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Message-ID: <lsq.1538257387.239210527@decadent.org.uk>
Date: Sat, 29 Sep 2018 22:43:07 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org,
"Linus Torvalds" <torvalds@...ux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 3.16 055/131] mm: drop support of non-linear mapping from
fault codepath
3.16.59-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
commit 9b4bdd2ffab9557ac43af7dff02e7dab1c8c58bd upstream.
We don't create non-linear mappings anymore. Let's drop code which
handles them on page fault.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[bwh: Backported to 3.16:
- Deleted code is slightly different
- Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
include/linux/mm.h | 16 +++++-------
mm/memory.c | 65 +++++++---------------------------------------
2 files changed, 16 insertions(+), 65 deletions(-)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -187,21 +187,19 @@ extern unsigned int kobjsize(const void
extern pgprot_t protection_map[16];
#define FAULT_FLAG_WRITE 0x01 /* Fault was a write access */
-#define FAULT_FLAG_NONLINEAR 0x02 /* Fault was via a nonlinear mapping */
-#define FAULT_FLAG_MKWRITE 0x04 /* Fault was mkwrite of existing pte */
-#define FAULT_FLAG_ALLOW_RETRY 0x08 /* Retry fault if blocking */
-#define FAULT_FLAG_RETRY_NOWAIT 0x10 /* Don't drop mmap_sem and wait when retrying */
-#define FAULT_FLAG_KILLABLE 0x20 /* The fault task is in SIGKILL killable region */
-#define FAULT_FLAG_TRIED 0x40 /* second try */
-#define FAULT_FLAG_USER 0x80 /* The fault originated in userspace */
+#define FAULT_FLAG_MKWRITE 0x02 /* Fault was mkwrite of existing pte */
+#define FAULT_FLAG_ALLOW_RETRY 0x04 /* Retry fault if blocking */
+#define FAULT_FLAG_RETRY_NOWAIT 0x08 /* Don't drop mmap_sem and wait when retrying */
+#define FAULT_FLAG_KILLABLE 0x10 /* The fault task is in SIGKILL killable region */
+#define FAULT_FLAG_TRIED 0x20 /* Second try */
+#define FAULT_FLAG_USER 0x40 /* The fault originated in userspace */
/*
* vm_fault is filled by the the pagefault handler and passed to the vma's
* ->fault function. The vma's ->fault is responsible for returning a bitmask
* of VM_FAULT_xxx flags that give details about how the fault was handled.
*
- * pgoff should be used in favour of virtual_address, if possible. If pgoff
- * is used, one may implement ->remap_pages to get nonlinear mapping support.
+ * pgoff should be used in favour of virtual_address, if possible.
*/
struct vm_fault {
unsigned int flags; /* FAULT_FLAG_xxx flags */
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1912,12 +1912,11 @@ int apply_to_page_range(struct mm_struct
EXPORT_SYMBOL_GPL(apply_to_page_range);
/*
- * handle_pte_fault chooses page fault handler according to an entry
- * which was read non-atomically. Before making any commitment, on
- * those architectures or configurations (e.g. i386 with PAE) which
- * might give a mix of unmatched parts, do_swap_page and do_nonlinear_fault
- * must check under lock before unmapping the pte and proceeding
- * (but do_wp_page is only called after already making such a check;
+ * handle_pte_fault chooses page fault handler according to an entry which was
+ * read non-atomically. Before making any commitment, on those architectures
+ * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
+ * parts, do_swap_page must check under lock before unmapping the pte and
+ * proceeding (but do_wp_page is only called after already making such a check;
* and do_anonymous_page can safely check later on).
*/
static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
@@ -2676,8 +2675,6 @@ void do_set_pte(struct vm_area_struct *v
entry = mk_pte(page, vma->vm_page_prot);
if (write)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- else if (pte_file(*pte) && pte_file_soft_dirty(*pte))
- pte_mksoft_dirty(entry);
if (anon) {
inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, address);
@@ -2818,8 +2815,7 @@ static int do_read_fault(struct mm_struc
* if page by the offset is not ready to be mapped (cold cache or
* something).
*/
- if (vma->vm_ops->map_pages && !(flags & FAULT_FLAG_NONLINEAR) &&
- fault_around_pages() > 1) {
+ if (vma->vm_ops->map_pages && fault_around_pages() > 1) {
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
do_fault_around(vma, address, pte, pgoff, flags);
if (!pte_same(*pte, orig_pte))
@@ -2949,7 +2945,7 @@ static int do_shared_fault(struct mm_str
return ret;
}
-static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
unsigned int flags, pte_t orig_pte)
{
@@ -2969,44 +2965,6 @@ static int do_linear_fault(struct mm_str
return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}
-/*
- * Fault of a previously existing named mapping. Repopulate the pte
- * from the encoded file_pte if possible. This enables swappable
- * nonlinear vmas.
- *
- * 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.
- */
-static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long address, pte_t *page_table, pmd_t *pmd,
- unsigned int flags, pte_t orig_pte)
-{
- pgoff_t pgoff;
-
- flags |= FAULT_FLAG_NONLINEAR;
-
- if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
- return 0;
-
- if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
- /*
- * Page table corrupted: show pte and kill process.
- */
- print_bad_pte(vma, address, orig_pte, NULL);
- return VM_FAULT_SIGBUS;
- }
-
- pgoff = pte_to_pgoff(orig_pte);
- if (!(flags & FAULT_FLAG_WRITE))
- return do_read_fault(mm, vma, address, pmd, pgoff, flags,
- orig_pte);
- if (!(vma->vm_flags & VM_SHARED))
- return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
- orig_pte);
- return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
-}
-
static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
unsigned long addr, int page_nid,
int *flags)
@@ -3121,15 +3079,12 @@ static int handle_pte_fault(struct mm_st
if (!pte_present(entry)) {
if (pte_none(entry)) {
if (vma->vm_ops)
- return do_linear_fault(mm, vma, address,
- pte, pmd, flags, entry);
+ return do_fault(mm, vma, address, pte,
+ pmd, flags, entry);
return do_anonymous_page(mm, vma, address,
pte, pmd, flags);
}
- if (pte_file(entry))
- return do_nonlinear_fault(mm, vma, address,
- pte, pmd, flags, entry);
return do_swap_page(mm, vma, address,
pte, pmd, flags, entry);
}
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