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efc412b645
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Brian Behlendorf efc412b645 Linux 4.2 compat: vfs_rename() 
The spa_config_write() function relies on the classic method of
making sure updates to the /etc/zfs/zpool.cache file are atomic.
It writes out a temporary version of the file and then uses
vn_rename() to switch it in to place.  This way there can never
exist a partial version of the file, it's all or nothing.

Conceptually this is a good strategy and it makes good sense
for platforms where it's easy to do a rename within the kernel.
Unfortunately, Linux is not one of those platforms.  Even doing
basic I/O to a file system from within the kernel is strongly
discouraged.  In order to support this at all the vn_rename()
implementation ends up being complex and fragile.  So fragile
that recent Linux 4.2 changes have broken it.

While it is possible to update vn_rename() to work with the
latest kernels a better long term strategy is to stop using
vn_rename() entirely.  Then all this complex, fragile code can
be removed.  Achieving this is straight forward because
config_write() is the only consumer of vn_rename().

This patch reworks spa_config_write() to update the cache file
in place.  The file will be truncated, written out, and then
synced to disk.  If an error is encountered the file will be
unlinked leaving the system in a consistent state.

This does expose a tiny tiny tiny window where a system could
crash at exactly the wrong moment could leave a partially written
cache file.  However, this is highly unlikely because the cache
file is 1) infrequently updated, 2) only a few kilobytes in size,
and 3) written with a single vn_rdwr() call.

If this were to somehow happen it poses no risk to pool.  Simply
removing the cache file will allow the pool to be imported cleanly.
Going forward this will be even less of an issue as we intend to
disable the use of a cache file by default.

