From: Suren Baghdasaryan <surenb@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com,
josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com,
laurent.dufour@fr.ibm.com, michel@lespinasse.org,
liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz,
minchan@google.com, dave@stgolabs.net,
punit.agrawal@bytedance.com, lstoakes@gmail.com,
hdanton@sina.com, apopple@nvidia.com, peterx@redhat.com,
ying.huang@intel.com, david@redhat.com, yuzhao@google.com,
dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk,
brauner@kernel.org, pasha.tatashin@soleen.com,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH v2 5/6] mm: implement folio wait under VMA lock
Date: Fri, 9 Jun 2023 11:49:14 -0700 [thread overview]
Message-ID: <CAJuCfpE4VYz-Z4_aS3d9-8FGtQ-F4f7adYcJqRk3P3Ks7WPgQA@mail.gmail.com> (raw)
In-Reply-To: <ZIM/O54Q0waFq/tx@casper.infradead.org>
On Fri, Jun 9, 2023 at 8:03 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Thu, Jun 08, 2023 at 05:51:57PM -0700, Suren Baghdasaryan wrote:
> > static inline bool folio_lock_or_retry(struct folio *folio,
> > - struct mm_struct *mm, unsigned int flags)
> > + struct vm_area_struct *vma, unsigned int flags,
> > + bool *lock_dropped)
>
> I hate these double-return-value functions.
>
> How about this for an API:
>
> vm_fault_t folio_lock_fault(struct folio *folio, struct vm_fault *vmf)
> {
> might_sleep();
> if (folio_trylock(folio))
> return 0;
> return __folio_lock_fault(folio, vmf);
> }
>
> Then the users look like ...
>
> > @@ -3580,8 +3581,10 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf)
> > if (!folio_try_get(folio))
> > return 0;
> >
> > - if (!folio_lock_or_retry(folio, vma->vm_mm, vmf->flags)) {
> > + if (!folio_lock_or_retry(folio, vma, vmf->flags, &lock_dropped)) {
> > folio_put(folio);
> > + if (lock_dropped && vmf->flags & FAULT_FLAG_VMA_LOCK)
> > + return VM_FAULT_VMA_UNLOCKED | VM_FAULT_RETRY;
> > return VM_FAULT_RETRY;
> > }
>
> ret = folio_lock_fault(folio, vmf);
> if (ret)
> return ret;
>
> > @@ -3837,9 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> > goto out_release;
> > }
> >
> > - locked = folio_lock_or_retry(folio, vma->vm_mm, vmf->flags);
> > -
> > - if (!locked) {
> > + if (!folio_lock_or_retry(folio, vma, vmf->flags, &lock_dropped)) {
> > + if (lock_dropped && vmf->flags & FAULT_FLAG_VMA_LOCK)
> > + ret |= VM_FAULT_VMA_UNLOCKED;
> > ret |= VM_FAULT_RETRY;
> > goto out_release;
> > }
>
> ret |= folio_lock_fault(folio, vmf);
> if (ret & VM_FAULT_RETRY)
> goto out_release;
>
> ie instead of trying to reconstruct what __folio_lock_fault() did from
> its outputs, we just let folio_lock_fault() tell us what it did.
Thanks for taking a look!
Ok, I think what you are suggesting is to have a new set of
folio_lock_fault()/__folio_lock_fault() functions which return
vm_fault_t directly, __folio_lock_fault() will use
__folio_lock_or_retry() internally and will adjust its return value
based on __folio_lock_or_retry()'s return and the lock releasing rules
described in the comments for __folio_lock_or_retry(). Is my
understanding correct?
next prev parent reply other threads:[~2023-06-09 18:49 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 0:51 [PATCH v2 0/6] Per-vma lock support for swap and userfaults Suren Baghdasaryan
2023-06-09 0:51 ` [PATCH v2 1/6] swap: remove remnants of polling from read_swap_cache_async Suren Baghdasaryan
2023-06-09 1:57 ` Huang, Ying
2023-06-09 3:13 ` Ming Lei
2023-06-09 18:50 ` Suren Baghdasaryan
2023-06-12 4:53 ` Christoph Hellwig
2023-06-09 0:51 ` [PATCH v2 2/6] mm: handle swap page faults under VMA lock if page is uncontended Suren Baghdasaryan
2023-06-09 20:25 ` Peter Xu
2023-06-09 20:35 ` Matthew Wilcox
2023-06-09 20:45 ` Peter Xu
2023-06-09 22:34 ` Suren Baghdasaryan
2023-06-12 13:59 ` Peter Xu
2023-06-12 16:09 ` Suren Baghdasaryan
2023-06-09 0:51 ` [PATCH v2 3/6] mm: add missing VM_FAULT_RESULT_TRACE name for VM_FAULT_COMPLETED Suren Baghdasaryan
2023-06-09 20:34 ` Peter Xu
2023-06-09 0:51 ` [PATCH v2 4/6] mm: drop VMA lock before waiting for migration Suren Baghdasaryan
2023-06-09 20:42 ` Peter Xu
2023-06-09 22:30 ` Suren Baghdasaryan
2023-06-10 1:29 ` Suren Baghdasaryan
2023-06-12 13:36 ` Peter Xu
2023-06-12 16:07 ` Suren Baghdasaryan
2023-06-12 18:34 ` Peter Xu
2023-06-12 18:44 ` Suren Baghdasaryan
2023-06-12 18:57 ` Peter Xu
2023-06-12 13:28 ` Peter Xu
2023-06-12 15:41 ` Suren Baghdasaryan
2023-06-09 0:51 ` [PATCH v2 5/6] mm: implement folio wait under VMA lock Suren Baghdasaryan
2023-06-09 15:03 ` Matthew Wilcox
2023-06-09 18:49 ` Suren Baghdasaryan [this message]
2023-06-09 18:55 ` Suren Baghdasaryan
2023-06-09 19:36 ` Matthew Wilcox
2023-06-09 22:49 ` Suren Baghdasaryan
2023-06-09 20:54 ` Peter Xu
2023-06-09 22:48 ` Suren Baghdasaryan
2023-06-12 13:56 ` Peter Xu
2023-06-09 0:51 ` [PATCH v2 6/6] mm: handle userfaults " Suren Baghdasaryan
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