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b18019d2d8
mirror_zfs/module/zfs
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Etienne Dechamps b18019d2d8 Fix synchronicity for ZVOLs. 
zvol_write() assumes that the write request must be written to stable storage
if rq_is_sync() is true. Unfortunately, this assumption is incorrect. Indeed,
"sync" does *not* mean what we think it means in the context of the Linux
block layer. This is well explained in linux/fs.h:

    WRITE:       A normal async write. Device will be plugged.
    WRITE_SYNC:  Synchronous write. Identical to WRITE, but passes down
                 the hint that someone will be waiting on this IO
                 shortly.
    WRITE_FLUSH: Like WRITE_SYNC but with preceding cache flush.
    WRITE_FUA:   Like WRITE_SYNC but data is guaranteed to be on
                 non-volatile media on completion.

In other words, SYNC does not *mean* that the write must be on stable storage
on completion. It just means that someone is waiting on us to complete the
write request. Thus triggering a ZIL commit for each SYNC write request on a
ZVOL is unnecessary and harmful for performance. To make matters worse, ZVOL
users have no way to express that they actually want data to be written to
stable storage, which means the ZIL is broken for ZVOLs.

The request for stable storage is expressed by the FUA flag, so we must
commit the ZIL after the write if the FUA flag is set. In addition, we must
commit the ZIL before the write if the FLUSH flag is set.

