btrfs: kill min_allocable_bytes in inc_block_group_ro

This is a relic from a time before we had a proper reservation mechanism
and you could end up with really full chunks at chunk allocation time.
This doesn't make sense anymore, so just kill it.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 6934a5b..66fa396 100644 (file)
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1185,21 +1185,8 @@ static int inc_block_group_ro(struct btrfs_block_group *cache, int force)
        struct btrfs_space_info *sinfo = cache->space_info;
        u64 num_bytes;
        u64 sinfo_used;
-       u64 min_allocable_bytes;
        int ret = -ENOSPC;
 
-       /*
-        * We need some metadata space and system metadata space for
-        * allocating chunks in some corner cases until we force to set
-        * it to be readonly.
-        */
-       if ((sinfo->flags &
-            (BTRFS_BLOCK_GROUP_SYSTEM | BTRFS_BLOCK_GROUP_METADATA)) &&
-           !force)
-               min_allocable_bytes = SZ_1M;
-       else
-               min_allocable_bytes = 0;
-
        spin_lock(&sinfo->lock);
        spin_lock(&cache->lock);
 
@@ -1217,10 +1204,9 @@ static int inc_block_group_ro(struct btrfs_block_group *cache, int force)
         * sinfo_used + num_bytes should always <= sinfo->total_bytes.
         *
         * Here we make sure if we mark this bg RO, we still have enough
-        * free space as buffer (if min_allocable_bytes is not 0).
+        * free space as buffer.
         */
-       if (sinfo_used + num_bytes + min_allocable_bytes <=
-           sinfo->total_bytes) {
+       if (sinfo_used + num_bytes <= sinfo->total_bytes) {
                sinfo->bytes_readonly += num_bytes;
                cache->ro++;
                list_add_tail(&cache->ro_list, &sinfo->ro_bgs);
@@ -1233,8 +1219,8 @@ out:
                btrfs_info(cache->fs_info,
                        "unable to make block group %llu ro", cache->start);
                btrfs_info(cache->fs_info,
-                       "sinfo_used=%llu bg_num_bytes=%llu min_allocable=%llu",
-                       sinfo_used, num_bytes, min_allocable_bytes);
+                       "sinfo_used=%llu bg_num_bytes=%llu",
+                       sinfo_used, num_bytes);
                btrfs_dump_space_info(cache->fs_info, cache->space_info, 0, 0);
        }
        return ret;