Jan Kara <jack@xxxxxxx> writes: > On Tue 07-02-12 15:39:06, Jeff Moyer wrote: >> Christoph Hellwig <hch@xxxxxxxxxxxxx> writes: >> > On Mon, Feb 06, 2012 at 11:33:29AM -0500, Jeff Moyer wrote: >> >> > code, right? Before that we'd drain the IO queue when cache flush is issued >> >> > and thus effectively wait for IO completion... >> >> >> >> Right, though hch seems to think even then the problem existed. >> > >> > I was wrong, using -o barrier it didn't. That was however not something >> > people using O_SYNC heavy production loads would do, they'd use disabled >> > caches and nobarrier. >> > >> >> > Also I was thinking whether we couldn't implement the fix in VFS. Basically >> >> > it would be the same like the fix for ext4. Like having a per-sb workqueue >> >> > and queue work calling generic_write_sync() from end_io handler when the >> >> > file is O_SYNC? That would solve the issue for all filesystems... >> >> >> >> Well, that would require buy-in from the other file system developers. >> >> What do the XFS folks think? >> > >> > I don't think using that code for XFS makes sene. But just like >> > generic_write_sync there's no reason it can't be added to generic code, >> > just make sure only generic_file_aio_write/__generic_file_aio_write use >> > it, but generic_file_buffered_write and generic_file_direct_write stay >> > clear of it. >> >> ext4_file_write (ext4's .aio_write routine) calls into >> generic_file_aio_write. So, I don't think we can generalize that this >> routine means that the file system doesn't install its own endio >> handler. What's more, we'd have to pass an endio routine down the call >> stack quite a ways. In all, I think that would be an uglier solution to >> the problem. Did I miss something? > I think it can be done in a relatively elegant way. POC patch (completely > untested) is attached. What do you think? All filesystems using > blockdev_direct_IO() can be easily converted to use this, gfs2 & ocfs2 can > also use the framework. That leaves only ext4, xfs & btrfs which need > special handling. Actually, maybe btrfs could be converted as well because > it doesn't seem to need to offload anything else to workqueue. But I'm not > really sure... I like it! -Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
