On 1/10/18 9:18 AM, Ilya Dryomov wrote: > Regular block device writes go through blkdev_write_iter(), which does > bdev_read_only(), while zeroout/discard/etc requests are never checked, > both userspace- and kernel-triggered. Add a generic catch-all check to > generic_make_request_checks() to actually enforce ioctl(BLKROSET) and > set_disk_ro(), which is used by quite a few drivers for things like > snapshots, read-only backing files/images, etc. > > Signed-off-by: Ilya Dryomov <[email protected]> > Reviewed-by: Sagi Grimberg <[email protected]> > --- > block/blk-core.c | 23 ++++++++++++++++++++++- > 1 file changed, 22 insertions(+), 1 deletion(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index f843ae4f858d..d132bec4a266 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -2123,6 +2123,20 @@ static inline int bio_check_eod(struct bio *bio, > unsigned int nr_sectors) > return 0; > } > > +static inline bool bio_check_ro(struct bio *bio) > +{ > + struct hd_struct *p; > + bool ret = false; > + > + rcu_read_lock(); > + p = __disk_get_part(bio->bi_disk, bio->bi_partno); > + if (!p || (p->policy && op_is_write(bio_op(bio)))) > + ret = true; > + rcu_read_unlock(); > + > + return ret; > +}> + > static noinline_for_stack bool > generic_make_request_checks(struct bio *bio) > { > @@ -2145,11 +2159,18 @@ generic_make_request_checks(struct bio *bio) > goto end_io; > } > > + if (unlikely(bio_check_ro(bio))) { > + printk(KERN_ERR > + "generic_make_request: Trying to write " > + "to read-only block-device %s (partno %d)\n", > + bio_devname(bio, b), bio->bi_partno); > + goto end_io; > + }
It's yet another check that adds part lookup and rcu lock/unlock in that path. Can we combine some of them? Make this part of the remap? This overhead impacts every IO, let's not bloat it more than absolutely necessary. -- Jens Axboe -- Jens Axboe
