linux-kernel - [PATCH 23/64] mm: huge pagecache: do not check mmap

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Date:   Mon,  5 Feb 2018 02:27:13 +0100
From:   Davidlohr Bueso <dbueso@...e.de>
To:     akpm@...ux-foundation.org, mingo@...nel.org
Cc:     peterz@...radead.org, ldufour@...ux.vnet.ibm.com, jack@...e.cz,
        mhocko@...nel.org, kirill.shutemov@...ux.intel.com,
        mawilcox@...rosoft.com, mgorman@...hsingularity.net,
        dave@...olabs.net, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 23/64] mm: huge pagecache: do not check mmap_sem state

From: Davidlohr Bueso <dave@...olabs.net>

*THIS IS A HACK*

By dropping the rwsem_is_locked checks in zap_pmd_range()
and zap_pud_range() we can avoid having to teach
file_operations about mmrange. For example in xfs:
iomap_dio_rw() is called by .read_iter file callbacks.

No-Yet-Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 mm/memory.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 7c69674cd9da..598a8c69e3d3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1422,8 +1422,6 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
 		next = pmd_addr_end(addr, end);
 		if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 			if (next - addr != HPAGE_PMD_SIZE) {
-				VM_BUG_ON_VMA(vma_is_anonymous(vma) &&
-				    !rwsem_is_locked(&tlb->mm->mmap_sem), vma);
 				__split_huge_pmd(vma, pmd, addr, false, NULL);
 			} else if (zap_huge_pmd(tlb, vma, pmd, addr))
 				goto next;
@@ -1459,7 +1457,6 @@ static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
 		next = pud_addr_end(addr, end);
 		if (pud_trans_huge(*pud) || pud_devmap(*pud)) {
 			if (next - addr != HPAGE_PUD_SIZE) {
-				VM_BUG_ON_VMA(!rwsem_is_locked(&tlb->mm->mmap_sem), vma);
 				split_huge_pud(vma, pud, addr);
 			} else if (zap_huge_pud(tlb, vma, pud, addr))
 				goto next;
-- 
2.13.6