1 files changed, 73 insertions, 22 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f619c3cb13b7..26479484180d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -33,6 +33,25 @@
 #include "locking.h"
 #include "free-space-cache.h"
 
+/* control flags for do_chunk_alloc's force field
+ * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk
+ * if we really need one.
+ *
+ * CHUNK_ALLOC_FORCE means it must try to allocate one
+ *
+ * CHUNK_ALLOC_LIMITED means to only try and allocate one
+ * if we have very few chunks already allocated.  This is
+ * used as part of the clustering code to help make sure
+ * we have a good pool of storage to cluster in, without
+ * filling the FS with empty chunks
+ *
+ */
+enum {
+        CHUNK_ALLOC_NO_FORCE = 0,
+        CHUNK_ALLOC_FORCE = 1,
+        CHUNK_ALLOC_LIMITED = 2,
+};
+
 static int update_block_group(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               u64 bytenr, u64 num_bytes, int alloc);
@@ -3019,7 +3038,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
         found->bytes_readonly = 0;
         found->bytes_may_use = 0;
         found->full = 0;
-        found->force_alloc = 0;
+        found->force_alloc = CHUNK_ALLOC_NO_FORCE;
         *space_info = found;
         list_add_rcu(&found->list, &info->space_info);
         atomic_set(&found->caching_threads, 0);
@@ -3150,7 +3169,7 @@ again:
                 if (!data_sinfo->full && alloc_chunk) {
                         u64 alloc_target;
 
-                        data_sinfo->force_alloc = 1;
+                        data_sinfo->force_alloc = CHUNK_ALLOC_FORCE;
                         spin_unlock(&data_sinfo->lock);
 alloc:
                         alloc_target = btrfs_get_alloc_profile(root, 1);
@@ -3160,7 +3179,8 @@ alloc:
 
                         ret = do_chunk_alloc(trans, root->fs_info->extent_root,
                                              bytes + 2 * 1024 * 1024,
-                                             alloc_target, 0);
+                                             alloc_target,
+                                             CHUNK_ALLOC_NO_FORCE);
                         btrfs_end_transaction(trans, root);
                         if (ret < 0) {
                                 if (ret != -ENOSPC)
@@ -3239,31 +3259,56 @@ static void force_metadata_allocation(struct btrfs_fs_info *info)
         rcu_read_lock();
         list_for_each_entry_rcu(found, head, list) {
                 if (found->flags & BTRFS_BLOCK_GROUP_METADATA)
-                        found->force_alloc = 1;
+                        found->force_alloc = CHUNK_ALLOC_FORCE;
         }
         rcu_read_unlock();
 }
 
 static int should_alloc_chunk(struct btrfs_root *root,
-                              struct btrfs_space_info *sinfo, u64 alloc_bytes)
+                              struct btrfs_space_info *sinfo, u64 alloc_bytes,
+                              int force)
 {
         u64 num_bytes = sinfo->total_bytes - sinfo->bytes_readonly;
+        u64 num_allocated = sinfo->bytes_used + sinfo->bytes_reserved;
         u64 thresh;
 
-        if (sinfo->bytes_used + sinfo->bytes_reserved +
-            alloc_bytes + 256 * 1024 * 1024 < num_bytes)
+        if (force == CHUNK_ALLOC_FORCE)
+                return 1;
+
+        /*
+         * in limited mode, we want to have some free space up to
+         * about 1% of the FS size.
+         */
+        if (force == CHUNK_ALLOC_LIMITED) {
+                thresh = btrfs_super_total_bytes(&root->fs_info->super_copy);
+                thresh = max_t(u64, 64 * 1024 * 1024,
+                               div_factor_fine(thresh, 1));
+
+                if (num_bytes - num_allocated < thresh)
+                        return 1;
+        }
+
+        /*
+         * we have two similar checks here, one based on percentage
+         * and once based on a hard number of 256MB.  The idea
+         * is that if we have a good amount of free
+         * room, don't allocate a chunk.  A good mount is
+         * less than 80% utilized of the chunks we have allocated,
+         * or more than 256MB free
+         */
+        if (num_allocated + alloc_bytes + 256 * 1024 * 1024 < num_bytes)
                 return 0;
 
