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b=eCuQFsqX0RlSNvadGGdwqeOAq7SEK1GckH7LMbV7URFlMoYrKPKpCEyLLemHVFqQ7 vHvoaXG9YJe8+d5/wi5v25ybaLs6vJfcHKYBOyx3sF6d85do50FPIlwMxrCbczoYCb ZQCyOAYXAcw06cZVTttOgm5lN7JCuvuQLovkwLdWyw3pnT0L5ymykHGeUixiyQ7r8k exrr43zrvRu+LM0Fr9YVP8RuXic2UKGegO8eoQmNI1i8d8wlsKV1YvbEo4JDrgeQeD FQcFRE7sVB2vVjSUCGmlPPH+1GCZWObs/yNaiAWpAu8J7YfRZZjvf3eu2/5MlayITU p6l5OyYxPHnxw== Message-ID: <19f5f950-d0f9-49c2-acf6-7b0ab277ab23@kernel.org> Date: Thu, 23 Apr 2026 16:27:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/memory: update stale locking comments for fault handlers To: Aditya Sharma , linux-mm@kvack.org Cc: akpm@linux-foundation.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org References: <20260331142936.229667-1-adi.sharma@zohomail.in> <20260405171834.15971-1-adi.sharma@zohomail.in> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260405171834.15971-1-adi.sharma@zohomail.in> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D35DA4000A X-Stat-Signature: ijc6cnxpjmyeqiwxqctof6qjn4ka8oum X-HE-Tag: 1776954447-780258 X-HE-Meta: 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 F4DAyhks sSTv83N2soV5ueBo8og/A/IBfercbyVSft6BO8cqO5aP/XtpiTY7sa3psjlJCcBfbtxuKRS2ykqeT0ZXda+TxyhG2Yy7mqtiU4l9pon3Ruh6Yg77qJNSKIBg5/EZJ4meP96X9kQZy5hon//XxMXRzsEs8QMwUw6zuX3xoKbvYL774pfyFcl00dtY5lG12t4qs9u/+c1p+mNXrAR8UwZceMcdQHQZSp6cHbZspoR0yhYQMODj8LV4w7aj8R2fW5exoRlfN Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/5/26 19:18, Aditya Sharma wrote: > Update the comments for wp_page_copy(), do_wp_page(), do_swap_page(), > do_anonymous_page(), __do_fault(), do_fault(), handle_pte_fault(), > __handle_mm_fault(), and handle_mm_fault() to concisely clarify that > they can be entered holding either the mmap_lock or the VMA lock, > and that the lock may be released upon returning VM_FAULT_RETRY. > > Additionally, make the following corrections: > - In do_anonymous_page(), correct the outdated claim that the function > is entered with the PTE "mapped but not yet locked". Since > handle_pte_fault() unmaps the empty PTE before routing to > do_pte_missing(), the comment now correctly states it is entered > with the PTE unmapped and unlocked. > - In __do_fault(), update the stale reference from __lock_page_retry() > to __folio_lock_or_retry(). > > Signed-off-by: Aditya Sharma Next time, please don't send as reply to your previous version > --- > v2: > - Simplified the comment to concisely state "either the VMA lock or > the mmap_lock" instead of a verbose explanation (per David Hildenbrand). > - Expanded the scope to cover 8 other fault handlers in mm/memory.c > that suffered from the same stale mmap_lock comments. > - Fixed an additional historical inaccuracy in do_anonymous_page() > regarding the PTE mapping state on entry. > - Updated a stale reference in __do_fault() from __lock_page_retry() > to __folio_lock_or_retry(). > > > mm/memory.c | 49 ++++++++++++++++++++++++++----------------------- > 1 file changed, 26 insertions(+), 23 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index c65e82c86..2b407e3f9 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3742,8 +3742,8 @@ vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf) > * Handle the case of a page which we actually need to copy to a new page, > * either due to COW or unsharing. > * > - * Called with mmap_lock locked and the old page referenced, but > - * without the ptl held. > + * Called with either the VMA lock or the mmap_lock (FAULT_FLAG_VMA_LOCK > + * tells you which) "Called with either the VMA lock or the mmap_lock *held*" Same for other cases. Can we shorten "FAULT_FLAG_VMA_LOCK tells you which" to "see FAULT_FLAG_VMA_LOCK" ? -- Cheers, David