BACKPORT: mmap locking API: rename mmap_sem to mmap_lock

Rename the mmap_sem field to mmap_lock.  Any new uses of this lock should
now go through the new mmap locking api.  The mmap_lock is still
implemented as a rwsem, though this could change in the future.

[akpm@linux-foundation.org: fix it for mm-gup-might_lock_readmmap_sem-in-get_user_pages_fast.patch]

Change-Id: I4d550763e380f418e10b6a80e2c88b4cc4caaeea
Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ying Han <yinghan@google.com>
Link: http://lkml.kernel.org/r/20200520052908.204642-11-walken@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/ia64/mm/fault.c

@@ -92,8 +92,8 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
 		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
 
-	/* mmap_sem is performance critical.... */
-	prefetchw(&mm->mmap_sem);
+	/* mmap_lock is performance critical.... */
+	prefetchw(&mm->mmap_lock);
 
 	/*
 	 * If we're in an interrupt or have no user context, we must not take the fault..

arch/mips/mm/fault.c

@@ -97,7 +97,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
 retry:
-	down_read(&mm->mmap_sem);
+	down_read(&mm->mmap_lock);
 	vma = find_vma(mm, address);
 	if (!vma)
 		goto bad_area;
@@ -182,7 +182,7 @@ good_area:
 			flags |= FAULT_FLAG_TRIED;
 
 			/*
-			 * No need to up_read(&mm->mmap_sem) as we would
+			 * No need to up_read(&mm->mmap_lock) as we would
 			 * have already released it in __lock_page_or_retry
 			 * in mm/filemap.c.
 			 */
@@ -191,7 +191,7 @@ good_area:
 		}
 	}
 
-	up_read(&mm->mmap_sem);
+	up_read(&mm->mmap_lock);
 	return;
 
 /*
@@ -199,7 +199,7 @@ good_area:
  * Fix it, but check if it's kernel or user first..
  */
 bad_area:
-	up_read(&mm->mmap_sem);
+	up_read(&mm->mmap_lock);
 
 bad_area_nosemaphore:
 	/* User mode accesses just cause a SIGSEGV */
@@ -251,14 +251,14 @@ out_of_memory:
 	 * We ran out of memory, call the OOM killer, and return the userspace
 	 * (which will retry the fault, or kill us if we got oom-killed).
 	 */
-	up_read(&mm->mmap_sem);
+	up_read(&mm->mmap_lock);
 	if (!user_mode(regs))
 		goto no_context;
 	pagefault_out_of_memory();
 	return;
 
 do_sigbus:
-	up_read(&mm->mmap_sem);
+	up_read(&mm->mmap_lock);
 
 	/* Kernel mode? Handle exceptions or die */
 	if (!user_mode(regs))

arch/powerpc/platforms/powernv/npu-dma.c

@@ -938,7 +938,7 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea,
 	if (!firmware_has_feature(FW_FEATURE_OPAL))
 		return -ENODEV;
 
-	WARN_ON(!rwsem_is_locked(&mm->mmap_sem));
+	WARN_ON(!rwsem_is_locked(&mm->mmap_lock));
 
 	for (i = 0; i < count; i++) {
 		is_write = flags[i] & NPU2_WRITE;

arch/x86/events/core.c

@@ -2126,7 +2126,7 @@ static void x86_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
 	 * For now, this can't happen because all callers hold mmap_sem
 	 * for write.  If this changes, we'll need a different solution.
 	 */
-	lockdep_assert_held_exclusive(&mm->mmap_sem);
+	lockdep_assert_held_exclusive(&mm->mmap_lock);
 
 	if (atomic_inc_return(&mm->context.perf_rdpmc_allowed) == 1)
 		on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);

arch/x86/mm/fault.c

@@ -1244,7 +1244,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	tsk = current;
 	mm = tsk->mm;
 
-	prefetchw(&mm->mmap_sem);
+	prefetchw(&mm->mmap_lock);
 
 	if (unlikely(kmmio_fault(regs, address)))
 		return;

drivers/char/adsprpc.c

@@ -1890,15 +1890,15 @@ static int get_args(uint32_t kernel, struct smq_invoke_ctx *ctx)
 			if (map->attr & FASTRPC_ATTR_NOVA) {
 				offset = 0;
 			} else {
-				down_read(&current->mm->mmap_sem);
+				down_read(&current->mm->mmap_lock);
 				VERIFY(err, NULL != (vma = find_vma(current->mm,
 								map->va)));
 				if (err) {
-					up_read(&current->mm->mmap_sem);
+					up_read(&current->mm->mmap_lock);
 					goto bail;
 				}
 				offset = buf_page_start(buf) - vma->vm_start;
-				up_read(&current->mm->mmap_sem);
+				up_read(&current->mm->mmap_lock);
 				VERIFY(err,
 					offset + len <= (uintptr_t)map->size);
 				if (err)
@@ -2022,11 +2022,11 @@ static int get_args(uint32_t kernel, struct smq_invoke_ctx *ctx)
 					uint64_t flush_len;
 					struct vm_area_struct *vma;
 
