| Message ID | CA+55aFzOU93LvBLWw5vvLLFFsMiHJuH8Yc=Zn4N6NSDwp5acUg@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 16 Feb 2015 16:21:30 -0800 Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Mon, Feb 16, 2015 at 4:02 PM, Jeff Layton <jlayton@poochiereds.net> wrote: > > > > Now that I look, it may be best to just revert this whole set for now. > > Linus, are you amenable to doing that? > > Sure. But I'd prefer seeing how hard it would be to fix things first. > If this was at the end of the release cycle, I'd revert it > immediately. As it is, try to see how had it is. > Fair enough. I just didn't want to hold up -rc1. I should be able to fix up the bugs within the next day or so. I've got a small stack of fixes that I'll send along soon. > The bugs I found might be as easy as just the attached (TOTALLY > UNTESTED) patch. The comment about a higher-priority process and > sched_resced() is just complete and utter crap. If somebody holds a > read lock and upgrades it to a write lock, there is absolutely *zero* > reason to let some higher-priority process get the write-lock first - > that's just simply semantically wrong bullshit. "Higher priority" does > not mean "can punch through locks". > The patch is pretty close to one that I have, so yes I think that will fix it. There is one bug in the first loop though -- "old_fl" should be set to "fl" there. I'm also happy to remove the "drop the spinlock" thing. It's bothered me for a while... > Removing the silly incorrect counts should be trivial too. There > really are not very many users, and they can just walk the list > instead. > Yes, that's a straightforward revert. > Now, if you've found other more fundamental bugs that look unfixable, > then that might mean that reverting it all is unavoidable, but.. > > Linus No, I don't think there's anything unfixable there. I did find another bug, but it's simple to fix.
diff --git a/fs/locks.c b/fs/locks.c index 4753218f308e..8fbf81429608 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -867,12 +867,11 @@ static int posix_locks_deadlock(struct file_lock *caller_fl, */ static int flock_lock_file(struct file *filp, struct file_lock *request) { - struct file_lock *new_fl = NULL; + struct file_lock *new_fl = NULL, *old_fl = NULL; struct file_lock *fl; struct file_lock_context *ctx; struct inode *inode = file_inode(filp); int error = 0; - bool found = false; LIST_HEAD(dispose); ctx = locks_get_lock_context(inode); @@ -894,27 +893,18 @@ static int flock_lock_file(struct file *filp, struct file_lock *request) continue; if (request->fl_type == fl->fl_type) goto out; - found = true; - locks_delete_lock_ctx(fl, &ctx->flc_flock_cnt, &dispose); + old_fl = NULL; break; } if (request->fl_type == F_UNLCK) { - if ((request->fl_flags & FL_EXISTS) && !found) + if (old_fl) + locks_delete_lock_ctx(old_fl, &ctx->flc_flock_cnt, &dispose); + else if (request->fl_flags & FL_EXISTS) error = -ENOENT; goto out; } - /* - * If a higher-priority process was blocked on the old file lock, - * give it the opportunity to lock the file. - */ - if (found) { - spin_unlock(&ctx->flc_lock); - cond_resched(); - spin_lock(&ctx->flc_lock); - } - find_conflict: list_for_each_entry(fl, &ctx->flc_flock, fl_list) { if (!flock_locks_conflict(request, fl)) @@ -928,6 +918,8 @@ find_conflict: } if (request->fl_flags & FL_ACCESS) goto out; + if (old_fl) + locks_delete_lock_ctx(old_fl, &ctx->flc_flock_cnt, &dispose); locks_copy_lock(new_fl, request); locks_insert_lock_ctx(new_fl, &ctx->flc_flock_cnt, &ctx->flc_flock); new_fl = NULL;