> > Trond also had a comment that if we extended the ioctl to work for all > > inodes (not just blkdev) and allowed some additional flags of what > > needs to be invalidated, the new ioctl would be also useful to NFS > > userspace - see Trond's email at > > > > http://www.spinics.net/lists/linux-fsdevel/msg78917.html > > > > and the following thread. I would prefer to cover that usecase when we > > are introducing new invalidation ioctl. Have you considered that Thanos? > > Sure, though I don't really know how to do it. I'll start by looking at the code > flow when someone does " echo 3 > /proc/sys/vm/drop_caches", unless you > already have a rough idea how to do that. I realise I haven't clearly understood what the semantics of this new ioctl should be. My initial goal was to implement an ioctl that would _completely_ invalidate the buffer cache of a block device when there is no file-system involved. Unless I'm mistaken the patch I posted achieves this goal. We now want to extend this patch to take care of cached metadata, which seems to be of particular importance for NFS, and I suspect that this piece of functionality will still be applicable to any kind of file-system, correct? Do we want this new ioctl to do what "echo 3 > /proc/sys/vm/drop_caches" does but on a more selective basis, which IIUC drops whatever can be dropped, but may not drop everything? If so, then we should more precisely define this ioctl as "drop *all* cached data and as much metadata you can, which may not be all of them". If this is the case, would adding a call to drop_pagecache_sb() on all super blocks whose .s_bdev equals the block device we're interested in suffice? -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
