Hello, these two patches fix handling of ENOSPC during DAX faults. The problem is that currently running transaction may be holding lots of already freed blocks which can be reallocated only once the transaction commits. Standard retry logic in ext4_iomap_end() does not work for DAX page fault handler since we hold current transaction open in ext4_dax_huge_fault() and thus retry logic cannot force the running transaction and as a result application gets SIGBUS due to premature ENOSPC error. These two patches fix the problem. I'm not too happy about patch 1/2 passing additional info (error code) from the fault handler but I don't see an easy better option since we want to also pass back special return values like VM_FAULT_FALLBACK. Comments are welcome. Honza
