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Wed, 10 Sep 2025 13:23:58 +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 tLSnDe57wWggDgAAD6G6ig (envelope-from ); Wed, 10 Sep 2025 13:23:58 +0000 Date: Wed, 10 Sep 2025 14:23:48 +0100 From: Pedro Falcato To: "Liam R. Howlett" Cc: Andrew Morton , maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Lorenzo Stoakes , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Jann Horn , Charan Teja Kalla , shikemeng@huaweicloud.com, kasong@tencent.com, nphamcs@gmail.com, bhe@redhat.com, baohua@kernel.org, chrisl@kernel.org, Matthew Wilcox Subject: Re: [PATCH v1 6/9] mm: Change dup_mmap() recovery Message-ID: References: <20250909190945.1030905-1-Liam.Howlett@oracle.com> <20250909190945.1030905-7-Liam.Howlett@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250909190945.1030905-7-Liam.Howlett@oracle.com> X-Rspamd-Action: no action X-Stat-Signature: yh7dy3yjdf8ngqe97u1n9akgg6baus7f X-Rspam-User: X-Rspamd-Queue-Id: 6D61020009 X-Rspamd-Server: rspam04 X-HE-Tag: 1757510642-732999 X-HE-Meta: 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 fnGeLklk vG7ZK5utCaImDkLi1tiVuFtJxYMFtd+EWSWB5OpiHL/3bylQFT/WHoXYVn4DDmQOTheJZPZZPJ51jPT6pMpmkMChVbfl/0vllPvfBhxoPAPx5a5QRfdAw4w55F3Yq6hNLQuQgv8JT4jwLUTlpm43hKYrCwFRsEMsbUHpksvYC1lWvyI89afaei8DeqPGbBzwmEE47c9OxznaWPIWYC8NxRb/EeO8lS1sfNMJ/uhQe+tCTHQpOK0FaJ2ELOAl455sjcuttrbWitT3msVvXyAxzB7SU5GXNkGC2/v0xSSKul1RDzDjl5fbQ2LLMS+lDz6P4gzESAd7Vz8YkXT0mZEhfU36BRDUQLqWofFTXrNFdEkJPkxuFKDqspOY71Q== 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 Tue, Sep 09, 2025 at 03:09:42PM -0400, Liam R. Howlett wrote: > When the dup_mmap() fails during the vma duplication or setup, don't > write the XA_ZERO entry in the vma tree. Instead, destroy the tree and > free the new resources, leaving an empty vma tree. > > Using XA_ZERO introduced races where the vma could be found between > dup_mmap() dropping all locks and exit_mmap() taking the locks. The > race can occur because the mm can be reached through the other trees > via successfully copied vmas and other methods such as the swapoff code. > > XA_ZERO was marking the location to stop vma removal and pagetable > freeing. The newly created arguments to the unmap_vmas() and > free_pgtables() serve this function. > > Replacing the XA_ZERO entry use with the new argument list also means > the checks for xa_is_zero() are no longer necessary so these are also > removed. > > Signed-off-by: Liam R. Howlett Reviewed-by: Pedro Falcato -- Pedro