Messages in this thread | | | Date | Sat, 25 Oct 2014 18:06:09 +0100 | From | Al Viro <> | Subject | Re: [GIT PULL] overlay filesystem v25 |
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On Sat, Oct 25, 2014 at 11:53:52AM +0200, Miklos Szeredi wrote:
> Yes, but it's not about race with copy-up (which the ovl_path_upper() > protects against), but race of two fsync calls with each other. If > there's no synchronization between them, then that od->upperfile does > indeed count as lockless access, no matter that the assignment was > done under lock.
p = global; if (!p) { // outside of lock p = alloc(); grab lock if (!global) { global = p; } else { destroy(p); p = global; } drop lock } is a very common pattern, especially if you look for cases when lock is a spinlock and allocation is blocking (in those cases you'll often see destroy() part done after dropping the lock; that's where what I fucked up in what I'd originally pushed. And it wasn't even needed - fput() under ->i_mutex is OK...)
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