-					down_read(&current->mm->mmap_sem);
+					down_read(&current->mm->mmap_lock);
 					VERIFY(err, NULL != (vma = find_vma(
 						current->mm, rpra[i].buf.pv)));
 					if (err) {
-						up_read(&current->mm->mmap_sem);
+						up_read(&current->mm->mmap_lock);
 						goto bail;
 					}
 					if (ctx->overps[oix]->do_cmo) {
@@ -2041,7 +2041,7 @@ static int get_args(uint32_t kernel, struct smq_invoke_ctx *ctx)
 						ctx->overps[oix]->mend -
 						ctx->overps[oix]->mstart;
 					}
-					up_read(&current->mm->mmap_sem);
+					up_read(&current->mm->mmap_lock);
 					dma_buf_begin_cpu_access_partial(
 						map->buf, DMA_TO_DEVICE, offset,
 						flush_len);

drivers/gpu/drm/etnaviv/etnaviv_gem.c

@@ -695,7 +695,7 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj)
 	struct etnaviv_gem_userptr *userptr = &etnaviv_obj->userptr;
 	int ret, pinned = 0, npages = etnaviv_obj->base.size >> PAGE_SHIFT;
 
-	might_lock_read(&current->mm->mmap_sem);
+	might_lock_read(&current->mm->mmap_lock);
 
 	if (userptr->mm != current->mm)
 		return -EPERM;

drivers/misc/okl4-link-shbuf.c

@@ -259,7 +259,7 @@ static int link_shbuf_mmap(struct file *file, struct vm_area_struct *vma)
 	pgprot_t prot;
 
 	/* Our caller should have taken the MM semaphore. */
-	if (WARN_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem)))
+	if (WARN_ON(!rwsem_is_locked(&vma->vm_mm->mmap_lock)))
 		return -EINVAL;
 
 	/*

fs/userfaultfd.c

@@ -235,7 +235,7 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
 	pte_t *ptep, pte;
 	bool ret = true;
 
-	VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
+	VM_BUG_ON(!rwsem_is_locked(&mm->mmap_locked));
 
 	ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
 
@@ -287,7 +287,7 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
 	pte_t *pte;
 	bool ret = true;
 
-	VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
+	VM_BUG_ON(!rwsem_is_locked(&mm->mmap_lock));
 
 	pgd = pgd_offset(mm, address);
 	if (!pgd_present(*pgd))
@@ -401,7 +401,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	 * Coredumping runs without mmap_sem so we can only check that
 	 * the mmap_sem is held, if PF_DUMPCORE was not set.
 	 */
-	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_lock));
 
 	ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
 	if (!ctx)

include/linux/mm_types.h

@@ -410,7 +410,7 @@ struct mm_struct {
 		spinlock_t page_table_lock; /* Protects page tables and some
 					     * counters
 					     */
-		struct rw_semaphore mmap_sem;
+		struct rw_semaphore mmap_lock;
 
 		struct list_head mmlist; /* List of maybe swapped mm's.	These
 					  * are globally strung together off

include/linux/mmap_lock.h

@@ -3,58 +3,58 @@
 
 static inline void mmap_init_lock(struct mm_struct *mm)
 {
-	init_rwsem(&mm->mmap_sem);
+	init_rwsem(&mm->mmap_lock);
 }
 
 static inline void mmap_write_lock(struct mm_struct *mm)
 {
-	down_write(&mm->mmap_sem);
+	down_write(&mm->mmap_lock);
 }
 
 static inline int mmap_write_lock_killable(struct mm_struct *mm)
 {
-	return down_write_killable(&mm->mmap_sem);
+	return down_write_killable(&mm->mmap_lock);
 }
 
 static inline bool mmap_write_trylock(struct mm_struct *mm)
 {
-	return down_write_trylock(&mm->mmap_sem) != 0;
+	return down_write_trylock(&mm->mmap_lock) != 0;
 }
 
 static inline void mmap_write_unlock(struct mm_struct *mm)
 {
-	up_write(&mm->mmap_sem);
+	up_write(&mm->mmap_lock);
 }
 
 static inline void mmap_write_downgrade(struct mm_struct *mm)
 {
-	downgrade_write(&mm->mmap_sem);
+	downgrade_write(&mm->mmap_lock);
 }
 
 static inline void mmap_read_lock(struct mm_struct *mm)
 {
-	down_read(&mm->mmap_sem);
+	down_read(&mm->mmap_lock);
 }
 
 static inline int mmap_read_lock_killable(struct mm_struct *mm)
 {
-	return down_read_killable(&mm->mmap_sem);
+	return down_read_killable(&mm->mmap_lock);
 }
 
