execve: improve interactivity with large arguments

This adds a preemption point during the copying of the argument and
environment strings for execve, in copy_strings().  There is already
a preemption point in the count() loop, so this doesn't add any new
points in the abstract sense.

When the total argument+environment strings are very large, the time
spent copying them can be much more than a normal user time slice.
So this change improves the interactivity of the rest of the system
when one process is doing an execve with very large arguments.

Signed-off-by: Roland McGrath <roland@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/exec.c b/fs/exec.c
index 1b63237fc6dced1062c392523fed094ce7dacc56..6f2d777431a8c2a6dbeac1cd9b5f2b3c3f9a4790 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -419,6 +419,8 @@ static int copy_strings(int argc, const char __user *const __user *argv,
                while (len > 0) {
                        int offset, bytes_to_copy;
 
+                       cond_resched();
+
                        offset = pos % PAGE_SIZE;
                        if (offset == 0)
                                offset = PAGE_SIZE;