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Tue, 7 Jan 2025 17:28:33 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Tcf1IkFkfWdkcAAAD6G6ig (envelope-from ); Tue, 07 Jan 2025 17:28:33 +0000 Message-ID: <929630d5-3a11-47f3-ac4d-4f162a11bbdc@suse.cz> Date: Tue, 7 Jan 2025 18:28:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 08/17] mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail Content-Language: en-US To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com References: <20241226170710.1159679-1-surenb@google.com> <20241226170710.1159679-9-surenb@google.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 908EB16001C X-Stat-Signature: yw7skus7eoj6wq4enanh8beknoix1ika X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1736270915-650155 X-HE-Meta: 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 f8jwXR5B ThBxWWF/NXR3WQO4X2lKSOW67pENAtDZSfCDH28kprhqfjtOtJbkzTwAtKkB56IFV8SqV0hZzAttLI2BB1q8OgZIO5w1Xxihqiknm+ko1Eiw8Ii8DXXwlGQIwNcery2zPSlGs5EHA45R+tg+2MkRUaUT0d0644dYkDgj08hM6LXturdOz8ZtbdLuZF4uIz9vsgaIQRV4uOu4z5fbbhp/atlrifj7S13MP8Mro3zCP8NjGcXYBIgN3yXqYQDmUdBDC8nazqJIPLZa8GRzw+/l5pwSWFOrmg8l8hD65W7y9VAqXq2HnvAjQNbI/I40H4OjnXmjbSDyx+y8Cf9IzZ3klr2BqxKeZl6ePz6Ctoludja77DPY= 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: List-Subscribe: List-Unsubscribe: On 12/26/24 18:07, Suren Baghdasaryan wrote: > With upcoming replacement of vm_lock with vm_refcnt, we need to handle a > possibility of vma_start_read_locked/vma_start_read_locked_nested failing > due to refcount overflow. Prepare for such possibility by changing these > APIs and adjusting their users. > > Signed-off-by: Suren Baghdasaryan > Cc: Lokesh Gidra Acked-by: Vlastimil Babka (I don't know if this can break some uffd users?) > @@ -1483,10 +1484,16 @@ static int uffd_move_lock(struct mm_struct *mm, > mmap_read_lock(mm); > err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); > if (!err) { > - vma_start_read_locked(*dst_vmap); > - if (*dst_vmap != *src_vmap) > - vma_start_read_locked_nested(*src_vmap, > - SINGLE_DEPTH_NESTING); > + if (vma_start_read_locked(*dst_vmap)) { > + if (*dst_vmap != *src_vmap) { > + if (!vma_start_read_locked_nested(*src_vmap, > + SINGLE_DEPTH_NESTING)) { > + vma_end_read(*dst_vmap); > + err = -EAGAIN; > + } > + } > + } else > + err = -EAGAIN; Nit: { } per style > } > mmap_read_unlock(mm); > return err;