From e457438423da154c70c44a9037bae38981c27529 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov <nborisov@suse.com>
Date: Fri, 16 Jun 2017 14:39:20 +0300
Subject: [PATCH 2/2] btrfs: Round down values which are written for
 total_bytes_size
Git-commit: 7dfb8be11b5d1db4325414ce16b8c164e08f52d8
Patch-mainline: v4.13 or v4.12-rc8 (next release)
References: bsc#1043912

We got an internal report about a file system not wanting to mount
following 99e3ecfcb9f4 ("Btrfs: add more validation checks for
superblock").

BTRFS error (device sdb1): super_total_bytes 1000203816960 mismatch with
fs_devices total_rw_bytes 1000203820544

Subtracting the numbers we get a difference of less than a 4kb. Upon
closer inspection it became apparent that mkfs actually rounds down the
size of the device to a multiple of sector size. However, the same
cannot be said for various functions which modify the total size and are
called from btrfs_balance as well as when adding a new device. So this
patch ensures that values being saved into on-disk data structures are
always rounded down to a multiple of sectorsize.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/ctree.h   |  1 +
 fs/btrfs/volumes.c | 18 +++++++++++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d83a0b55bd39..98b0a51d651e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1513,6 +1513,7 @@ static inline void btrfs_set_device_total_bytes(struct extent_buffer *eb,
 {
 	BUILD_BUG_ON(sizeof(u64) !=
 		     sizeof(((struct btrfs_dev_item *)0))->total_bytes);
+	WARN_ON(!IS_ALIGNED(val, eb->fs_info->dev_root->sectorsize));
 	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
 }
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index dfaf353dd9a7..025036eb939a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2386,7 +2386,8 @@ int btrfs_init_new_device(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 = i_size_read(bdev->bd_inode);
+	device->total_bytes = round_down(i_size_read(bdev->bd_inode),
+					 root->sectorsize);
 	device->disk_total_bytes = device->total_bytes;
 	device->commit_total_bytes = device->total_bytes;
 	device->dev_root = root->fs_info->dev_root;
@@ -2425,7 +2426,7 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 
 	tmp = btrfs_super_total_bytes(root->fs_info->super_copy);
 	btrfs_set_super_total_bytes(root->fs_info->super_copy,
-				    tmp + device->total_bytes);
+		round_down(tmp + device->total_bytes, root->sectorsize));
 
 	tmp = btrfs_super_num_devices(root->fs_info->super_copy);
 	btrfs_set_super_num_devices(root->fs_info->super_copy,
@@ -2690,6 +2691,8 @@ int btrfs_grow_device(struct btrfs_trans_handle *trans,
 	if (!device->writeable)
 		return -EACCES;
 
+	new_size = round_down(new_size, device->dev_root->sectorsize);
+
 	lock_chunks(device->dev_root);
 	old_total = btrfs_super_total_bytes(super_copy);
 	diff = new_size - device->total_bytes;
@@ -2702,7 +2705,8 @@ int btrfs_grow_device(struct btrfs_trans_handle *trans,
 
 	fs_devices = device->dev_root->fs_info->fs_devices;
 
-	btrfs_set_super_total_bytes(super_copy, old_total + diff);
+	btrfs_set_super_total_bytes(super_copy,
+		round_down(old_total + diff, device->dev_root->sectorsize));
 	device->fs_devices->total_rw_bytes += diff;
 
 	btrfs_device_set_total_bytes(device, new_size);
@@ -4372,7 +4376,10 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
 	struct btrfs_super_block *super_copy = root->fs_info->super_copy;
 	u64 old_total = btrfs_super_total_bytes(super_copy);
 	u64 old_size = btrfs_device_get_total_bytes(device);
-	u64 diff = old_size - new_size;
+	u64 diff;
+
+	new_size = round_down(new_size, root->sectorsize);
+	diff = old_size - new_size;
 
 	if (device->is_tgtdev_for_dev_replace)
 		return -EINVAL;
@@ -4501,7 +4508,8 @@ again:
 			      &root->fs_info->fs_devices->resized_devices);
 
 	WARN_ON(diff > old_total);
-	btrfs_set_super_total_bytes(super_copy, old_total - diff);
+	btrfs_set_super_total_bytes(super_copy,
+			round_down(old_total - diff, root->sectorsize));
 	unlock_chunks(root);
 
 	/* Now btrfs_update_device() will change the on-disk size. */
-- 
2.7.4