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.
