From: Anand Jain <anand.j...@oracle.com>

Hot replace / auto replace is important volume manager feature
and is critical to the data center operations, so that the degraded
volume can be brought back to a healthy state at the earliest and
without manual intervention.

This modifies the existing replace code to suite the need of auto
replace, in the long run I hope both the codes to be merged.

Signed-off-by: Anand Jain <anand.j...@oracle.com>
Tested-by: Austin S. Hemmelgarn <ahferro...@gmail.com>
Tested-by: Yauhen Kharuzhy <yauhen.kharu...@zavadatar.com>
---
v6: update the printk for space device error to ratelimit

 fs/btrfs/dev-replace.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/dev-replace.h |  1 +
 2 files changed, 44 insertions(+)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 5ec7fa860391..83af64907547 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -937,3 +937,46 @@ void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info 
*fs_info)
                                     &fs_info->fs_state));
        }
 }
+
+int btrfs_auto_replace_start(struct btrfs_root *root, u64 src_devid)
+{
+       int ret;
+       char *tgt_path;
+       struct btrfs_fs_info *fs_info = root->fs_info;
+
+       if (!src_devid)
+               return -EINVAL;
+
+       if (fs_info->sb->s_flags & MS_RDONLY)
+               return -EROFS;
+
+       btrfs_dev_replace_lock(&fs_info->dev_replace, 0);
+       if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
+               btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
+               return -EBUSY;
+       }
+       btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
+
+       if (btrfs_get_spare_device(&tgt_path)) {
+               btrfs_info_rl(root->fs_info,
+                       "No spare device found/configured in the kernel");
+               return -EINVAL;
+       }
+
+       if (atomic_xchg(
+               &root->fs_info->mutually_exclusive_operation_running, 1)) {
+               ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
+       } else {
+               ret = btrfs_dev_replace_start(root, tgt_path, src_devid, NULL,
+               BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS);
+               atomic_set(
+                       &root->fs_info->mutually_exclusive_operation_running, 
0);
+       }
+
+       if (ret)
+               btrfs_put_spare_device(tgt_path);
+
+       kfree(tgt_path);
+
+       return ret;
+}
diff --git a/fs/btrfs/dev-replace.h b/fs/btrfs/dev-replace.h
index e922b42d91df..54b0812c8ba4 100644
--- a/fs/btrfs/dev-replace.h
+++ b/fs/btrfs/dev-replace.h
@@ -46,4 +46,5 @@ static inline void btrfs_dev_replace_stats_inc(atomic64_t 
*stat_value)
 {
        atomic64_inc(stat_value);
 }
+int btrfs_auto_replace_start(struct btrfs_root *root, u64 src_devid);
 #endif
-- 
2.7.0

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