1 files changed, 97 insertions, 81 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 8f6761c27c68..1ec7417c7f00 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -68,7 +68,6 @@ struct loop_device {
 	struct list_head        idle_worker_list;
 	struct rb_root          worker_tree;
 	struct timer_list       timer;
-	bool			use_dio;
 	bool			sysfs_inited;
 
 	struct request_queue	*lo_queue;
@@ -182,41 +181,44 @@ static bool lo_bdev_can_use_dio(struct loop_device *lo,
 	return true;
 }
 
-static void __loop_update_dio(struct loop_device *lo, bool dio)
+static bool lo_can_use_dio(struct loop_device *lo)
 {
-	struct file *file = lo->lo_backing_file;
-	struct inode *inode = file->f_mapping->host;
-	struct block_device *backing_bdev = NULL;
-	bool use_dio;
+	struct inode *inode = lo->lo_backing_file->f_mapping->host;
 
-	if (S_ISBLK(inode->i_mode))
-		backing_bdev = I_BDEV(inode);
-	else if (inode->i_sb->s_bdev)
-		backing_bdev = inode->i_sb->s_bdev;
+	if (!(lo->lo_backing_file->f_mode & FMODE_CAN_ODIRECT))
+		return false;
 
-	use_dio = dio && (file->f_mode & FMODE_CAN_ODIRECT) &&
-		(!backing_bdev || lo_bdev_can_use_dio(lo, backing_bdev));
+	if (S_ISBLK(inode->i_mode))
+		return lo_bdev_can_use_dio(lo, I_BDEV(inode));
+	if (inode->i_sb->s_bdev)
+		return lo_bdev_can_use_dio(lo, inode->i_sb->s_bdev);
+	return true;
+}
 
-	if (lo->use_dio == use_dio)
-		return;
+/*
+ * Direct I/O can be enabled either by using an O_DIRECT file descriptor, or by
+ * passing in the LO_FLAGS_DIRECT_IO flag from userspace.  It will be silently
+ * disabled when the device block size is too small or the offset is unaligned.
+ *
+ * loop_get_status will always report the effective LO_FLAGS_DIRECT_IO flag and
+ * not the originally passed in one.
+ */
+static inline void loop_update_dio(struct loop_device *lo)
+{
+	bool dio_in_use = lo->lo_flags & LO_FLAGS_DIRECT_IO;
 
-	/* flush dirty pages before changing direct IO */
-	vfs_fsync(file, 0);
+	lockdep_assert_held(&lo->lo_mutex);
+	WARN_ON_ONCE(lo->lo_state == Lo_bound &&
+		     lo->lo_queue->mq_freeze_depth == 0);
 
-	/*
-	 * The flag of LO_FLAGS_DIRECT_IO is handled similarly with
-	 * LO_FLAGS_READ_ONLY, both are set from kernel, and losetup
-	 * will get updated by ioctl(LOOP_GET_STATUS)
-	 */
-	if (lo->lo_state == Lo_bound)
-		blk_mq_freeze_queue(lo->lo_queue);
-	lo->use_dio = use_dio;
-	if (use_dio)
+	if (lo->lo_backing_file->f_flags & O_DIRECT)
 		lo->lo_flags |= LO_FLAGS_DIRECT_IO;
-	else
+	if ((lo->lo_flags & LO_FLAGS_DIRECT_IO) && !lo_can_use_dio(lo))
 		lo->lo_flags &= ~LO_FLAGS_DIRECT_IO;
-	if (lo->lo_state == Lo_bound)
-		blk_mq_unfreeze_queue(lo->lo_queue);
+
+	/* flush dirty pages before starting to issue direct I/O */
+	if ((lo->lo_flags & LO_FLAGS_DIRECT_IO) && !dio_in_use)
+		vfs_fsync(lo->lo_backing_file, 0);
 }
 
 /**
@@ -311,6 +313,13 @@ static void loop_clear_limits(struct loop_device *lo, int mode)
 		lim.discard_granularity = 0;
 	}
 
+	/*
+	 * XXX: this updates the queue limits without freezing the queue, which
+	 * is against the locking protocol and dangerous.  But we can't just
+	 * freeze the queue as we're inside the ->queue_rq method here.  So this
+	 * should move out into a workqueue unless we get the file operations to
+	 * advertise if they support specific fallocate operations.
+	 */
 	queue_limits_commit_update(lo->lo_queue, &lim);
 }
 
@@ -520,12 +529,6 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 	}
 }
 
-static inline void loop_update_dio(struct loop_device *lo)
-{
-	__loop_update_dio(lo, (lo->lo_backing_file->f_flags & O_DIRECT) |
-				lo->use_dio);
-}
-
 static void loop_reread_partitions(struct loop_device *lo)
 {
 	int rc;
@@ -964,7 +967,6 @@ loop_set_status_from_info(struct loop_device *lo,
 
