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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
cmd Illumos #3464 2013-09-04 16:01:24 -07:00
config Stop runtime pointer modifications in autotools checks 2013-09-13 13:30:55 -07:00
dracut Refresh dracut module setup 2013-03-21 12:51:06 -07:00
etc Improve OpenRC init script 2013-06-18 17:03:25 -07:00
include Illumos #3464 2013-09-04 16:01:24 -07:00
lib Illumos #3464 2013-09-04 16:01:24 -07:00
man Illumos #3464 2013-09-04 16:01:24 -07:00
module Reduce the stack usage of dsl_dataset_remove_clones_key 2013-09-25 15:18:32 -07:00
patches Adding grub2 mkconfig support patch 2012-07-30 16:17:23 -07:00
rpm Tag zfs-0.6.2 2013-08-22 13:33:26 -07:00
scripts Add kmod repo integration 2013-08-01 09:48:07 -07:00
udev Open pools asynchronously after module load 2013-07-03 09:24:38 -07:00
.gitignore Ignore *.{deb,rpm,tar.gz} files in the top directory. 2013-04-24 16:18:59 -07:00
AUTHORS Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
autogen.sh build: do not call boilerplate ourself 2013-04-02 10:55:20 -07:00
configure.ac Illumos #2882, #2883, #2900 2013-09-04 15:49:00 -07:00
copy-builtin Consistent menuconfig name 2012-08-26 13:49:37 -07:00
COPYRIGHT Refresh links to web site 2013-03-06 15:46:41 -08:00
DISCLAIMER Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
Makefile.am build: do not call boilerplate ourself 2013-04-02 10:55:20 -07:00
META Tag zfs-0.6.2 2013-08-22 13:33:26 -07:00
OPENSOLARIS.LICENSE Add CDDL license file 2008-12-01 14:49:34 -08:00
README.markdown Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
zfs-script-config.sh.in Retire zpool_id infrastructure 2013-01-29 12:23:17 -08:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

README.markdown

Native ZFS for Linux!

ZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the Illumos community.

ZFS on Linux, which is also known as ZoL, is currently feature complete. It includes fully functional and stable SPA, DMU, ZVOL, and ZPL layers.

Full documentation for installing ZoL on your favorite Linux distribution can be found at: http://zfsonlinux.org