2 files changed, 40 insertions, 2 deletions

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index c935a774a9f..d9b97d4960e 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -41,6 +41,7 @@
 #define BTRFS_INODE_NEEDS_FULL_SYNC		7
 #define BTRFS_INODE_COPY_EVERYTHING		8
 #define BTRFS_INODE_IN_DELALLOC_LIST		9
+#define BTRFS_INODE_READDIO_NEED_LOCK		10
 
 /* in memory btrfs inode */
 struct btrfs_inode {
@@ -217,4 +218,22 @@ static inline int btrfs_inode_in_log(struct inode *inode, u64 generation)
 	return 0;
 }
 
+/*
+ * Disable DIO read nolock optimization, so new dio readers will be forced
+ * to grab i_mutex. It is used to avoid the endless truncate due to
+ * nonlocked dio read.
+ */
+static inline void btrfs_inode_block_unlocked_dio(struct inode *inode)
+{
+	set_bit(BTRFS_INODE_READDIO_NEED_LOCK, &BTRFS_I(inode)->runtime_flags);
+	smp_mb();
+}
+
+static inline void btrfs_inode_resume_unlocked_dio(struct inode *inode)
+{
+	smp_mb__before_clear_bit();
+	clear_bit(BTRFS_INODE_READDIO_NEED_LOCK,
+		  &BTRFS_I(inode)->runtime_flags);
+}
+
 #endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d11f38d8696..c6ee8f1063f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3888,6 +3888,12 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
 
 		/* we don't support swapfiles, so vmtruncate shouldn't fail */
 		truncate_setsize(inode, newsize);
+
+		/* Disable nonlocked read DIO to avoid the end less truncate */
+		btrfs_inode_block_unlocked_dio(inode);
+		inode_dio_wait(inode);
+		btrfs_inode_resume_unlocked_dio(inode);
+
 		ret = btrfs_truncate(inode);
 		if (ret && inode->i_nlink)
 			btrfs_orphan_del(NULL, inode);
@@ -6670,6 +6676,8 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
 	size_t count = 0;
+	int flags = 0;
+	bool wakeup = false;
 	ssize_t ret;
 
 	if (check_direct_IO(BTRFS_I(inode)->root, rw, iocb, iov,
@@ -6681,13 +6689,22 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 		ret = btrfs_delalloc_reserve_space(inode, count);
 		if (ret)
 			return ret;
+	} else {
+		atomic_inc(&inode->i_dio_count);
+		smp_mb__after_atomic_inc();
+		if (unlikely(test_bit(BTRFS_INODE_READDIO_NEED_LOCK,
+				      &BTRFS_I(inode)->runtime_flags))) {
+			inode_dio_done(inode);
+			flags = DIO_LOCKING | DIO_SKIP_HOLES;
+		} else {
+			wakeup = true;
+		}
 	}
 
 	ret = __blockdev_direct_IO(rw, iocb, inode,
 			BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev,
 			iov, offset, nr_segs, btrfs_get_blocks_direct, NULL,
-			btrfs_submit_direct, 0);
-
+			btrfs_submit_direct, flags);
 	if (rw & WRITE) {
 		if (ret < 0 && ret != -EIOCBQUEUED)
 			btrfs_delalloc_release_space(inode, count);
@@ -6700,6 +6717,8 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 		}
 		btrfs_delalloc_release_metadata(inode, 0);
 	}
+	if (wakeup)
+		inode_dio_done(inode);
 
 	return ret;
 }