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Subject[PATCH v4 5/8] mm: Pass 'address' to map to do_set_pte() and drop FAULT_FLAG_PREFAULT
Date
Rather than modifying the 'address' field of the 'struct vm_fault'
passed to do_set_pte(), leave that to identify the real faulting address
and pass in the virtual address to be mapped by the new pte as a
separate argument.

This makes FAULT_FLAG_PREFAULT redundant, as a prefault entry can be
identified simply by comparing the new address parameter with the
faulting address, so remove the redundant flag at the same time.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
include/linux/mm.h | 7 ++-----
mm/filemap.c | 21 +++++++--------------
mm/memory.c | 10 +++++-----
3 files changed, 14 insertions(+), 24 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b4a5cb9bff7d..e0f056753bef 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -434,7 +434,6 @@ extern pgprot_t protection_map[16];
* @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
* @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
* @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
- * @FAULT_FLAG_PREFAULT: Fault was a prefault.
*
* About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
* whether we would allow page faults to retry by specifying these two
@@ -465,7 +464,6 @@ extern pgprot_t protection_map[16];
#define FAULT_FLAG_REMOTE 0x80
#define FAULT_FLAG_INSTRUCTION 0x100
#define FAULT_FLAG_INTERRUPTIBLE 0x200
-#define FAULT_FLAG_PREFAULT 0x400

/*
* The default fault flags that should be used by most of the
@@ -503,8 +501,7 @@ static inline bool fault_flag_allow_retry_first(unsigned int flags)
{ FAULT_FLAG_USER, "USER" }, \
{ FAULT_FLAG_REMOTE, "REMOTE" }, \
{ FAULT_FLAG_INSTRUCTION, "INSTRUCTION" }, \
- { FAULT_FLAG_INTERRUPTIBLE, "INTERRUPTIBLE" }, \
- { FAULT_FLAG_PREFAULT, "PREFAULT" }
+ { FAULT_FLAG_INTERRUPTIBLE, "INTERRUPTIBLE" }

/*
* vm_fault is filled by the pagefault handler and passed to the vma's
@@ -995,7 +992,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
}

vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page);
-void do_set_pte(struct vm_fault *vmf, struct page *page);
+void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr);

vm_fault_t finish_fault(struct vm_fault *vmf);
vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf);
diff --git a/mm/filemap.c b/mm/filemap.c
index a6dc97906c8e..fb7a8d9b5603 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3018,8 +3018,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
struct file *file = vma->vm_file;
struct address_space *mapping = file->f_mapping;
pgoff_t last_pgoff = start_pgoff;
- unsigned long address = vmf->address;
- unsigned long flags = vmf->flags;
+ unsigned long addr;
XA_STATE(xas, &mapping->i_pages, start_pgoff);
struct page *head, *page;
unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
@@ -3035,8 +3034,8 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
goto out;
}

- vmf->address = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
- vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl);
+ addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
do {
page = find_subpage(head, xas.xa_index);
if (PageHWPoison(page))
@@ -3045,7 +3044,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
if (mmap_miss > 0)
mmap_miss--;

- vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
+ addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
vmf->pte += xas.xa_index - last_pgoff;
last_pgoff = xas.xa_index;

@@ -3053,16 +3052,12 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
goto unlock;

/* We're about to handle the fault */
- if (vmf->address == address) {
- vmf->flags &= ~FAULT_FLAG_PREFAULT;
+ if (vmf->address == addr)
ret = VM_FAULT_NOPAGE;
- } else {
- vmf->flags |= FAULT_FLAG_PREFAULT;
- }

- do_set_pte(vmf, page);
+ do_set_pte(vmf, page, addr);
/* no need to invalidate: a not-present page won't be cached */
- update_mmu_cache(vma, vmf->address, vmf->pte);
+ update_mmu_cache(vma, addr, vmf->pte);
unlock_page(head);
continue;
unlock:
@@ -3072,8 +3067,6 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
rcu_read_unlock();
- vmf->flags = flags;
- vmf->address = address;
WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
return ret;
}
diff --git a/mm/memory.c b/mm/memory.c
index f0e7c589ca9d..7b1307873325 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3733,11 +3733,11 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
}
#endif

-void do_set_pte(struct vm_fault *vmf, struct page *page)
+void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
{
struct vm_area_struct *vma = vmf->vma;
bool write = vmf->flags & FAULT_FLAG_WRITE;
- bool prefault = vmf->flags & FAULT_FLAG_PREFAULT;
+ bool prefault = vmf->address != addr;
pte_t entry;

flush_icache_page(vma, page);
@@ -3753,13 +3753,13 @@ void do_set_pte(struct vm_fault *vmf, struct page *page)
/* copy-on-write page */
if (write && !(vma->vm_flags & VM_SHARED)) {
inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, vmf->address, false);
+ page_add_new_anon_rmap(page, vma, addr, false);
lru_cache_add_inactive_or_unevictable(page, vma);
} else {
inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
page_add_file_rmap(page, false);
}
- set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
+ set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
}

/**
@@ -3819,7 +3819,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
ret = 0;
/* Re-check under ptl */
if (likely(pte_none(*vmf->pte)))
- do_set_pte(vmf, page);
+ do_set_pte(vmf, page, vmf->address);
else
ret = VM_FAULT_NOPAGE;

--
2.30.0.284.gd98b1dd5eaa7-goog
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