From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: + mmap-locking-api-add-mmap_read_trylock_non_owner.patch added to -mm tree Date: Wed, 20 May 2020 20:24:40 -0700 Message-ID: <20200521032440.VIuWIBEg_%akpm@linux-foundation.org> References: <20200513175005.1f4839360c18c0238df292d1@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:60860 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728137AbgEUDYm (ORCPT ); Wed, 20 May 2020 23:24:42 -0400 In-Reply-To: <20200513175005.1f4839360c18c0238df292d1@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: daniel.m.jordan@oracle.com, dbueso@suse.de, hughd@google.com, jgg@ziepe.ca, jglisse@redhat.com, jhubbard@nvidia.com, ldufour@linux.ibm.com, Liam.Howlett@oracle.com, mm-commits@vger.kernel.org, peterz@infradead.org, rientjes@google.com, vbabka@suse.cz, walken@google.com, willy@infradead.org, yinghan@google.com The patch titled Subject: mmap locking API: add mmap_read_trylock_non_owner() has been added to the -mm tree. Its filename is mmap-locking-api-add-mmap_read_trylock_non_owner.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mmap-locking-api-add-mmap_read_trylock_non_owner.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mmap-locking-api-add-mmap_read_trylock_non_owner.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Michel Lespinasse Subject: mmap locking API: add mmap_read_trylock_non_owner() Add a couple APIs used by kernel/bpf/stackmap.c only: - mmap_read_trylock_non_owner() - mmap_read_unlock_non_owner() (may be called from a work queue). It's still not ideal that bpf/stackmap subverts the lock ownership in this way. Thanks to Peter Zijlstra for suggesting this API as the least-ugly way of addressing this in the short term. Link: http://lkml.kernel.org/r/20200520052908.204642-8-walken@google.com Signed-off-by: Michel Lespinasse Reviewed-by: Daniel Jordan Reviewed-by: Vlastimil Babka Cc: Davidlohr Bueso Cc: David Rientjes Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: Jerome Glisse Cc: John Hubbard Cc: Laurent Dufour Cc: Liam Howlett Cc: Matthew Wilcox Cc: Peter Zijlstra Cc: Ying Han Signed-off-by: Andrew Morton --- include/linux/mmap_lock.h | 14 ++++++++++++++ kernel/bpf/stackmap.c | 17 +++++------------ 2 files changed, 19 insertions(+), 12 deletions(-) --- a/include/linux/mmap_lock.h~mmap-locking-api-add-mmap_read_trylock_non_owner +++ a/include/linux/mmap_lock.h @@ -56,4 +56,18 @@ static inline void mmap_read_unlock(stru up_read(&mm->mmap_sem); } +static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm) +{ + if (down_read_trylock(&mm->mmap_sem)) { + rwsem_release(&mm->mmap_sem.dep_map, _RET_IP_); + return true; + } + return false; +} + +static inline void mmap_read_unlock_non_owner(struct mm_struct *mm) +{ + up_read_non_owner(&mm->mmap_sem); +} + #endif /* _LINUX_MMAP_LOCK_H */ --- a/kernel/bpf/stackmap.c~mmap-locking-api-add-mmap_read_trylock_non_owner +++ a/kernel/bpf/stackmap.c @@ -33,7 +33,7 @@ struct bpf_stack_map { /* irq_work to run up_read() for build_id lookup in nmi context */ struct stack_map_irq_work { struct irq_work irq_work; - struct rw_semaphore *sem; + struct mm_struct *mm; }; static void do_up_read(struct irq_work *entry) @@ -44,8 +44,7 @@ static void do_up_read(struct irq_work * return; work = container_of(entry, struct stack_map_irq_work, irq_work); - up_read_non_owner(work->sem); - work->sem = NULL; + mmap_read_unlock_non_owner(work->mm); } static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work); @@ -317,7 +316,7 @@ static void stack_map_get_build_id_offse * with build_id. */ if (!user || !current || !current->mm || irq_work_busy || - mmap_read_trylock(current->mm) == 0) { + !mmap_read_trylock_non_owner(current->mm)) { /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; @@ -342,16 +341,10 @@ static void stack_map_get_build_id_offse } if (!work) { - mmap_read_unlock(current->mm); + mmap_read_unlock_non_owner(current->mm); } else { - work->sem = ¤t->mm->mmap_sem; + work->mm = current->mm; irq_work_queue(&work->irq_work); - /* - * The irq_work will release the mmap_sem with - * up_read_non_owner(). The rwsem_release() is called - * here to release the lock from lockdep's perspective. - */ - rwsem_release(¤t->mm->mmap_sem.dep_map, _RET_IP_); } } _ Patches currently in -mm which might be from walken@google.com are mmap-locking-api-initial-implementation-as-rwsem-wrappers.patch mmu-notifier-use-the-new-mmap-locking-api.patch dma-reservations-use-the-new-mmap-locking-api.patch mmap-locking-api-use-coccinelle-to-convert-mmap_sem-rwsem-call-sites.patch mmap-locking-api-convert-mmap_sem-call-sites-missed-by-coccinelle.patch mmap-locking-api-convert-nested-write-lock-sites.patch mmap-locking-api-add-mmap_read_trylock_non_owner.patch mmap-locking-api-add-mmap_lock_initializer.patch mmap-locking-api-add-mmap_assert_locked-and-mmap_assert_write_locked.patch mmap-locking-api-rename-mmap_sem-to-mmap_lock.patch mmap-locking-api-convert-mmap_sem-api-comments.patch mmap-locking-api-convert-mmap_sem-comments.patch