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@xxxxxxxxxx> > > > > > > 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. 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... 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. > > > > > > > > > --- > > > > fs/fuse/file.c | 1 + > > > > 1 file changed, 1 insertion(+) > > > > > > > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > > > > index ec238fb5a584..07d0efcb050c 100644 > > > > --- a/fs/fuse/file.c > > > > +++ b/fs/fuse/file.c > > > > @@ -1669,6 +1669,7 @@ static int fuse_writepage_locked(struct page *page) > > > > err_free: > > > > fuse_request_free(req); > > > > err: > > > > + mapping_set_error(page->mapping, error); > > > > end_page_writeback(page); > > > > return error; > > > > } > > > > -- > > > > 2.9.3 > > > > > > > > > > > > -- > > Jeff Layton <jlayton@xxxxxxxxxx> -- Jeff Layton <jlayton@xxxxxxxxxx>
