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Brian Behlendorf 3b9fd93d0b Fix zsb->z_hold_mtx deadlock 
The zfs_znode_hold_enter() / zfs_znode_hold_exit() functions are used to
serialize access to a znode and its SA buffer while the object is being
created or destroyed.  This kind of locking would normally reside in the
znode itself but in this case that's impossible because the znode and SA
buffer may not yet exist.  Therefore the locking is handled externally
with an array of mutexs and AVLs trees which contain per-object locks.

In zfs_znode_hold_enter() a per-object lock is created as needed, inserted
in to the correct AVL tree and finally the per-object lock is held.  In
zfs_znode_hold_exit() the process is reversed.  The per-object lock is
released, removed from the AVL tree and destroyed if there are no waiters.

This scheme has two important properties:

1) No memory allocations are performed while holding one of the z_hold_locks.
   This ensures evict(), which can be called from direct memory reclaim, will
   never block waiting on a z_hold_locks which just happens to have hashed
   to the same index.

2) All locks used to serialize access to an object are per-object and never
   shared.  This minimizes lock contention without creating a large number
   of dedicated locks.

On the downside it does require znode_lock_t structures to be frequently
allocated and freed.  However, because these are backed by a kmem cache
and very short lived this cost is minimal.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4106
 		2016-01-29 09:52:12 -08:00
..
fm Improve on the ZFS events documentation 2015-06-09 11:19:19 -07:00
fs Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
Makefile.am Add temporary mount options 2015-09-03 14:14:55 -07:00
arc.h Illumos 6214 - zpools going south 2015-09-11 11:14:38 -07:00
arc_impl.h Illumos 6214 - zpools going south 2015-09-11 11:14:38 -07:00
avl.h Illumos 4745 - fix AVL code misspellings 2015-07-10 11:58:37 -07:00
avl_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
blkptr.h Illumos 4757, 4913 2014-08-01 14:28:05 -07:00
bplist.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
bpobj.h Illumos 5810 - zdb should print details of bpobj 2015-05-11 15:10:24 -07:00
bptree.h Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
dbuf.h Illumos 6267 - dn_bonus evicted too early 2015-10-13 15:32:16 -07:00
ddt.h Add ddt, ddt_entry, and l2arc_hdr caches 2014-01-07 10:33:11 -08:00
dmu.h zvol processing should use struct bio 2015-09-04 15:30:24 -04:00
dmu_impl.h Illumos 4757, 4913 2014-08-01 14:28:05 -07:00
dmu_objset.h Illumos 6267 - dn_bonus evicted too early 2015-10-13 15:32:16 -07:00
dmu_send.h Illumos 5765 - add support for estimating send stream size with lzc_send_space when source is a bookmark 2015-05-13 09:03:59 -07:00
dmu_traverse.h Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
dmu_tx.h dmu_tx kstat cleanup 2014-03-04 12:22:24 -08:00
dmu_zfetch.h Fix zstream_t incorrect type 2013-12-10 10:09:27 -08:00
dnode.h Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
dsl_bookmark.h Illumos 4368, 4369. 2014-07-29 10:55:29 -07:00
dsl_dataset.h Illumos 5765 - add support for estimating send stream size with lzc_send_space when source is a bookmark 2015-05-13 09:03:59 -07:00
dsl_deadlist.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
dsl_deleg.h Illumos 4368, 4369. 2014-07-29 10:55:29 -07:00
dsl_destroy.h Illumos #3888 2013-11-04 11:18:14 -08:00
dsl_dir.h Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
dsl_pool.h Illumos 5981 - Deadlock in dmu_objset_find_dp 2015-07-06 09:31:35 -07:00
dsl_prop.h Illumos #3464 2013-09-04 16:01:24 -07:00
dsl_scan.h Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
dsl_synctask.h Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_userhold.h Illumos #3740 2013-11-04 11:17:48 -08:00
efi_partition.h Move partition scanning from userspace to module. 2012-07-17 09:17:31 -07:00
metaslab.h Illumos 5213 - panic in metaslab_init due to space_map_open returning ENXIO 2014-11-14 15:37:45 -08:00
metaslab_impl.h Illumos 4976-4984 - metaslab improvements 2014-08-18 08:40:49 -07:00
mntent.h Honor xattr=sa dataset property 2015-09-19 13:32:34 -07:00
multilist.h Illumos 5497 - lock contention on arcs_mtx 2015-06-11 10:27:25 -07:00
nvpair.h Replace __va_list with va_list 2014-08-13 10:35:00 -07:00
nvpair_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