 	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
 	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
-	lo->lo_flags = info->lo_flags;
 	return 0;
 }
 
@@ -977,12 +979,12 @@ static unsigned int loop_default_blocksize(struct loop_device *lo,
 	return SECTOR_SIZE;
 }
 
-static int loop_reconfigure_limits(struct loop_device *lo, unsigned int bsize)
+static void loop_update_limits(struct loop_device *lo, struct queue_limits *lim,
+		unsigned int bsize)
 {
 	struct file *file = lo->lo_backing_file;
 	struct inode *inode = file->f_mapping->host;
 	struct block_device *backing_bdev = NULL;
-	struct queue_limits lim;
 	u32 granularity = 0, max_discard_sectors = 0;
 
 	if (S_ISBLK(inode->i_mode))
@@ -995,22 +997,20 @@ static int loop_reconfigure_limits(struct loop_device *lo, unsigned int bsize)
 
 	loop_get_discard_config(lo, &granularity, &max_discard_sectors);
 
-	lim = queue_limits_start_update(lo->lo_queue);
-	lim.logical_block_size = bsize;
-	lim.physical_block_size = bsize;
-	lim.io_min = bsize;
-	lim.features &= ~(BLK_FEAT_WRITE_CACHE | BLK_FEAT_ROTATIONAL);
+	lim->logical_block_size = bsize;
+	lim->physical_block_size = bsize;
+	lim->io_min = bsize;
+	lim->features &= ~(BLK_FEAT_WRITE_CACHE | BLK_FEAT_ROTATIONAL);
 	if (file->f_op->fsync && !(lo->lo_flags & LO_FLAGS_READ_ONLY))
-		lim.features |= BLK_FEAT_WRITE_CACHE;
+		lim->features |= BLK_FEAT_WRITE_CACHE;
 	if (backing_bdev && !bdev_nonrot(backing_bdev))
-		lim.features |= BLK_FEAT_ROTATIONAL;
-	lim.max_hw_discard_sectors = max_discard_sectors;
-	lim.max_write_zeroes_sectors = max_discard_sectors;
+		lim->features |= BLK_FEAT_ROTATIONAL;
+	lim->max_hw_discard_sectors = max_discard_sectors;
+	lim->max_write_zeroes_sectors = max_discard_sectors;
 	if (max_discard_sectors)
-		lim.discard_granularity = granularity;
+		lim->discard_granularity = granularity;
 	else
-		lim.discard_granularity = 0;
-	return queue_limits_commit_update(lo->lo_queue, &lim);
+		lim->discard_granularity = 0;
 }
 
 static int loop_configure(struct loop_device *lo, blk_mode_t mode,
@@ -1019,6 +1019,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 {
 	struct file *file = fget(config->fd);
 	struct address_space *mapping;
+	struct queue_limits lim;
 	int error;
 	loff_t size;
 	bool partscan;
@@ -1063,6 +1064,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 	error = loop_set_status_from_info(lo, &config->info);
 	if (error)
 		goto out_unlock;
+	lo->lo_flags = config->info.lo_flags;
 
 	if (!(file->f_mode & FMODE_WRITE) || !(mode & BLK_OPEN_WRITE) ||
 	    !file->f_op->write_iter)
@@ -1084,13 +1086,15 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 	disk_force_media_change(lo->lo_disk);
 	set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
 
-	lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
 	lo->lo_device = bdev;
 	lo->lo_backing_file = file;
 	lo->old_gfp_mask = mapping_gfp_mask(mapping);
 	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 
-	error = loop_reconfigure_limits(lo, config->block_size);
+	lim = queue_limits_start_update(lo->lo_queue);
+	loop_update_limits(lo, &lim, config->block_size);
+	/* No need to freeze the queue as the device isn't bound yet. */
+	error = queue_limits_commit_update(lo->lo_queue, &lim);
 	if (error)
 		goto out_unlock;
 
@@ -1150,7 +1154,12 @@ static void __loop_clr_fd(struct loop_device *lo)
 	lo->lo_sizelimit = 0;
 	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
 
-	/* reset the block size to the default */
+	/*
+	 * Reset the block size to the default.
+	 *
+	 * No queue freezing needed because this is called from the final
+	 * ->release call only, so there can't be any outstanding I/O.
+	 */
 	lim = queue_limits_start_update(lo->lo_queue);
 	lim.logical_block_size = SECTOR_SIZE;
 	lim.physical_block_size = SECTOR_SIZE;
@@ -1244,7 +1253,6 @@ static int
 loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 {
 	int err;
-	int prev_lo_flags;
 	bool partscan = false;
 	bool size_changed = false;
 
@@ -1263,21 +1271,19 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 		invalidate_bdev(lo->lo_device);
 	}
 
