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arc=pass ("microsoft.com:s=arcselector9901:i=1") ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1655305303; a=rsa-sha256; cv=pass; b=XWAIJVhxMn0qZ7zsHldqTqx2wry0OAnRYmkcWgZqY07tkQP/yNJ1bvAqyHES4W8EoGnt1s kC6GQ4ZMGouCu1CXWTMiUpbnbPB492wY2WmR3s/6HhX5+fQ3BCg1bktAKYVTaiMDFUH3Yz nGuV7UH4KQ7XcxC9lMCgP3Afw6YwWO8= X-Stat-Signature: o78o4u16ned3dwbwf31k3zyy15won9md X-Rspamd-Queue-Id: E318A10011E X-Rspam-User: X-Rspamd-Server: rspam05 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=lQmaxaKY; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=V60miAKB; dmarc=pass (policy=none) header.from=oracle.com; spf=none (imf05.hostedemail.com: domain of liam.howlett@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=liam.howlett@oracle.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-HE-Tag: 1655305300-362062 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: * Lukas Bulwahn [220614 07:33]: > Dear Matthew, dear Liam, >=20 > The commit afcf76df48f9 ("mm/mlock: use vma iterator and maple state inst= ead > of vma linked list") refactors the function count_mm_mlocked_page_nr() in > mm/mlock.c, such that the special case: >=20 > if (mm =3D=3D NULL) > mm =3D current->mm; >=20 > is now dead code. Before the refactoring, after this if statement, the va= riable > mm was used further in vma =3D find_vma(mm, start) in the following line,= but now, > with the introduction of VMA_ITERATOR(vmi, mm, start) before the if state= ment, > the assignment within the if statement is simply ignored. >=20 > I assume that: > - If the semantics of this function shall be preserved, the VMA_ITERATOR = macro > needs to move after the if statement. >=20 > - or, if the consideration of the special case on mm =3D=3D NULL is actua= lly > obsolete with this refactoring, it could be simply deleted. I think this code was never necessary. This statement was added in the same commit that added the only user of the function [1], which passes in current->mm as the argument. >=20 > I will keep it up to you how this issue is correctly resolved. >=20 > This was discovered due to tracking all dead stores that clang-analyzer r= eports > on an x86 defconfig. The underlying issue here is more severe than "just = a dead > store in the kernel code base", but it is probably easy for you to resolv= e. >=20 Thanks for the report. This code should be dropped. [1] Commit ID 0cf2f6f6dc605 Regards, Liam