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Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked when it fails

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On Tue 25-04-17 06:35:13, Jeff Layton wrote:
> On Tue, 2017-04-25 at 10:17 +0200, Jan Kara wrote:
> > On Mon 24-04-17 13:14:36, Jeff Layton wrote:
> > > On Mon, 2017-04-24 at 18:04 +0200, Jan Kara wrote:
> > > > On Mon 24-04-17 09:22:49, Jeff Layton wrote:
> > > > > This ensures that we see errors on fsync when writeback fails.
> > > > > 
> > > > > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > > > 
> > > > Hum, but do we really want to clobber mapping errors with temporary stuff
> > > > like ENOMEM? Or do you want to handle that in mapping_set_error?
> > > > 
> > > 
> > > Right now we don't really have such a thing as temporary errors in the
> > > writeback codepath. If you return an error here, the data doesn't stay
> > > dirty or anything, and I think we want to ensure that that gets reported
> > > via fsync.
> > > 
> > > I'd like to see us add better handling for retryable errors for stuff
> > > like ENOMEM or EAGAIN. I think this is the first step toward that
> > > though. Once we have more consistent handling of writeback errors in
> > > general, then we can start doing more interesting things with retryable
> > > errors.
> > > 
> > > So yeah, I this is the right thing to do for now.
> > 
> > OK, fair enough. And question number 2):
> > 
> > Who is actually responsible for setting the error in the mapping when error
> > happens inside ->writepage()? Is it the ->writepage() callback or the
> > caller of ->writepage()? Or something else? Currently it seems to be a
> > strange mix (e.g. mm/page-writeback.c: __writepage() calls
> > mapping_set_error() when ->writepage() returns error) so I'd like to
> > understand what's the plan and have that recorded in the changelogs.
> > 
> 
> That's an excellent question.
> 
> I think we probably want the writepage/launder_page operations to call
> mapping_set_error. That makes it possible for filesystems (e.g. NFS) to
> handle their own error tracking and reporting without using the new
> infrastructure. If they never call mapping_set_error then we'll always
> just return whatever their ->fsync operation returns on an fsync.

OK, makes sense. It is also in line with what you did for DAX, 9p, or here
for FUSE. So feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

for this patch but please also add a sentense that ->writepage() is
responsible for calling mapping_set_error() if it fails and page is not
redirtied to the changelogs of patches changing writepage handlers.

> I'll make another pass through the tree and see whether we have some
> mapping_set_error calls that should be removed, and will flesh out
> vfs.txt to state this. Maybe that file needs a whole section on
> writeback error reporting? Hmmm...

I think it would be nice to have all the logic described in one place. So
+1 from me.

> That probably also means that I should drop patch 8 from this series
> (mm: ensure that we set mapping error if writeout fails), since that
> should be happening in writepage already.

