Btrfs: don't steal from the global reserve if we don't have the space

btrfs_evict_inode() needs to be more careful about stealing from the
global_rsv.  We dont' want to end up aborting commit with ENOSPC just
because the evict_inode code was too greedy.

Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 88537c5..141df0c 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5010,6 +5010,7 @@ void btrfs_evict_inode(struct inode *inode)
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *rsv, *global_rsv;
+       int steal_from_global = 0;
        u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
        int ret;
 
@@ -5077,9 +5078,20 @@ void btrfs_evict_inode(struct inode *inode)
                 * hard as possible to get this to work.
                 */
                if (ret)
-                       ret = btrfs_block_rsv_migrate(global_rsv, rsv, min_size);
+                       steal_from_global++;
+               else
+                       steal_from_global = 0;
+               ret = 0;
 
-               if (ret) {
+               /*
+                * steal_from_global == 0: we reserved stuff, hooray!
+                * steal_from_global == 1: we didn't reserve stuff, boo!
+                * steal_from_global == 2: we've committed, still not a lot of
+                * room but maybe we'll have room in the global reserve this
+                * time.
+                * steal_from_global == 3: abandon all hope!
+                */
+               if (steal_from_global > 2) {
                        btrfs_warn(root->fs_info,
                                "Could not get space for a delete, will truncate on mount %d",
                                ret);
@@ -5095,6 +5107,36 @@ void btrfs_evict_inode(struct inode *inode)
                        goto no_delete;
                }
 
+               /*
+                * We can't just steal from the global reserve, we need tomake
+                * sure there is room to do it, if not we need to commit and try
+                * again.
+                */
+               if (steal_from_global) {
+                       if (!btrfs_check_space_for_delayed_refs(trans, root))
+                               ret = btrfs_block_rsv_migrate(global_rsv, rsv,
+                                                             min_size);
+                       else
+                               ret = -ENOSPC;
+               }
+
+               /*
+                * Couldn't steal from the global reserve, we have too much
+                * pending stuff built up, commit the transaction and try it
+                * again.
+                */
+               if (ret) {
+                       ret = btrfs_commit_transaction(trans, root);
+                       if (ret) {
+                               btrfs_orphan_del(NULL, inode);
+                               btrfs_free_block_rsv(root, rsv);
+                               goto no_delete;
+                       }
+                       continue;
+               } else {
+                       steal_from_global = 0;
+               }
+
                trans->block_rsv = rsv;
 
                ret = btrfs_truncate_inode_items(trans, root, inode, 0, 0);