On Mon, Apr 4, 2016 at 1:06 PM, Shaun Tancheff <shaun@xxxxxxxxxxxx> wrote: > Recursive endio calls can exceed 16k stack. Tested with > 32k stack and observed: > > Depth Size Location (293 entries) > ----- ---- -------- > 0) 21520 16 __module_text_address+0x12/0x60 > 1) 21504 8 __module_address+0x5/0x140 > 2) 21496 24 __module_text_address+0x12/0x60 > 3) 21472 16 is_module_text_address+0xe/0x20 > 4) 21456 8 __kernel_text_address+0x50/0x80 > 5) 21448 136 print_context_stack+0x5a/0xf0 > 6) 21312 144 dump_trace+0x14c/0x300 > 7) 21168 8 save_stack_trace+0x2f/0x50 > 8) 21160 88 set_track+0x64/0x130 > 9) 21072 96 free_debug_processing+0x200/0x290 > 10) 20976 176 __slab_free+0x164/0x290 > 11) 20800 48 kmem_cache_free+0x1b0/0x1e0 > 12) 20752 16 mempool_free_slab+0x17/0x20 > 13) 20736 48 mempool_free+0x2f/0x90 > 14) 20688 16 bvec_free+0x36/0x40 > 15) 20672 32 bio_free+0x3b/0x60 > 16) 20640 16 bio_put+0x23/0x30 > 17) 20624 64 end_bio_extent_writepage+0xcf/0xe0 > 18) 20560 48 bio_endio+0x57/0x90 > 19) 20512 48 btrfs_end_bio+0xa8/0x160 > 20) 20464 48 bio_endio+0x57/0x90 > 21) 20416 112 dec_pending+0x121/0x270 > 22) 20304 64 clone_endio+0x7a/0x100 > 23) 20240 48 bio_endio+0x57/0x90 > ... > 277) 1264 64 clone_endio+0x7a/0x100 > 278) 1200 48 bio_endio+0x57/0x90 > 279) 1152 112 dec_pending+0x121/0x270 > 280) 1040 64 clone_endio+0x7a/0x100 > 281) 976 48 bio_endio+0x57/0x90 > 282) 928 80 blk_update_request+0x8f/0x340 > 283) 848 80 scsi_end_request+0x33/0x1c0 > 284) 768 112 scsi_io_completion+0xb5/0x620 > 285) 656 48 scsi_finish_command+0xcf/0x120 > 286) 608 48 scsi_softirq_done+0x126/0x150 > 287) 560 24 blk_done_softirq+0x78/0x90 > 288) 536 136 __do_softirq+0xfd/0x280 > 289) 400 16 run_ksoftirqd+0x28/0x50 > 290) 384 64 smpboot_thread_fn+0x105/0x160 > 291) 320 144 kthread+0xc9/0xe0 > 292) 176 176 ret_from_fork+0x3f/0x70 > > Based on earlier patch by Mikulas Patocka <mpatocka@xxxxxxxxxx>. > https://lkml.org/lkml/2008/6/24/18 Looks a empty link, and the following had the discussion too: http://linux-kernel.2935.n7.nabble.com/PATCH-1-2-Avoid-bio-endio-recursion-td306043.html > > Signed-off-by: Shaun Tancheff <shaun.tancheff@xxxxxxxxxxx> > --- > block/bio.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 54 insertions(+), 3 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index d42e69c..4ac19f6 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -1733,6 +1733,59 @@ static inline bool bio_remaining_done(struct bio *bio) > return false; > } > > +static DEFINE_PER_CPU(struct bio **, bio_end_queue) = { NULL }; The idea looks very nice, but this patch can't be applid to current block-next branch. Looks it might be simpler to implement the approach by using percpu bio_list. > + > +static struct bio *unwind_bio_endio(struct bio *bio) > +{ > + struct bio ***bio_end_queue_ptr; > + struct bio *bio_queue; > + struct bio *chain_bio = NULL; > + int error = bio->bi_error; > + unsigned long flags; > + > + local_irq_save(flags); If we may resue current->bio_list for this purpose, disabling irq should have been avoided, but looks it is difficult to do in that way, maybe impossible. Also not realistic to introduce a new per-task variable. > + bio_end_queue_ptr = this_cpu_ptr(&bio_end_queue); > + > + if (*bio_end_queue_ptr) { > + **bio_end_queue_ptr = bio; > + *bio_end_queue_ptr = &bio->bi_next; > + bio->bi_next = NULL; > + } else { > + bio_queue = NULL; > + *bio_end_queue_ptr = &bio_queue; Suggest to comment that bio_queue is the bottom-most stack variable, otherwise looks a bit tricky to understand. > + > +next_bio: > + if (bio->bi_end_io == bio_chain_endio) { > + struct bio *parent = bio->bi_private; > + > + bio_put(bio); > + chain_bio = parent; > + goto out; > + } > + > + if (bio->bi_end_io) { > + if (!bio->bi_error) > + bio->bi_error = error; > + bio->bi_end_io(bio); > + } > + > + if (bio_queue) { > + bio = bio_queue; > + bio_queue = bio->bi_next; > + if (!bio_queue) > + *bio_end_queue_ptr = &bio_queue; > + goto next_bio; > + } > + *bio_end_queue_ptr = NULL; > + } > + > +out: > + > + local_irq_restore(flags); > + > + return chain_bio; > +} > + > /** > * bio_endio - end I/O on a bio > * @bio: bio > @@ -1762,9 +1815,7 @@ void bio_endio(struct bio *bio) > bio_put(bio); > bio = parent; > } else { > - if (bio->bi_end_io) > - bio->bi_end_io(bio); > - bio = NULL; > + bio = unwind_bio_endio(bio); > } > } > } > -- > 1.9.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-block" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
