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Howlett" , Vlastimil Babka Subject: Re: [PATCH v4] mm/userfaultfd: detect VMA replacement after copy retry in mfill_copy_folio_retry() Message-ID: References: <20260331134158.622084-1-devnexen@gmail.com> <20260331200148.cc0c95deaf070579a68af041@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D283E140007 X-Stat-Signature: qh9p6snnf4316ic9zu9faqnzh3ftgfdk X-Rspam-User: X-HE-Tag: 1775102567-7916 X-HE-Meta: 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 pLaxQxyV DpPP2 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 01, 2026 at 03:22:03PM -0400, Peter Xu wrote: > > The other thing is I just noticed the err code was changed to -EINVAL for > snapshot changed cases, sorry I didn't follow previously as closely on the > discussion. I think it should be -EAGAIN. It's because the userapp can't > resolve -EINVAL failures and app will crash. In a VMA change use case, we > should return -EAGAIN to imply the app to retry, rather than crashing. No. The return value should express that the VMA is invalid. -EINVAL could work, but looking now at the manual -ENOENT would be even better: ENOENT (since Linux 4.11) The faulting process has changed its virtual memory layout simultaneously with an outstanding UFFDIO_COPY operation. > Thanks, > -- > Peter Xu -- Sincerely yours, Mike.