On Thu, Jun 13, 2019 at 04:13:15PM +0200, Miklos Szeredi wrote: > On Wed, Jun 12, 2019 at 8:31 PM J . Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > > > How do opens for execute work? I guess they create a struct file with > > FMODE_EXEC and FMODE_RDONLY set and they decrement i_writecount. Do > > they also increment i_readcount? Reading do_open_execat and alloc_file, > > looks like it does, so, good, they should conflict with write leases, > > which sounds right. > > Right, but then why this: > > > > + /* Eliminate deny writes from actual writers count */ > > > + if (wcount < 0) > > > + wcount = 0; > > It's basically a no-op, as you say. And it doesn't make any sense > logically, since denying writes *should* deny write leases as well... Yes. I feel like the negative writecount case is a little nonobvious, so maybe replace that by a comment, something like this?: --b. diff --git a/fs/locks.c b/fs/locks.c index 2056595751e8..379829b913c1 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1772,11 +1772,12 @@ check_conflicting_open(struct file *filp, const long arg, int flags) if (arg == F_RDLCK && wcount > 0) return -EAGAIN; - /* Eliminate deny writes from actual writers count */ - if (wcount < 0) - wcount = 0; - - /* Make sure that only read/write count is from lease requestor */ + /* + * Make sure that only read/write count is from lease requestor. + * Note that this will result in denying write leases when wcount + * is negative, which is what we want. (We shouldn't grant + * write leases on files open for execution.) + */ if (filp->f_mode & FMODE_WRITE) self_wcount = 1; else if (filp->f_mode & FMODE_READ)
