[PATCH v2 2/5] btrfs: call btrfs_close_devices from ->kill_sb

[Johannes Thumshirn <jth@kernel.org>]

From: Christoph Hellwig <hch@lst.de>

blkdev_put must not be called under sb->s_umount to avoid a lock order
reversal with disk->open_mutex once call backs from block devices to
the file system using the holder ops are supported.  Move the call
to btrfs_close_devices into btrfs_free_fs_info so that it is closed
from ->kill_sb (which is also called from the mount failure handling
path unlike ->put_super) as well as when an fs_info is freed because
an existing superblock already exists.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/disk-io.c |  4 ++--
 fs/btrfs/super.c   | 29 ++++++++++++++++-------------
 2 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 0d6ad7512f21..6360d44acaa9 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1247,6 +1247,8 @@ void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
 	struct percpu_counter *em_counter = &fs_info->evictable_extent_maps;
 
 	percpu_counter_destroy(&fs_info->stats_read_blocks);
+	if (fs_info->fs_devices)
+		btrfs_close_devices(fs_info->fs_devices);
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
 	percpu_counter_destroy(&fs_info->delalloc_bytes);
 	percpu_counter_destroy(&fs_info->ordered_bytes);
@@ -3681,7 +3683,6 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 
 	iput(fs_info->btree_inode);
 fail:
-	btrfs_close_devices(fs_info->fs_devices);
 	ASSERT(ret < 0);
 	return ret;
 }
@@ -4428,7 +4429,6 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
 	iput(fs_info->btree_inode);
 
 	btrfs_mapping_tree_free(fs_info);
-	btrfs_close_devices(fs_info->fs_devices);
 }
 
 void btrfs_mark_buffer_dirty(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index b9e08a59da4e..eaecf1525078 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1869,10 +1869,8 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 	if (ret)
 		return ret;
 
-	if (!(fc->sb_flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
-		ret = -EACCES;
-		goto error;
-	}
+	if (!(fc->sb_flags & SB_RDONLY) && fs_devices->rw_devices == 0)
+		return -EACCES;
 
 	bdev = fs_devices->latest_dev->bdev;
 
@@ -1886,21 +1884,20 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 	 * otherwise it's tied to the lifetime of the super_block.
 	 */
 	sb = sget_fc(fc, btrfs_fc_test_super, set_anon_super_fc);
-	if (IS_ERR(sb)) {
-		ret = PTR_ERR(sb);
-		goto error;
-	}
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
 
 	set_device_specific_options(fs_info);
 
 	if (sb->s_root) {
-		btrfs_close_devices(fs_devices);
 		/*
 		 * At this stage we may have RO flag mismatch between
 		 * fc->sb_flags and sb->s_flags.  Caller should detect such
 		 * mismatch and reconfigure with sb->s_umount rwsem held if
 		 * needed.
 		 */
+		if ((fc->sb_flags ^ sb->s_flags) & SB_RDONLY)
+			ret = -EBUSY;
 	} else {
 		snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
 		shrinker_debugfs_rename(sb->s_shrink, "sb-btrfs:%s", sb->s_id);
@@ -1916,10 +1913,6 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 
 	fc->root = dget(sb->s_root);
 	return 0;
-
-error:
-	btrfs_close_devices(fs_devices);
-	return ret;
 }
 
 /*
@@ -1997,8 +1990,18 @@ static int btrfs_get_tree_super(struct fs_context *fc)
  */
 static int btrfs_reconfigure_for_mount(struct fs_context *fc)
 {
+	struct btrfs_fs_info *fs_info = fc->s_fs_info;
 	int ret = 0;
 
+	/*
+	 * We got a reference to our fs_devices, so we need to close it here to
+	 * make sure we don't leak our reference on the fs_devices.
+	 */
+	if (fs_info->fs_devices) {
+		btrfs_close_devices(fs_info->fs_devices);
+		fs_info->fs_devices = NULL;
+	}
+
 	if (!(fc->sb_flags & SB_RDONLY) && (fc->root->d_sb->s_flags & SB_RDONLY))
 		ret = btrfs_reconfigure(fc);
 
-- 
2.49.0