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Shutemov" , Rik van Riel , Johannes Weiner , Minchan Kim , Linux Kernel Mailing List , Linux MM , David Hildenbrand Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 1897E20004 X-Stat-Signature: ghy57p9qwtakbi4r5m54jteitbmxs63s Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=IOYNnQWm; spf=pass (imf31.hostedemail.com: domain of shy828301@gmail.com designates 209.85.208.44 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-HE-Tag: 1645739809-94887 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: On Thu, Feb 24, 2022 at 1:29 PM Yang Shi wrote: > > On Thu, Feb 24, 2022 at 10:51 AM Vlastimil Babka wrote: > > > > On 5/14/21 11:30, Miaohe Lin wrote: > > > Since commit 99cb0dbd47a1 ("mm,thp: add read-only THP support for > > > (non-shmem) FS"), read-only THP file mapping is supported. But it > > > forgot to add checking for it in transparent_hugepage_enabled(). > > > To fix it, we add checking for read-only THP file mapping and also > > > introduce helper transhuge_vma_enabled() to check whether thp is > > > enabled for specified vma to reduce duplicated code. We rename > > > transparent_hugepage_enabled to transparent_hugepage_active to make > > > the code easier to follow as suggested by David Hildenbrand. > > > > > > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") > > > Reviewed-by: Yang Shi > > > Signed-off-by: Miaohe Lin > > > > FYI, I stumbled upon needing this for my reproducer for the read() > > corruption [1] to work, and I think it's still not ideal. I also needed > > madvise(MADV_HUGEPAGE) for the executable file mapping to make sure > > khugepaged acts on my process. Yeah, commit 99cb0dbd47a1 suggests madvise. > > Yet, khugepaged will happily collapse file mappings even without madvise > > anyway. However, it might not know about the mm at all unless > > __khugepaged_enter() has been applied at least on one of its vma's. > > madvise() is one way to do it for executable file mappings, but it can also > > happen through e.g. do_huge_pmd_anonymous_page() on another mapping, which > > has nothing to do with the file mapping. > > So what I'm trying to say is that we are somewhat inconsistent - the rules > > to consider a vma in khugepaged seem to be clear and result of admin > > configuration and madvise, but the rules to consider a mm for khugepaged > > (which is the only way to collapse file mappings) are not completely > > identical and there might be "random luck" involved. > > Yes, khugepaged_enter() is not called for file vma explicitly. My wild > guess is THP for readonly fs was assumed to be collapsed by explicit > demand from the users, for example, madvise. > > To achieve more consistent behavior we could call khugepaged_enter() > for file fault just like what huge anonymous fault does. Of course we > need to fix khugepaged_enter() to do the proper check as well. Or we could follow shmem's implementation to call khugepaged_enter() in .mmap method for each filesystem so that khugepaged_enter() doesn't have to be called for each filemap_fault(). Luckily most filesystems use generic_file_mmap(). > > > > > [1] https://lore.kernel.org/all/df3b5d1c-a36b-2c73-3e27-99e74983de3a@suse.cz/ > > > > > --- > > > v3->v4: > > > collect Reviewed-by tag > > > define transhuge_vma_enabled next to transhuge_vma_suitable > > > --- > > > fs/proc/task_mmu.c | 2 +- > > > include/linux/huge_mm.h | 57 +++++++++++++++++++++++++---------------- > > > mm/huge_memory.c | 11 +++++++- > > > mm/khugepaged.c | 4 +-- > > > mm/shmem.c | 3 +-- > > > 5 files changed, 48 insertions(+), 29 deletions(-) > > > > > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > > > index fc9784544b24..7389df326edd 100644 > > > --- a/fs/proc/task_mmu.c > > > +++ b/fs/proc/task_mmu.c > > > @@ -832,7 +832,7 @@ static int show_smap(struct seq_file *m, void *v) > > > __show_smap(m, &mss, false); > > > > > > seq_printf(m, "THPeligible: %d\n", > > > - transparent_hugepage_enabled(vma)); > > > + transparent_hugepage_active(vma)); > > > > > > if (arch_pkeys_enabled()) > > > seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma)); > > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > > > index 0a526f211fec..7b7f7b52ccb8 100644 > > > --- a/include/linux/huge_mm.h > > > +++ b/include/linux/huge_mm.h > > > @@ -115,9 +115,34 @@ extern struct kobj_attribute shmem_enabled_attr; > > > > > > extern unsigned long transparent_hugepage_flags; > > > > > > +static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, > > > + unsigned long haddr) > > > +{ > > > + /* Don't have to check pgoff for anonymous vma */ > > > + if (!vma_is_anonymous(vma)) { > > > + if (!IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > > > + HPAGE_PMD_NR)) > > > + return false; > > > + } > > > + > > > + if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) > > > + return false; > > > + return true; > > > +} > > > + > > > +static inline bool transhuge_vma_enabled(struct