On Thu, 2018-04-12 at 14:31 -0700, Matthew Wilcox wrote: > On Thu, Apr 12, 2018 at 05:14:54PM -0400, Jeff Layton wrote: > > On Thu, 2018-04-12 at 13:28 -0700, Matthew Wilcox wrote: > > > On Thu, Apr 12, 2018 at 01:13:22PM -0700, Andres Freund wrote: > > > > I think a per-file or even per-blockdev/fs error state that'd be > > > > returned by fsync() would be more than sufficient. > > > > > > Ah; this was my suggestion to Jeff on IRC. That we add a per- > > > superblock > > > wb_err and then allow syncfs() to return it. So you'd open an fd on > > > a directory (for example), and call syncfs() which would return -EIO > > > or -ENOSPC if either of those conditions had occurred since you > > > opened > > > the fd. > > > > Not a bad idea and shouldn't be too costly. mapping_set_error could > > flag the superblock one before or after the one in the mapping. > > > > We'd need to define what happens if you interleave fsync and syncfs > > calls on the same inode though. How do we handle file->f_wb_err in that > > case? Would we need a second field in struct file to act as the per-sb > > error cursor? > > Ooh. I hadn't thought that through. Bleh. I don't want to add a field > to struct file for this uncommon case. > > Maybe O_PATH could be used for this? It gets you a file descriptor on > a particular filesystem, so syncfs() is defined, but it can't report > a writeback error. So if you open something O_PATH, you can use the > file's f_wb_err for the mapping's error cursor. > That might work. It'd be a syscall behavioral change so we'd need to document that well. It's probably innocuous though -- I doubt we have a lot of callers in the field opening files with O_PATH and calling syncfs on them. -- Jeff Layton <jlayton@xxxxxxxxxx>