Yes.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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[PATCH v3 00/20] fs: introduce new writeback error reporting and convert existing API as a wrapper around it Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 09/20] 9p: set mapping error when writeback fails in launder_page Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 09/20] 9p: set mapping error when writeback fails in  launder_page Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
    Re: [PATCH v3 09/20] 9p: set mapping error when writeback fails in  launder_page Jan Kara <jack@suse.cz> - 2017-04-24 18:00 +0200
  [PATCH v3 08/20] mm: ensure that we set mapping error if writeout() fails Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 08/20] mm: ensure that we set mapping error if  writeout() fails Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
    Re: [PATCH v3 08/20] mm: ensure that we set mapping error if  writeout() fails Jan Kara <jack@suse.cz> - 2017-04-24 18:00 +0200
  [PATCH v3 04/20] fs: check for writeback errors after syncing out buffers in generic_file_fsync Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 04/20] fs: check for writeback errors after syncing  out buffers in generic_file_fsync Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
    Re: [PATCH v3 04/20] fs: check for writeback errors after syncing  out buffers in generic_file_fsync Jan Kara <jack@suse.cz> - 2017-04-24 17:50 +0200
  [PATCH v3 06/20] dax: set errors in mapping when writeback fails Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 06/20] dax: set errors in mapping when writeback fails Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
    Re: [PATCH v3 06/20] dax: set errors in mapping when writeback fails Jan Kara <jack@suse.cz> - 2017-04-24 18:00 +0200
    Re: [PATCH v3 06/20] dax: set errors in mapping when writeback fails Ross Zwisler <ross.zwisler@linux.intel.com> - 2017-04-24 21:20 +0200
  [PATCH v3 12/20] lib: add errseq_t type and infrastructure for handling it Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 03/20] buffer: use mapping_set_error instead of setting the flag Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 10/20] fuse: set mapping error in writepage_locked when it fails Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked  when it fails Jan Kara <jack@suse.cz> - 2017-04-24 18:10 +0200
      Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked  when it fails Jeff Layton <jlayton@redhat.com> - 2017-04-24 19:20 +0200
        Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked  when it fails Jan Kara <jack@suse.cz> - 2017-04-25 11:50 +0200
          Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked  when it fails Jeff Layton <jlayton@redhat.com> - 2017-04-25 12:40 +0200
            Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked  when it fails Jan Kara <jack@suse.cz> - 2017-04-25 13:30 +0200
              Re: [PATCH v3 10/20] fuse: set mapping error in writepage_locked  when it fails Jeff Layton <jlayton@redhat.com> - 2017-04-25 18:50 +0200
  [PATCH v3 01/20] mm: drop "wait" parameter from write_one_page Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 01/20] mm: drop "wait" parameter from write_one_page Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
  [PATCH v3 15/20] mm: remove AS_EIO and AS_ENOSPC flags Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 18/20] mm: clean up error handling in write_one_page Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 16/20] mm: don't TestClearPageError in __filemap_fdatawait_range Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 20/20] gfs2: clean up some filemap_* calls Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 20/20] gfs2: clean up some filemap_* calls Bob Peterson <rpeterso@redhat.com> - 2017-04-24 16:20 +0200
      Re: [PATCH v3 20/20] gfs2: clean up some filemap_* calls Jeff Layton <jlayton@redhat.com> - 2017-04-24 19:00 +0200
        Re: [PATCH v3 20/20] gfs2: clean up some filemap_* calls Bob Peterson <rpeterso@redhat.com> - 2017-04-24 19:50 +0200
          Re: [PATCH v3 20/20] gfs2: clean up some filemap_* calls Jeff Layton <jlayton@redhat.com> - 2017-04-24 20:00 +0200
  [PATCH v3 07/20] nilfs2: set the mapping error when calling SetPageError on writeback Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
    Re: [PATCH v3 07/20] nilfs2: set the mapping error when calling  SetPageError on writeback Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
  [PATCH v3 13/20] fs: new infrastructure for writeback error handling and reporting Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 17/20] cifs: cleanup writeback handling errors and comments Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 19/20] jbd2: don't reset error in journal_finish_inode_data_buffers Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:30 +0200
  [PATCH v3 02/20] mm: fix mapping_set_error call in me_pagecache_dirty Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:40 +0200
  [PATCH v3 05/20] orangefs: don't call filemap_write_and_wait from fsync Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:40 +0200
    Re: [PATCH v3 05/20] orangefs: don't call filemap_write_and_wait  from fsync Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
      Re: [PATCH v3 05/20] orangefs: don't call filemap_write_and_wait from fsync Mike Marshall <hubcap@omnibond.com> - 2017-04-24 20:30 +0200
  [PATCH v3 14/20] fs: retrofit old error reporting API onto new infrastructure Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:40 +0200
  [PATCH v3 11/20] cifs: set mapping error when page writeback fails in writepage or launder_pages Jeff Layton <jlayton@redhat.com> - 2017-04-24 15:40 +0200
    Re: [PATCH v3 11/20] cifs: set mapping error when page writeback  fails in writepage or launder_pages Christoph Hellwig <hch@infradead.org> - 2017-04-24 17:30 +0200
      Re: [PATCH v3 11/20] cifs: set mapping error when page writeback  fails in writepage or launder_pages Jeff Layton <jlayton@redhat.com> - 2017-04-24 19:20 +0200

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