-	/* I/O need to be drained during transfer transition */
+	/* I/O needs to be drained before changing lo_offset or lo_sizelimit */
 	blk_mq_freeze_queue(lo->lo_queue);
 
-	prev_lo_flags = lo->lo_flags;
-
 	err = loop_set_status_from_info(lo, info);
 	if (err)
 		goto out_unfreeze;
 
-	/* Mask out flags that can't be set using LOOP_SET_STATUS. */
-	lo->lo_flags &= LOOP_SET_STATUS_SETTABLE_FLAGS;
-	/* For those flags, use the previous values instead */
-	lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_SETTABLE_FLAGS;
-	/* For flags that can't be cleared, use previous values too */
-	lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_CLEARABLE_FLAGS;
+	partscan = !(lo->lo_flags & LO_FLAGS_PARTSCAN) &&
+		(info->lo_flags & LO_FLAGS_PARTSCAN);
+
+	lo->lo_flags &= ~(LOOP_SET_STATUS_SETTABLE_FLAGS |
+			  LOOP_SET_STATUS_CLEARABLE_FLAGS);
+	lo->lo_flags |= (info->lo_flags & LOOP_SET_STATUS_SETTABLE_FLAGS);
 
 	if (size_changed) {
 		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
@@ -1285,17 +1291,13 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 		loop_set_size(lo, new_size);
 	}
 
-	/* update dio if lo_offset or transfer is changed */
-	__loop_update_dio(lo, lo->use_dio);
+	/* update the direct I/O flag if lo_offset changed */
+	loop_update_dio(lo);
 
 out_unfreeze:
 	blk_mq_unfreeze_queue(lo->lo_queue);
-
-	if (!err && (lo->lo_flags & LO_FLAGS_PARTSCAN) &&
-	     !(prev_lo_flags & LO_FLAGS_PARTSCAN)) {
+	if (partscan)
 		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
-		partscan = true;
-	}
 out_unlock:
 	mutex_unlock(&lo->lo_mutex);
 	if (partscan)
@@ -1444,20 +1446,32 @@ static int loop_set_capacity(struct loop_device *lo)
 
 static int loop_set_dio(struct loop_device *lo, unsigned long arg)
 {
-	int error = -ENXIO;
-	if (lo->lo_state != Lo_bound)
-		goto out;
+	bool use_dio = !!arg;
 
-	__loop_update_dio(lo, !!arg);
-	if (lo->use_dio == !!arg)
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+	if (use_dio == !!(lo->lo_flags & LO_FLAGS_DIRECT_IO))
 		return 0;
-	error = -EINVAL;
- out:
-	return error;
+
+	if (use_dio) {
+		if (!lo_can_use_dio(lo))
+			return -EINVAL;
+		/* flush dirty pages before starting to use direct I/O */
+		vfs_fsync(lo->lo_backing_file, 0);
+	}
+
+	blk_mq_freeze_queue(lo->lo_queue);
+	if (use_dio)
+		lo->lo_flags |= LO_FLAGS_DIRECT_IO;
+	else
+		lo->lo_flags &= ~LO_FLAGS_DIRECT_IO;
+	blk_mq_unfreeze_queue(lo->lo_queue);
+	return 0;
 }
 
 static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 {
+	struct queue_limits lim;
 	int err = 0;
 
 	if (lo->lo_state != Lo_bound)
@@ -1469,8 +1483,11 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 	sync_blockdev(lo->lo_device);
 	invalidate_bdev(lo->lo_device);
 
+	lim = queue_limits_start_update(lo->lo_queue);
+	loop_update_limits(lo, &lim, arg);
+
 	blk_mq_freeze_queue(lo->lo_queue);
-	err = loop_reconfigure_limits(lo, arg);
+	err = queue_limits_commit_update(lo->lo_queue, &lim);
 	loop_update_dio(lo);
 	blk_mq_unfreeze_queue(lo->lo_queue);
 
@@ -1854,7 +1871,7 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
 		cmd->use_aio = false;
 		break;
 	default:
-		cmd->use_aio = lo->use_dio;
+		cmd->use_aio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
 		break;
 	}
 
@@ -2023,8 +2040,7 @@ static int loop_add(int i)
 	lo->tag_set.queue_depth = hw_queue_depth;
 	lo->tag_set.numa_node = NUMA_NO_NODE;
 	lo->tag_set.cmd_size = sizeof(struct loop_cmd);
-	lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING |
-		BLK_MQ_F_NO_SCHED_BY_DEFAULT;
+	lo->tag_set.flags = BLK_MQ_F_STACKING | BLK_MQ_F_NO_SCHED_BY_DEFAULT;
 	lo->tag_set.driver_data = lo;
 
 	err = blk_mq_alloc_tag_set(&lo->tag_set);