[patch 5/5] mm: merge nopfn with fault handler

Nick Piggin
2006-10-10T14:22:23Z

Remove ->nopfn and reimplement the only existing handler using ->fault

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/drivers/char/mspec.c
===================================================================
--- linux-2.6.orig/drivers/char/mspec.c
+++ linux-2.6/drivers/char/mspec.c
@@ -178,24 +178,25 @@ mspec_close(struct vm_area_struct *vma)

/*
- * mspec_nopfn
+ * mspec_fault
*
* Creates a mspec page and maps it to user space.
*/
-static unsigned long
-mspec_nopfn(struct vm_area_struct *vma, unsigned long address)
+static struct page *
+mspec_fault(struct fault_data *fdata)
{
unsigned long paddr, maddr;
unsigned long pfn;
- int index;
- struct vma_data *vdata = vma->vm_private_data;
+ int index = fdata->pgoff;
+ struct vma_data *vdata = fdata->vma->vm_private_data;

- index = (address - vma->vm_start) >> PAGE_SHIFT;
maddr = (volatile unsigned long) vdata->maddr[index];
if (maddr == 0) {
maddr = uncached_alloc_page(numa_node_id());
- if (maddr == 0)
- return NOPFN_OOM;
+ if (maddr == 0) {
+ fdata->type = VM_FAULT_OOM;
+ return NULL;
+ }

spin_lock(&vdata->lock);
if (vdata->maddr[index] == 0) {
@@ -215,13 +216,21 @@ mspec_nopfn(struct vm_area_struct *vma,

pfn = paddr >> PAGE_SHIFT;

- return pfn;
+ fdata->type = VM_FAULT_MINOR;
+ /*
+ * vm_insert_pfn can fail with -EBUSY, but in that case it will
+ * be because another thread has installed the pte first, so it
+ * is no problem.
+ */
+ vm_insert_pfn(fdata->vma, fdata->address, pfn);
+
+ return NULL;
}

static struct vm_operations_struct mspec_vm_ops = {
.open = mspec_open,
.close = mspec_close,
- .nopfn = mspec_nopfn
+ .fault = mspec_fault,
};

/*
Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h
+++ linux-2.6/include/linux/mm.h
@@ -223,7 +223,6 @@ struct vm_operations_struct {
void (*close)(struct vm_area_struct * area);
struct page * (*fault)(struct vm_area_struct *vma, struct fault_data * fdata);
struct page * (*nopage)(struct vm_area_struct * area, unsigned long address, int *type);
- unsigned long (*nopfn)(struct vm_area_struct * area, unsigned long address);
int (*populate)(struct vm_area_struct * area, unsigned long address, unsigned long len, pgprot_t prot, unsigned long pgoff, int nonblock);

/* notification that a previously read-only page is about to become
@@ -635,12 +634,6 @@ static inline int page_mapped(struct pag
#define NOPAGE_OOM ((struct page *) (-1))

/*
- * Error return values for the *_nopfn functions
- */
-#define NOPFN_SIGBUS ((unsigned long) -1)
-#define NOPFN_OOM ((unsigned long) -2)
-
-/*
* Different kinds of faults, as returned by handle_mm_fault().
* Used to decide whether a process gets delivered SIGBUS or
* just gets major/minor fault counters bumped up.
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c
+++ linux-2.6/mm/memory.c
@@ -1278,6 +1278,11 @@ EXPORT_SYMBOL(vm_insert_page);
*
* This function should only be called from a vm_ops->fault handler, and
* in that case the handler should return NULL.
+ *
+ * vma cannot be a COW mapping.
+ *
+ * As this is called only for pages that do not currently exist, we
+ * do not need to flush old virtual caches or the TLB.
*/
int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
{
@@ -2336,54 +2341,6 @@ static int do_nonlinear_fault(struct mm_
}

/*
- * do_no_pfn() tries to create a new page mapping for a page without
- * a struct_page backing it
- *
- * As this is called only for pages that do not currently exist, we
- * do not need to flush old virtual caches or the TLB.
- *
- * We enter with non-exclusive mmap_sem (to exclude vma changes,
- * but allow concurrent faults), and pte mapped but not yet locked.
- * We return with mmap_sem still held, but pte unmapped and unlocked.
- *
- * It is expected that the ->nopfn handler always returns the same pfn
- * for a given virtual mapping.
- *
- * Mark this `noinline' to prevent it from bloating the main pagefault code.
- */
-static noinline int do_no_pfn(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long address, pte_t *page_table, pmd_t *pmd,
- int write_access)
-{
- spinlock_t *ptl;
- pte_t entry;
- unsigned long pfn;
- int ret = VM_FAULT_MINOR;
-
- pte_unmap(page_table);
- BUG_ON(!(vma->vm_flags & VM_PFNMAP));
- BUG_ON(is_cow_mapping(vma->vm_flags));
-
- pfn = vma->vm_ops->nopfn(vma, address & PAGE_MASK);
- if (pfn == NOPFN_OOM)
- return VM_FAULT_OOM;
- if (pfn == NOPFN_SIGBUS)
- return VM_FAULT_SIGBUS;
-
- page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
-
- /* Only go through if we didn't race with anybody else... */
- if (pte_none(*page_table)) {
- entry = pfn_pte(pfn, vma->vm_page_prot);
- if (write_access)
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- set_pte_at(mm, address, page_table, entry);
- }
- pte_unmap_unlock(page_table, ptl);
- return ret;
-}
-
-/*
* Fault of a previously existing named mapping. Repopulate the pte
* from the encoded file_pte if possible. This enables swappable
* nonlinear vmas.
@@ -2454,9 +2411,6 @@ static inline int handle_pte_fault(struc
if (vma->vm_ops->fault || vma->vm_ops->nopage)
return do_linear_fault(mm, vma, address,
pte, pmd, write_access, entry);
- if (unlikely(vma->vm_ops->nopfn))
- return do_no_pfn(mm, vma, address, pte,
- pmd, write_access);
}
return do_anonymous_page(mm, vma, address,
pte, pmd, write_access);