On Fri, Oct 28 2016 at 3:45pm -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > Otherwise users can easily shoot themselves in the foot by creating the > situation where the top-level stacked device (e.g. DM multipath) has a > larger max_sectors_kb than the underlying device(s). Which will > certainly lead to IO errors due to the "over max size limit" check in > blk_cloned_rq_check_limits(). > > Use of WARN_ON_ONCE() gives users visibility into which application > attempted to perform this unsupported max_sectors_kb change. > > This is a crude, yet effective, solution that forces the use of system > software (e.g. udev rules or multipathd) to tweak max_sectors_kb of the > underlying devices _before_ a layer like DM multipath is layered ontop. > > Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> > --- > block/blk-sysfs.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 9cc8d7c..cce43d7 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -199,8 +199,12 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count) > unsigned long max_sectors_kb, > max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1, > page_kb = 1 << (PAGE_SHIFT - 10); > - ssize_t ret = queue_var_store(&max_sectors_kb, page, count); > + ssize_t ret; > + > + if (WARN_ON_ONCE(blk_queue_stackable(q))) > + return -EINVAL; > > + ret = queue_var_store(&max_sectors_kb, page, count); > if (ret < 0) > return ret; > > -- > 2.8.4 (Apple Git-73) Jens, Never heard from you on this patch. Would you like me to resend without the WARN_ON_ONCE? (Failing is enough, the userspace code that attempts to set max_sectors_kb on DM multipath will get the user's attention) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
