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Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Rik van Riel , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH v4 06/10] mm/mremap: check remap conditions earlier Message-Id: <20250720112914.6692e658f4c5b7f4349214be@linux-foundation.org> In-Reply-To: <8fc92a38-c636-465e-9a2f-2c6ac9cb49b8@lucifer.local> References: <8b4161ce074901e00602a446d81f182db92b0430.1752770784.git.lorenzo.stoakes@oracle.com> <8fc92a38-c636-465e-9a2f-2c6ac9cb49b8@lucifer.local> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4371E40005 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: gaowtwtipeyuqqqd7pxk89yny8ox6gzu X-HE-Tag: 1753036156-465582 X-HE-Meta: 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 AU02ZqY6 uhsXN20Dz9BrR+gS02SiJ/87EkUJRL2+i8hFT6Jw74qUHNdL7nzitxBVNeP87xDOz6hKuMrTY+oEgyL5aKDBSZD3UWxZTkQmpkEFqf9rNpS0sMW5wa/cd4ADPjmkF0KpEZnTEZSp+3tfuW0QF6GE5Vn/xUwjZEu0g/JM4KMEZZ9rqXnWgVjmZCuEk42HdTqNWnjoCZMS72OFxioIRizutDuFGHR/Y3heq0DIJ8L1NJVFVE2wJU6K2tHL+7N5jRW5WIQQh4RWYkpeXfPU6j5dSxb2xAw== 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 Sun, 20 Jul 2025 12:04:42 +0100 Lorenzo Stoakes wrote: > Hi Andrew, > > It turns out there's some undocumented, unusual behaviour in mremap() > around shrinking of a range which was previously missed, but an LTP test > flagged up (seemingly by accident). > > Basically, if you specify an input range that spans multiple VMAs, this is > in nearly all cases rejected (this is the point of this series, after all, > for VMA moves). > > However, it turns out if you a. shrink a range and b. the new size spans > only a single VMA in the original range - then this requirement is entirely > dropped. > > So I need to slightly adjust the logic to account for this. I will also be > documenting this in the man page as it appears the man page contradicts > this or is at least very unclear. > > I attach a fix-patch, however there's some very trivial conflicts caused > due to code being moved around. > OK, I applied this as a -fix. Moved the two new hunks into check_prep_vma(). Made sure the "We are expanding and the VMA .." hunk landed properly in check_prep_vma(). I've pushed out the result, please check current mm-unstable.