Kohsuke Kawaguchi 77831e1738 Reduce the stack usage of dsl_dataset_remove_clones_key ... dataset_remove_clones_key does recursion, so if the recursion goes deep it can overrun the linux kernel stack size of 8KB. I have seen this happen in the actual deployment, and subsequently confirmed it by running a test workload on a custom-built kernel that uses 32KB stack. See the following stack trace as an example of the case where it would have run over the 8KB stack kernel: Depth Size Location (42 entries) ----- ---- -------- 0) 11192 72 __kmalloc+0x2e/0x240 1) 11120 144 kmem_alloc_debug+0x20e/0x500 2) 10976 72 dbuf_hold_impl+0x4a/0xa0 3) 10904 120 dbuf_prefetch+0xd3/0x280 4) 10784 80 dmu_zfetch_dofetch.isra.5+0x10f/0x180 5) 10704 240 dmu_zfetch+0x5f7/0x10e0 6) 10464 168 dbuf_read+0x71e/0x8f0 7) 10296 104 dnode_hold_impl+0x1ee/0x620 8) 10192 16 dnode_hold+0x19/0x20 9) 10176 88 dmu_buf_hold+0x42/0x1b0 10) 10088 144 zap_lockdir+0x48/0x730 11) 9944 128 zap_cursor_retrieve+0x1c4/0x2f0 12) 9816 392 dsl_dataset_remove_clones_key.isra.14+0xab/0x190 13) 9424 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 14) 9032 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 15) 8640 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 16) 8248 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 17) 7856 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 18) 7464 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 19) 7072 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 20) 6680 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 21) 6288 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 22) 5896 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 23) 5504 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 24) 5112 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 25) 4720 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 26) 4328 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 27) 3936 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 28) 3544 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 29) 3152 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 30) 2760 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 31) 2368 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 32) 1976 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 33) 1584 392 dsl_dataset_remove_clones_key.isra.14+0x10c/0x190 34) 1192 232 dsl_dataset_destroy_sync+0x311/0xf60 35) 960 72 dsl_sync_task_group_sync+0x12f/0x230 36) 888 168 dsl_pool_sync+0x48b/0x5c0 37) 720 184 spa_sync+0x417/0xb00 38) 536 184 txg_sync_thread+0x325/0x5b0 39) 352 48 thread_generic_wrapper+0x7a/0x90 40) 304 128 kthread+0xc0/0xd0 41) 176 176 ret_from_fork+0x7c/0xb0 This change reduces the stack usage in dsl_dataset_remove_clones_key by allocating structures in heap, not in stack. This is not a fundamental fix, as one can create an arbitrary large data set that runs over any fixed size stack, but this will make the problem far less likely. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Kohsuke Kawaguchi <kk@kohsuke.org> Closes #1726		2013-09-25 15:18:32 -07:00
..
avl	Add script for builtin module building.	2012-07-26 13:45:09 -07:00
nvpair	Illumos #3464	2013-09-04 16:01:24 -07:00
unicode	Add script for builtin module building.	2012-07-26 13:45:09 -07:00
zcommon	Illumos #2882, #2883, #2900	2013-09-04 15:49:00 -07:00
zfs	Reduce the stack usage of dsl_dataset_remove_clones_key	2013-09-25 15:18:32 -07:00
zpios	Illumos #3464	2013-09-04 16:01:24 -07:00
.gitignore	gitignore: anchor entries at their respective directory	2013-04-02 10:50:17 -07:00
Makefile.in	Add KMODDIR to install target	2013-03-06 15:46:40 -08:00