Btrfs: fix unprotected device's variants on 32bits machine

->total_bytes,->disk_total_bytes,->bytes_used is protected by chunk
lock when we change them, but sometimes we read them without any lock,
and we might get unexpected value. We fix this problem like inode's
i_size.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

4 files changed, 124 insertions, 29 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 1be03d8..da7ac14 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -418,7 +418,7 @@ int btrfs_dev_replace_start(struct btrfs_root *root,
 
 	/* the disk copy procedure reuses the scrub code */
 	ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
-			      src_device->total_bytes,
+			      btrfs_device_get_total_bytes(src_device),
 			      &dev_replace->scrub_progress, 0, 1);
 
 	ret = btrfs_dev_replace_finishing(root->fs_info, ret);
@@ -555,11 +555,12 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 	memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 	memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 	memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
-	tgt_device->total_bytes = src_device->total_bytes;
-	tgt_device->disk_total_bytes = src_device->disk_total_bytes;
+	btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
+	btrfs_device_set_disk_total_bytes(tgt_device,
+					  src_device->disk_total_bytes);
+	btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 	ASSERT(list_empty(&src_device->resized_list));
 	tgt_device->commit_total_bytes = src_device->commit_total_bytes;
-	tgt_device->bytes_used = src_device->bytes_used;
 	tgt_device->commit_bytes_used = src_device->bytes_used;
 	if (fs_info->sb->s_bdev == src_device->bdev)
 		fs_info->sb->s_bdev = tgt_device->bdev;
@@ -650,6 +651,7 @@ void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
 			      struct btrfs_ioctl_dev_replace_args *args)
 {
 	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	struct btrfs_device *srcdev;
 
 	btrfs_dev_replace_lock(dev_replace);
 	/* even if !dev_replace_is_valid, the values are good enough for
@@ -672,8 +674,9 @@ void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
 		break;
 	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
+		srcdev = dev_replace->srcdev;
 		args->status.progress_1000 = div64_u64(dev_replace->cursor_left,
-			div64_u64(dev_replace->srcdev->total_bytes, 1000));
+			div64_u64(btrfs_device_get_total_bytes(srcdev), 1000));
 		break;
 	}
 	btrfs_dev_replace_unlock(dev_replace);
@@ -832,7 +835,7 @@ static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info)
 
 	ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
 			      dev_replace->committed_cursor_left,
-			      dev_replace->srcdev->total_bytes,
+			      btrfs_device_get_total_bytes(dev_replace->srcdev),
 			      &dev_replace->scrub_progress, 0, 1);
 	ret = btrfs_dev_replace_finishing(fs_info, ret);
 	WARN_ON(ret);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f60d1ca..0ff2127 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1553,7 +1553,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 		goto out_free;
 	}
 
-	old_size = device->total_bytes;
+	old_size = btrfs_device_get_total_bytes(device);
 
 	if (mod < 0) {
 		if (new_size > old_size) {
@@ -2740,8 +2740,8 @@ static long btrfs_ioctl_dev_info(struct btrfs_root *root, void __user *arg)
 	}
 
 	di_args->devid = dev->devid;
-	di_args->bytes_used = dev->bytes_used;
-	di_args->total_bytes = dev->total_bytes;
+	di_args->bytes_used = btrfs_device_get_bytes_used(dev);
+	di_args->total_bytes = btrfs_device_get_total_bytes(dev);
 	memcpy(di_args->uuid, dev->uuid, sizeof(di_args->uuid));
 	if (dev->name) {
 		struct rcu_string *name;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d8e4a3d..41da102 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1308,7 +1308,7 @@ again:
 
 	if (device->bytes_used > 0) {
 		u64 len = btrfs_dev_extent_length(leaf, extent);
-		device->bytes_used -= len;
+		btrfs_device_set_bytes_used(device, device->bytes_used - len);
 		spin_lock(&root->fs_info->free_chunk_lock);
 		root->fs_info->free_chunk_space += len;
 		spin_unlock(&root->fs_info->free_chunk_lock);
@@ -1462,8 +1462,10 @@ static int btrfs_add_device(struct btrfs_trans_handle *trans,
 	btrfs_set_device_io_align(leaf, dev_item, device->io_align);
 	btrfs_set_device_io_width(leaf, dev_item, device->io_width);
 	btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
-	btrfs_set_device_total_bytes(leaf, dev_item, device->disk_total_bytes);
-	btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
+	btrfs_set_device_total_bytes(leaf, dev_item,
+				     btrfs_device_get_disk_total_bytes(device));
+	btrfs_set_device_bytes_used(leaf, dev_item,
+				    btrfs_device_get_bytes_used(device));
 	btrfs_set_device_group(leaf, dev_item, 0);
 	btrfs_set_device_seek_speed(leaf, dev_item, 0);
 	btrfs_set_device_bandwidth(leaf, dev_item, 0);
@@ -2330,7 +2332,8 @@ int btrfs_init_dev_replace_tgtdev(struct btrfs_root *root, char *device_path,
 	}
 