-        if (sinfo->bytes_used + sinfo->bytes_reserved +
-            alloc_bytes < div_factor(num_bytes, 8))
+        if (num_allocated + alloc_bytes < div_factor(num_bytes, 8))
                 return 0;
 
         thresh = btrfs_super_total_bytes(&root->fs_info->super_copy);
+
+        /* 256MB or 5% of the FS */
         thresh = max_t(u64, 256 * 1024 * 1024, div_factor_fine(thresh, 5));
 
         if (num_bytes > thresh && sinfo->bytes_used < div_factor(num_bytes, 3))
                 return 0;
-
         return 1;
 }
 
@@ -3289,17 +3334,17 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
 
         spin_lock(&space_info->lock);
         if (space_info->force_alloc)
-                force = 1;
+                force = space_info->force_alloc;
         if (space_info->full) {
                 spin_unlock(&space_info->lock);
                 goto out;
         }
 
-        if (!force && !should_alloc_chunk(extent_root, space_info,
-                                          alloc_bytes)) {
+        if (!should_alloc_chunk(extent_root, space_info, alloc_bytes, force)) {
                 spin_unlock(&space_info->lock);
                 goto out;
         }
+
         spin_unlock(&space_info->lock);
 
         /*
@@ -3327,7 +3372,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                 space_info->full = 1;
         else
                 ret = 1;
-        space_info->force_alloc = 0;
+        space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
         spin_unlock(&space_info->lock);
 out:
         mutex_unlock(&extent_root->fs_info->chunk_mutex);
@@ -5303,11 +5348,13 @@ loop:
 
                 if (allowed_chunk_alloc) {
                         ret = do_chunk_alloc(trans, root, num_bytes +
-                                             2 * 1024 * 1024, data, 1);
+                                             2 * 1024 * 1024, data,
+                                             CHUNK_ALLOC_LIMITED);
                         allowed_chunk_alloc = 0;
                         done_chunk_alloc = 1;
-                } else if (!done_chunk_alloc) {
-                        space_info->force_alloc = 1;
+                } else if (!done_chunk_alloc &&
+                           space_info->force_alloc == CHUNK_ALLOC_NO_FORCE) {
+                        space_info->force_alloc = CHUNK_ALLOC_LIMITED;
                 }
 
                 if (loop < LOOP_NO_EMPTY_SIZE) {
@@ -5393,7 +5440,8 @@ again:
          */
         if (empty_size || root->ref_cows)
                 ret = do_chunk_alloc(trans, root->fs_info->extent_root,
-                                     num_bytes + 2 * 1024 * 1024, data, 0);
+                                     num_bytes + 2 * 1024 * 1024, data,
+                                     CHUNK_ALLOC_NO_FORCE);
 
         WARN_ON(num_bytes < root->sectorsize);
         ret = find_free_extent(trans, root, num_bytes, empty_size,
@@ -5405,7 +5453,7 @@ again:
                 num_bytes = num_bytes & ~(root->sectorsize - 1);
                 num_bytes = max(num_bytes, min_alloc_size);
                 do_chunk_alloc(trans, root->fs_info->extent_root,
-                               num_bytes, data, 1);
+                               num_bytes, data, CHUNK_ALLOC_FORCE);
                 goto again;
         }
         if (ret == -ENOSPC && btrfs_test_opt(root, ENOSPC_DEBUG)) {
@@ -8109,13 +8157,15 @@ int btrfs_set_block_group_ro(struct btrfs_root *root,
 
         alloc_flags = update_block_group_flags(root, cache->flags);
         if (alloc_flags != cache->flags)
-                do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags, 1);
+                do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags,
+                               CHUNK_ALLOC_FORCE);
 
         ret = set_block_group_ro(cache);
         if (!ret)
                 goto out;
         alloc_flags = get_alloc_profile(root, cache->space_info->flags);
-        ret = do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags, 1);
+        ret = do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags,
+                             CHUNK_ALLOC_FORCE);
         if (ret < 0)
                 goto out;
         ret = set_block_group_ro(cache);
@@ -8128,7 +8178,8 @@ int btrfs_force_chunk_alloc(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root, u64 type)
 {
         u64 alloc_flags = get_alloc_profile(root, type);
-        return do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags, 1);
+        return do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags,
+                              CHUNK_ALLOC_FORCE);
 }
 
 /*