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Howlett" , linux-mm@kvack.org, Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka Subject: Re: [PATCH 4/6] binder: Remove mmap_lock fallback Message-ID: References: <20260429181954.F50224AE@davehans-spike.ostc.intel.com> <20260429182000.93887DFB@davehans-spike.ostc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260429182000.93887DFB@davehans-spike.ostc.intel.com> X-Rspam-User: X-Rspamd-Queue-Id: 0DE3440008 X-Rspamd-Server: rspam06 X-Stat-Signature: krend3gpjponrzzufsy76wio1wkwz4dr X-HE-Tag: 1778261373-645237 X-HE-Meta: U2FsdGVkX1848rUW+hibFuDWfJAkvdCqeKHrWDmfpgBqgcdv8w1cOoNpzEtj3GVuqB8YhoS36Veij8BY8nVjStVuLJjjcrRx+8TmsCLr6jc8WJCaUp7SnbH6L2ddDyu9evgDTLjp3ZwSxBwfpdoMxe5gLxuiXpq0SPWYj1O2hGK1t+0+sWAK9Y8q2FITJ5JRHHjhQKupX/tycHlQYTgVFYk3aPlXJcNH5nVxgkZpPjrh8eG2pUSJ30xAaV2+moo5TyYMDd/Tqp8fnFZZO/9NiiEXBvrjmDXYY5+T+rgZFbwQcjdUjm0EDAUIik3hg0CbTxZ5jPqV45VZMwffbUHEx6jsmVV6dHMxJNFwjdHeWS1PIx9DyYZ7mENT5JUSwjFD/+PMfPY9lzVyDDFXJL4dTU+HCsLkLwBrPPqZ+vkUmtk0LMTIRCLfL56uggKHDObsiYCKQNqxoZ+/TiBTY3l1cmGGMZ+4vPfSFla5/ykfkZN0v9F6WSXPaUcWDS/iMmCBlsC4VxG0S8pRjrXlSc1ACVdozONnbCIwr6q2y2Ul/m/wvQtAIOVnBSetNMs4wynKi296bc8XfPdHS8918SL7UMGCoQRaNfqCUxYFbC749IGlcxjhzJeY5lU9Ot7rudlOgXh9PTdWs7we2fSCwDBE1Fre+p//ZAZ4lTjcq6LZWSxbKx2AN6nVYF64YBcPWVHj2EsmLalwiZwFfZvy3zYJebhrSVD5OK+9IyAX8GR3rvH8UlR1NIIbcWaLIZBRh3ZCc0kIQ60AG9F38pTKMOnGuIm9FKVadK7CoA5CUw3T+Uj7mXsEWm7OOKVoh8whGqXE5I65eRftlpuNLlHm4IP+yKStMcdfL40MhYHMy+WfFEeMtD/mf6NSljhwZhjc0rvAUTKhuB7lrguqvyAQnxlTrWpBxOpcikuttEuXO/BtVWxnssyafNQCZ/VkOW6nBunLPXlSR1L96A9S/nGzQM5 3kt8jBWV 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 29, 2026 at 11:20:00AM -0700, Dave Hansen wrote: > > From: Dave Hansen > > Previously, the per-VMA locking could fail in the face of writers > which necessitate a fallback to mmap_lock. The new > lock_vma_under_rcu_wait() will wait for writers instead of failing. > > Use the new helper. Wait for writers. Remove the fallback to mmap_lock. > > Signed-off-by: Dave Hansen LGTM in principal, though again not a binder dev so just an A-b :) Acked-by: Lorenzo Stoakes > Cc: Suren Baghdasaryan > Cc: Andrew Morton > Cc: "Liam R. Howlett" > Cc: Lorenzo Stoakes > Cc: Vlastimil Babka > Cc: Shakeel Butt > Cc: linux-mm@kvack.org > --- > > b/drivers/android/binder_alloc.c | 17 +++++------------ > 1 file changed, 5 insertions(+), 12 deletions(-) > > diff -puN drivers/android/binder_alloc.c~binder-vma-waiter drivers/android/binder_alloc.c > --- a/drivers/android/binder_alloc.c~binder-vma-waiter 2026-04-29 11:18:51.307654829 -0700 > +++ b/drivers/android/binder_alloc.c 2026-04-29 11:18:51.310654944 -0700 > @@ -259,21 +259,14 @@ static int binder_page_insert(struct bin > struct vm_area_struct *vma; > int ret = -ESRCH; > > - /* attempt per-vma lock first */ > - vma = lock_vma_under_rcu(mm, addr); > - if (vma) { > - if (binder_alloc_is_mapped(alloc)) > - ret = vm_insert_page(vma, addr, page); > - vma_end_read(vma); > + vma = lock_vma_under_rcu_wait(mm, addr); Yeah this name is definitely iffy haha! > + if (!vma) > return ret; > - } > > - /* fall back to mmap_lock */ > - mmap_read_lock(mm); > - vma = vma_lookup(mm, addr); > - if (vma && binder_alloc_is_mapped(alloc)) > + if (binder_alloc_is_mapped(alloc)) > ret = vm_insert_page(vma, addr, page); > - mmap_read_unlock(mm); > + > + vma_end_read(vma); > > return ret; > } > _