 
-	if (i_size_read(bdev->bd_inode) < srcdev->total_bytes) {
+	if (i_size_read(bdev->bd_inode) <
+	    btrfs_device_get_total_bytes(srcdev)) {
 		btrfs_err(fs_info, "target device is smaller than source device!");
 		ret = -EINVAL;
 		goto error;
@@ -2360,11 +2363,11 @@ int btrfs_init_dev_replace_tgtdev(struct btrfs_root *root, char *device_path,
 	device->io_width = root->sectorsize;
 	device->io_align = root->sectorsize;
 	device->sector_size = root->sectorsize;
-	device->total_bytes = srcdev->total_bytes;
-	device->disk_total_bytes = srcdev->disk_total_bytes;
+	device->total_bytes = btrfs_device_get_total_bytes(srcdev);
+	device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
+	device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 	ASSERT(list_empty(&srcdev->resized_list));
 	device->commit_total_bytes = srcdev->commit_total_bytes;
-	device->bytes_used = srcdev->bytes_used;
 	device->commit_bytes_used = device->bytes_used;
 	device->dev_root = fs_info->dev_root;
 	device->bdev = bdev;
@@ -2435,8 +2438,10 @@ static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
 	btrfs_set_device_io_align(leaf, dev_item, device->io_align);
 	btrfs_set_device_io_width(leaf, dev_item, device->io_width);
 	btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
-	btrfs_set_device_total_bytes(leaf, dev_item, device->disk_total_bytes);
-	btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
+	btrfs_set_device_total_bytes(leaf, dev_item,
+				     btrfs_device_get_disk_total_bytes(device));
+	btrfs_set_device_bytes_used(leaf, dev_item,
+				    btrfs_device_get_bytes_used(device));
 	btrfs_mark_buffer_dirty(leaf);
 
 out:
@@ -2464,8 +2469,8 @@ static int __btrfs_grow_device(struct btrfs_trans_handle *trans,
 	btrfs_set_super_total_bytes(super_copy, old_total + diff);
 	device->fs_devices->total_rw_bytes += diff;
 
-	device->total_bytes = new_size;
-	device->disk_total_bytes = new_size;
+	btrfs_device_set_total_bytes(device, new_size);
+	btrfs_device_set_disk_total_bytes(device, new_size);
 	btrfs_clear_space_info_full(device->dev_root->fs_info);
 	if (list_empty(&device->resized_list))
 		list_add_tail(&device->resized_list,
@@ -3110,11 +3115,12 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
 	/* step one make some room on all the devices */
 	devices = &fs_info->fs_devices->devices;
 	list_for_each_entry(device, devices, dev_list) {
-		old_size = device->total_bytes;
+		old_size = btrfs_device_get_total_bytes(device);
 		size_to_free = div_factor(old_size, 1);
 		size_to_free = min(size_to_free, (u64)1 * 1024 * 1024);
 		if (!device->writeable ||
-		    device->total_bytes - device->bytes_used > size_to_free ||
+		    btrfs_device_get_total_bytes(device) -
+		    btrfs_device_get_bytes_used(device) > size_to_free ||
 		    device->is_tgtdev_for_dev_replace)
 			continue;
 
@@ -3920,8 +3926,8 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
 	struct btrfs_key key;
 	struct btrfs_super_block *super_copy = root->fs_info->super_copy;
 	u64 old_total = btrfs_super_total_bytes(super_copy);
-	u64 old_size = device->total_bytes;
-	u64 diff = device->total_bytes - new_size;
+	u64 old_size = btrfs_device_get_total_bytes(device);
+	u64 diff = old_size - new_size;
 
 	if (device->is_tgtdev_for_dev_replace)
 		return -EINVAL;
@@ -3934,7 +3940,7 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
 
 	lock_chunks(root);
 
-	device->total_bytes = new_size;
+	btrfs_device_set_total_bytes(device, new_size);
 	if (device->writeable) {
 		device->fs_devices->total_rw_bytes -= diff;
 		spin_lock(&root->fs_info->free_chunk_lock);
@@ -4000,7 +4006,7 @@ again:
 		ret = -ENOSPC;
 		lock_chunks(root);
 
