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Howlett" Cc: linux-kernel@vger.kernel.org, patches@lists.linux.dev, maple-tree@lists.infradead.org, Vlastimil Babka Subject: [RFC 03/11] mm/mmap/vma_merge: use the proper vma pointer in case 3 Date: Fri, 24 Feb 2023 11:00:14 +0100 Message-Id: <20230224100022.11268-4-vbabka@suse.cz> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230224100022.11268-1-vbabka@suse.cz> References: <20230224100022.11268-1-vbabka@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: D08291C002F X-Rspamd-Server: rspam01 X-Stat-Signature: d39npdoeyzy1q4foyyjcwf3t4ag9p3wk X-HE-Tag: 1677232842-453879 X-HE-Meta: U2FsdGVkX1/IUA+TZzRyxX4ZIyh9BOlng5RTLIliSDy67A9zIx3Qg1UPpLB9l3QzhMIhfYhwpGaRLaJbpNt0STF05JsBHvQWBK3kIcGb61b3owu17FNUwug9XTOEFyhz6CIk+I/36omC5/ODreYXHPa13zNJRTrlzr8PwacjAGOOM47dX0qnhHPpX90nLpqZRrKcBCvMHIOBoYC0Lbb6mONb8NGYYLas/OBJ+E6wq4BG1LxteeD8MBYbpum2eVdjI7O+YiFgYxVEhUt0sG36oc813aRu5xnmiWFyVDZoodWLa98z5MfzZ5dr/qPK3+PzNUvnwY99nC/jqunygwaPyRm+1duCi0chQr0/uTTF5K165LogRUSj51OwV5rRnDAYGZPiD67Pqa+wACtWMPnKdTfnNpiFOsg5ymnxvjrBxNZ4fVl0359PVJhi7hS3h9yVUMCD6O/j4me9NwP6bKWYxDuOG61yS+RvTxdhwzgB2Pwq/0aaN9dXvcfgtGniRbLJGyss8UGqoMeB9uC7DEYFZCbRNcx7zZv1Gvnjkjh+h5SpVgf1vckfUqQQWJ9fRWoU63Ipu2UncQ60cVctf9Hk07kBkKwX0hthZHV1kQaJgU1Fvih0eDHwMrClNIQO90cTsrcMWufrQmJToa7RCAb4TxzCqJwYgO+dac8KjjW6v7xsyU/GHUeIT1LuAgUnCgyQlnXnyeIL/GEffL21AiXnBe8ThY9U+1vQsLtQGtmzRQGj7VSDEiZchhPn/vWTAQeVvSzT+pS9KrWosKgT7zBiQF03qXFm7cNuABT9Hn3PaYcvjyqzlcAkkVA+aN99ke7dt+9uizjJpc8CIOvrIXtDWoIG4ll0kwVzNFiqTsYPYjUietFp0xIlTZD+o0677GGIaDdvN6wSfn+8rQ3dATbD5lgcfX63iOmvFhzIaDxFowKn2uXtKm/ADE/Y0Al+kbIbrLP+Qb7jvZX+hlXU+w7 +LygOeT4 AeKrZHo5X8XcLtkVQCe/qge6v+TSG6KsLXCtzkjetyVEVUdT8+7bJkFTgRj9Z+8zuB6Pf3AmryJ2k8jaVFniN9AuN8Eon+tlFQbWd5sf70woEHPrpjdZMyDDsoNeuviFzqCwoqNUXB+fswcSe2K4soFDSiIhJaOnLxpLGpkvUAXgTk9sX6CES6vBzpLcdK3EExMEvgBKx9vKK/E7teOkQuN0NI813DVPNUBD6LQwArVFNmCJuBnVd2rA1yg== 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: In case 3 we we use 'next' for everything but vma_pgoff. So use 'next' for that as well, instead of 'mid', for consistency. Then in case 8 we have to use 'mid' explicitly, which should also make the intent more obvious. Adjust the diagram for cases 1-3 in the comment to match the code - we are using 'next' for case 3 so mark the range with XXXX instead of NNNN. For case 2 that's a no-op as the code doesn't touch 'next' or 'mid'. For case 1 it's now wrong but that will be fixed next. No functional change. Signed-off-by: Vlastimil Babka --- mm/mmap.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 0a8b052e3022..1af4c9bc2c87 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -857,11 +857,11 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags, * mmap, brk or case 4 below case 5 below * mremap move: * AAAA AAAA - * PPPP NNNN PPPPNNNNXXXX + * PPPP XXXX PPPPNNNNXXXX * might become might become * PPPPPPPPPPPP 1 or PPPPPPPPPPPP 6 or - * PPPPPPPPNNNN 2 or PPPPPPPPXXXX 7 or - * PPPPNNNNNNNN 3 PPPPXXXXXXXX 8 + * PPPPPPPPXXXX 2 or PPPPPPPPXXXX 7 or + * PPPPXXXXXXXX 3 PPPPXXXXXXXX 8 * * It is important for case 8 that the vma NNNN overlapping the * region AAAA is never going to extended over XXXX. Instead XXXX must @@ -978,9 +978,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma = next; /* case 3 */ vma_start = addr; vma_end = next->vm_end; - vma_pgoff = mid->vm_pgoff; + vma_pgoff = next->vm_pgoff; err = 0; if (mid != next) { /* case 8 */ + vma_pgoff = mid->vm_pgoff; remove = mid; err = dup_anon_vma(next, mid); } -- 2.39.2