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charset=us-ascii Content-Disposition: inline In-Reply-To: <20241122174416.1367052-3-surenb@google.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D958140006 X-Stat-Signature: tmdozyw7t5dnpq4qsj4ytbeaahaupn4t X-Rspam-User: X-HE-Tag: 1732496287-280762 X-HE-Meta: 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 HPtCWcYF 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000049, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Nov 22, 2024 at 09:44:16AM -0800, Suren Baghdasaryan wrote: >Add helper functions to speculatively perform operations without >read-locking mmap_lock, expecting that mmap_lock will not be >write-locked and mm is not modified from under us. > >Suggested-by: Peter Zijlstra >Signed-off-by: Suren Baghdasaryan >Reviewed-by: Liam R. Howlett >--- >Changes since v2 [1] >- Added SOB, per Liam Howlett > >[1] https://lore.kernel.org/all/20241121162826.987947-3-surenb@google.com/ > > include/linux/mmap_lock.h | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > >diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h >index 9715326f5a85..8ac3041df053 100644 >--- a/include/linux/mmap_lock.h >+++ b/include/linux/mmap_lock.h >@@ -71,6 +71,7 @@ static inline void mmap_assert_write_locked(const struct mm_struct *mm) > } > > #ifdef CONFIG_PER_VMA_LOCK >+ > static inline void mm_lock_seqcount_init(struct mm_struct *mm) > { > seqcount_init(&mm->mm_lock_seq); >@@ -87,11 +88,39 @@ static inline void mm_lock_seqcount_end(struct mm_struct *mm) > do_raw_write_seqcount_end(&mm->mm_lock_seq); > } > >-#else >+static inline bool mmap_lock_speculate_try_begin(struct mm_struct *mm, unsigned int *seq) >+{ >+ /* >+ * Since mmap_lock is a sleeping lock, and waiting for it to become >+ * unlocked is more or less equivalent with taking it ourselves, don't >+ * bother with the speculative path if mmap_lock is already write-locked >+ * and take the slow path, which takes the lock. >+ */ >+ return raw_seqcount_try_begin(&mm->mm_lock_seq, *seq); >+} >+ >+static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq) >+{ >+ return do_read_seqcount_retry(&mm->mm_lock_seq, seq); Just curious why we don't use read_seqcount_retry(). Looks this is the only user outside seqlock.h. >+} >+ >+#else /* CONFIG_PER_VMA_LOCK */ >+ > static inline void mm_lock_seqcount_init(struct mm_struct *mm) {} > static inline void mm_lock_seqcount_begin(struct mm_struct *mm) {} > static inline void mm_lock_seqcount_end(struct mm_struct *mm) {} >-#endif >+ >+static inline bool mmap_lock_speculate_try_begin(struct mm_struct *mm, unsigned int *seq) >+{ >+ return false; >+} >+ >+static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq) >+{ >+ return true; >+} >+ >+#endif /* CONFIG_PER_VMA_LOCK */ > > static inline void mmap_init_lock(struct mm_struct *mm) > { >-- >2.47.0.371.ga323438b13-goog -- Wei Yang Help you, Help me