On 13 Dec 2017, at 12:18, J. Bruce Fields wrote: > On Fri, Dec 08, 2017 at 05:16:26PM -0500, J. Bruce Fields wrote: >> Last year Christoph noticed a bug that could result in a file being >> unnecessarily sillyrenamed after O_DIRECT writes get ENOSPC: >> >> http://lkml.kernel.org/r/20160616150146.GA14015@xxxxxxxxxxxxx >> >> It's reproduceable on upstream, over v3 or v4. >> >> I looked into it some more, and it seems to reproduce whenever a write >> system call results in multiple WRITE calls, only some of which receive >> ENOSPC. I think that's resulting in a leak of the wb_kref on some >> nfs_pages (possibly the ones corresponding to the ENOSPC failures?). >> Those nfs_pages in turn hold references on nfs_{lock,open}_contexts. So >> a "rm" on the client (even after the file is closed) results in a >> sillyrename. >> >> I'll keep looking at this, but the relevant code is pretty opaque to me >> so far. Any ideas welcomed. > > Actually it looks like a leak of dreq->io_count? That prevents commits > from being sent (which I'm also seeing in network traces--the succesfull > WRITEs are unstable but never get committed), which means > nfs_direct_commit_complete() is never called, and the reference taken on > wb_kref in the request_commit case of nfs_direct_write_completion is > never put. This sounds to me like the problem Scott's working - he sent a patch yesterday "nfs/pnfs: fix nfs_direct_req ref leak when i/o falls back to the mds". I think the the rule should be that once we call nfs_pgio_completion_ops->init_hdr, we have to finish with ->completion. However, there are some paths where that is not the case. The callgraph in between nfs_pgheader_init() and nfs_initiate_pgio() in nfs_generic_pg_pgios() for this case might show where we're bailing out early. Ben -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
