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Date: Tue, 1 Mar 2022 17:07:07 +0800 From: Miaohe Lin <linmiaohe@...wei.com> To: Yang Shi <shy828301@...il.com> CC: <linux-mm@...ck.org>, <linux-fsdevel@...r.kernel.org>, <linux-ext4@...r.kernel.org>, <linux-xfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <vbabka@...e.cz>, <kirill.shutemov@...ux.intel.com>, <songliubraving@...com>, <riel@...riel.com>, <willy@...radead.org>, <ziy@...dia.com>, <akpm@...ux-foundation.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>, <darrick.wong@...cle.com> Subject: Re: [PATCH 2/8] mm: khugepaged: remove redundant check for VM_NO_KHUGEPAGED On 2022/3/1 7:57, Yang Shi wrote: > The hugepage_vma_check() called by khugepaged_enter_vma_merge() does > check VM_NO_KHUGEPAGED. Remove the check from caller and move the check > in hugepage_vma_check() up. > > More checks may be run for VM_NO_KHUGEPAGED vmas, but MADV_HUGEPAGE is > definitely not a hot path, so cleaner code does outweigh. > > Signed-off-by: Yang Shi <shy828301@...il.com> > --- > mm/khugepaged.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 131492fd1148..82c71c6da9ce 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -366,8 +366,7 @@ int hugepage_madvise(struct vm_area_struct *vma, > * register it here without waiting a page fault that > * may not happen any time soon. > */ > - if (!(*vm_flags & VM_NO_KHUGEPAGED) && > - khugepaged_enter_vma_merge(vma, *vm_flags)) > + if (khugepaged_enter_vma_merge(vma, *vm_flags)) > return -ENOMEM; > break; > case MADV_NOHUGEPAGE: > @@ -446,6 +445,9 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > if (!transhuge_vma_enabled(vma, vm_flags)) > return false; > > + if (vm_flags & VM_NO_KHUGEPAGED) > + return false; > + This patch does improve the readability. But I have a question. It seems VM_NO_KHUGEPAGED is not checked in the below if-condition: /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && (vm_flags & VM_EXEC)) { struct inode *inode = vma->vm_file->f_inode; return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } If we return false due to VM_NO_KHUGEPAGED here, it seems it will affect the return value of this CONFIG_READ_ONLY_THP_FOR_FS condition check. Or am I miss something? Thanks. > if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - > vma->vm_pgoff, HPAGE_PMD_NR)) > return false; > @@ -471,7 +473,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > return false; > if (vma_is_temporary_stack(vma)) > return false; > - return !(vm_flags & VM_NO_KHUGEPAGED); > + > + return true; > } > > int __khugepaged_enter(struct mm_struct *mm) >
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