On Fri, Nov 7, 2014 at 6:16 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > On Fri, 7 Nov 2014, Mikulas Patocka wrote: > >> For reasons 1 and 2, I wouldn't really deal with "thin" targets at all - >> they may be created or deleted independent on pool status. Instead, we >> should block all active bios inside the pool - the bios are already >> registered in dm_deferred_set or in the prison, so all you need to do is >> to set a flag pool's presuspend method that causes all new bios to be >> queues and the wait until the prison is empty and the counters in >> deferred_set reach zero. > > Here I'm sending a proof-of-concept patch that makes it possible to > prevent bios from coming into the thin pool when the pool is suspended. It > doesn't modify any generic dm code. > > This patch may not be perfect (I don't know all bio paths in dm-thin in > detail, so I may have missed something), but it shows that it is possible > to suspend all bios without modifying the common dm code. I hope Joe > reviewes it and possibly fixes it. > > The patch is for 3.18-rc3, it needs other thin patches, the full patch > series is at > http://people.redhat.com/~mpatocka/patches/kernel/dm-thin-suspend/series.html > > Mikulas > > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > --- > drivers/md/dm-bio-prison.c | 29 +++++++++++++++++++++++++++ > drivers/md/dm-bio-prison.h | 3 ++ > drivers/md/dm-thin.c | 47 +++++++++++++++++++++++++++++++++++++++++---- > 3 files changed, 75 insertions(+), 4 deletions(-) > > Index: linux-2.6/drivers/md/dm-thin.c > =================================================================== > --- linux-2.6.orig/drivers/md/dm-thin.c 2014-11-08 00:02:42.000000000 +0100 > +++ linux-2.6/drivers/md/dm-thin.c 2014-11-08 00:02:42.000000000 +0100 > @@ -194,6 +194,8 @@ struct pool { > struct dm_thin_new_mapping *next_mapping; > mempool_t *mapping_pool; > > + atomic_t suspended; > + > process_bio_fn process_bio; > process_bio_fn process_discard; > I'm not seeing how using an unprotected atomic_t is thread-safe considering both the thin-pool and thin targets will be accessing it concurrently. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
