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Thu, 26 Mar 2020 00:02:51 -0700 (PDT) Date: Thu, 26 Mar 2020 00:02:33 -0700 In-Reply-To: <20200326070236.235835-1-walken@google.com> Message-Id: <20200326070236.235835-6-walken@google.com> Mime-Version: 1.0 References: <20200326070236.235835-1-walken@google.com> X-Mailer: git-send-email 2.25.1.696.g5e7596f4ac-goog Subject: [PATCH 5/8] mmap locking API: convert nested write lock sites From: Michel Lespinasse To: Andrew Morton , linux-mm Cc: LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Matthew Wilcox , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han , Michel Lespinasse X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Add API for nested write locks and convert the few call sites doing that. Signed-off-by: Michel Lespinasse --- arch/um/include/asm/mmu_context.h | 5 +++-- include/linux/mmap_lock.h | 11 +++++++++++ kernel/fork.c | 4 ++-- 3 files changed, 16 insertions(+), 4 deletions(-) diff --git a/arch/um/include/asm/mmu_context.h b/arch/um/include/asm/mmu_context.h index 62262c5c7785..cc15173f7518 100644 --- a/arch/um/include/asm/mmu_context.h +++ b/arch/um/include/asm/mmu_context.h @@ -8,6 +8,7 @@ #include #include +#include #include @@ -47,9 +48,9 @@ static inline void activate_mm(struct mm_struct *old, struct mm_struct *new) * when the new ->mm is used for the first time. */ __switch_mm(&new->context.id); - down_write_nested(&new->mmap_sem, 1); + mmap_write_lock_nested(new, 1); uml_setup_stubs(new); - mmap_write_unlock(new); + mmap_write_unlock_nested(new); } static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index cffd25afe92b..40a972a26857 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -11,6 +11,11 @@ static inline void mmap_write_lock(struct mm_struct *mm) down_write(&mm->mmap_sem); } +static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass) +{ + down_write_nested(&mm->mmap_sem, subclass); +} + static inline int mmap_write_lock_killable(struct mm_struct *mm) { return down_write_killable(&mm->mmap_sem); @@ -26,6 +31,12 @@ static inline void mmap_write_unlock(struct mm_struct *mm) up_write(&mm->mmap_sem); } +/* Pairs with mmap_write_lock_nested() */ +static inline void mmap_write_unlock_nested(struct mm_struct *mm) +{ + up_write(&mm->mmap_sem); +} + static inline void mmap_downgrade_write_lock(struct mm_struct *mm) { downgrade_write(&mm->mmap_sem); diff --git a/kernel/fork.c b/kernel/fork.c index c321910d46e8..3460308b2213 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -497,7 +497,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, /* * Not linked in yet - no deadlock potential: */ - down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); + mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING); /* No ordering required: file already has been exposed. */ RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); @@ -612,7 +612,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, /* a new mm has just been created */ retval = arch_dup_mmap(oldmm, mm); out: - mmap_write_unlock(mm); + mmap_write_unlock_nested(mm); flush_tlb_mm(oldmm); mmap_write_unlock(oldmm); dup_userfaultfd_complete(&uf);