Bottom line not using vn_rename() allows us to make ZoL more
robust against upstream kernel changes.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3653
2015-08-19 16:04:33 -07:00
..
arc.c Update arc_memory_throttle() to check pageout 2015-07-30 11:52:12 -07:00
blkptr.c Illumos 4757, 4913 2014-08-01 14:28:05 -07:00
bplist.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
bpobj.c Illumos 5810 - zdb should print details of bpobj 2015-05-11 15:10:24 -07:00
bptree.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
dbuf_stats.c Illumos 5497 - lock contention on arcs_mtx 2015-06-11 10:27:25 -07:00
dbuf.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
ddt_zap.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
ddt.c Handle zap_lookup() failure in ddt_object_load() 2015-08-19 14:32:50 -07:00
dmu_diff.c Illumos 5369 - arc flags should be an enum 2015-06-11 10:27:25 -07:00
dmu_object.c Illumos 3693 - restore_object uses at least two transactions to restore an object 2014-10-21 15:26:50 -07:00
dmu_objset.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
dmu_send.c Illumos 5946, 5945 2015-07-06 09:31:30 -07:00
dmu_traverse.c Wait interruptibly in prefetch thread 2015-06-16 16:18:11 -07:00
dmu_tx.c Illumos 5911 - ZFS "hangs" while deleting file 2015-07-06 09:31:42 -07:00
dmu_zfetch.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
dmu.c Check for NULL in dmu_free_long_range_impl() 2015-07-28 13:30:53 -07:00
dnode_sync.c Illumos 5911 - ZFS "hangs" while deleting file 2015-07-06 09:31:42 -07:00
dnode.c Illumos 5911 - ZFS "hangs" while deleting file 2015-07-06 09:31:42 -07:00
dsl_bookmark.c Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_dataset.c Illumos 5909 - ensure that shared snap names don't become too long after promotion 2015-07-06 09:21:30 -07:00
dsl_deadlist.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
dsl_deleg.c Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_destroy.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
dsl_dir.c Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_pool.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
dsl_prop.c Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_scan.c Illumos 5347 - idle pool may run itself out of space 2015-07-14 10:35:21 -07:00
dsl_synctask.c Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
dsl_userhold.c Illumos 4951 - ZFS administrative commands should use reserved space 2015-05-04 09:41:10 -07:00
fm.c zfsdev_getminor() should check for invalid file handles 2015-06-22 17:02:13 -07:00
gzip.c cstyle: Resolve C style issues 2013-12-18 16:46:35 -08:00
lz4.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
lzjb.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
Makefile.in Support parallel build trees (VPATH builds) 2015-07-17 13:42:51 -07:00
metaslab.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
multilist.c Illumos 5497 - lock contention on arcs_mtx 2015-06-11 10:27:25 -07:00
range_tree.c Illumos 5163 - arc should reap range_seg_cache 2015-06-25 08:58:16 -07:00
refcount.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
rrwlock.c Illumos 5008 - lock contention (rrw_exit) while running a read only load 2015-07-06 09:34:13 -07:00
sa.c Illumos 5562 - ZFS sa_handle's violate kmem invariants, debug kernels panic on boot 2015-05-11 15:10:57 -07:00
sha256.c Add linux sha2 support 2010-08-31 13:41:59 -07:00
spa_boot.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
spa_config.c Linux 4.2 compat: vfs_rename() 2015-08-19 16:04:33 -07:00
spa_errlog.c Illumos 4914 - zfs on-disk bookmark structure should be named *_phys_t 2014-08-06 14:48:41 -07:00
spa_history.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
spa_misc.c Update all default taskq settings 2015-06-25 08:58:16 -07:00
spa_stats.c Illumos 5369 - arc flags should be an enum 2015-06-11 10:27:25 -07:00
spa.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
space_map.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
space_reftree.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
trace.c Illumos 5497 - lock contention on arcs_mtx 2015-06-11 10:27:25 -07:00
txg.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
uberblock.c Illumos 5347 - idle pool may run itself out of space 2015-07-14 10:35:21 -07:00
unique.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
vdev_cache.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
vdev_disk.c Linux 4.2 compat: remove bio->bi_cnt access 2015-07-17 09:16:08 -07:00
vdev_file.c Update all default taskq settings 2015-06-25 08:58:16 -07:00
vdev_label.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
vdev_mirror.c Illumos #5244 - zio pipeline callers should explicitly invoke next stage 2015-04-30 15:07:47 -07:00
vdev_missing.c Illumos #5244 - zio pipeline callers should explicitly invoke next stage 2015-04-30 15:07:47 -07:00
vdev_queue.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
vdev_raidz.c Illumos #5244 - zio pipeline callers should explicitly invoke next stage 2015-04-30 15:07:47 -07:00
vdev_root.c Illumos #3598 2013-10-31 14:58:04 -07:00
vdev.c Remove unused variable in vdev_add_child() 2015-06-11 10:22:38 -07:00
zap_leaf.c Illumos 5314 - Remove "dbuf phys" db->db_data pointer aliases in ZFS 2015-04-28 16:25:20 -07:00
zap_micro.c Add parenthesis to the ternary operator 2015-08-19 11:28:41 -07:00
zap.c Illumos 3654,3656 2015-05-04 09:41:09 -07:00
zfeature_common.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zfeature.c Use cached feature info in spa_add_feature_stats() 2015-03-05 14:11:10 -08:00
zfs_acl.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
zfs_byteswap.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
zfs_ctldir.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
zfs_debug.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
zfs_dir.c Revert "Revert "Revert "Fix unlink/xattr deadlock""" 2014-08-11 16:12:36 -07:00
zfs_fm.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
zfs_fuid.c Illumos #3522 2013-10-30 14:51:27 -07:00
zfs_ioctl.c Failure of userland copy should return EFAULT 2015-07-14 10:20:35 -07:00
zfs_log.c Illumos 5027 - zfs large block support 2015-05-11 12:23:16 -07:00
zfs_onexit.c zfsdev_getminor() should check for invalid file handles 2015-06-22 17:02:13 -07:00
zfs_replay.c Linux AIO Support 2014-09-05 15:11:43 -07:00
zfs_rlock.c Change KM_PUSHPAGE -> KM_SLEEP 2015-01-16 14:41:26 -08:00
zfs_sa.c Illumos 5056 - ZFS deadlock on db_mtx and dn_holds 2015-04-28 16:25:34 -07:00
zfs_vfsops.c Illumos 5008 - lock contention (rrw_exit) while running a read only load 2015-07-06 09:34:13 -07:00
zfs_vnops.c Fix "BUG: Bad page state" caused by writeback flag 2015-07-29 07:38:15 -07:00
zfs_znode.c Add logic to try and recover an inode with an invalid mode 2015-07-17 15:33:35 -07:00
zil.c Align thread priority with Linux defaults 2015-07-28 13:36:47 -07:00
zio_checksum.c Illumos 4757, 4913 2014-08-01 14:28:05 -07:00
zio_compress.c Illumos 5661 - ZFS: "compression = on" should use lz4 if feature is enabled 2015-07-10 12:11:45 -07:00
zio_inject.c Illumos 5497 - lock contention on arcs_mtx 2015-06-11 10:27:25 -07:00
zio.c Illumos 5369 - arc flags should be an enum 2015-06-11 10:27:25 -07:00
zle.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
zpl_ctldir.c Mark additional functions as PF_FSTRANS 2015-04-17 09:35:24 -07:00
zpl_export.c Return -ESTALE to force lookup for missing NFS file handles 2015-05-14 11:16:52 -07:00
zpl_file.c Linux 4.1 compat: use read_iter() / write_iter() 2015-06-18 12:06:59 -07:00
zpl_inode.c Linux 4.2 compat: follow_link() / put_link() 2015-07-17 09:18:16 -07:00
zpl_super.c Extend PF_FSTRANS critical regions 2015-04-24 09:54:22 -07:00
zpl_xattr.c Mark additional functions as PF_FSTRANS 2015-04-17 09:35:24 -07:00
zrlock.c Illumos 5812 - assertion failed in zrl_tryenter(): zr_owner==NULL 2015-04-30 14:43:40 -07:00
zvol.c Bound zvol_threads module option 2015-07-29 07:42:11 -07:00