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mm: allow vmas with vm_ops to be speculatively handled

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Right now only anonymous pages are speculatively faulted, thus
leaving out a large percentage of faults still requiring to
take mmap_sem. These were left out since there can be fault
handlers mainly in the fs layer which may use vma in unknown
ways. This patch covers filemap_fault and shmem_fault and
enables speculative fault for all those vmas with vm_ops.
None of the other common fault handlers is seen to use or
modify vma.

Change-Id: I4f87909002f7ac64945f048ba0169a4cac7a15ab
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
This commit is contained in:
Vinayak Menon 2018-12-11 18:03:55 +05:30
parent cf8acfa8c9
commit 0947fbfea4
5 changed files with 19 additions and 23 deletions
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3
include/linux/vm_event_item.h
View file

@ -111,7 +111,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PGPGOUTCLEAN, PSWPIN, PSWPOUT,
SWAP_RA_HIT,
#endif
#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
SPECULATIVE_PGFAULT,
SPECULATIVE_PGFAULT_ANON,
SPECULATIVE_PGFAULT_FILE,
#endif
NR_VM_EVENT_ITEMS
};

8
mm/filemap.c
View file

@ -2477,12 +2477,12 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
pgoff_t offset = vmf->pgoff;
/* If we don't want any read-ahead, don't bother */
if (vmf->vma->vm_flags & VM_RAND_READ)
if (vmf->vma_flags & VM_RAND_READ)
return fpin;
if (!ra->ra_pages)
return fpin;
if (vmf->vma->vm_flags & VM_SEQ_READ) {
if (vmf->vma_flags & VM_SEQ_READ) {
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
page_cache_sync_readahead(mapping, ra, file, offset,
ra->ra_pages);
@ -2526,7 +2526,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
pgoff_t offset = vmf->pgoff;
/* If we don't want any read-ahead, don't bother */
if (vmf->vma->vm_flags & VM_RAND_READ)
if (vmf->vma_flags & VM_RAND_READ)
return fpin;
if (ra->mmap_miss > 0)
ra->mmap_miss--;
@ -2549,7 +2549,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
* it in the page cache, and handles the special cases reasonably without
* having a lot of duplicated code.
*
* vma->vm_mm->mmap_sem must be held on entry.
* vma->vm_mm->mmap_sem must be held on entry (except FAULT_FLAG_SPECULATIVE).
*
* If our return value has VM_FAULT_RETRY set, it's because
* lock_page_or_retry() returned 0.

24
mm/memory.c
View file

@ -4215,6 +4215,7 @@ static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
{
pte_t entry;
int ret = 0;
if (unlikely(pmd_none(*vmf->pmd))) {
/*
@ -4267,8 +4268,6 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
if (!vmf->pte) {
if (vma_is_anonymous(vmf->vma))
return do_anonymous_page(vmf);
else if (vmf->flags & FAULT_FLAG_SPECULATIVE)
return VM_FAULT_RETRY;
else
return do_fault(vmf);
}
@ -4302,10 +4301,12 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
*/
if (vmf->flags & FAULT_FLAG_WRITE)
flush_tlb_fix_spurious_fault(vmf->vma, vmf->address);
if (vmf->flags & FAULT_FLAG_SPECULATIVE)
ret = VM_FAULT_RETRY;
}
unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
return 0;
return ret;
}
/*
@ -4449,22 +4450,12 @@ int __handle_speculative_fault(struct mm_struct *mm, unsigned long address,
return VM_FAULT_RETRY;
}
/*
* Can't call vm_ops service has we don't know what they would do
* with the VMA.
* This include huge page from hugetlbfs.
*/
if (vmf.vma->vm_ops) {
trace_spf_vma_notsup(_RET_IP_, vmf.vma, address);
return VM_FAULT_RETRY;
}
/*
* __anon_vma_prepare() requires the mmap_sem to be held
* because vm_next and vm_prev must be safe. This can't be guaranteed
* in the speculative path.
*/
if (unlikely(!vmf.vma->anon_vma)) {
if (unlikely(vma_is_anonymous(vmf.vma) && !vmf.vma->anon_vma)) {
trace_spf_vma_notsup(_RET_IP_, vmf.vma, address);
return VM_FAULT_RETRY;
}
@ -4606,7 +4597,10 @@ int __handle_speculative_fault(struct mm_struct *mm, unsigned long address,
* If there is no need to retry, don't return the vma to the caller.
*/
if (ret != VM_FAULT_RETRY) {
count_vm_event(SPECULATIVE_PGFAULT);
if (vma_is_anonymous(vmf.vma))
count_vm_event(SPECULATIVE_PGFAULT_ANON);
else
count_vm_event(SPECULATIVE_PGFAULT_FILE);
put_vma(vmf.vma);
*vma = NULL;
}

4
mm/shmem.c
View file

@ -2023,10 +2023,10 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
sgp = SGP_CACHE;
if ((vma->vm_flags & VM_NOHUGEPAGE) ||
if ((vmf->vma_flags & VM_NOHUGEPAGE) ||
test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
sgp = SGP_NOHUGE;
else if (vma->vm_flags & VM_HUGEPAGE)
else if (vmf->vma_flags & VM_HUGEPAGE)
sgp = SGP_HUGE;
err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,

3
mm/vmstat.c
View file

@ -1295,7 +1295,8 @@ const char * const vmstat_text[] = {
"swap_ra_hit",
#endif
#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
"speculative_pgfault"
"speculative_pgfault_anon",
"speculative_pgfault_file",
#endif
#endif /* CONFIG_VM_EVENT_COUNTERS */
};