reacts to SIGKILL "quickly enough", a core dump can take a lot of time. In particular this can help oom-killer. We add the new trivial helper, dump_interrupted() to add the comments and to simplify the potential freezer changes. Perhaps it will have more callers. Ideally it should do try_to_freeze() but then we need the unpleasant changes in dump_write() and wait_for_dump_helpers(). It is not trivial to change dump_write() to restart if f_op->write() fails because of freezing(). We need to handle the short writes, we need to clear TIF_SIGPENDING (and we can't rely on recalc_sigpending() unless we change it to check PF_DUMPCORE). And if the buggy f_op->write() sets TIF_SIGPENDING we can not distinguish this case from the race with freeze_task() + __thaw_task(). So we simply accept the fact that the freezer can truncate a core-dump but at least you can reliably suspend. Hopefully we can tolerate this unlikely case and the necessary complications doesn't worth a trouble. But if we decide to make the coredumping freezable later we can do this on top of this change. Signed-off-by: Oleg Nesterov Acked-by: Mandeep Singh Baines Cc: Neil Horman Cc: "Rafael J. Wysocki" Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/coredump.c b/fs/coredump.c index acc4448c28e7..aa8ac69a548f 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -418,6 +418,17 @@ static void coredump_finish(struct mm_struct *mm, bool core_dumped) mm->core_state = NULL; } +static bool dump_interrupted(void) +{ + /* + * SIGKILL or freezing() interrupt the coredumping. Perhaps we + * can do try_to_freeze() and check __fatal_signal_pending(), + * but then we need to teach dump_write() to restart and clear + * TIF_SIGPENDING. + */ + return signal_pending(current); +} + static void wait_for_dump_helpers(struct file *file) { struct pipe_inode_info *pipe; @@ -641,7 +652,7 @@ void do_coredump(siginfo_t *siginfo) goto close_fail; if (displaced) put_files_struct(displaced); - core_dumped = binfmt->core_dump(&cprm); + core_dumped = !dump_interrupted() && binfmt->core_dump(&cprm); if (ispipe && core_pipe_limit) wait_for_dump_helpers(cprm.file); @@ -669,7 +680,9 @@ fail: */ int dump_write(struct file *file, const void *addr, int nr) { - return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr; + return !dump_interrupted() && + access_ok(VERIFY_READ, addr, nr) && + file->f_op->write(file, addr, nr, &file->f_pos) == nr; } EXPORT_SYMBOL(dump_write); @@ -678,7 +691,8 @@ int dump_seek(struct file *file, loff_t off) int ret = 1; if (file->f_op->llseek && file->f_op->llseek != no_llseek) { - if (file->f_op->llseek(file, off, SEEK_CUR) < 0) + if (dump_interrupted() || + file->f_op->llseek(file, off, SEEK_CUR) < 0) return 0; } else { char *buf = (char *)get_zeroed_page(GFP_KERNEL);