On Mon, Dec 31, 2012 at 8:11 AM, Jan Kara <jack@xxxxxxx> wrote: > On Sat 22-12-12 00:43:30, Andy Lutomirski wrote: >> On Sat, Dec 22, 2012 at 12:29 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: >> > NAK, we went through great trouble to get rid of the nasty layering >> > violation where the VM called file_update_time directly just a short >> > while ago, reintroducing that is a massive step back. >> > [...] > >> The original version of this patch did the update in ->writepage and >> ->writepages, but that may have had lock ordering issues. (I wasn't >> able to confirm that there was any actual problem.) > Well, your call of mapping_flush_cmtime() from do_writepages() is easy to > move to generic_writepages(). Thus filesystem can easily implement it's own > ->writepages() callback if time update doesn't suit it. That sounds fine to me. Updating the handful of filesystems in there isn't a big deal. >With the call from > remove_vma() it is more problematic (and the calling context there is > harder as well because we hold mmap_sem). We could maybe leave the call > upto filesystem's ->release callback (and provide generic ->release handler > which just calls mapping_flush_cmtime()). It won't be perfect because that > gets called only after the last file descriptor for that struct file is > closed (i.e., if a process forks and child inherits mappings, ->release gets > called only after both parent and the child unmap the file) but it should > catch 99% of the real world cases. Christoph, would the be OK with > you? I'm not sure that 99% is good enough -- I'd be nervous about breaking some build or versioning system. vm_ops->close is almost a good place for this, except that it's called on some failure paths and it will mess up is_mergeable_vma if lots of filesystems suddenly have a ->close operation. What about adding vm_ops->flush, which would be called in remove_vma and possibly msync(MS_ASYNC)? I think that all real filesystems (i.e. things that care about cmtime updates) have vm_operations. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
