65  * MAKING RESERVATIONS, FLUSHING NORMALLY (non-priority)
94  * MAKING RESERVATIONS, FLUSHING HIGH PRIORITY
101  * THE FLUSHING STATES
426 	 * If we aren't flushing all things, let us overcommit up to  in calc_available_free_space()
654 		 * flushing loops and hope for the best.  Delalloc will expand  in shrink_delalloc()
686 		 * marked clean.  We don't use filemap_fwrite for flushing  in shrink_delalloc()
732 		 * flushing so we can stop flushing if we decide we don't need  in shrink_delalloc()
871 	 * We may be flushing because suddenly we have less space than we had  in btrfs_calc_reclaim_metadata_size()
874 	 * appropriate pressure on the flushing state machine.  in btrfs_calc_reclaim_metadata_size()
907 	 * that devoted to other reservations then there's no sense in flushing,  in need_preemptive_reclaim()
908 	 * we don't have a lot of things that need flushing.  in need_preemptive_reclaim()
922 	 * pinned then we want to start flushing.  in need_preemptive_reclaim()
962 	 * around.  Preemptive flushing is only useful in that it can free up  in need_preemptive_reclaim()
972 	 * clearly be heavy enough to warrant preemptive flushing.  In the case  in need_preemptive_reclaim()
973 	 * of heavy DIO or ordered reservations, preemptive flushing will just  in need_preemptive_reclaim()
978 	 * can keep flushing.  This is to avoid the case where we start  in need_preemptive_reclaim()
979 	 * flushing, and now delalloc == ordered and we stop preemptively  in need_preemptive_reclaim()
980 	 * flushing when we could still have several gigs of delalloc to flush.  in need_preemptive_reclaim()
1026  * We've exhausted our flushing, start failing tickets.
1029  * @space_info - the space info we were flushing
1031  * We call this when we've exhausted our flushing ability and haven't made
1075 		 * We're just throwing tickets away, so more flushing may not  in maybe_fail_all_tickets()
1140 		 * under heavy pressure, so allow one trip through the flushing  in btrfs_async_reclaim_metadata_space()
1152 		 * through the flushing state machine skip ALLOC_CHUNK_FORCE and  in btrfs_async_reclaim_metadata_space()
1177  * This handles pre-flushing of metadata space before we get to the point that
1181  * watermark of space by flushing whichever reservation pool is currently the
1233 		 * We really want to avoid flushing delalloc too much, as it  in btrfs_preempt_reclaim_metadata_space()
1278  *   Space is freed from flushing delalloc in one of two ways.
1462 	 * turned into error mode due to a transaction abort when flushing space  in priority_reclaim_metadata_space()
1547  * Do the appropriate flushing and waiting for a ticket.
1606  * This returns true if this flush state will go through the ordinary flushing
1625 	 * and freeing space, like there is with flushing delayed refs or  in maybe_clamp_preempt()
1659  * flush out space to make room.  It will do this by flushing delalloc if
1680 	 * flushing methods can trigger transaction commits.  in __reserve_bytes()
1737 	 * the list and we will do our own flushing further down.  in __reserve_bytes()
1755 				 * our preemptive flushing is unable to keep  in __reserve_bytes()
1757 				 * preemptive flushing in order to keep up with  in __reserve_bytes()
1806  * flush out space to make room.  It will do this by flushing delalloc if