On Tue, May 02 2017, Ming Lei wrote: > On Tue, May 02, 2017 at 01:42:24PM +1000, NeilBrown wrote: >> This patch converts bioset_create() and >> bioset_create_nobvec() to not create a workqueue so >> alloctions will never trigger punt_bios_to_rescuer(). It >> also introduces bioset_create_rescued() and >> bioset_create_nobvec_rescued() which preserve the old >> behaviour. >> >> All callers of bioset_create() and bioset_create_nobvec(), >> that are inside block device drivers, are converted to the >> _rescued() version. > > The above comment about *_nobvec() need to be updated.
Yes - thanks. I'll post an updated version. > >> >> biosets used by filesystems or other top-level users do not >> need rescuing as the bio can never be queued behind other >> bios. This includes fs_bio_set, blkdev_dio_pool, >> btrfs_bioset, xfs_ioend_bioset, drbd_md_io_bio_set, >> and one allocated by target_core_iblock.c. >> >> biosets used by md/raid to not need rescuing as >> their usage was recently audited to revised to never >> risk deadlock. >> >> It is hoped that most, if not all, of the remaining biosets >> can end up being the non-rescued version. >> >> Signed-off-by: NeilBrown <ne...@suse.com> >> --- >> block/bio.c | 12 ++++++++++-- >> block/blk-core.c | 2 +- >> drivers/md/bcache/super.c | 6 ++++-- >> drivers/md/dm-crypt.c | 2 +- >> drivers/md/dm-io.c | 2 +- >> drivers/md/dm.c | 5 +++-- >> include/linux/bio.h | 1 + >> 7 files changed, 21 insertions(+), 9 deletions(-) > > DRBD can stack on block device too, so I guess it might need > BIOSET_NEED_RESCUER? A bioset only needs a rescuer is an allocation is made from the bioset inside a make_request_fn. The bioset in DRBD is drbd_md_io_bio_set is used for metadata IO, and I think it is only used in a worker thread, where rescuing cannot help. But that is probably subtle enough that I should leave the removal of the rescuer to a subsequent patch. So I'll give DRBD the flag when I update the changelog comment. Thanks, NeilBrown
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