[RFC,23/24] do_mmap: use locked=false in vm_mmap_pgoff() and aio_setup_ring()

Commit Message

Michel Lespinasse Feb. 24, 2020, 8:30 p.m. UTC

Change vm_mmap_pgoff() and aio_setup_ring() to call do_mmap()
with locked=false.

Moving the mmap_sem acquisition to within do_mmap()
enables it to acquire a fine grained lock in the future.

Signed-off-by: Michel Lespinasse <[e-mail]>
---
 fs/aio.c  | 12 ++----------
 mm/util.c |  8 +++-----
 2 files changed, 5 insertions(+), 15 deletions(-)

Patch

diff --git fs/aio.c fs/aio.c
index 018bd24d6204..0092855326eb 100644
--- fs/aio.c
+++ fs/aio.c
@@ -460,7 +460,6 @@  static const struct address_space_operations aio_ctx_aops = {
 static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
 {
 	struct aio_ring *ring;
-	struct mm_struct *mm = current->mm;
 	unsigned long size, unused;
 	int nr_pages;
 	int i;
@@ -519,20 +518,13 @@  static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
 	ctx->mmap_size = nr_pages * PAGE_SIZE;
 	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
 
-	if (mm_write_lock_killable(mm)) {
-		ctx->mmap_size = 0;
-		aio_free_ring(ctx);
-		return -EINTR;
-	}
-
 	ctx->mmap_base = do_mmap(ctx->aio_ring_file, 0, ctx->mmap_size,
 				PROT_READ | PROT_WRITE,
-				MAP_SHARED, 0, 0, true, &unused, NULL);
-	mm_write_unlock(mm);
+				MAP_SHARED, 0, 0, false, &unused, NULL);
 	if (IS_ERR((void *)ctx->mmap_base)) {
 		ctx->mmap_size = 0;
 		aio_free_ring(ctx);
-		return -ENOMEM;
+		return (ctx->mmap_base == -EINTR) ? -EINTR : -ENOMEM;
 	}
 
 	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
diff --git mm/util.c mm/util.c
index 337b006aef6d..916bc7ac9bf2 100644
--- mm/util.c
+++ mm/util.c
@@ -501,12 +501,10 @@  unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 
 	ret = security_mmap_file(file, prot, flag);
 	if (!ret) {
-		if (mm_write_lock_killable(mm))
-			return -EINTR;
 		ret = do_mmap(file, addr, len, prot, flag, 0, pgoff,
-				true, &populate, &uf);
-		mm_write_unlock(mm);
-		userfaultfd_unmap_complete(mm, &uf);
+				false, &populate, &uf);
+		if (ret != -EINTR)
+			userfaultfd_unmap_complete(mm, &uf);
 		if (populate)
 			mm_populate(ret, populate);
 	}