On Mon, 2008-01-28 at 12:33 -0600, Steve French wrote: > On Jan 28, 2008 2:17 AM, Andi Kleen <ak@xxxxxxx> wrote: > > > I completely agree. If one thread writes A and another writes B then the > > > kernel should record either A or B, not ((A & 0xffffffff00000000) | (B & > > > 0xffffffff)) > > > > The problem is pretty nasty unfortunately. To solve it properly I think > > the file_operations->read/write prototypes would need to be changed > > because otherwise it is not possible to do atomic relative updates > > of f_pos. Right now the actual update is burrowed deeply in the low level > > read/write implementation. But that would be a huge impact all over > > the tree :/ > > If there were a wrapper around reads and writes of f_pos as there is > for i_size e.g. it would hit a lot of code, but not as many as I had > originally thought. the most important ones are in the vfs itself, where > there are only 59 uses of the field (not all need to be changed). ext3 > has fewer (25), and cifs only 12 uses. Most of the uses in ext3 and cifs deal with a directory's f_pos in readdir, which is protected by i_mutex, so I don't think we need to worry about them at all. -- David Kleikamp IBM Linux Technology Center - 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