Also, we must inform the block layer that we actually support FLUSH and FUA.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-07 16:23:06 -08:00
..
arc.c Cleanup ZFS debug infrastructure 2012-02-02 11:24:30 -08:00
bplist.c Fix gcc missing parenthesis warnings 2010-08-31 08:38:35 -07:00
bpobj.c Update to onnv_147 2010-08-26 14:24:34 -07:00
dbuf.c Illumos #764: panic in zfs:dbuf_sync_list 2011-08-01 12:09:11 -07:00
ddt_zap.c Fix stack ddt_zap_lookup() 2011-05-31 12:17:27 -07:00
ddt.c Fix stack ddt_class_contains() 2011-05-31 12:17:27 -07:00
dmu_diff.c Update to onnv_147 2010-08-26 14:24:34 -07:00
dmu_object.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
dmu_objset.c Merge branch 'zpl' 2011-02-18 09:31:25 -08:00
dmu_send.c Illumos #755: dmu_recv_stream builds incomplete guid_to_ds_map 2011-10-18 11:18:14 -07:00
dmu_traverse.c Revert "Fix stack traverse_visitbp()" 2011-05-31 12:17:27 -07:00
dmu_tx.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
dmu_zfetch.c Add missing ZFS tunables 2011-05-04 10:02:37 -07:00
dmu.c Suppress large kmem_alloc() warning 2011-02-10 09:27:22 -08:00
dnode_sync.c Fix dbuf eviction assertion 2010-08-31 08:38:45 -07:00
dnode.c Improve meta data performance 2011-11-03 10:19:21 -07:00
dsl_dataset.c Illumos #1092: zfs refratio property 2011-08-01 12:09:11 -07:00
dsl_deadlist.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
dsl_deleg.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
dsl_dir.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
dsl_pool.c Add missing ZFS tunables 2011-05-04 10:02:37 -07:00
dsl_prop.c Fix enum compiler warning 2011-02-23 12:52:51 -08:00
dsl_scan.c Add missing ZFS tunables 2011-05-04 10:02:37 -07:00
dsl_synctask.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
fm.c Add missing ZFS tunables 2011-05-04 10:02:37 -07:00
gzip.c Fix zmod.h usage in userspace 2010-08-31 08:38:46 -07:00
lzjb.c Fix stack lzjb 2010-08-31 08:38:49 -07:00
Makefile.in Implemented NFS export_operations. 2011-04-29 12:36:13 -07:00
metaslab.c Illumos #1051: zfs should handle imbalanced luns 2011-08-01 12:09:11 -07:00
refcount.c Fix gcc uninitialized variable warnings 2010-08-31 08:38:43 -07:00
rrwlock.c Enable rrwlock.c compilation 2010-12-07 16:05:25 -08:00
sa.c Implement SA based xattrs 2011-11-28 15:45:51 -08:00
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 Prototype/structure update for Linux 2011-02-10 09:27:21 -08:00
spa_errlog.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
spa_history.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
spa_misc.c Cleanup ZFS debug infrastructure 2012-02-02 11:24:30 -08:00
spa.c Reduce number of zio free threads 2012-01-17 08:54:00 -08:00
space_map.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
txg.c Illumos #1313: Integer overflow in txg_delay() 2011-08-01 12:09:43 -07:00
uberblock.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
unique.c Fix gcc ident pragma warnings 2010-08-27 15:34:02 -07:00
vdev_cache.c Illumos #175: zfs vdev cache consumes excessive memory 2011-08-01 12:09:11 -07:00
vdev_disk.c Linux 2.6.37 compat, WRITE_FLUSH_FUA 2011-06-17 14:37:26 -07:00
vdev_file.c Prototype/structure update for Linux 2011-02-10 09:27:21 -08:00
vdev_label.c Fix gcc uninitialized variable warnings 2010-08-31 08:38:43 -07:00
vdev_mirror.c Fix gcc c90 compliance warnings 2010-08-27 15:28:32 -07:00
vdev_missing.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
vdev_queue.c Add missing ZFS tunables 2011-05-04 10:02:37 -07:00
vdev_raidz.c Fix variables named current 2010-08-31 08:38:44 -07:00
vdev_root.c Fix gcc c90 compliance warnings 2010-08-27 15:28:32 -07:00
vdev.c Allow setting bootfs on any pool 2012-01-17 13:49:07 -08:00
zap_leaf.c Fix gcc uninitialized variable warnings 2010-08-31 08:38:43 -07:00
zap_micro.c Export symbols for the full ZAP API 2011-09-27 16:12:36 -07:00
zap.c Fix rw_init() usage 2010-08-31 08:38:46 -07:00
zfs_acl.c Linux compat 2.6.39: mount_nodev() 2011-07-01 13:36:39 -07:00
zfs_byteswap.c Add linux kernel module support 2010-08-31 13:41:58 -07:00
zfs_debug.c Cleanup ZFS debug infrastructure 2012-02-02 11:24:30 -08:00
zfs_dir.c Allow multiple values per directory entry 2012-02-02 11:22:08 -08:00
zfs_fm.c Initial zio delay timing 2010-10-12 14:55:02 -07:00
zfs_fuid.c Drop HAVE_XVATTR macros 2011-03-02 11:44:34 -08:00
zfs_ioctl.c Cleanup ZFS debug infrastructure 2012-02-02 11:24:30 -08:00
zfs_log.c Drop HAVE_XVATTR macros 2011-03-02 11:44:34 -08:00
zfs_onexit.c Add linux kernel device support 2010-08-31 13:41:50 -07:00
zfs_replay.c Use Linux ATTR_ versions 2011-03-03 11:29:15 -08:00
zfs_rlock.c Range lock performance improvements 2011-03-08 12:44:06 -08:00
zfs_sa.c Export symbol zfs_attr_table 2012-01-27 09:23:36 -08:00
zfs_vfsops.c Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
zfs_vnops.c Allow multiple values per directory entry 2012-02-02 11:22:08 -08:00
zfs_znode.c Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
zil.c Illumos #883: ZIL reuse during remount corruption 2011-08-01 12:09:11 -07:00
zio_checksum.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
zio_compress.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
zio_inject.c Add missing ZFS tunables 2011-05-04 10:02:37 -07:00
zio.c Illumos #734: Use taskq_dispatch_ent() interface 2011-12-14 09:19:30 -08:00
zle.c Update core ZFS code from build 121 to build 141. 2010-05-28 13:45:14 -07:00
zpl_export.c Linux compat 2.6.39: mount_nodev() 2011-07-01 13:36:39 -07:00
zpl_file.c Linux 3.1 compat, fops->fsync() 2011-11-10 10:03:08 -08:00
zpl_inode.c Allow xattrs on symlinks 2011-11-29 10:24:24 -08:00
zpl_super.c Linux 3.3 compat, sops->show_options() 2012-02-03 10:02:01 -08:00
zpl_xattr.c Apply the ZoL coding standard to zpl_xattr.c 2012-01-12 15:12:03 -08:00
zrlock.c Export ZFS symbols needed by Lustre. 2010-09-17 16:24:15 -07:00
zvol.c Fix synchronicity for ZVOLs. 2012-02-07 16:23:06 -08:00