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Subject[PATCH RFC 4/6] btrfs: Check if the filesystem is has mixed type of devices
Date
From: Michal Rostecki <mrostecki@suse.com>

Add the btrfs_check_mixed() function which checks if the filesystem has
the mixed type of devices (non-rotational and rotational). This
information is going to be used in roundrobin raid1 read policy.

Signed-off-by: Michal Rostecki <mrostecki@suse.com>
---
fs/btrfs/volumes.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
fs/btrfs/volumes.h | 7 +++++++
2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1ac364a2f105..1ad30a595722 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -617,6 +617,35 @@ static int btrfs_free_stale_devices(const char *path,
return ret;
}

+/*
+ * Checks if after adding the new device the filesystem is going to have mixed
+ * types of devices (non-rotational and rotational).
+ *
+ * @fs_devices: list of devices
+ * @new_device_rotating: if the new device is rotational
+ *
+ * Returns true if there are mixed types of devices, otherwise returns false.
+ */
+static bool btrfs_check_mixed(struct btrfs_fs_devices *fs_devices,
+ bool new_device_rotating)
+{
+ struct btrfs_device *device, *prev_device;
+
+ list_for_each_entry(device, &fs_devices->devices, dev_list) {
+ if (prev_device == NULL &&
+ device->rotating != new_device_rotating)
+ return true;
+ if (prev_device != NULL &&
+ (device->rotating != prev_device->rotating ||
+ device->rotating != new_device_rotating))
+ return true;
+
+ prev_device = device;
+ }
+
+ return false;
+}
+
/*
* This is only used on mount, and we are protected from competing things
* messing with our fs_devices by the uuid_mutex, thus we do not need the
@@ -629,6 +658,7 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
struct request_queue *q;
struct block_device *bdev;
struct btrfs_super_block *disk_super;
+ bool rotating;
u64 devid;
int ret;

@@ -669,8 +699,12 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
}

q = bdev_get_queue(bdev);
- if (!blk_queue_nonrot(q))
+ rotating = !blk_queue_nonrot(q);
+ device->rotating = rotating;
+ if (rotating)
fs_devices->rotating = true;
+ if (!fs_devices->mixed)
+ fs_devices->mixed = btrfs_check_mixed(fs_devices, rotating);

device->bdev = bdev;
clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
@@ -2418,6 +2452,7 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
fs_devices->open_devices = 0;
fs_devices->missing_devices = 0;
fs_devices->rotating = false;
+ fs_devices->mixed = false;
list_add(&seed_devices->seed_list, &fs_devices->seed_list);

generate_random_uuid(fs_devices->fsid);
@@ -2522,6 +2557,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
int seeding_dev = 0;
int ret = 0;
bool locked = false;
+ bool rotating;

if (sb_rdonly(sb) && !fs_devices->seeding)
return -EROFS;
@@ -2621,8 +2657,12 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path

atomic64_add(device->total_bytes, &fs_info->free_chunk_space);

- if (!blk_queue_nonrot(q))
+ rotating = !blk_queue_nonrot(q);
+ device->rotating = rotating;
+ if (rotating)
fs_devices->rotating = true;
+ if (!fs_devices->mixed)
+ fs_devices->mixed = btrfs_check_mixed(fs_devices, rotating);

orig_super_total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
btrfs_set_super_total_bytes(fs_info->super_copy,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 6e544317a377..594f1207281c 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -147,6 +147,9 @@ struct btrfs_device {
/* I/O stats for raid1 mirror selection */
struct percpu_counter inflight;
atomic_t last_offset;
+
+ /* If the device is rotational */
+ bool rotating;
};

/*
@@ -274,6 +277,10 @@ struct btrfs_fs_devices {
* nonrot flag set
*/
bool rotating;
+ /* Set when we find or add both nonrot and rot disks in the
+ * filesystem
+ */
+ bool mixed;

struct btrfs_fs_info *fs_info;
/* sysfs kobjects */
--
2.30.0
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