Commit bbff39cc6cbc ("hugetlb: allocate vma lock for all sharable vmas")
removed the pmd sharable checks in the vma lock helper routines.
However, it left the functional version of helper routines behind #ifdef
CONFIG_ARCH_WANT_HUGE_PMD_SHARE. Therefore, the vma lock is not being
used for sharable vmas on architectures that do not support pmd sharing.
On these architectures, a potential fault/truncation race is exposed
that could leave pages in a hugetlb file past i_size until the file is
removed.
Move the functional vma lock helpers outside the ifdef, and remove the
non-functional stubs. Since the vma lock is not just for pmd sharing,
rename the routine __vma_shareable_flags_pmd.
Fixes: bbff39cc6cbc ("hugetlb: allocate vma lock for all sharable vmas")
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
mm/hugetlb.c | 333 +++++++++++++++++++++++----------------------------
1 file changed, 148 insertions(+), 185 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e36ca75311a5..9c251faeb6f5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -255,6 +255,152 @@ static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
return subpool_inode(file_inode(vma->vm_file));
}
+/*
+ * hugetlb vma_lock helper routines
+ */
+static bool __vma_shareable_lock(struct vm_area_struct *vma)
+{
+ return vma->vm_flags & (VM_MAYSHARE | VM_SHARED) &&
+ vma->vm_private_data;
+}
+
+void hugetlb_vma_lock_read(struct vm_area_struct *vma)
+{
+ if (__vma_shareable_lock(vma)) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ down_read(&vma_lock->rw_sema);
+ }
+}
+
+void hugetlb_vma_unlock_read(struct vm_area_struct *vma)
+{
+ if (__vma_shareable_lock(vma)) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ up_read(&vma_lock->rw_sema);
+ }
+}
+
+void hugetlb_vma_lock_write(struct vm_area_struct *vma)
+{
+ if (__vma_shareable_lock(vma)) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ down_write(&vma_lock->rw_sema);
+ }
+}
+
+void hugetlb_vma_unlock_write(struct vm_area_struct *vma)
+{
+ if (__vma_shareable_lock(vma)) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ up_write(&vma_lock->rw_sema);
+ }
+}
+
+int hugetlb_vma_trylock_write(struct vm_area_struct *vma)
+{
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ if (!__vma_shareable_lock(vma))
+ return 1;
+
+ return down_write_trylock(&vma_lock->rw_sema);
+}
+
+void hugetlb_vma_assert_locked(struct vm_area_struct *vma)
+{
+ if (__vma_shareable_lock(vma)) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ lockdep_assert_held(&vma_lock->rw_sema);
+ }
+}
+
+void hugetlb_vma_lock_release(struct kref *kref)
+{
+ struct hugetlb_vma_lock *vma_lock = container_of(kref,
+ struct hugetlb_vma_lock, refs);
+
+ kfree(vma_lock);
+}
+
+static void __hugetlb_vma_unlock_write_put(struct hugetlb_vma_lock *vma_lock)
+{
+ struct vm_area_struct *vma = vma_lock->vma;
+
+ /*
+ * vma_lock structure may or not be released as a result of put,
+ * it certainly will no longer be attached to vma so clear pointer.
+ * Semaphore synchronizes access to vma_lock->vma field.
+ */
+ vma_lock->vma = NULL;
+ vma->vm_private_data = NULL;
+ up_write(&vma_lock->rw_sema);
+ kref_put(&vma_lock->refs, hugetlb_vma_lock_release);
+}
+
+static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma)
+{
+ if (__vma_shareable_lock(vma)) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ __hugetlb_vma_unlock_write_put(vma_lock);
+ }
+}
+
+static void hugetlb_vma_lock_free(struct vm_area_struct *vma)
+{
+ /*
+ * Only present in sharable vmas.
+ */
+ if (!vma || !__vma_shareable_lock(vma))
+ return;
+
+ if (vma->vm_private_data) {
+ struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
+
+ down_write(&vma_lock->rw_sema);
+ __hugetlb_vma_unlock_write_put(vma_lock);
+ }
+}
+
+static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
+{
+ struct hugetlb_vma_lock *vma_lock;
+
+ /* Only establish in (flags) sharable vmas */
+ if (!vma || !(vma->vm_flags & VM_MAYSHARE))
+ return;
+
+ /* Should never get here with non-NULL vm_private_data */
+ if (vma->vm_private_data)
+ return;
+
+ vma_lock = kmalloc(sizeof(*vma_lock), GFP_KERNEL);
+ if (!vma_lock) {
+ /*
+ * If we can not allocate structure, then vma can not
+ * participate in pmd sharing. This is only a possible
+ * performance enhancement and memory saving issue.
+ * However, the lock is also used to synchronize page
+ * faults with truncation. If the lock is not present,
+ * unlikely races could leave pages in a file past i_size
+ * until the file is removed. Warn in the unlikely case of
+ * allocation failure.
+ */
+ pr_warn_once("HugeTLB: unable to allocate vma specific lock\n");
+ return;
+ }
+
+ kref_init(&vma_lock->refs);
+ init_rwsem(&vma_lock->rw_sema);
+ vma_lock->vma = vma;
+ vma->vm_private_data = vma_lock;
+}
+
/* Helper that removes a struct file_region from the resv_map cache and returns
* it for use.
