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-rw-r--r--arch/s390/mm/pgtable.c8
-rw-r--r--include/linux/mm.h5
-rw-r--r--kernel/futex.c2
-rw-r--r--mm/gup.c30
4 files changed, 34 insertions, 11 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 4e54492..84bddda 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -585,7 +585,7 @@ int gmap_fault(struct gmap *gmap, unsigned long gaddr,
rc = vmaddr;
goto out_up;
}
- if (fixup_user_fault(current, gmap->mm, vmaddr, fault_flags)) {
+ if (fixup_user_fault(current, gmap->mm, vmaddr, fault_flags, NULL)) {
rc = -EFAULT;
goto out_up;
}
@@ -727,7 +727,8 @@ int gmap_ipte_notify(struct gmap *gmap, unsigned long gaddr, unsigned long len)
break;
}
/* Get the page mapped */
- if (fixup_user_fault(current, gmap->mm, addr, FAULT_FLAG_WRITE)) {
+ if (fixup_user_fault(current, gmap->mm, addr, FAULT_FLAG_WRITE,
+ NULL)) {
rc = -EFAULT;
break;
}
@@ -802,7 +803,8 @@ retry:
if (!(pte_val(*ptep) & _PAGE_INVALID) &&
(pte_val(*ptep) & _PAGE_PROTECT)) {
pte_unmap_unlock(ptep, ptl);
- if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE)) {
+ if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE,
+ NULL)) {
up_read(&mm->mmap_sem);
return -EFAULT;
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 792f246..1d6ec55 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1194,7 +1194,8 @@ int invalidate_inode_page(struct page *page);
extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, unsigned int flags);
extern int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long address, unsigned int fault_flags);
+ unsigned long address, unsigned int fault_flags,
+ bool *unlocked);
#else
static inline int handle_mm_fault(struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long address,
@@ -1206,7 +1207,7 @@ static inline int handle_mm_fault(struct mm_struct *mm,
}
static inline int fixup_user_fault(struct task_struct *tsk,
struct mm_struct *mm, unsigned long address,
- unsigned int fault_flags)
+ unsigned int fault_flags, bool *unlocked)
{
/* should never happen if there's no MMU */
BUG();
diff --git a/kernel/futex.c b/kernel/futex.c
index eed92a8..c6f5145 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -604,7 +604,7 @@ static int fault_in_user_writeable(u32 __user *uaddr)
down_read(&mm->mmap_sem);
ret = fixup_user_fault(current, mm, (unsigned long)uaddr,
- FAULT_FLAG_WRITE);
+ FAULT_FLAG_WRITE, NULL);
up_read(&mm->mmap_sem);
return ret < 0 ? ret : 0;
diff --git a/mm/gup.c b/mm/gup.c
index aa21c4b..b64a361 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -618,6 +618,8 @@ EXPORT_SYMBOL(__get_user_pages);
* @mm: mm_struct of target mm
* @address: user address
* @fault_flags:flags to pass down to handle_mm_fault()
+ * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
+ * does not allow retry
*
* This is meant to be called in the specific scenario where for locking reasons
* we try to access user memory in atomic context (within a pagefault_disable()
@@ -629,22 +631,28 @@ EXPORT_SYMBOL(__get_user_pages);
* The main difference with get_user_pages() is that this function will
* unconditionally call handle_mm_fault() which will in turn perform all the
* necessary SW fixup of the dirty and young bits in the PTE, while
- * handle_mm_fault() only guarantees to update these in the struct page.
+ * get_user_pages() only guarantees to update these in the struct page.
*
* This is important for some architectures where those bits also gate the
* access permission to the page because they are maintained in software. On
* such architectures, gup() will not be enough to make a subsequent access
* succeed.
*
- * This has the same semantics wrt the @mm->mmap_sem as does filemap_fault().
+ * This function will not return with an unlocked mmap_sem. So it has not the
+ * same semantics wrt the @mm->mmap_sem as does filemap_fault().
*/
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long address, unsigned int fault_flags)
+ unsigned long address, unsigned int fault_flags,
+ bool *unlocked)
{
struct vm_area_struct *vma;
vm_flags_t vm_flags;
- int ret;
+ int ret, major = 0;
+
+ if (unlocked)
+ fault_flags |= FAULT_FLAG_ALLOW_RETRY;
+retry:
vma = find_extend_vma(mm, address);
if (!vma || address < vma->vm_start)
return -EFAULT;
@@ -654,6 +662,7 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
return -EFAULT;
ret = handle_mm_fault(mm, vma, address, fault_flags);
+ major |= ret & VM_FAULT_MAJOR;
if (ret & VM_FAULT_ERROR) {
if (ret & VM_FAULT_OOM)
return -ENOMEM;
@@ -663,8 +672,19 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
return -EFAULT;
BUG();
}
+
+ if (ret & VM_FAULT_RETRY) {
+ down_read(&mm->mmap_sem);
+ if (!(fault_flags & FAULT_FLAG_TRIED)) {
+ *unlocked = true;
+ fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ fault_flags |= FAULT_FLAG_TRIED;
+ goto retry;
+ }
+ }
+
if (tsk) {
- if (ret & VM_FAULT_MAJOR)
+ if (major)
tsk->maj_flt++;
else
tsk->min_flt++;
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