range_tree.h Illumos #4374 2014-07-30 09:20:35 -07:00
refcount.h Illumos #3464 2013-09-04 16:01:24 -07:00
rrwlock.h Illumos 5008 - lock contention (rrw_exit) while running a read only load 2015-07-06 09:34:13 -07:00
sa.h Prevent SA length overflow 2016-01-29 09:41:14 -08:00
sa_impl.h Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
sdt.h Swap DTRACE_PROBE* with Linux tracepoints 2014-11-17 11:13:55 -08:00
spa.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
spa_boot.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
spa_impl.h Illumos 5818 - zfs {ref}compressratio is incorrect with 4k sector size 2015-06-10 16:24:01 -07:00
space_map.h Illumos 5164-5165 - space map fixes 2014-10-23 15:30:32 -07:00
space_reftree.h Illumos #4101, #4102, #4103, #4105, #4106 2014-07-22 09:39:16 -07:00
trace.h Remove duplicate typedefs from trace.h 2015-01-06 16:53:24 -08:00
trace_acl.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_arc.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_dbgmsg.h Add dbgmsg kstat 2015-09-04 16:08:14 -07:00
trace_dbuf.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_dmu.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_dnode.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_multilist.h Fix build failure with Linux 4.1 and FTRACE 2015-08-18 16:47:21 -07:00
trace_txg.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_zil.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
trace_zrlock.h Fix build failure with Linux 4.1 and FTRACE 2015-07-29 07:35:06 -07:00
txg.h Illumos 4753 - increase number of outstanding async writes when sync task is waiting 2014-09-23 13:50:55 -07:00
txg_impl.h Illumos #4045 write throttle & i/o scheduler performance work 2013-12-06 09:32:43 -08:00
u8_textprep.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
u8_textprep_data.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
uberblock.h Illumos 5347 - idle pool may run itself out of space 2015-07-14 10:35:21 -07:00
uberblock_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
uio_impl.h Add basic uio support 2011-02-10 09:21:43 -08:00
unique.h Illumos #3742 2013-11-04 10:55:25 -08:00
uuid.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
vdev.h Illumos 5269 - zpool import slow 2015-06-09 13:48:02 -07:00
vdev_disk.h cstyle: Resolve C style issues 2013-12-18 16:46:35 -08:00
vdev_file.h Update all default taskq settings 2015-06-25 08:58:16 -07:00
vdev_impl.h Disable LBA weighting on files and SSDs 2015-09-01 15:22:07 -07:00
xvattr.h Add xvattr support 2011-03-02 11:43:50 -08:00
zap.h Add zap_prefetch() interface 2015-12-23 17:29:34 -08:00
zap_impl.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zap_leaf.h Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
zfeature.h Illumos 4370, 4371 2014-07-28 14:29:58 -07:00
zfs_acl.h Illumos #3742 2013-11-04 10:55:25 -08:00
zfs_context.h Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
zfs_ctldir.h Use spa as key besides objsetid for snapentry 2015-12-23 17:29:34 -08:00
zfs_debug.h Add dbgmsg kstat 2015-09-04 16:08:14 -07:00
zfs_delay.h cstyle: Resolve C style issues 2013-12-18 16:46:35 -08:00
zfs_dir.h Prototype/structure update for Linux 2011-02-10 09:27:21 -08:00
zfs_fuid.h Prototype/structure update for Linux 2011-02-10 09:27:21 -08:00
zfs_ioctl.h zfsdev_getminor() should check for invalid file handles 2015-06-22 17:02:13 -07:00
zfs_onexit.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zfs_rlock.h Illumos #3742 2013-11-04 10:55:25 -08:00
zfs_sa.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zfs_stat.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zfs_vfsops.h Fix zsb->z_hold_mtx deadlock 2016-01-29 09:52:12 -08:00
zfs_vnops.h Add zfs_iput_async() interface 2014-08-11 16:11:43 -07:00
zfs_znode.h Fix zsb->z_hold_mtx deadlock 2016-01-29 09:52:12 -08:00
zil.h Illumos 5269 - zpool import slow 2015-06-09 13:48:02 -07:00
zil_impl.h Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zio.h Fix vdev_queue_aggregate() deadlock 2015-12-23 17:29:34 -08:00
zio_checksum.h Constify structures containing function pointers 2013-03-04 08:49:32 -08:00
zio_compress.h Illumos #3742 2013-11-04 10:55:25 -08:00
zio_impl.h Illumos #3836 2013-11-05 12:14:56 -08:00
zpl.h Add temporary mount options 2015-09-03 14:14:55 -07:00
zrlock.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
zvol.h Check large block feature flag on volumes 2015-08-28 09:25:03 -07:00