vm_area_struct *vma, > > > + unsigned long vm_flags) > > > +{ > > > + /* Explicitly disabled through madvise. */ > > > + if ((vm_flags & VM_NOHUGEPAGE) || > > > + test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > > > + return false; > > > + return true; > > > +} > > > + > > > /* > > > * to be used on vmas which are known to support THP. > > > - * Use transparent_hugepage_enabled otherwise > > > + * Use transparent_hugepage_active otherwise > > > */ > > > static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma) > > > { > > > @@ -128,15 +153,12 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma) > > > if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX)) > > > return false; > > > > > > - if (vma->vm_flags & VM_NOHUGEPAGE) > > > + if (!transhuge_vma_enabled(vma, vma->vm_flags)) > > > return false; > > > > > > if (vma_is_temporary_stack(vma)) > > > return false; > > > > > > - if (test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > > > - return false; > > > - > > > if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG)) > > > return true; > > > > > > @@ -150,22 +172,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma) > > > return false; > > > } > > > > > > -bool transparent_hugepage_enabled(struct vm_area_struct *vma); > > > - > > > -static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, > > > - unsigned long haddr) > > > -{ > > > - /* Don't have to check pgoff for anonymous vma */ > > > - if (!vma_is_anonymous(vma)) { > > > - if (!IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > > > - HPAGE_PMD_NR)) > > > - return false; > > > - } > > > - > > > - if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) > > > - return false; > > > - return true; > > > -} > > > +bool transparent_hugepage_active(struct vm_area_struct *vma); > > > > > > #define transparent_hugepage_use_zero_page() \ > > > (transparent_hugepage_flags & \ > > > @@ -351,7 +358,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma) > > > return false; > > > } > > > > > > -static inline bool transparent_hugepage_enabled(struct vm_area_struct *vma) > > > +static inline bool transparent_hugepage_active(struct vm_area_struct *vma) > > > { > > > return false; > > > } > > > @@ -362,6 +369,12 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, > > > return false; > > > } > > > > > > +static inline bool transhuge_vma_enabled(struct vm_area_struct *vma, > > > + unsigned long vm_flags) > > > +{ > > > + return false; > > > +} > > > + > > > static inline void prep_transhuge_page(struct page *page) {} > > > > > > static inline bool is_transparent_hugepage(struct page *page) > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > > index 76ca1eb2a223..4f37867eed12 100644 > > > --- a/mm/huge_memory.c > > > +++ b/mm/huge_memory.c > > > @@ -63,7 +63,14 @@ static struct shrinker deferred_split_shrinker; > > > static atomic_t huge_zero_refcount; > > > struct page *huge_zero_page __read_mostly; > > > > > > -bool transparent_hugepage_enabled(struct vm_area_struct *vma) > > > +static inline bool file_thp_enabled(struct vm_area_struct *vma) > > > +{ > > > + return transhuge_vma_enabled(vma, vma->vm_flags) && vma->vm_file && > > > + !inode_is_open_for_write(vma->vm_file->f_inode) && > > > + (vma->vm_flags & VM_EXEC); > > > +} > > > + > > > +bool transparent_hugepage_active(struct vm_area_struct *vma) > > > { > > > /* The addr is used to check if the vma size fits */ > > > unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; > > > @@ -74,6 +81,8 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma) > > > return __transparent_hugepage_enabled(vma); > > > if (vma_is_shmem(vma)) > > > return shmem_huge_enabled(vma); > > > + if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) > > > + return file_thp_enabled(vma); > > > > > > return false; > > > } > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > > index 6c0185fdd815..d97b20fad6e8 100644 > > > --- a/mm/khugepaged.c > > > +++ b/mm/khugepaged.c > > > @@ -442,9 +442,7 @@ static inline int khugepaged_test_exit(struct mm_struct *mm) > > > static bool hugepage_vma_check(struct vm_area_struct *vma, > > > unsigned long vm_flags) > > > { > > > - /* Explicitly disabled through madvise. */ > > > - if ((vm_flags & VM_NOHUGEPAGE) || > > > - test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > > > + if (!transhuge_vma_enabled(vma, vm_flags)) > > > return false; > > > > > > /* Enabled via shmem mount options or sysfs settings. */ > > > diff --git a/mm/shmem.c b/mm/shmem.c > > > index a08cedefbfaa..1dcbec313c70 100644 > > > --- a/mm/shmem.c > > > +++ b/mm/shmem.c > > > @@ -4032,8 +4032,7 @@ bool shmem_huge_enabled(struct vm_area_struct *vma) > > > loff_t i_size; > > > pgoff_t off; > > > > > > - if ((vma->vm_flags & VM_NOHUGEPAGE) || > > > - test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > > > + if (!transhuge_vma_enabled(vma, vma->vm_flags)) > > > return false; > > > if (shmem_huge == SHMEM_HUGE_FORCE) > > > return true; > >