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Thu, 29 Jun 2023 20:45:50 -0700 (PDT) MIME-Version: 1.0 References: <20230630020436.1066016-1-surenb@google.com> <20230630020436.1066016-5-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 29 Jun 2023 20:45:39 -0700 Message-ID: Subject: Re: [PATCH v6 4/6] mm: change folio_lock_or_retry to use vm_fault directly To: Matthew Wilcox 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: E63D180016 X-Stat-Signature: 6opkbyb4ntxr88eoqost66kj3rekk6gn X-HE-Tag: 1688096751-465701 X-HE-Meta: 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 +hMsvI4H KvmbaaHwjryQLzNqydlv8z2/h6g+3WM2fqReLKP7f77GYZaUIJgoTCouO2zyuYvmNcgWjEXVvkh6ieOk6PHTZ3zhtqW05Jz/f4wZPvD3WbHFh+qwOTWmv5gqxx4o9YeDl/3t3KgMI/lES+fJ+9MtyrRUJknh7FGnG7OuWZ5GezfrZ0gNoRLjY6VTfZSxPwp9I34kGSt2m9WXeGc40Bx7nRnU7Wm+mPLgG0qLEgsPq3rfJbahm3j6J1FA+o7e4SMw9sDBkzFaW7HEeNU+jW1JXXpbEIZRAzK6lU1K6B9C5uLQomV0l2CXQj3PpKORKtmSBFbQNAAq4p7LR1urhiq4OR3xJLA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 29, 2023 at 8:36=E2=80=AFPM Matthew Wilcox wrote: > > On Thu, Jun 29, 2023 at 07:04:33PM -0700, Suren Baghdasaryan wrote: > > Change folio_lock_or_retry to accept vm_fault struct and return the > > vm_fault_t directly. > > I thought we decided to call this folio_lock_fault()? > > > +static inline vm_fault_t folio_lock_or_retry(struct folio *folio, > > + struct vm_fault *vmf) > > { > > might_sleep(); > > - return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, f= lags); > > + return folio_trylock(folio) ? 0 : __folio_lock_or_retry(folio, vm= f); > > No, don't use the awful ternary operator. The || form is used > everywhere else. Ok, but folio_trylock() returns a boolean while folio_lock_or_retry should return vm_fault_t. How exactly do you suggest changing this? Something like this perhaps: static inline vm_fault_t folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf) { might_sleep(); if (folio_trylock(folio)) return 0; return __folio_lock_or_retry(folio, mm, flags); } ? > > > /* > > * Return values: > > - * true - folio is locked; mmap_lock is still held. > > - * false - folio is not locked. > > + * 0 - folio is locked. > > + * VM_FAULT_RETRY - folio is not locked. > > I don't think we want to be so prescriptive here. It returns non-zero > if the folio is not locked. The precise value is not something that > callers should depend on. Ok, I'll change it to "non-zero" here. >