*/
@@ -6557,7 +6703,8 @@ bool hugetlb_reserve_pages(struct inode *inode,
}
/*
- * vma specific semaphore used for pmd sharing synchronization
+ * vma specific semaphore used for pmd sharing and fault/truncation
+ * synchronization
*/
hugetlb_vma_lock_alloc(vma);
@@ -6813,149 +6960,6 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
*end = ALIGN(*end, PUD_SIZE);
}
-static bool __vma_shareable_flags_pmd(struct vm_area_struct *vma)
-{
- return vma->vm_flags & (VM_MAYSHARE | VM_SHARED) &&
- vma->vm_private_data;
-}
-
-void hugetlb_vma_lock_read(struct vm_area_struct *vma)
-{
- if (__vma_shareable_flags_pmd(vma)) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- down_read(&vma_lock->rw_sema);
- }
-}
-
-void hugetlb_vma_unlock_read(struct vm_area_struct *vma)
-{
- if (__vma_shareable_flags_pmd(vma)) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- up_read(&vma_lock->rw_sema);
- }
-}
-
-void hugetlb_vma_lock_write(struct vm_area_struct *vma)
-{
- if (__vma_shareable_flags_pmd(vma)) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- down_write(&vma_lock->rw_sema);
- }
-}
-
-void hugetlb_vma_unlock_write(struct vm_area_struct *vma)
-{
- if (__vma_shareable_flags_pmd(vma)) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- up_write(&vma_lock->rw_sema);
- }
-}
-
-int hugetlb_vma_trylock_write(struct vm_area_struct *vma)
-{
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- if (!__vma_shareable_flags_pmd(vma))
- return 1;
-
- return down_write_trylock(&vma_lock->rw_sema);
-}
-
-void hugetlb_vma_assert_locked(struct vm_area_struct *vma)
-{
- if (__vma_shareable_flags_pmd(vma)) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- lockdep_assert_held(&vma_lock->rw_sema);
- }
-}
-
-void hugetlb_vma_lock_release(struct kref *kref)
-{
- struct hugetlb_vma_lock *vma_lock = container_of(kref,
- struct hugetlb_vma_lock, refs);
-
- kfree(vma_lock);
-}
-
-static void __hugetlb_vma_unlock_write_put(struct hugetlb_vma_lock *vma_lock)
-{
- struct vm_area_struct *vma = vma_lock->vma;
-
- /*
- * vma_lock structure may or not be released as a result of put,
- * it certainly will no longer be attached to vma so clear pointer.
- * Semaphore synchronizes access to vma_lock->vma field.
- */
- vma_lock->vma = NULL;
- vma->vm_private_data = NULL;
- up_write(&vma_lock->rw_sema);
- kref_put(&vma_lock->refs, hugetlb_vma_lock_release);
-}
-
-static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma)
-{
- if (__vma_shareable_flags_pmd(vma)) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- __hugetlb_vma_unlock_write_put(vma_lock);
- }
-}
-
-static void hugetlb_vma_lock_free(struct vm_area_struct *vma)
-{
- /*
- * Only present in sharable vmas.
- */
- if (!vma || !__vma_shareable_flags_pmd(vma))
- return;
-
- if (vma->vm_private_data) {
- struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
-
- down_write(&vma_lock->rw_sema);
- __hugetlb_vma_unlock_write_put(vma_lock);
- }
-}
-
-static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
-{
- struct hugetlb_vma_lock *vma_lock;
-
- /* Only establish in (flags) sharable vmas */
- if (!vma || !(vma->vm_flags & VM_MAYSHARE))
- return;
-
- /* Should never get here with non-NULL vm_private_data */
- if (vma->vm_private_data)
- return;
-
- vma_lock = kmalloc(sizeof(*vma_lock), GFP_KERNEL);
- if (!vma_lock) {
- /*
- * If we can not allocate structure, then vma can not
- * participate in pmd sharing. This is only a possible
- * performance enhancement and memory saving issue.
- * However, the lock is also used to synchronize page
- * faults with truncation. If the lock is not present,
- * unlikely races could leave pages in a file past i_size
- * until the file is removed. Warn in the unlikely case of
- * allocation failure.
- */
- pr_warn_once("HugeTLB: unable to allocate vma specific lock\n");
- return;
- }
-
- kref_init(&vma_lock->refs);
- init_rwsem(&vma_lock->rw_sema);
- vma_lock->vma = vma;
- vma->vm_private_data = vma_lock;
-}
-
/*
* Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
* and returns the corresponding pte. While this is not necessary for the
@@ -7044,47 +7048,6 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
#else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
-void hugetlb_vma_lock_read(struct vm_area_struct *vma)
-{
-}
-
-void hugetlb_vma_unlock_read(struct vm_area_struct *vma)
-{
-}
-
-void hugetlb_vma_lock_write(struct vm_area_struct *vma)
-{
-}
-
-void hugetlb_vma_unlock_write(struct vm_area_struct *vma)
-{
-}
-
-int hugetlb_vma_trylock_write(struct vm_area_struct *vma)
-{
- return 1;
-}
-
-void hugetlb_vma_assert_locked(struct vm_area_struct *vma)
-{
-}
-
-void hugetlb_vma_lock_release(struct kref *kref)
-{
-}
-
-static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma)
-{
-}
-
-static void hugetlb_vma_lock_free(struct vm_area_struct *vma)
-{
-}
-
-static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
-{
-}
-
pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pud_t *pud)
{
--
2.38.1
