On Wed, 2010-11-17 at 23:57 +1100, Nick Piggin wrote: > On Wed, Nov 17, 2010 at 04:23:58AM -0800, Michel Lespinasse wrote: > > When faulting in pages for mlock(), we want to break COW for anonymous > > or file pages within VM_WRITABLE, non-VM_SHARED vmas. However, there is > > no need to write-fault into VM_SHARED vmas since shared file pages can > > be mlocked first and dirtied later, when/if they actually get written to. > > Skipping the write fault is desirable, as we don't want to unnecessarily > > cause these pages to be dirtied and queued for writeback. > > It's not just to break COW, but to do block allocation and such > (filesystem's page_mkwrite op). That needs to at least be explained > in the changelog. Agreed, the 0/3 description actually does mention this. > Filesystem doesn't have a good way to fully pin required things > according to mlock, but page_mkwrite provides some reasonable things > (like block allocation / reservation). Right, but marking all pages dirty isn't really sane. I can imagine making the reservation but not marking things dirty solution, although it might be lots harder to implement, esp since some filesystems don't actually have a page_mkwrite() implementation. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href