-		device->total_bytes = old_size;
+		btrfs_device_set_total_bytes(device, old_size);
 		if (device->writeable)
 			device->fs_devices->total_rw_bytes += diff;
 		spin_lock(&root->fs_info->free_chunk_lock);
@@ -4018,7 +4024,7 @@ again:
 	}
 
 	lock_chunks(root);
-	device->disk_total_bytes = new_size;
+	btrfs_device_set_disk_total_bytes(device, new_size);
 	if (list_empty(&device->resized_list))
 		list_add_tail(&device->resized_list,
 			      &root->fs_info->fs_devices->resized_devices);
@@ -4429,8 +4435,10 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	if (ret)
 		goto error_del_extent;
 
-	for (i = 0; i < map->num_stripes; i++)
-		map->stripes[i].dev->bytes_used += stripe_size;
+	for (i = 0; i < map->num_stripes; i++) {
+		num_bytes = map->stripes[i].dev->bytes_used + stripe_size;
+		btrfs_device_set_bytes_used(map->stripes[i].dev, num_bytes);
+	}
 
 	spin_lock(&extent_root->fs_info->free_chunk_lock);
 	extent_root->fs_info->free_chunk_space -= (stripe_size *
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index f79d532..76600a3 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -32,6 +32,19 @@ struct btrfs_pending_bios {
 	struct bio *tail;
 };
 
+/*
+ * Use sequence counter to get consistent device stat data on
+ * 32-bit processors.
+ */
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+#include <linux/seqlock.h>
+#define __BTRFS_NEED_DEVICE_DATA_ORDERED
+#define btrfs_device_data_ordered_init(device)	\
+	seqcount_init(&device->data_seqcount)
+#else
+#define btrfs_device_data_ordered_init(device) do { } while (0)
+#endif
+
 struct btrfs_device {
 	struct list_head dev_list;
 	struct list_head dev_alloc_list;
@@ -61,6 +74,10 @@ struct btrfs_device {
 	int can_discard;
 	int is_tgtdev_for_dev_replace;
 
+#ifdef __BTRFS_NEED_DEVICE_DATA_ORDERED
+	seqcount_t data_seqcount;
+#endif
+
 	/* the internal btrfs device id */
 	u64 devid;
 
@@ -133,6 +150,73 @@ struct btrfs_device {
 	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
 };
 
+/*
+ * If we read those variants at the context of their own lock, we needn't
+ * use the following helpers, reading them directly is safe.
+ */
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+#define BTRFS_DEVICE_GETSET_FUNCS(name)					\
+static inline u64							\
+btrfs_device_get_##name(const struct btrfs_device *dev)			\
+{									\
+	u64 size;							\
+	unsigned int seq;						\
+									\
+	do {								\
+		seq = read_seqcount_begin(&dev->data_seqcount);		\
+		size = dev->name;					\
+	} while (read_seqcount_retry(&dev->data_seqcount, seq));	\
+	return size;							\
+}									\
+									\
+static inline void							\
+btrfs_device_set_##name(struct btrfs_device *dev, u64 size)		\
+{									\
+	preempt_disable();						\
+	write_seqcount_begin(&dev->data_seqcount);			\
+	dev->name = size;						\
+	write_seqcount_end(&dev->data_seqcount);			\
+	preempt_enable();						\
+}
+#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
+#define BTRFS_DEVICE_GETSET_FUNCS(name)					\
+static inline u64							\
+btrfs_device_get_##name(const struct btrfs_device *dev)			\
+{									\
+	u64 size;							\
+									\
+	preempt_disable();						\
+	size = dev->name;						\
+	preempt_enable();						\
+	return size;							\
+}									\
+									\
+static inline void							\
+btrfs_device_set_##name(struct btrfs_device *dev, u64 size)		\
+{									\
+	preempt_disable();						\
+	dev->name = size;						\
+	preempt_enable();						\
+}
+#else
+#define BTRFS_DEVICE_GETSET_FUNCS(name)					\
+static inline u64							\
+btrfs_device_get_##name(const struct btrfs_device *dev)			\
+{									\
+	return dev->name;						\
+}									\
+									\
+static inline void							\
+btrfs_device_set_##name(struct btrfs_device *dev, u64 size)		\
+{									\
+	dev->name = size;						\
+}
+#endif
+
+BTRFS_DEVICE_GETSET_FUNCS(total_bytes);
+BTRFS_DEVICE_GETSET_FUNCS(disk_total_bytes);
+BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
+
 struct btrfs_fs_devices {
 	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */