btrfs: parameterize dev_extent_min for chunk allocation

Currently, we ignore a device whose available space is less than
"BTRFS_STRIPE_LEN * dev_stripes". This is a lower limit for current
allocation policy (to maximize the number of stripes). This commit
parameterizes dev_extent_min, so that other policies can set their own
lower limitat to ignore a device with insufficient space.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 888009b..1f7ad23 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4805,6 +4805,7 @@ struct alloc_chunk_ctl {
        int nparity;
        u64 max_stripe_size;
        u64 max_chunk_size;
+       u64 dev_extent_min;
        u64 stripe_size;
        u64 chunk_size;
        int ndevs;
@@ -4838,6 +4839,7 @@ static void init_alloc_chunk_ctl_policy_regular(
        /* We don't want a chunk larger than 10% of writable space */
        ctl->max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
                                  ctl->max_chunk_size);
+       ctl->dev_extent_min = BTRFS_STRIPE_LEN * ctl->dev_stripes;
 }
 
 static void init_alloc_chunk_ctl(struct btrfs_fs_devices *fs_devices,
@@ -4873,7 +4875,6 @@ static int gather_device_info(struct btrfs_fs_devices *fs_devices,
        struct btrfs_device *device;
        u64 total_avail;
        u64 dev_extent_want = ctl->max_stripe_size * ctl->dev_stripes;
-       u64 dev_extent_min = BTRFS_STRIPE_LEN * ctl->dev_stripes;
        int ret;
        int ndevs = 0;
        u64 max_avail;
@@ -4901,7 +4902,7 @@ static int gather_device_info(struct btrfs_fs_devices *fs_devices,
                        total_avail = 0;
 
                /* If there is no space on this device, skip it. */
-               if (total_avail == 0)
+               if (total_avail < ctl->dev_extent_min)
                        continue;
 
                ret = find_free_dev_extent(device, dev_extent_want, &dev_offset,
@@ -4912,12 +4913,12 @@ static int gather_device_info(struct btrfs_fs_devices *fs_devices,
                if (ret == 0)
                        max_avail = dev_extent_want;
 
-               if (max_avail < dev_extent_min) {
+               if (max_avail < ctl->dev_extent_min) {
                        if (btrfs_test_opt(info, ENOSPC_DEBUG))
                                btrfs_debug(info,
                        "%s: devid %llu has no free space, have=%llu want=%llu",
                                            __func__, device->devid, max_avail,
-                                           dev_extent_min);
+                                           ctl->dev_extent_min);
                        continue;
                }