On Tue, Mar 01, 2005 at 14:44:52 +0100, Arjan van de Ven wrote: > On Tue, 2005-03-01 at 05:19 -0800, arvind k wrote: > > Hi All, > > > > I understand that PG_locked flag is set in page->flags > > before initiating I/O on a page to avoid parallel > > I/Os. But I am wondering how we avoid other processes > > and threads from accessing the same page in userspace > > if it is mapped(MAP_SHARED) to the address space of > > multiple processes. > > we don't... and that's ok > what will happen is that the writes those processes do get written out > again later anyway, so there's no data loss involved... In fact, there IS a data-loss involved, because one of the applications overwrites data written by the other. However, the applications are fully aware that they have a shared read-write mapping and it's thus THEIR business to do all necessary synchronization. Kernel just writes the final result to disk. ------------------------------------------------------------------------------- Jan 'Bulb' Hudec <bulb@xxxxxx>
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