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([2409:8a28:f4f:a9a4:11bc:4825:e7fe:2e0e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-218a1e4ffd9sm21702895ad.142.2024.12.14.22.29.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 14 Dec 2024 22:30:01 -0800 (PST) Message-ID: <18bc52f4-ab02-495f-8f8f-87f69ea5b914@bytedance.com> Date: Sun, 15 Dec 2024 14:29:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/12] Revert "mm: pgtable: make ptlock be freed by RCU" Content-Language: en-US To: Yu Zhao Cc: peterz@infradead.org, tglx@linutronix.de, david@redhat.com, jannh@google.com, hughd@google.com, willy@infradead.org, muchun.song@linux.dev, vbabka@kernel.org, lorenzo.stoakes@oracle.com, akpm@linux-foundation.org, rientjes@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1fdb3ee32e6958ad82229941b2213ef76b7c4705.1734164094.git.zhengqi.arch@bytedance.com> From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024/12/15 02:29, Yu Zhao wrote: > On Sat, Dec 14, 2024 at 2:03 AM Qi Zheng wrote: >> >> This reverts commit 2f3443770437e49abc39af26962d293851cbab6d. >> >> Signed-off-by: Qi Zheng > > Bloating struct pt_lock is unnecessary. Glad to see it's reverted. Indeed! > > Acked-by: Yu Zhao Thanks! Once the review of this patch series is completed, we can simply drop "mm: pgtable: make ptlock be freed by RCU" from mm tree. > > >> --- >> include/linux/mm.h | 2 +- >> include/linux/mm_types.h | 9 +-------- >> mm/memory.c | 22 ++++++---------------- >> 3 files changed, 8 insertions(+), 25 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index e7902980439cc..5e73e53c34e9e 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -2988,7 +2988,7 @@ void ptlock_free(struct ptdesc *ptdesc); >> >> static inline spinlock_t *ptlock_ptr(struct ptdesc *ptdesc) >> { >> - return &(ptdesc->ptl->ptl); >> + return ptdesc->ptl; >> } >> #else /* ALLOC_SPLIT_PTLOCKS */ >> static inline void ptlock_cache_init(void) >> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >> index df8f5152644ec..5d8779997266e 100644 >> --- a/include/linux/mm_types.h >> +++ b/include/linux/mm_types.h >> @@ -434,13 +434,6 @@ FOLIO_MATCH(flags, _flags_2a); >> FOLIO_MATCH(compound_head, _head_2a); >> #undef FOLIO_MATCH >> >> -#if ALLOC_SPLIT_PTLOCKS >> -struct pt_lock { >> - spinlock_t ptl; >> - struct rcu_head rcu; >> -}; >> -#endif >> - >> /** >> * struct ptdesc - Memory descriptor for page tables. >> * @__page_flags: Same as page flags. Powerpc only. >> @@ -485,7 +478,7 @@ struct ptdesc { >> union { >> unsigned long _pt_pad_2; >> #if ALLOC_SPLIT_PTLOCKS >> - struct pt_lock *ptl; >> + spinlock_t *ptl; >> #else >> spinlock_t ptl; >> #endif >> diff --git a/mm/memory.c b/mm/memory.c >> index d9af83dd86bbf..83765632e20b0 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -7041,34 +7041,24 @@ static struct kmem_cache *page_ptl_cachep; >> >> void __init ptlock_cache_init(void) >> { >> - page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(struct pt_lock), 0, >> + page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0, >> SLAB_PANIC, NULL); >> } >> >> bool ptlock_alloc(struct ptdesc *ptdesc) >> { >> - struct pt_lock *pt_lock; >> + spinlock_t *ptl; >> >> - pt_lock = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL); >> - if (!pt_lock) >> + ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL); >> + if (!ptl) >> return false; >> - ptdesc->ptl = pt_lock; >> + ptdesc->ptl = ptl; >> return true; >> } >> >> -static void ptlock_free_rcu(struct rcu_head *head) >> -{ >> - struct pt_lock *pt_lock; >> - >> - pt_lock = container_of(head, struct pt_lock, rcu); >> - kmem_cache_free(page_ptl_cachep, pt_lock); >> -} >> - >> void ptlock_free(struct ptdesc *ptdesc) >> { >> - struct pt_lock *pt_lock = ptdesc->ptl; >> - >> - call_rcu(&pt_lock->rcu, ptlock_free_rcu); >> + kmem_cache_free(page_ptl_cachep, ptdesc->ptl); >> } >> #endif >> >> -- >> 2.20.1 >>