From: "Matthew Wilcox (Oracle)" willy@infradead.org
mainline inclusion from mainline-v6.7-rc1 commit 164b06f238b986317131e6b61b2f22aabcbc2cc0 category: other bugzilla: https://gitee.com/openeuler/kernel/issues/I8K7C7
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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It is usually safe to call wp_page_copy() under the VMA lock. The only unsafe situation is when no anon_vma has been allocated for this VMA, and we have to look at adjacent VMAs to determine if their anon_vma can be shared. Since this happens only for the first COW of a page in this VMA, the majority of calls to wp_page_copy() do not need to fall back to the mmap_sem.
Add vmf_anon_prepare() as an alternative to anon_vma_prepare() which will return RETRY if we currently hold the VMA lock and need to allocate an anon_vma. This lets us drop the check in do_wp_page().
Link: https://lkml.kernel.org/r/20231006195318.4087158-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Reviewed-by: Suren Baghdasaryan surenb@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Tong Tiangen tongtiangen@huawei.com --- mm/memory.c | 39 ++++++++++++++++++++++++++------------- 1 file changed, 26 insertions(+), 13 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c index f4667bfae83b..73cbca4ed65d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3044,6 +3044,21 @@ static inline void wp_page_reuse(struct vm_fault *vmf, struct folio *folio) count_vm_event(PGREUSE); }
+static vm_fault_t vmf_anon_prepare(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + + if (likely(vma->anon_vma)) + return 0; + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + vma_end_read(vma); + return VM_FAULT_RETRY; + } + if (__anon_vma_prepare(vma)) + return VM_FAULT_OOM; + return 0; +} + /* * Handle the case of a page which we actually need to copy to a new page, * either due to COW or unsharing. @@ -3071,27 +3086,29 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) pte_t entry; int page_copied = 0; struct mmu_notifier_range range; - int ret; + vm_fault_t ret;
delayacct_wpcopy_start();
if (vmf->page) old_folio = page_folio(vmf->page); - if (unlikely(anon_vma_prepare(vma))) - goto oom; + ret = vmf_anon_prepare(vmf); + if (unlikely(ret)) + goto out;
if (is_zero_pfn(pte_pfn(vmf->orig_pte))) { new_folio = vma_alloc_zeroed_movable_folio(vma, vmf->address); if (!new_folio) goto oom; } else { + int err; new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vmf->address, false); if (!new_folio) goto oom;
- ret = __wp_page_copy_user(&new_folio->page, vmf->page, vmf); - if (ret) { + err = __wp_page_copy_user(&new_folio->page, vmf->page, vmf); + if (err) { /* * COW failed, if the fault was solved by other, * it's fine. If not, userspace would re-fault on @@ -3104,7 +3121,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) folio_put(old_folio);
delayacct_wpcopy_end(); - return ret == -EHWPOISON ? VM_FAULT_HWPOISON : 0; + return err == -EHWPOISON ? VM_FAULT_HWPOISON : 0; } kmsan_copy_page_meta(&new_folio->page, vmf->page); } @@ -3214,11 +3231,13 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) oom_free_new: folio_put(new_folio); oom: + ret = VM_FAULT_OOM; +out: if (old_folio) folio_put(old_folio);
delayacct_wpcopy_end(); - return VM_FAULT_OOM; + return ret; }
/** @@ -3444,12 +3463,6 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) return 0; } copy: - if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma->anon_vma) { - pte_unmap_unlock(vmf->pte, vmf->ptl); - vma_end_read(vmf->vma); - return VM_FAULT_RETRY; - } - /* * Ok, we need to copy. Oh, well.. */