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. 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). -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>