On 06/19/2019 09:47 AM, Anshuman Khandual wrote:

+#ifdef CONFIG_MEMORY_HOTPLUG
+	/*
+	 * FIXME: We should have called remove_pagetable(start, end, true).
+	 * vmemmap and vmalloc virtual range might share intermediate kernel
+	 * page table entries. Removing vmemmap range page table pages here
+	 * can potentially conflict with a cuncurrent vmalloc() allocation.
+	 *
+	 * This is primarily because valloc() does not take init_mm ptl for
+	 * the entire page table walk and it's modification. Instead it just
+	 * takes the lock while allocating and installing page table pages
+	 * via [p4d|pud|pmd|pte]_aloc(). A cuncurrently vanishing page table
+	 * entry via memory hotremove can cause vmalloc() kernel page table
+	 * walk pointers to be invalid on the fly which can cause corruption
+	 * or worst, a crash.

There are couple of typos above which I will fix along with other reviews.

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