[PATCH v3 4/4] btrfs: add helper btrfs_num_devices() to deduce num_devices
From: Anand Jain <hidden>
Date: 2018-08-02 11:56:38
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
When the replace is running the fs_devices::num_devices also includes the replace device, however in some operations like device delete and balance it needs the actual num_devices without the repalce devices, so now the function btrfs_num_devices() just provides that. And here is a scenario how balance and repalce items could co-exist. Consider balance is started and paused, now start the replace followed by a power-recycle of the system. During following mount, the open_ctree() first restarts the balance so it must check for the replace device otherwise our num_devices calculation will be wrong. Signed-off-by: Anand Jain <redacted> --- v2->v3: update changelog with not so obvious balance and repalce co-existance secnario v1->v2: add comments fs/btrfs/volumes.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index fe74fefc75f7..8844904f9009 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c@@ -1854,6 +1854,21 @@ void btrfs_assign_next_active_device(struct btrfs_device *device, fs_info->fs_devices->latest_bdev = next_device->bdev; } +/* Returns btrfs_fs_devices::num_devices excluding replace device if any */ +static inline u64 btrfs_num_devices(struct btrfs_fs_info *fs_info) +{ + u64 num_devices = fs_info->fs_devices->num_devices; + + btrfs_dev_replace_read_lock(&fs_info->dev_replace); + if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) { + BUG_ON(num_devices < 1); + num_devices--; + } + btrfs_dev_replace_read_unlock(&fs_info->dev_replace); + + return num_devices; +} + int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, u64 devid) {
@@ -1865,13 +1880,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, mutex_lock(&uuid_mutex); - num_devices = fs_devices->num_devices; - btrfs_dev_replace_read_lock(&fs_info->dev_replace); - if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) { - BUG_ON(num_devices < 1); - num_devices--; - } - btrfs_dev_replace_read_unlock(&fs_info->dev_replace); + num_devices = btrfs_num_devices(fs_info); ret = btrfs_check_raid_min_devices(fs_info, num_devices - 1); if (ret)
@@ -3721,13 +3730,8 @@ int btrfs_balance(struct btrfs_fs_info *fs_info, } } - num_devices = fs_info->fs_devices->num_devices; - btrfs_dev_replace_read_lock(&fs_info->dev_replace); - if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) { - BUG_ON(num_devices < 1); - num_devices--; - } - btrfs_dev_replace_read_unlock(&fs_info->dev_replace); + num_devices = btrfs_num_devices(fs_info); + allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE | BTRFS_BLOCK_GROUP_DUP; if (num_devices > 1) allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
--
2.7.0