Anybody know of a reliable way to cause buffer cache pages to be purged (not written to disk, but released)??
Problem: In a shared disk environment, changes made by the owner (R/W) are not seen by R/O sharers in a timely fashion. This is especially problematic when the Linux virtual machine has a sizable virtual memory size allowing it to have lots of buffercache. In small memory Linux images, the changes are recognized fairly quickly, you can force by editing a sizeable file which will cause the buffercache pages to be re-used (stolen). I realize that this is unsafe in the general sense (writing to a minidisk that is shared by others), but I believe that it is fairly safe in the usage I am attempting. Have tried several variations of commands on both the owner and sharers. Sync'ing and even shutting down the owner (to make sure the buffers are written) does not have any effect. On the sharing systems, 'mount -o remount', various other mount options and various blockdev options (flushbufs, rereadpt) don't seem to help. Interestingly enough, 'blockdev --rereadpt' will cause deleted files to be noticed immediately, but not newly created files (I would have thought it wouldn't have affected either, but was trying about anything!). Have scoured some kernel code and believe there are routines that will do what is needed. Usually used when unmounting a device or some other act of removing, but don't see a way to force them to be called via any system call/command available. Any ideas?? Cheers, Mark
