[PATCH 3/7] btrfs: change the device allocation_hint property via sysfs

[Goffredo Baroncelli <kreijack@tiscali.it>]

From: Goffredo Baroncelli <kreijack@inwind.it>

This patch allow to change the allocation_hint property writing
a numerical value in the file.

/sysfs/fs/btrfs/<UUID>/devinfo/<devid>/allocation_hint

To update this field it is added the property "allocation_hint" in
btrfs-prog too.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 fs/btrfs/sysfs.c   | 62 +++++++++++++++++++++++++++++++++++++++++++++-
 fs/btrfs/volumes.c |  2 +-
 fs/btrfs/volumes.h |  2 ++
 3 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index c1c903187e19..9070d0370343 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1584,7 +1584,67 @@ static ssize_t btrfs_devinfo_allocation_hint_show(struct kobject *kobj,
 	return scnprintf(buf, PAGE_SIZE, "0x%08llx\n",
 		device->type & BTRFS_DEV_ALLOCATION_HINT_MASK);
 }
-BTRFS_ATTR(devid, allocation_hint, btrfs_devinfo_allocation_hint_show);
+
+static ssize_t btrfs_devinfo_allocation_hint_store(struct kobject *kobj,
+				 struct kobj_attribute *a,
+				 const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_root *root;
+	struct btrfs_device *device;
+	int ret;
+	struct btrfs_trans_handle *trans;
+
+	u64 type, prev_type;
+
+	device = container_of(kobj, struct btrfs_device, devid_kobj);
+	fs_info = device->fs_info;
+	if (!fs_info)
+		return -EPERM;
+
+	root = fs_info->chunk_root;
+	if (sb_rdonly(fs_info->sb))
+		return -EROFS;
+
+	ret = kstrtou64(buf, 0, &type);
+	if (ret < 0)
+		return -EINVAL;
+
+	/* for now, allow to touch only the 'allocation hint' bits */
+	if (type & ~BTRFS_DEV_ALLOCATION_HINT_MASK)
+		return -EINVAL;
+
+	/* check if a change is really needed */
+	if ((device->type & BTRFS_DEV_ALLOCATION_HINT_MASK) == type)
+		return len;
+
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	prev_type = device->type;
+	device->type = (device->type & ~BTRFS_DEV_ALLOCATION_HINT_MASK) | type;
+
+	ret = btrfs_update_device(trans, device);
+
+	if (ret < 0) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		goto abort;
+	}
+
+	ret = btrfs_commit_transaction(trans);
+	if (ret < 0)
+		goto abort;
+
+	return len;
+abort:
+	device->type = prev_type;
+	return  ret;
+}
+BTRFS_ATTR_RW(devid, allocation_hint, btrfs_devinfo_allocation_hint_show,
+				      btrfs_devinfo_allocation_hint_store);
+
 
 /*
  * Information about one device.
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a91e51b0ca81..c43a8a36ff5b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2841,7 +2841,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	return ret;
 }
 
-static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
+noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
 					struct btrfs_device *device)
 {
 	int ret;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index bd297f23d19e..93ac27d8097c 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -636,5 +636,7 @@ int btrfs_bg_type_to_factor(u64 flags);
 const char *btrfs_bg_type_to_raid_name(u64 flags);
 int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info);
 bool btrfs_repair_one_zone(struct btrfs_fs_info *fs_info, u64 logical);
+int btrfs_update_device(struct btrfs_trans_handle *trans,
+			struct btrfs_device *device);
 
 #endif
-- 
2.34.1