 static inline bool mmap_read_trylock(struct mm_struct *mm)
 {
-	return down_read_trylock(&mm->mmap_sem) != 0;
+	return down_read_trylock(&mm->mmap_lock) != 0;
 }
 
 static inline void mmap_read_unlock(struct mm_struct *mm)
 {
-	up_read(&mm->mmap_sem);
+	up_read(&mm->mmap_lock);
 }
 
 static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
 {
-	if (down_read_trylock(&mm->mmap_sem)) {
-		rwsem_release(&mm->mmap_sem.dep_map, _RET_IP_);
+	if (down_read_trylock(&mm->mmap_lock)) {
+		rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_);
 		return true;
 	}
 	return false;
@@ -62,7 +62,7 @@ static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
 
 static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
 {
-	up_read_non_owner(&mm->mmap_sem);
+	up_read_non_owner(&mm->mmap_lock);
 }
 
 #endif /* _LINUX_MMAP_LOCK_H */

kernel/fork.c

@@ -449,7 +449,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 	/*
 	 * Not linked in yet - no deadlock potential:
 	 */
-	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
+	down_write_nested(&mm->mmap_lock, SINGLE_DEPTH_NESTING);
 
 	/* No ordering required: file already has been exposed. */
 	RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));

mm/gup.c

@@ -1292,7 +1292,7 @@ long populate_vma_page_range(struct vm_area_struct *vma,
 	VM_BUG_ON(end   & ~PAGE_MASK);
 	VM_BUG_ON_VMA(start < vma->vm_start, vma);
 	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
-	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
+	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
 
 	gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
 	if (vma->vm_flags & VM_LOCKONFAULT)

mm/init-mm.c

@@ -30,7 +30,7 @@ struct mm_struct init_mm = {
 	.pgd		= swapper_pg_dir,
 	.mm_users	= ATOMIC_INIT(2),
 	.mm_count	= ATOMIC_INIT(1),
-	.mmap_sem	= __RWSEM_INITIALIZER(init_mm.mmap_sem),
+	.mmap_lock	= __RWSEM_INITIALIZER(init_mm.mmap_lock),
 	.page_table_lock =  __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
 	.arg_lock	=  __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
 	.mmlist		= LIST_HEAD_INIT(init_mm.mmlist),

mm/khugepaged.c

@@ -1316,7 +1316,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
 				 * mmap_sem in read mode.
 				 */
 				if (vma->anon_vma) {
-					up_write(&mm->mmap_sem);
+					up_write(&mm->mmap_lock);
 					continue;
 				}
 				mmu_notifier_invalidate_range_start(mm, addr,

mm/memory.c

@@ -1272,7 +1272,7 @@ static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
 		next = pud_addr_end(addr, end);
 		if (pud_trans_huge(*pud) || pud_devmap(*pud)) {
 			if (next - addr != HPAGE_PUD_SIZE) {
-				VM_BUG_ON_VMA(!rwsem_is_locked(&tlb->mm->mmap_sem), vma);
+				VM_BUG_ON_VMA(!rwsem_is_locked(&tlb->mm->mmap_lock), vma);
 				split_huge_pud(vma, pud, addr);
 			} else if (zap_huge_pud(tlb, vma, pud, addr))
 				goto next;
@@ -4628,7 +4628,7 @@ void __might_fault(const char *file, int line)
 	__might_sleep(file, line, 0);
 #if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
 	if (current->mm)
-		might_lock_read(&current->mm->mmap_sem);
+		might_lock_read(&current->mm->mmap_lock);
 #endif
 }
 EXPORT_SYMBOL(__might_fault);

mm/mmap.c

@@ -3452,7 +3452,7 @@ static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
 		 * The LSB of head.next can't change from under us
 		 * because we hold the mm_all_locks_mutex.
 		 */
-		down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
+		down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock);
 		/*
 		 * We can safely modify head.next after taking the
 		 * anon_vma->root->rwsem. If some other vma in this mm shares
@@ -3482,7 +3482,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
 		 */
 		if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
 			BUG();
-		down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
+		down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock);
 	}
 }
 

mm/mmu_notifier.c

@@ -255,7 +255,7 @@ bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
 	int id;
 	bool ret = false;
 
-	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_lock));
 
 	if (!mm_has_notifiers(mm))
 		return ret;

mm/pagewalk.c

@@ -303,7 +303,7 @@ int walk_page_range(unsigned long start, unsigned long end,
 	if (!walk->mm)
 		return -EINVAL;
 
-	VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm);
+	VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_lock), walk->mm);
 
 	vma = find_vma(walk->mm, start);
 	do {
@@ -346,7 +346,7 @@ int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk)
 	if (!walk->mm)
 		return -EINVAL;
 
-	VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
+	VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_lock));
 	VM_BUG_ON(!vma);
 	walk->vma = vma;
 	err = walk_page_test(vma->vm_start, vma->vm_end, walk);