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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id i3-20020a056820138300b0031c0d227905sm1829839oow.19.2022.03.03.20.36.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Mar 2022 20:36:38 -0800 (PST) Date: Thu, 3 Mar 2022 20:36:37 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: Andrew Morton cc: Oleg Nesterov , Liam Howlett , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH mmotm] mempolicy: mbind_range() set_policy() after vma_merge() Message-ID: <319e4db9-64ae-4bca-92f0-ade85d342ff@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org v2.6.34 commit 9d8cebd4bcd7 ("mm: fix mbind vma merge problem") introduced vma_merge() to mbind_range(); but unlike madvise, mlock and mprotect, it put a "continue" to next vma where its precedents go to update flags on current vma before advancing: that left vma with the wrong setting in the infamous vma_merge() case 8. v3.10 commit 1444f92c8498 ("mm: merging memory blocks resets mempolicy") tried to fix that in vma_adjust(), without fully understanding the issue. v3.11 commit 3964acd0dbec ("mm: mempolicy: fix mbind_range() && vma_adjust() interaction") reverted that, and went about the fix in the right way, but chose to optimize out an unnecessary mpol_dup() with a prior mpol_equal() test. But on tmpfs, that also pessimized out the vital call to its ->set_policy(), leaving the new mbind unenforced. Just delete that optimization now (though it could be made conditional on vma not having a set_policy). Also remove the "next" variable: it turned out to be blameless, but also pointless. Fixes: 3964acd0dbec ("mm: mempolicy: fix mbind_range() && vma_adjust() interaction") Signed-off-by: Hugh Dickins --- mm/mempolicy.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -786,7 +786,6 @@ static int vma_replace_policy(struct vm_area_struct *vma, static int mbind_range(struct mm_struct *mm, unsigned long start, unsigned long end, struct mempolicy *new_pol) { - struct vm_area_struct *next; struct vm_area_struct *prev; struct vm_area_struct *vma; int err = 0; @@ -801,8 +800,7 @@ static int mbind_range(struct mm_struct *mm, unsigned long start, if (start > vma->vm_start) prev = vma; - for (; vma && vma->vm_start < end; prev = vma, vma = next) { - next = vma->vm_next; + for (; vma && vma->vm_start < end; prev = vma, vma = vma->vm_next) { vmstart = max(start, vma->vm_start); vmend = min(end, vma->vm_end); @@ -817,10 +815,6 @@ static int mbind_range(struct mm_struct *mm, unsigned long start, anon_vma_name(vma)); if (prev) { vma = prev; - next = vma->vm_next; - if (mpol_equal(vma_policy(vma), new_pol)) - continue; - /* vma_merge() joined vma && vma->next, case 8 */ goto replace; } if (vma->vm_start != vmstart) {