btrfs: handle U64_MAX for shrink_delalloc

Data allocations are going to want to pass in U64_MAX for flushing
space, adjust shrink_delalloc to handle this properly.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Nikolay Borisov <nborisov@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/space-info.c b/fs/btrfs/space-info.c
index 9c79bdfd145b11cdd80a9458c5578135fcd930f3..2b48b37216ebd2e27af1afc855eb99b38e4758ed 100644 (file)
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -530,8 +530,19 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
        int loops;
 
        /* Calc the number of the pages we need flush for space reservation */
-       items = calc_reclaim_items_nr(fs_info, to_reclaim);
-       to_reclaim = items * EXTENT_SIZE_PER_ITEM;
+       if (to_reclaim == U64_MAX) {
+               items = U64_MAX;
+       } else {
+               /*
+                * to_reclaim is set to however much metadata we need to
+                * reclaim, but reclaiming that much data doesn't really track
+                * exactly, so increase the amount to reclaim by 2x in order to
+                * make sure we're flushing enough delalloc to hopefully reclaim
+                * some metadata reservations.
+                */
+               items = calc_reclaim_items_nr(fs_info, to_reclaim) * 2;
+               to_reclaim = items * EXTENT_SIZE_PER_ITEM;
+       }
 
        trans = (struct btrfs_trans_handle *)current->journal_info;
        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
@@ -742,7 +753,7 @@ static void flush_space(struct btrfs_fs_info *fs_info,
                break;
        case FLUSH_DELALLOC:
        case FLUSH_DELALLOC_WAIT:
-               shrink_delalloc(fs_info, num_bytes * 2,
+               shrink_delalloc(fs_info, num_bytes,
                                state == FLUSH_DELALLOC_WAIT);
                break;
        case FLUSH_DELAYED_REFS_NR: