Messages in this thread | | | Date | Fri, 6 Jul 2007 15:27:18 +0530 | From | "sridhar lanka" <> | Subject | PG_locked vs PG_writeback |
| |
I see that in 2.6 kernels, page lock (PG_locked) is cleared and PG_writeback is set when the page is submitted for i/o. Refer __block_write_full_page().
However the header file says that
" During disk I/O, PG_locked is used. This bit is set before I/O and * reset when I/O completes. page_waitqueue(page) is a wait queue of all tasks * waiting for the I/O on this page to complete. "
Is the comment correct?
Does this mean that a page can be written to (dirtied) while the same page is being written to by the low level driver. From what i can see PG_locked is only ensuring that 2 threads don't read the same page but does not gate writes or flushes of the page (partially). On the other hand PG_writeback is gating another write if the same page is already being flushed.
appreciate help. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |