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
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 };
+
+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);
+ 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;
+
+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
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