Hi, On 2020-03-09 13:50:59 -0400, Jeff Layton wrote: > The PostgreSQL devs asked a while back for some way to tell whether > there have been any writeback errors on a superblock w/o having to do > any sort of flush -- just "have there been any so far". Indeed. > I sent a patch a few weeks ago to make syncfs() return errors when there > have been writeback errors on the superblock. It's not merged yet, but > once we have something like that in place, we could expose info from the > errseq_t to userland using this interface. I'm still a bit worried about the details of errseq_t being exposed to userland. Partially because it seems to restrict further evolution of errseq_t, and partially because it will likely up with userland trying to understand it (it's e.g. just too attractive to report a count of errors etc). Is there a reason to not instead report a 64bit counter instead of the cookie? In contrast to the struct file case we'd only have the space overhead once per superblock, rather than once per #files * #fd. And it seems that the maintenance of that counter could be done without widespread changes, e.g. instead/in addition to your change: > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index ccb14b6a16b5..897439475315 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -51,7 +51,10 @@ static inline void mapping_set_error(struct address_space *mapping, int error) > return; > > /* Record in wb_err for checkers using errseq_t based tracking */ > - filemap_set_wb_err(mapping, error); > + __filemap_set_wb_err(mapping, error); > + > + /* Record it in superblock */ > + errseq_set(&mapping->host->i_sb->s_wb_err, error); > > /* Record it in flags for now, for legacy callers */ > if (error == -ENOSPC) Btw, seems like mapping_set_error() should have a non-inline cold path? Greetings, Andres Freund
