Btrfs: try committing transaction before returning ENOSPC

This fixes a problem where we could return -ENOSPC when we may actually have
plenty of space, the space is just pinned.  Instead of returning -ENOSPC
immediately, commit the transaction first and then try and do the allocation
again.

This patch also does chunk allocation for metadata if we pass the 80%
threshold for metadata space.  This will help with stack usage since the chunk
allocation will happen early on, instead of when the allocation is happening.

Signed-off-by: Josef Bacik <jbacik@redhat.com>

1 files changed, 47 insertions, 10 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e11875e97c2f..6b5966aacf44 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2017,26 +2017,49 @@ int btrfs_check_metadata_free_space(struct btrfs_root *root)
         struct btrfs_fs_info *info = root->fs_info;
         struct btrfs_space_info *meta_sinfo;
         u64 alloc_target, thresh;
+        int committed = 0, ret;
 
         /* get the space info for where the metadata will live */
         alloc_target = btrfs_get_alloc_profile(root, 0);
         meta_sinfo = __find_space_info(info, alloc_target);
 
-        /*
-         * if the metadata area isn't maxed out then there is no sense in
-         * checking how much is used, since we can always allocate a new chunk
-         */
-        if (!meta_sinfo->full)
-                return 0;
-
+again:
         spin_lock(&meta_sinfo->lock);
-        thresh = meta_sinfo->total_bytes * 95;
+        if (!meta_sinfo->full)
+                thresh = meta_sinfo->total_bytes * 80;
+        else
+                thresh = meta_sinfo->total_bytes * 95;
 
         do_div(thresh, 100);
 
         if (meta_sinfo->bytes_used + meta_sinfo->bytes_reserved +
             meta_sinfo->bytes_pinned + meta_sinfo->bytes_readonly > thresh) {
+                struct btrfs_trans_handle *trans;
+                if (!meta_sinfo->full) {
+                        meta_sinfo->force_alloc = 1;
+                        spin_unlock(&meta_sinfo->lock);
+
+                        trans = btrfs_start_transaction(root, 1);
+                        if (!trans)
+                                return -ENOMEM;
+
+                        ret = do_chunk_alloc(trans, root->fs_info->extent_root,
+                                             2 * 1024 * 1024, alloc_target, 0);
+                        btrfs_end_transaction(trans, root);
+                        goto again;
+                }
                 spin_unlock(&meta_sinfo->lock);
+
+                if (!committed) {
+                        committed = 1;
+                        trans = btrfs_join_transaction(root, 1);
+                        if (!trans)
+                                return -ENOMEM;
+                        ret = btrfs_commit_transaction(trans, root);
+                        if (ret)
+                                return ret;
+                        goto again;
+                }
                 return -ENOSPC;
         }
         spin_unlock(&meta_sinfo->lock);
@@ -2052,7 +2075,7 @@ int btrfs_check_data_free_space(struct btrfs_root *root, struct inode *inode,
                                 u64 bytes)
 {
         struct btrfs_space_info *data_sinfo;
-        int ret = 0;
+        int ret = 0, committed = 0;
 
         /* make sure bytes are sectorsize aligned */
         bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
@@ -2065,13 +2088,14 @@ again:
             data_sinfo->bytes_delalloc - data_sinfo->bytes_reserved -
             data_sinfo->bytes_pinned - data_sinfo->bytes_readonly -
             data_sinfo->bytes_may_use < bytes) {
+                struct btrfs_trans_handle *trans;
+
                 /*
                  * if we don't have enough free bytes in this space then we need
                  * to alloc a new chunk.
                  */
                 if (!data_sinfo->full) {
                         u64 alloc_target;
-                        struct btrfs_trans_handle *trans;
 
                         data_sinfo->force_alloc = 1;
                         spin_unlock(&data_sinfo->lock);
@@ -2090,6 +2114,19 @@ again:
                         goto again;
                 }
                 spin_unlock(&data_sinfo->lock);
+
+                /* commit the current transaction and try again */
+                if (!committed) {
+                        committed = 1;
+                        trans = btrfs_join_transaction(root, 1);
+                        if (!trans)
+                                return -ENOMEM;
+                        ret = btrfs_commit_transaction(trans, root);
+                        if (ret)
+                                return ret;
+                        goto again;
+                }
+
                 printk(KERN_ERR "no space left, need %llu, %llu delalloc bytes"
                        ", %llu bytes_used, %llu bytes_reserved, "
                        "%llu bytes_pinned, %llu bytes_readonly, %llu may use"